Title of Invention	"METHOD OF PRODUCING SPECIFIC PATHOGEN FREE HAMSTER FOR THE PREPARATION OF A VARIETY OF BIOLOGICAL PRODUCTS"
Abstract	The present invention relates to a method of producing a SPF (specific pathogen free: SPF) hamster for the preparation of a variety of biological products. More particularly, the present invention relates to a method of producing the SPF hamster for the preparation of a variety of biological products, that is free of microbiological contaminants such as parasites, bacteria, and exogenous- and endogenous viruses, etc. with the potential to cause diseases. Since the SPF hamster produced according to the method of the present invention carries no contaminants such as parasites, bacteria, and exogenous- and endogenous viruses, etc., the primary cells originated from said SPF hamster and the biological products using the same do not induce any opportunistic infection by microbial contaminants that can be present in animal cells used for existing biological products such as vaccine, etc. Therefore, the SPF hamster produced according to the present invention can be safely used for preparing a variety of biological products that are applied to a human.

Title of Invention

"METHOD OF PRODUCING SPECIFIC PATHOGEN FREE HAMSTER FOR THE PREPARATION OF A VARIETY OF BIOLOGICAL PRODUCTS"

Abstract

The present invention relates to a method of producing a SPF (specific pathogen free: SPF) hamster for the preparation of a variety of biological products. More particularly, the present invention relates to a method of producing the SPF hamster for the preparation of a variety of biological products, that is free of microbiological contaminants such as parasites, bacteria, and exogenous- and endogenous viruses, etc. with the potential to cause diseases. Since the SPF hamster produced according to the method of the present invention carries no contaminants such as parasites, bacteria, and exogenous- and endogenous viruses, etc., the primary cells originated from said SPF hamster and the biological products using the same do not induce any opportunistic infection by microbial contaminants that can be present in animal cells used for existing biological products such as vaccine, etc. Therefore, the SPF hamster produced according to the present invention can be safely used for preparing a variety of biological products that are applied to a human.

Full Text	Method of producing specific pathogen free hamster for the preparation of a variety of biological products TECHNICAL FIELD The present invention relates to a method of producing SPF (specific pathogen free: SPF) hamster for the preparation of a variety of biological products. More particularly, the present invention relates to a method of producing SPF hamster for the preparation of a variety of biological products, which are free of microbiological contaminants such as various parasites, bacteria, and exogenous- and endogenous viruses, etc. that have a potential to cause diseases. BACKGROUND ART Immunization based on vaccination is a means for a human host to acquire defensive and active immunity without causing any diseases in the host, in which antigens related to infectious diseases are used. For example, a disease-related pathogenic antigen or a pathogen itself appropriately induces only specific immune reactions mediated by humoral immunoregulatory B lymphocyte or cell-mediated immunoregulatory T lymphocyte in the host, and therefore a defensive antibody titer is increased to be the same as or similar to the immune status during the recovery period when the host is naturally infected, or the memorized activity of cytotoxic T lymphocyte is constantly maintained. Depending on the type of antigen and preparation method used, vaccines are divided into toxoid vaccine, inactivated inactivated vaccine, attenuated live vaccine, and recombinant DNA vaccine, etc. Most of the vaccines developed so far are either inactivated vaccine or attenuated vaccine, and they are prepared by a process comprising steps of inoculating live viruses into a certain cell type with animal origin, culturing and harvesting them, then purifying or appropriately processing them. Due to the biological characteristic that virus proliferation is possible only in a living cell, cells of animal origins including human ones should be used as a cell substrate for the preparation of virus vaccines. Cell lines used for the preparation of vaccines are broadly classified into primary cells, diploid cells, and continuous cell lines. Diploid cells and continuous cell Hnes are prepared by freezing cell lines at a certain passage, and later established and controlled as master or working cell bank system for production. When a vaccine preparation is in need, required amount of cells are thawed, then cultured within specific passages, and used as the cell line for the preparation of the vaccine. Meanwhile, it is the primary cells that are used for preparing polio-, measles-, German measles-, Japanses encephalitis- or yellow fever live vaccines. For each lot of vaccine preparation, initial cells, which are isolated directly from animals such as chicken, dog, monkey, or hamster and subsequently cultivated, are used for the vaccine preparation. As such, quality management related to the safety of animal group itself as a source material is of great concern. After years of studying the safety of PMK cell (primary monkey kidney cell), used for the preparation of polio vaccines which made a huge contribution to the eradication of paralytic polio during the vaccination program started from 1950s, it has been found that there are twenty different kinds of latent viruses in the PMK cell, and some of them may induce fatal diseases in human beings. For example, SV40 virus, which is one of the simian viruses that can cause cancer in rodents, was found years after the vaccination in the many lots of polio inactivated vaccine and polio live vaccine that have been inoculated into several millions of young children. It was also found that said virus can transform normal human cells into a cancer cell in vitro (Hayflick L. Science. 276(5311):337-341, 1997). Such a finding inevitably invites disputes on the possible carcinogenic property of the polio vaccine based on PMK cells. Similarly, measles-, mumps-, or yellow fever vaccines for which chicken embryonic cells are used as a cell substrate were found to be contaminated with a live avian retroviruses (Avian leukosis virus), after their wide spread and use. Such incidents draw many concerns about the possible carcinogenic effect of the vaccines on human beings. More disputes were followed later about the safety of the vaccines in relation to the microbial contaminants latent in the cell substrate, which were used for the vaccine preparation. For such reasons, with respect to the animals that are used as a source material for preparing biological products such as vaccines, it is now internationally recommended to use animal groups which are proved to be SPF (specific pathogen free). SPF animals are generally selected based on several tests such as autopsy, microscopic test, culture test, serological test and histopathological test, etc. However, said tests are only useful for examining only the infection with parasites, bacteria, and some major viruses, and no clear standard has been established for the selection of the SPF animals. Compared to the SPF rat or the SPF mouse for which the international standard for determining the microbiological contamination is acknowledged, there is no such an established international standard for the selection of the SPF hamster. The SPF hamster now commercially available is a VAF (viral antigen free) hamster that is free of microbiological contamination with several kinds of viruses. Even for Charles River Laboratories, Inc., or Harlan Sprague Dawley, Inc., which are internationally recognized as major sources for supplying SPF animals, the VAF hamster was selected with a simple detection test for 3 to 15 kinds of bacteria, 2 to 3 kinds of parasites, and 5 or 6 kinds of viruses. The VAF hamsters obtained from one of said two companies were often found with viral contamination. Moreover, for some cases, virus cannot be detected at all for long period of time due to symptomless infection. Therefore, there is a great possibility that the biological products such as vaccines, etc. based on the commercially available VAF hamsters are contaminated with microorganisms which can be harmful to human beings. Thus, the safety of such biological products has not been guaranteed until now. A cell line that is usually used for preparing the vaccines with the SPF hamster is PHK cell (primary hamster kidney cell). Examples of the biological products that are prepared based on the PHK cell include; live attenuated vaccine against Japanese encephalitis, inactivated vaccine against Japanese encephalitis, Rabies vaccine, vaccine against Dengue fever, vaccine against hemorrhage fever with renal syndrome, and vaccine against tick-borne encephalitis. These vaccines are prepared by utilizing the biological characteristic of each antigen virus that can proliferate efficiently and stably in the PHK cells. Therefore, it becomes more important to establish the SPF hamster as a source material for preparing the PHK cell that can be used as a cell substrate in various vaccine preparations. In connection with this, after carrying out many studies to develop a hamster which can be safely used for the preparation of the biological products for human beings, the present inventors established the SPF hamster group which is free of many parasites, bacteria, and endogenous- and exogenous viruses that have a potency to cause diseases. Further, by verifying the safety of the PHK cell originated from said SPF hamster and the biological products prepared using the PHK cells, the present invention was completed. DISCLOSURE OF THE INVENTION Therefore, the purpose of the present invention is to provide a method of producing a hamster colony that can be safely used for the preparation of biological products. In order to achieve the above-described purpose of invention, the present invention provides a method of producing a SPF hamster for the preparation of biological products, comprising the steps of: (a) Firstly, selecting hamsters which are free of infection by carrying out contamination test for parasites, bacteria and hamster viruses, propagating the selected hamsters by sister-brother mating, and then secondly, selecting hamsters not infected with said microorganisms from the propagated hamsters; (b) mating the selected hamsters, obtaining uterus from the female hamster on the 12th to 14th day after pregnancy, introducing the resulting uterus into an isolator, obtaining embryos by C-section, and then breeding the embryos with a surrogate mother inside the barrier area with a class of less than 10,000; and (c) propagating the hamsters bred in the above step (b) by sister-brother mating, carrying out microbiological contamination test for parasites, bacteria, hamster viruses, mouse viruses, endogenous hamster retroviruses, hamster polyoma virus (HPyV), hamster lymphoma virus and unknown hamster viruses, and then selecting the hamsters not infected with said microorganisms from the above-propagated hamsters. In the present invention, the term 'biological products' (or, 'biologicals') refer to vaccines, cultures, and other preparations which are made from living organisms or their products and are intended for use in diagnosing, immunizing, or treating humans or animals, or in related researches. The present invention is described in detail herein below. The present invention is characterized in that it provides a method of producing the SPF hamster which can be safely used for the preparation of biological products for human and animals. In addition, the present invention is characterized in that, in order to stably and consistently provide primary cells for the preparation of said biological products, a germ-free hamster group which is free of microbiological contaminants such parasites, bacteria, and endogenous or exogenous viruses, etc, is established and the standard and the method for determining the safety of said hamster are provided. The hamsters of the present invention include every kind of hamsters which are used for preparing biological products. Preferably, it is golden syrian hamster. Specifically in the present invention, the golden hamster group that has been used in Chengdu Institute of Biological Products, China as an animal source for the cell substrate of the vaccine preparation is selected and served to provide original embryo to be transferred to a clean surrogate mother. In one embodiment of the present invention, microbiological contamination test was carried out for the above-described golden hamster group against parasites, bacteria and hamster viruses, and a hamster group free of microbial contamination was selected firstly. The selected hamsters were allowed to propagate in a breeding room for laboratory animals, and said microbiological contamination test was carried out again. Consequently, a hamster group free of microbial contamination was selected for a second time. For said microbiological contamination test, any methods publicly known in the pertinent art can be used. Specifically, the present inventors carried out the microbiological contamination test for 6 endogenous- and exogenous parasites, 11 bacteria, and 7 hamster viruses listed in the following Table 1, using the method described in Reference Example 1. Table 1 Subject for the microbiological contamination test to select a pregnant mother (Table Removed) In another embodiment of the present invention, in order to select a pregnant mother (a female hamster which becomes pregnant with an embryo that is later transferred to a surrogate mother), two female hamsters with experience of at least one previous parturition were put together in a single cage with a male hamster with mating experience. Subsequently, the vaginal plug-developed female hamster was selected and treated to have the first day of the pregnancy and kept being fed. In addition, the above-described microbiological contamination test was carried out for a VAF hamster obtained from Charles River Lab. Inc. The hamster confirmed to be free of the contamination was used as a surrogate mother (a female hamster that receives the embryo from the pregnant mother and nurses it until the weaning period). Figure 1 illustrates a brief diagram for producing a SPF hamster of the present invention. Some uterus was taken out from the pregnant mother by C-section on the 12th to 14lh day of pregnancy, and it was introduced into the inside of the isolator via dipping bath full of aseptic solution. The proper moment for carrying out C-section can be decided depending on the abdominal distension, congestion- and relaxation degree of vaginal orfice of the pregnant mother. For said aseptic solution, peracetic acid solution, 2% Mikro-quat solution, or iodine solution can be used. Preferably, peracetic acid solution is used. Moreover, the concentration of said peracetic acid solution is preferably between 0.1 and 0.2%. After obtaining the embryo from the uterus, it is bred with the surrogate mother. The breeding is preferably carried out in the SPF barrier area with class less than 10,000, in accordance with the guide for animal experiment (edited by KAMS, Korean Academy of Medical Science). Specifically, the present inventors carried out the breeding in the SPF barrier area provided by Department of Laboratory Animal Medicine, Medical Research Center, Yonsei University College of Medicine, Korea, which is adjusted with the conditions of: temperature of 22-26°C, relative humidity of 45-55%, ventilation frequency of 8-12 times per hour, light intensity of more than 25 lux, and a class less than 10,000. The animals were allowed to propagate based on sister-brother mating. Yet in another embodiment of the present invention, in order to select a SPF hamster group from the propagated hamsters, microbiological contamination test was carried out for various kinds of parasites, bacteria, and viruses, as listed in Tables 2, 3 and 4. In Tables 2, 3 and 4 described below, the subject for the microbiological contamination test of the present invention in order to select the SPF hamster is compared to the test subject to the existing VAF hamster from Charles River Laboratories, Inc. or Harlan Sprague Dawley, Inc. Table 2 Subject for the microbiological contamination test to select a SPF hamster group of the present invention: bacteria (Table Removed) Table 3 Subject for the microbiological contamination test to select the SPF hamster group of the present invention: parasites (Table Removed) Table 4 Subject for the microbiological contamination test to select the SPF hamster group of the present invention: viruses (Table Removed) First of all, the present inventors carried out the microbiological contamination test for the bacteria and parasites described in the above Table 2 and Table 3, and 10 specified hamster viruses and 16 specified mouse viruses described in Table 4. As a result, a SPF hamster group which was confirmed to be free of microbial contamination was selected (see. Table 5 to Table 9). The microbiological contamination test for the bacteria and the parasites were requested to the Department of Laboratory Animal Medicine, Medical Research Center. Yonsei University College of Medicine, Korea, and the microbiological contamination test for the specified hamster- and mouse viruses were requested to Q-One Biotech Ltd., Glasgow, of the United Kingdom. With respect to the test for said hamster viruses, in addition to the serological test, hamster antibody production test (HAP test) against the 10 specified exogenous viruses described in Table 4 was carried out using the PHK cells isolated from the hamster. The HAP test is a modification of the Mouse Antibody Production test (MAP test), first developed by Rove and co-workers (Rowe WP et al, J. Exp. Med., 109:379-391,1959; and Rowe WP et al, Virology 11:645-649, 1960). It is a sensitive, specific and comprehensive method for detecting viruses that are shown to infect hamster tissues. It involves inoculation of highly susceptible host-hamsters, free of the 10 specified exogenous viruses - followed by sensitive and specific serological assays for detection of viral antibodies. 3 routes of inoculation are used to assure the maximum opportunity for any adventitious viruses to infect the test animal. The per os inocuclum provides enteric viruses with access to the alimentary canal. The intranasal inoculum provides respiratory viruses with entry into the respiratory system. The intraperitoneal inoculum provides the viruses an acceptable route to the internal organs, while by passing the mucous membranes of the alimentary canal. With respect to the test for said mouse viruses, mouse antibody production test (MAP test) against the 16 specified viruses described in Table 4 was carried out (Rowe WP., et al, J. Exp. Med., 109:379-391, 1959; Rowe WP., et al., In, The Problems of Laboratory Animal Disease, pp 132-141. ed. RC Harris. Academic Press Inc., New York, 1962; Smith AL., In, Viral and Mycoplasmal Infections of Laboratory Rodents. pp 731-750 eds PN Bhatt, RO Jacoby, MC Morse and AE New. Academic Press Inc., New York, 1986). The MAP test has been used extensively for more than 20 years as the primary method for detecting adventitious murine viruses in cell and/or tumor lines. The test is based on production of antibodies in inoculated mice against any murine viruses that are present in the test material. 4 routes of inoculation are used to assure the maximum opportunity for any adventitious viruses to infect the test animal. The per os inoculum provides enteric viruses (MHV & GDVII) with access to the alimentary canal. The intranasal inoculum provides respiratory viruses (PVM & SEND) with entry into the respiratory system. The intraperitoneal inoculum provides the viruses with an acceptable route to the internal organs, while bypassing the mucous membranes of the alimentary canal. The puncture site also serves as an entry route for ectromelia. The intracerebral inoculum provides LCMV with a direct route to the meninges of the brain. In the LCM challenge experiment, mice are challenged with a known lethal strain of virus and observed each working day for up to 12 days for morbidity and mortality. If an avirulent strain of LCMV is present in the test article, it will render theses mice immune to challenge and they will survive. If the test article is free of such an avirulent strain, the mice will die from the challenge dose in 4-12 days. Whether infection of the test animal has occurred and therefore, whether the test material contained virus, is determined by various techniques for different possible viruses. The serological techniques that can be used in the present invention include indirect fluorescent antibody (IFA), enzyme linked immunosorbent assay (ELISA), complement fixation (CFA), immuno-electron microscopy (IEM) and haemagglutination inhibition (HAI). Thereafter, in order to examine whether or not a latent virus that may cause an opportunistic infection is present in the selected SPF hamster group, the infection test with hamster polyoma virus (hereinafter, referred to 'HPyV'), was examined. Syrian hamsters are susceptible to infection by HPyV which can induce hair follicle epitheliomas. The viral genome consists of double stranded DNA of approximately 5.3 kb and the organization of the open reading frames is typical of polyomaviruses (Delmas V, et al., EMBO Journal, 4:1279-1286, 1985). The use of real time PCR detection allows the quantitative determination of the copy number of a nucleic acid target molecule. Real time PCR detection utilizes the 5' exonuclease activity of Taq polymerase to hydrolyze an internal Taq Man probe labeled with fluorescent reporter and quencher dye (Lee LG, et al., Nucleic Acids Research 21:3761-3766, 1993). Calculation of the copy number is based on when amplification of a target is first detected on an ABI 7700 sequence detection system. The 7700 system determines the threshold cycle (CT), which is the fractional cycle number at which fluorescence passes above a fixed threshold baseline. • Absolute quantitation is performed by comparing the standard curve generated by known numbers of target molecule with unknown samples (PE Applied Biosystems, 1997, Relative quantitation of gene expression, User Bulletin # 2. ABI PRISM 7700 Sequence detection system). The amount of HPyV genomic DNA present in the test sample is determined by comparing test sample CT values to those obtained from a known amount of recombinant plasmid molecules containing HPyV DNA used to produce a standard curve. Under the conditions used the assay routinely detects 100 pHPyV genomes. As a result, no HPyV-specific sequences were detected in any tissue of the SPF hamster of the present invention (see, Table 10). Cell lines used for the preparation of the biological products may produce retrovirus with an extended host range. Therefore, it is determined as to whether or not the SPF hamster of the present invention is infected with the endogenous hamster retrovirus (endogenous hamster leukemia virus). If the infection is confirmed for the SPF hamster, it is also determined as to whether or not human cells can be infected with the retro virus present in the SPF hamster. The following detector cell lines can be used to determine whether retrovirus capable of infecting human or primate cells is present in the test article cell line; human diploid cell line MRC-5, Burkitt's lymphoma cell line Raji, African green monkey kidney cell line Vero, baby hamster kidney cell line BHK, etc. MRC-5 and Raji cells are used to determine whether retrovirus capable of infecting human cells is present. C-type retrovirus replicates in MRC-5 cells while Raji cells are also permissive for D-type retrovirus (including Squirrel monkey retrovirus). Co-cultivation with Vero cells indicates the presence of retrovirus capable of infecting primates, while BHK cells represent a cell line of hamster cell line. The reason of using such a variety of the detector cells is that the expression opportunity for the unknown viruses that may be latent in the test article cells can be increased by co-cultivating the test article cells with various host cells. For such a test, the test article cells are co-cultivated with the detector cells and, at passage 1, the test article cells are removed. The detector cells are maintained over at least 5 passages in order to amplify a low-level infectious virus. Post passage 5 of culture (or at a later passage if appropriate) the supernatant is harvested from the cultures and tested for the presence of retrovirus by product enhanced reverse transcriptase (PERT) assay. The PERT assay is an extremely sensitive assay for the detection of reverse transcriptase (RT) activity and has been reported to be up to 106-fold more sensitive than conventional RT assays (Silver J, et al.. Nucleic Acids Research, 21: 3593-3594, 1993; and Pyra H, et al.. PNAS, U.S.A., 91:1544-1548, 1994). Due to the fact that BHK cells have an endogenous retrovirus and, as a result, generate a positive result by PERT assay, supematants harvested from the BHK culture are tested for the presence of retrovirus by RT assay. Specifically, in the present invention, the PHK cells isolated from SPF hamster according to the present invention are co-cultivated with MRC-5 and Raji cells, respectively. As a result, reverse transcriptase (RT) activity, which is an indicator for the retrovirus activity, was not found for the human cell lines co-cultivated with the PHK cells (see, Table 11 and Table 12). As a third test, the SPF hamster of the present invention was examined for the infection with unknown viral contaminants. For this, the detector cells that are co-cultivated with the PHK cells originated from the SPF hamster of the present invention are examined microscopically for evidence of CPE over the culture period. In addition, the detector cells are haemadsorbed using red blood cells (rbcs) originated from various animals, i.e., guinea pig, chicken, human, etc. Specifically, in the present invention, the PHK cells isolated from the SPF hamster according to the present invention are co-cultivated with MRC-5, Raji and Vero cells, respectively. The detector cells are also haemadsorbed with a mixture of guinea pig rbcs, chiken rbcs and human type 'O' rbcs. As a result, no cytophathic effect (CPE) or haemadsorption was observed for said different kinds of the detector cells that were co-cultivated with the PHK cells of the present invention. As a final test, the SPF hamster produced according to the present invention was examined for the infection with an unknown lymphoma-causing virus, using an immuno-suppressant drug, cyclosporin. The SPF hamster group of the present invention showed no tumor development or other tumor-like symptoms for a period of 100 days after the hamster's immunological function was suppressed. As it has been described above, the SPF hamster of the present invention and the PHK cells originated therefrom are proved to be free of bacteria, parasites, 10 specified hamster viruses, 16 specified mouse viruses, hamster polyoma virus, endogenous retroviruses (hamster leukemia viruses), unknown hamster lymphoma viruses that may have a potential to induce malignant lymphoma, and other unknown hamsters. Meanwhile, for the VAF series hamsters developed by Charles River Laboratory Inc. or by Harlan Sprague Dawley, Inc., the absence of only a few bacteria, parasites and 4-5 specific hamster viruses were confirmed, and an extensive safety verification as in the present invention has not been carried out (see, Tables 2, 3, and 4). Therefore, the SPF hamster produced according to the present invention is superior in its safety to the existing VAF or other SPF hamsters. As such, it is evident that the primary cells, preferably PHK cells, originated from the SPF hamster according to the present invention can be advantageously used as a cell substrate for the preparation of the biological products. Said biological products include vaccines against all the viruses that are able to proliferate in the primary cells originated from a SPF hamster as a host cell (cell substrate). Specific examples include the live attenuated vaccine against Japanese encephalitis as prepared in the present invention (Tsai et al., Japanese encephalitis vaccine. 3rd ed. Vaccines, ed. S.A. Plotkin and W. Orenstein., 1999, Philadelphia: WB Saunders, 672-710), inactivated vaccine against Japanese encephalitis (Lu et al., Japanese encephalitis vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 528), Rabies vaccine (Plotkin SA, et al., Rabies vaccine, In Plotkin SA, Orenstein WA, eds. (1999) Vaccines (3rd ed.), Philadelphia, PA: WB Saunders company, 743-766; Lu et al, Rabies vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 552), vaccine for Dengue fever, vaccine against hemorrhage fever with renal syndrome (Lu et al., Hemorrhagic fever vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 652), and vaccine against tick-borne encephalitis (Lu et al., Tick-borne encephalitis vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 540), etc. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a brief diagram showing the process of producing a SPF hamster of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will hereinafter be described in further detail by examples. It should, however, be borne in mind that the present invention is not limited to or by the examples. Microbiological Contamination Test 1-1) Examination for parasites Presence of any exogenous parasites was determined using light microscopic examination with specimen picked up by a tape. Meanwhile, in order to examine presence of any endogenous parasites, test animals were sacrificed and cut open, and then tissue specimens of stomach, small intestine, and large intestine were prepared. Specimens obtained so were dyed with hematoxylin and eosin, and men examined under a light microscope. 1-2) Examination for bacteria Presence of bacteria was examined based on the following three methods. a. Culture method - for all of the bacteria except Helicobacter spp.. Mycoplasma pulmonis, and Clostridium piliforme Using a sterile swab, materials in the trachea, nasal cavity and intestinal tract were collected and spread over the culture plate for bacteriological examination. Consequently, it was treated in accordance with the SOP(Standard Operating Procedure). b. PCR method - for Heliecobacter spp. PCR was carried out using the forward primer of-SEQ ID NO. 1 and the reverse primer of SEQ ID NO. 2 (J. Clin. Microbiol., 35(6): 1620-1623, 1997; J. Clin. Microbiol., 39(11): 3920-3926, 2001). The PCR reaction was carried out under the operating condition of denaturation (94 °C, 30 seconds), annealing (55 °C, 30 seconds), and extension (72 "C, 2 minutes), amplified for 30 cycle, and the final step was performed at 720 for 5 minutes. The resulting PCR products were identified by an electrophoresis, which is based on 1.5% NuSieve agarose gel (FMC BioProducts, Rockland, Maine). c. ELISA method - for Mycoplasma pulmonis and Clostridium piliforme The examination was carried out using Monilisa kit (ICLAS, Main Research Center for Test Animals, Japan) and Murin antigen kit (Intracel, USA) in accordance with the manufacturer's protocols. 1-3) Examination for viruses Viruses were examined based on ELISA method. The ELISA was carried out using Monilisa kit (ICLAS, Main Research Center for Test Animals, Japan) and Murin antigen kit (Intracel, USA) in accordance with the manufacturer's protocols. Especially, the examination for the seven hamster viruses listed in the above-described Table 1 was carried out in accordance with a method of Smith (Smith AL. (1986) Serologic tests for detection of antibody to rodent viruses. In, Viral and Mycoplasmal Infections of Laboratory Rodents, pp 731-750. eds. PN Bhatt, RO Jacoby, MC Morse and AE New. Academic Press Inc., Orlando) and a method of Lewis et al. (Lewis AM, Rowe WP, Turner HC and Heubner RJ. (1965) Lymphocytic choriomeningitis virus in hamster rumor: spread to hamsters and humans. Science, 150, 363-364). Examinations for other viruses except the hamster viruses are described in detail in the corresponding examples. Preparation of a surgical isolator Inside of a surgical isolator (Daehan Biolink Co. Ltd., Korea) was sterilized with alcohol and Hibiclean solution, and then the positive pressure was maintained by operating airflow. A dipping bath was filled with 0.2% peracetic acid solution. Operational tools and other necessaries were placed inside the isolator for a surgical operation, and a blood agar plate (SIGMA) was also prepared for the examination of microbiological contaminants that can be present in a specimen obtained immediately from the embryo. Selection of hamsters for the production of the SPF hamsters 1-1) First selection of the hamster group For the Golden syrian hamsters obtained from Chengdu Institute of Biological Products, China, the microbiological contamination test of Table 1 was carried out in accordance with the method described in Reference Example 1. As a result, the hamster group with no contaminants was selected first. 1-2) Propagation of the first-selected hamster group and the second selection The hamsters selected first in the above Example 1 -1) were propagated in the breeding room for laboratory animals more than 3 generations by sister-brother mating. The microbiological contamination test described in the above-described Example 1-1) was carried out again and the animal with no contaminants was secondly selected. Thereafter, the selected animals were allocated into new groups and then propagated. Production and propagation of the SPF hamster 2-1) Selections of a pregnant mother and a surrogate mother In order to select a pregnant mother which can provide an embryo via C-section, two female hamsters with experience of at least one previous parturition were selected from the hamster group of the Example 1-2) and then put together in a single cage with a male hamster with mating experience. Next day, the female hamster developing vaginal plug was selected and treated to have the first day of the pregnancy, and kept being fed. In addition, for the VAF Golden Syrian hamsters (Harlan, USA) obtained from Charles River Lab. Inc., the microbiological contamination test described in the above Example 1-1) was carried out, and the hamsters confirmed to be free of contaminants were mated using the same method as above for the pregnant mother. The surrogate mother was therefore obtained. The mating for the surrogate mother was carried out one day ahead of the pregnant mother. The animals, which gave birth one day before the expected birth date of the pregnant mother, were selected and used as a surrogate mother for an embryo of the pregnant mother. 2-2) Production of the embryo by C-section Suitable time for carrying out C-section was determined based on the abdominal distension and congestion- and relaxation degree of vaginal orfice of the pregnant mother. On the 13.5 day after the pregnancy, C-section was carried out. First, the pregnant mother was sacrificed with CO2 gas injection, and the outside of the dead body was cleaned with a disinfection soap (Iodex Hand Soap, QUIP LABORATORIES INC., USA) and disinfected with alcoholic gauze. Iodine solution was also used for further disinfection. For the disinfection, the vaginal opening area and the genital area of the pregnant mother were thoroughly cleaned with extra caution. The abdomen of the dead animal was cut open and its uterus was taken out. Regions flanking each ovary were ligated with a forcep and cut out with a surgical scissors. The cervical region of the uterus was ligated again with the forcep and cut with the scissors. The incised area was disinfected with the iodine solution and, with the uterine cornu headed downward, the uterus was passed through the dipping bath of the isolator prepared in the above Reference Example 2 and introduced into the inside of the isolator (see, Figure 1). Thereafter, the disinfection solution on the surface of the uterus was removed as fast as possible using disinfected gauze and cotton balls, and then the uterus was cut open to obtain the embryo. The embryos obtained therefrom were then transferred to an operating table that was previously prepared and warmed. Caution has to be taken not to have the embryo in a contact with the chemical solution such as the disinfection solution, etc. About half an hour iater, the condition of the embryos was checked out and the embryos capable of managing self-breathing were selected. Then, the surrogate mother's excreta were applied to the embryos and eight embryos were assigned to each of the surrogate mothers. Using the placenta, etc., which was isolated during the operation, the microbiological contamination test for the embryos was carried out. Breeding and propagation of the embryo in a sterile environment The embryos obtained from the above Example 2 were bred in the SPF barrier area provided by Department of Laboratory Animal Medicine, Medical Research Center, Yonsei University College of Medicine, Korea. The condition for said barrier region is adjusted as follows; temperature of 22-26'C, relative humidity of 45-55%, ventilation frequency of 8-12 times per hour, light intensity of more than 25 lux, and class less than 10,000. For drinking water, ionized drinking water that is supplemented with chloride of below 2% concentration was provided. For feeding stock, rodent general diet (Lab Diet Co., USA), which is sterilized by irradiation, was provided. For organization of hamster generation, the bred hamsters were grouped so that more than 8 propagating groups are present in each of the generations. In order to achieve the propagation via inbreeding, the sister-brother mating method was adopted, in which the mating is carried out within the same litter. Selection of the SPF hamsters 4-1) Bacterial and parasitic contamination test For each of the hamsters selected from the propagated group of Example 3, the microbiological contamination test was carried out for the bacteria and parasites listed in Table 2 and Table 3. The test was carried out according to the method described in the above Reference Example 1. As described in Table 5 below, it was confirmed that the parasites and bacteria were not detected in the selected hamster groups. Table 5 Bacterial- and parasitic contamination test result (Table Removed) -: Not detected 4-2) Viral contamination test For the hamsters selected in accordance with Example 4-1), microbiological contamination test was carried out for various kinds of viruses. All viral contamination tests were requested to Q-One Biotech Ltd., Glasgow, United Kingdom. 4-2-1) Test for 10 specified hamster viruses a. Serological test ELISA analysis was carried out for the serum obtained from the 5 animals of each test group which has been selected in Example 4-1) (Smith AL., Viral and Mycoplasmal Infections of Laboratory Rodents. 731-750, 1986; Lewis AM et ai. Science, 150: 363-364, 1965; Baum SG et ai, N. Eng. Med, 274: 934-936, 1966). First, the microtiter plates were pre-coated with antibody against the 10 specified hamster viruses of Table 4. The prepared serum samples were added to the each well and the plates were incubated at room temperature for 1 hour. The serum of VAF LVG Syrian hamsters, 3-4 weeks old (female), bread in barrier-maintained colonies, was used as a negative control. The serum of the hamsters previously exposed to the antigen of each virus was used as a positive control. The plates were then washed 3 times with PBS/0.05% Tween 20 and peroxidase-conjugated anti-species IgG was added to the each well of the plates. The plates were again incubated at room temperature for 1 hour, and then they were washed 3 times with PBS/0.05% Tween 20. Subsequently, o-Phenylenediamine and urea/F^O? substrate were added into each well of the plates. The plates were then incubated at the room temperature in the dark for 20 minutes. After the incubation, the absorbance was read at 490nm to detect the presence of the specified hamster viruses. As a result, the hamster group, which is completely free of any of the hamster viruses, was selected. The test results for the selected hamsters are summarized in Table 6 described below. Table 6 Serological test results for the hamster viruses (Table Removed) NC: Negative control PC: Positive control -: Not detected "+: Detected b. Hamster antibody production test (HAP test) In order to examine more precisely as to whether the above-described 10 specified viruses, known to infect hamster tissues, have been present in the hamster group selected in the above Step a., HAP test was carried out. The HAP test employed in the present invention is a slight modification of the MAP test, first developed by Rowe, et al. (Rowe WP et ai, J. Exp. Med., 109:379-391, 1959; and Rowe WP et ai. Virology 11:645-649, 1960). The PHK cells isolated from the hamster selected in the above Step a. were inoculated into the female VAF LVG Syrian hamster, 3-4 weeks old (female). During the test period, the inoculated hamsters were maintained in autoclaved microisolation units containing bedding, water and feed, to preclude infection with viruses other than those contaminating the PHK cells. On the 28th day after the inoculation, serum samples were collected from all animals. All serum samples were assayed for 10 different viral antibodies using serological assays. The antibody for HANT was determined by carrying out IFA (indirect immunofluorescence assay) in accordance with the method of Hartley et al. (Hartley JW et al, Virology, 11:645-649, 1960). The antibodies for the rest of other 9 viruses were determined by EL1SA assay. As shown in Table 7 below, it was confirmed that no antibodies were produced against any of the tested hamster viruses. These results were consistent with those of the above step a. Table 7 HAP test results (Table Removed) -: Not detected 4-2-2) Test for 16 specified mouse viruses In order to confirm as to whether the hamster group selected in the above Example 4-2-1) has been infected with the mouse viruses or not, MAP test was carried out for the PHK cells isolated from said hamsters (Rowe WP., el al, J. Exp. Med., 109:379-391, 1959; Rowe WP., et al., In, The Problems of Laboratory Animal Disease. pp 132-141. ed. RC Harris. Academic Press Inc., New York, 1962; Smith AL., In, Viral and Mycoplasmal Infections of Laboratory Rodents, pp 731-750 eds PN Bhan, RO Jacoby, MC Morse and AE New. Academic Press Inc., New York, 1986). First of all, 20 VAF mice (strain CD 1, obtained from Harlan UK Ltd.) were inoculated with the PHK cells obtained from the hamsters of the above Step a. On the 4th day after the inoculation, 4 mice were sacrificed and their plasmas were isolated. Using the spectrophotometric assay, the level of LDH (lactate dehydrogenase) activity was measured to examine the presence of LDV (Lactate dehydrogenase-elevating virus). As a result, it was confirmed that the LDH activity of the mouse inoculated with the PHK cells of the present invention was the same as that of the negative control (see, the following Table 8). Such results suggest that the hamsters selected in the above 4-2-1) are free of LDV. Table 8 LDV infection test results (Table Removed) On the 23rd day after the inoculation, 4 mice were challenged to a known lethal strain of LCMV (Lymphocytic choriomeningitis virus, Armstrong stains) and observed each working day for up to 12 days for morbidity and mortality. If the above-described PHK cells are not infected with LCMV, the animals will die within 4 to 12 days. The 4 mice inoculated with the hamster PHK cells of the present invention died within 12th day after the LCMV inoculation. This result suggests that the hamsters produced according to the present invention are free of LCMV. On the 31s' day after the inoculation, serum samples were isolated from the remaining mice and assayed for the presence of antibody against the mouse viruses by the serological test. As described in Table 9 below, the mouse viruses of 15 different kinds were not detected in the serum of the mouse inoculated with the PHK cells of the present invention. Table 9 MAP test results (Table Removed) -: Not detected With the tests as described in the above, the present inventors established the SPF hamster group which are confirmed to be free of any contamination with 19 kinds of bacteria, 6 kinds of parasites as well as 10 kinds of the hamster viruses, and 16 kinds of the mouse viruses. Additional test for the infection with various kinds of viruses The present inventors carried out further experiments for the SPF hamster group selected in Example 4 to determine the endogenous or exogenous viral infection. 5-1) Test for hamster polyoma virus (HPyV) infection From one test animal obtained from the selected SPF hamster group of Example 4, liver-, spleen-, lymph node-, lung- and kidney tissues were isolated according to the known method. Then, using the ABI 7700 sequence detection system (PE Applied Biosystems, 1997, Relative quantitation of gene expression, User Bulletin #2), the presence of HPyV-specific sequences was determined for the tissues obtained. PCR reactions were carried out in single well of 96 well reaction plates. The DNA isolated from said tissues was used as a template. The TaqMan PCR reagent mix (containing TagMan buffer A, Mg'T, dNTPs, AmpErase UNG, AmpliTaq Gold DNA polymerase, TaqMan HPyV-specific primers and fluorescent probe) was placed into the reaction. The reaction plate was placed into the ABI 7700 instrument where AmpErase, and AmpliTaq activation and amplification reactions were carried out. Said AmpErase reaction was carried out at 50C for 2 minutes, and subsequently, AmpliTaq Gold activation reaction was carried out at 95C0 for 10 min. In addition, the PCR reaction conditions were as follows: 40 cycles consisting of denaturation at 95C for 15 seconds and annealing/extension at 60C for 1 minute. For the control, the negative control and the positive control were prepared in which PCR was carried out without a template and the recombinant pHaPV containing HPyV target gene was used as a template, respectively. The results are shown in Table 10 below. Accordingly, it is confirmed that no HpyV-specific sequences were detected in all tissues of the SPF hamster according to the present invention. Table 10 Test results for the hamster polyoma virus (Table Removed) -: Not detected +: Detected 5-2) Test for the retrovirus infection The PHK cells isolated from the SPF hamster of Example 4 were co-cultivated with human diploid cell line MRC-5 and human Burkitts lymphoma cell line Raji, respectively, and then the production of the retrovirus was examined. First, the PHK cells isolated from the SPF hamster of the present invention were co-cultivated with the detector cells, MRC-5 or Raji cells, for 4-5 days. The detector cell lines were obtained from the American Type Culture Collection (ATCC). At passage 1, the PHK cells were removed and the detector cells cultured over 5 passages. In order to minimize false positive signals from reverse transcriptase (RT) -like activity of DNA polymerase, CT NEAT (activated calf-thymus DNA) that interferes with RT-like activity of DNA polymerase was added. For positive control, virus like particles (VLPs) were treated in. Consequently, supernatant was harvested from the detector cells post passage 5 of culture. These were tested for the presence of retrovirus by PERT assay (product enhanced reverse transcriptase assay), in accordance with the publicly known method (Lugert R, et al, Biotechniques, 20(2):210-217, 1996; Pyra H, et al, PNAS. U.S.A., 91:1544-1548, 1994). The detector cells inoculated onto the base of duplicate transwell plates. As a result, no RT activity was detected in the PHK cells inoculated cultures (see, Table 11 and Table 12 in this regard). Such results indicate that the PHK cells of the SPF hamster of the present invention are not contaminated with the retrovirus that can infect a human. Table 11 Test results tor the retroviruses: MRC-5 cell line (Table Removed) d: threshold cycle + : positive -: negative Table 12 Test results for the retroviruses: Raji cell line (Table Removed) Cj: threshold cycle + : positive -: negative 5-3) Test for the unknown hamster viral infection The presence of possible unknown hamster viral contamination that can induce the opportunistic infection of various detector cells in the SPF hamster of the present invention was also examined. For the detector cells, the human diploid cell line MRC-5, the human Burkitt's lymphoma cell line Raji, and the African green monkey kidney cell line Vero were used and the detector cells were obtained form the ATCC. The detector cells, MRC-5, Raji or Vero cells, were co-cultivated with the PHK cells isolated from the SPF hamster of the present invention for 4-5 days. At passage 1, the PHK cells were removed and the detector cells cultured over 5 passages. Then, the detector cells were examined microscopically for evidence of CPE over the culture period. As a result, no CPE was observed in the inoculated cultures throughout the culture period. In addition, the detector cells were tested for the ability to haemadsorb the mixture of guinea pig rbcs. chicken rbcs and human type 'O' rbcs. The PHK cells of the SPF hamster of the present invention were subjected to hameadsorption with the mixture of guinea pig rbcs, chicken rbcs and human type 'O' rbcs at 4C for at least 30 minutes. The negative controls were detector cells inoculated with culture medium and the postivie controls were MRC-5 cells inoculated with Influenza A virus. As a result, hameadsorption with human type 'O', chiken and guinea pig rbcs was not observed in the negative control and the PHK cells inoculated cultures at post passage 5. On the other hand, the haemadsorption was observed in the positive control. Considering that CPE and hameadsorption were not observed for the PHK cells which have been the co-cultured with various kinds of detector cells for a long period of time, it can be said mat unknown viral contaminants with the hamster origin are noi present in the PHK cells of the SPF hamster of the present invention. 5-4) Test for the unknown hamster lymphoma virus infection To the 20 newborn SPF hamster babies, an immunosuppressant drug, cyclosporin was administered in order to suppress their immunoactivity. After having confirmed the decreased immunoreactivity, the animals were used as the test group. The hamsters of the test group were bred for more than 100 days and the development of malignant lymphoma or other tumor was monitored every week. For the positive control, 20 hamsters inoculated with HeLa tumor cells (ATCC) were prepared. For the negative control, 10 healthy hamsters not administered with said immunosuppressant drug were prepared. After 100 days, the test animals which have been determined to be free of malignant lymphoma or other tumor were sacrificed and subjected to an autopsy. For each of the sacrificed animals, traces of tumors in lymph node, spleen, pancreas, kidney, lung and liver, etc. were exmained. Other abnormality was also examined. The result shows that tumor or other tumor-like lesion was not found for the SPF hamster of the present invention for 100 days after the immunosuppression. BP), for approximately 1 hour. The cells were incubated for an additional 3-4 days to propagate the virus after replacing the medium containing the virus. After having observed the CPE of 75% or more, the virus containing suspension was harvested, clarified & sterile filtered and stored at 2-81 for QC testing. Then, final formulation (adding stabilizer), filling and lyophilization was performed. Experimental example 1> Safety test for the live attenuated JE vaccine of the present invention In order to confirm the human safety of the live attenuated JE vaccine, which has been prepared using the PHK cells of the SPF hamster according to the present invention (Example 5), the safety test was carried out. 1-1) Examination for HPyV In order to determine as to whether or not HpyV is present in the live attenuated JE vaccine of the present invention, the presence of HpyV specific sequences was determined using ABI 7700 sequence probe system and the method as described in Example 5-1). The results are summarized in the following Table 13. Table 13 Test results for the hamster polyoma viruses (Table Removed) -: Not detected +: Detected 1-2) HAP test In order to determine as to whether or not the hamster viruses are present in the live attenuated JE vaccine of the present invention, HAP test was carried out using the method as described in Step b. of Example 4-2-1). The results are summarized in the following Table 14, and as obvious as it is, none of the hamster viruses were detected in the live attenuated JE vaccine of the present invention. Table 14 HAP test results (Table Removed) *-: Not detected 1-3) MAP test with LCM challenge In order to examine as to whether or not the mouse viruses are present in the live attenuated JE vaccine of the present invention. MAP test was carried out using the method as described in Example 4-2-2). The live attenuated JE vaccine of the Example 6 was resuspended in 1.5 mℓ DMEM medium per vial. The neutralizing antiserum was diluted 1 in 10 using DMEM medium. Then, said vaccine and the diluted neutralizing antiserum were mixed in the ratio of 1:1 and incubated at 37C for 1 hour to produce the test samples. 20 SPF mice (strain CD1, Harlan UK Ltd.) were inoculated with the samples. On the 13th day after the inoculation, 4 mice were sacrificed and their plasma were assayed for the level of LDH activity using a spectrophotometric assay. As described in Table 15 below, LDH activity for the mouse inoculated with the PHK cells of the present invention is slightly lower than that of the negative control. Table 15 LDV infection test results (Table Removed) On the 14th day after the inoculation, 4 mice were challenged with LCM virus (Amstrong strain) and observed each working day for up to 12 days for morbidity and mortality. 7 days later, all of the mice were dead. From this result, it is confirmed that the live attenuated JE vaccine, which has been prepared using the PHK cells of the present invention, carries no LCM virus. In addition, on the 34th day after the inoculation, the remaining mice were bled and their sera were subjected to the serological test. As indicated in the following Table 16, none of the 1 5 kinds of the mouse viruses were detected. Table 16 MAP test results (Table Removed) '-: Not detected 1-4) PERT assay For the live attenuated JE vaccine of the present invention, the presence of retrovirus was determined. The present inventors performed the PERT assay that is useful to detect particles of reverse transcriptase with enzymatic activity, in very high sensitivitN. First. 3 ml of the live vaccine as prepared in Example 6 were clarified by centrifugation at approximately ll,000g for 10 minutes, and passed through 0.45 µm sterile filter to remove remaining debris. Then, the resulting vaccine was pelleted by ultracentrifugation at l00.000g for 60 minutes. Each pellet was resuspended in 100 µℓ of disruption buffer solution to release RT activity. The PERT assay was then carried out using the method disclosed by Pyra, et al. (Pyra H, et ai, Proc. Nat. Acad. Sci., 91:1544-1548, 1994). As a result, the live attenuated JE vaccine of the present invention was confirmed to be negative for RT activity. Such result suggests that no retrovirus is present in the live attenuated JE vaccine of the present invention. 1-5) In vitro assay for unknown viral contaminants The present inventors identified the presence of viral contaminations in the live attenuated JE vaccine of the present invention by co-cultivating it with a detector cell line. The human near-triploid cell line H9 (ATCC) was used as a detector cell. First, seed stock of the live attenuated JE vaccine of the present invention was cultivated with H9 cell line. At passage 1, the seed stock was removed. The detector cells were maintained over at least 5 passages. The detector cells were examined microscopically for evidence of CPE over the culture period. No CPE was observed in the H9 cultures. Post passage 5 of culture, the supernatant was harvested from H9 cultures and tested for the presence of retrovirus by PERT assay (Pyra H. et ai, Proc. Natl. Acad. Sci. USA, 9:1544-1548, 1994). RT activity was not detected in seed stock inoculated H9 cultures. In addition, the H9 cells inoculated with the live attenuated JE vaccine of the present invention were haemadsorbed using the mixture of guinea pig rbcs, chicken rbcs and human type 'O' rbcs at 4°C for at least 30 min. As a result, no haemadsorption was observed in the H9 cells. Because CPE, RT activity and haemadsorption were not detected in the H9 cells inoculated with the live attenuated JE vaccine of the present invention, it can be said that the live attenuated JE vaccine of the present invention carries no viral contaminants. 1-6) In vivo assay for unknown viral contaminants To detect the adventitious viral agents in the live attenuated JE vaccine of the present invention by inoculation of embryonated eggs, suckling mice, adult mice, and guinea pigs, according to CPMP and FDA requirements (Committee for Proprietary Medicinal Products: Ad Hoc Working Party on Biotechnology/Pharmacy. J. Biol. Stand., 17:213-222, 1989; and Points to consider in characterization of cell lines used to produce biologicals, 1993. Center for Biologies Evaluation and Research. Food and Drug Administration, Gethesda MD 20205, USA), the present invention performed the following in vivo assay. (1) Sample preparation The live attenuated JE vaccine of the present invention, which has been prepared in Example 6, was resuspended in 1.5 µℓ DMEM medium per vial. The neutralizing antiserum was diluted 1 in 10 using DMEM medium. Said vaccine was mixed with the diluted antiserum in the ratio of 1:1 and incubated at 3712 for 1 hour. (2) Animal test a. Test with suckling mice First of all, safety of the vaccine prepared according to the present invention was determined for the suckling mice. Minimum of 20 suckling mice (SPF. strain CD 1), from 2 or more litters were inoculated with the sample prepared in the above step (1) by the intramuscular (0.01 mℓ), intraperitoneal (0.1 mℓ) and intracerebral (0.01 mℓ) routes (1st inoculation). Another set of the suckling mice was inoculated similarly with DMEM medium and served as the negative controls. The mice were observed for a period of 14 days for any ill effects such as weakness, tremors, paralysis or death. 14 days later, the mice were sacrificed. The organs of the mice were isolated, dissolved, and homogenized. The organ suspension was administered to a new set of suckling mice by the same method as in the First Inoculation (2nd inoculation). The mice were also observed for 14 days. For the lst inoculation, 19 out of 20 mice survived 24 hours after the inoculation (95% survival). No evidence of viral infection was observed following post mortem examination in the suckling dead mouse. For the 2"" inoculation, all of the mice survived 24 hours after the inoculation (100% survival). b. Test with adult mice 10 adult mice (SPF, strain CD 1) were inoculated with the sample by the intramuscular (0.1 mℓ), intraperitoneal (0.5 mℓ) and intracerebral (0.03 mℓ) routes. The negative control mice were inoculated similarly with DMEM medium. Then, the mice were observed for 28 days for any ill effects. As a result, all of the mice survived 24 hours after the inoculation (100% survival). c. Test with a guinea pig As a final test, 5 adult guinea pigs (SPF. strain Duncan Hartley) were inoculated with the sample by intramuscular injection (0.5 ml). For the negative control. 5 guinea pigs were inoculated similarly with DMEM medium. The guinea pigs were observed for a period of 28 days for any ill effects. As a result, it was found that all of the guinea pigs survived 24 hours after the inoculation (100% survival). (3) Test with embryonated eggs a. Amniotic inoculation For amniotic inoculation, 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the amniotic cavity. Another 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of DMEM medium into the amniotic cavity and served as the negative controls. A third set of 10, ten to eleven-day old embryonated hens' eggs were inoculated with 0.1 ml of Influenza-A virus into the amniotic cavity and served as the positive controls. After the inoculation, the eggs were incubated at 35-36 X: for 5 days. The amniotic fluids were harvested and pooled. The pooled amniotic fluids were assayed for haemagglutination (HA) activity. The HA assay was performed in microtiter plates by making serial 2-fold dilutions of the amniotic fluids. The erythrocytes obtained from washed chicken and guinea pig were added separately as 0.5% suspensions and replicate plates were observed for HA activity after incubation for 1-2 hours at 2-8°C and after 1-2 hours at 17-20°C. The result shows that, the levels of HA activity in the amniotic fluid of the test eggs are similar to those of the negative control. In addition, according to the viability test 24 hours after the inoculation, 8 out of the 9 test eggs remained viable (89% viability). b. Allantoic inoculations For allantoic inoculations, 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the allantoic cavity (1st passage). Another 10, ten to eleven-day old SPF embryonated hens" eggs were inoculated with 0.1 ml of DMEM medium into the allantoic cavity and served as the negative controls. A third set of 10, ten to eleven-day old embryonated hens' eggs were inoculated with 0.1 ml of Influenza-A virus (ATCC VR-547) into the allantoic cavity and served as the positive controls. After the inoculation, the eggs were incubated at 35-36C for 3 days. The allantoic fluids were harvested and pooled. A portion of the pooled fluids was frozen and stored at or below -70C until either assayed for HA activity or subpassaged into a new set of embryonated eggs. The pooled allantoic fluids, derived from embryonated eggs initially inoculated with the sample via the allantoic route, were passaged by inoculation of 0.2 ml into each of 7, ten to eleven-day old eggs (2nd passage). The allantoic fluids derived from eggs initially inoculated with DMEM medium were similarly passaged into a new wet of 7, ten to eleven-day old eggs. The allantoic fluids derived from eggs initially inoculated with Influenza-A were similarly passaged into a new set of 7, ten to eleven-day old eggs. 3 days later, the allantoic fluids were harversted, pooled and assayed for HA activity. The HA assays were performed according to the same method as described in the amniotic test. The assay result shows that, the levels of HA in the allantoic fluid of the test eggs are similar to those of the negative control. In addition, according to the viability test 24 hours after the inoculation, all of the embryonated hen's eggs remained viable for the Is' passage (100% viability), and 5 out of the 7 embryonated hen's eggs remained viable for the 2nd passage (71% viability). c. Yolk sac inoculations For yolk sac inoculations, 10, six to seven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the yolk sac (1st passage). Another 10, six to seven-day old SPF embryonated hen's eggs were inoculated with 0.1 ml of DMEM medium and served as the negative controls. The eggs were incubated at 35-36°C for 9 days. Later, the embryos were then examined for viability. The yolk sacs were harvested, washed and pooled. A 10% suspension was prepared and subpassaged into a new set of 7, six to seven-day old SPF embryonated eggs (2nd passage). A 10% yolk sac suspension was also prepared from the DMEM injected eggs, subpassaged into a new set of 7, six to seven-day eggs and served as the negative controls. All embryos were examined 9 days later for viability. The result shows that, all of the 10 test eggs remained viable 24 hours after the inoculation for the 1st passage (100% viability), and all out of 7 test eggs remained viable for the 2nd passage (100% viability). With the above experimental results taken together, it is confirmed that the live attenuated JE vaccine, which is prepared by using the PHK cells originated from the SPF hamster of the present invention is free of any viral contaminants. INDUSTRIAL APPLICABILITY As described in the above, the SPF hamster produced according to the method of the present invention does not carry any parasites, bacteria, or other various endogenous or exogenous viral contaminants. Therefore, the primary cells originated form the SPF hamster and the biological products prepared using the same will not cause the opportunistic infection by microbial contaminants that can be present in the animal cells used for the preparation of the existing biological products such as vaccine, etc. Accordingly, the SPF hamster of the present invention, hamster tissues originated therefrom and their culture supematants can be safely used for the preparation of diverse biological products intended for human use. WHAT IS CLAIMED IS: 1. A method of producing a SPF (specific pathogen free) hamster for the preparation of biological products, comprising the steps of: (a) firstly, selecting the hamsters which are free of infection by carrying out contamination test for parasites, bacteria and hamster viruses, propagating the selected hamsters by sister-brother mating, and then secondly, selecting the hamsters not infected with said microorganisms from the propagated hamsters; (b) mating the selected hamsters, obtaining uterus from the female hamster on the 12th to 14th day after pregnancy, introducing the resulting uterus into an isolator, obtaining embryos by C-section, and then breeding the embryos with a surrogate mother inside the barrier area with class of less than 10,000; and (c) propagating the hamsters bred in the above step (b) by sister-brother mating, carrying out the microbiological contamination test for parasites, bacteria, hamster viruses, mouse liruses, endogenous hamster retroviruses, hamster polyoma virus (HPyV), hamster lymphoma virus and unknown hamster viruses, and then selecting the hamsters not infected with said microorganisms from the above-propagated hamsters. 2. The method according to claim 1, wherein said SPF hamster for the preparation of biological products is used for preparing primary hamster kidney cell (PHK cell). 3. The method according to claim 1, wherein said hamster of the step (a) is golden Syrian hamster. 4. The method according to claim 1, wherein said parasites of the steps (a) or (c) consist of endoparasites and ectoparasites. 5. The method according to claim 4, wherein said endoparasites consist of Capillaria hepatica, Hymenolepsis spp., Encephalitozoon cuniculi, Girdia muris, Spironucleus muris and Syphacia spp. 6. The method according to claim 1, wherein said bacteria of the step (a) consist of Bordetella bronchiseptica, Corynebactehum kutscheri, Helicobacter spp., Mycoplasma pulmonis, Salmonella spp., Salmonella typhimurium, Streptococcus pneumoniae, Pseudomonas aeruginosa, Pasteurella pneumotropica, Staphylococcus aureus and Clostridium piliforme. 7. The method according to claim 1, wherein said hamster viruses of the step (a) consist of Sendai (SEND), Pneumoina virus of mice (PVM). Minute virus of mice (MVM), Kilham rat virus (KRV), Reovirus type 3 (Reo-3), Lymphocytic choriomeningitis virus (LCMV) and Toolans H-l virus (H-l). 8. The method according to claim 1, wherein said surrogate mother of the step (b) is a viral antigen free (VAF) hamster. 9. The method according to claim 1, wherein said bacteria of the step (c) further comprise Pseudomonas spp., Pasteurella spp.. Klebsiella oxytoca, Pasteurella multocida, Klebsiella pneumoniae, Beta Streptococcus group B, Beta Streptococcus group G, and Beta Streptococcus spp.. in addition to the bacteria of the step (a). 10. The method according to claim 1, wherein the hamster viruses of the step (c) further comprise Theilers mouse encephalomyelitis virus (GD-7), Simian virus 5 (SV5), and Hantaan virus (HANT), in addition to the hamster viruses of the step (a). 11. The method according to claim 1, wherein said mouse viruses of the step (c) consist of Lymphocytic choriomeningitis virus (LCMV), Mouse hepatitis virus (MHV), Pneumoina virus of mice (PVM), Minute virus of mice (MVM), Sendai (SEND), Ectromelia (ECTRO), Epizootic diarrhea of infant mice (EDIM), Reovirus type 3 (Reo-3), Mouse encephalomyelitis (GDVII), Mouse adenovirus (MAD), Polyoma viurs (POLY), Hantaan virus (HANT), Mouse thymic virus (MTV), Mouse cytomegalovirus (MCMV), Mouse, pneumonitis virus (K) and Lactate dehydrogenase-elevating virus (LDV). 12. The method according to claim 1, wherein said biological products are selected from a group consisting of the live attenuated vaccine against Japanese encephalitis, inactivated vaccine against Japanese encephalitis, Rabies vaccine, vaccine against Dengue fever, vaccine against hemorrhage fever with renal syndrome, and vaccine against tick-borne encephalitis. 13. A method of producing a SPF (Specific Pathogen Free) hamster substantially as herein described with reference to the foregoing description and the accompanying drawings.

Full Text

Method of producing specific pathogen free hamster for the preparation of a variety of biological products
TECHNICAL FIELD
The present invention relates to a method of producing SPF (specific pathogen free: SPF) hamster for the preparation of a variety of biological products. More particularly, the present invention relates to a method of producing SPF hamster for the preparation of a variety of biological products, which are free of microbiological contaminants such as various parasites, bacteria, and exogenous- and endogenous viruses, etc. that have a potential to cause diseases.
BACKGROUND ART
Immunization based on vaccination is a means for a human host to acquire defensive and active immunity without causing any diseases in the host, in which antigens related to infectious diseases are used. For example, a disease-related pathogenic antigen or a pathogen itself appropriately induces only specific immune reactions mediated by humoral immunoregulatory B lymphocyte or cell-mediated immunoregulatory T lymphocyte in the host, and therefore a defensive antibody titer is increased to be the same as or similar to the immune status during the recovery period when the host is naturally infected, or the memorized activity of cytotoxic T lymphocyte is constantly maintained. Depending on the type of antigen and preparation method used, vaccines are divided into toxoid vaccine, inactivated inactivated vaccine, attenuated live vaccine, and recombinant DNA vaccine, etc. Most of the vaccines developed so far are either inactivated vaccine or attenuated vaccine, and they are prepared by a process comprising steps of inoculating live viruses into a

certain cell type with animal origin, culturing and harvesting them, then purifying or appropriately processing them. Due to the biological characteristic that virus proliferation is possible only in a living cell, cells of animal origins including human ones should be used as a cell substrate for the preparation of virus vaccines. Cell lines used for the preparation of vaccines are broadly classified into primary cells, diploid cells, and continuous cell lines. Diploid cells and continuous cell Hnes are prepared by freezing cell lines at a certain passage, and later established and controlled as master or working cell bank system for production. When a vaccine preparation is in need, required amount of cells are thawed, then cultured within specific passages, and used as the cell line for the preparation of the vaccine.
Meanwhile, it is the primary cells that are used for preparing polio-, measles-, German measles-, Japanses encephalitis- or yellow fever live vaccines. For each lot of vaccine preparation, initial cells, which are isolated directly from animals such as chicken, dog, monkey, or hamster and subsequently cultivated, are used for the vaccine preparation. As such, quality management related to the safety of animal group itself as a source material is of great concern. After years of studying the safety of PMK cell (primary monkey kidney cell), used for the preparation of polio vaccines which made a huge contribution to the eradication of paralytic polio during the vaccination program started from 1950s, it has been found that there are twenty different kinds of latent viruses in the PMK cell, and some of them may induce fatal diseases in human beings. For example, SV40 virus, which is one of the simian viruses that can cause cancer in rodents, was found years after the vaccination in the many lots of polio inactivated vaccine and polio live vaccine that have been inoculated into several millions of young children. It was also found that said virus can transform normal human cells into a cancer cell in vitro (Hayflick L. Science. 276(5311):337-341, 1997). Such a finding inevitably invites disputes on the possible carcinogenic property of the polio vaccine

based on PMK cells. Similarly, measles-, mumps-, or yellow fever vaccines for which chicken embryonic cells are used as a cell substrate were found to be contaminated with a live avian retroviruses (Avian leukosis virus), after their wide spread and use. Such incidents draw many concerns about the possible carcinogenic effect of the vaccines on human beings. More disputes were followed later about the safety of the vaccines in relation to the microbial contaminants latent in the cell substrate, which were used for the vaccine preparation. For such reasons, with respect to the animals that are used as a source material for preparing biological products such as vaccines, it is now internationally recommended to use animal groups which are proved to be SPF (specific pathogen free).
SPF animals are generally selected based on several tests such as autopsy, microscopic test, culture test, serological test and histopathological test, etc. However, said tests are only useful for examining only the infection with parasites, bacteria, and some major viruses, and no clear standard has been established for the selection of the SPF animals. Compared to the SPF rat or the SPF mouse for which the international standard for determining the microbiological contamination is acknowledged, there is no such an established international standard for the selection of the SPF hamster. The SPF hamster now commercially available is a VAF (viral antigen free) hamster that is free of microbiological contamination with several kinds of viruses. Even for Charles River Laboratories, Inc., or Harlan Sprague Dawley, Inc., which are internationally recognized as major sources for supplying SPF animals, the VAF hamster was selected with a simple detection test for 3 to 15 kinds of bacteria, 2 to 3 kinds of parasites, and 5 or 6 kinds of viruses. The VAF hamsters obtained from one of said two companies were often found with viral contamination. Moreover, for some cases, virus cannot be detected at all for long period of time due to symptomless infection. Therefore, there is a great possibility that the biological products such as vaccines, etc. based on the

commercially available VAF hamsters are contaminated with microorganisms which can be harmful to human beings. Thus, the safety of such biological products has not been guaranteed until now.
A cell line that is usually used for preparing the vaccines with the SPF hamster is PHK cell (primary hamster kidney cell). Examples of the biological products that are prepared based on the PHK cell include; live attenuated vaccine against Japanese encephalitis, inactivated vaccine against Japanese encephalitis, Rabies vaccine, vaccine against Dengue fever, vaccine against hemorrhage fever with renal syndrome, and vaccine against tick-borne encephalitis. These vaccines are prepared by utilizing the biological characteristic of each antigen virus that can proliferate efficiently and stably in the PHK cells. Therefore, it becomes more important to establish the SPF hamster as a source material for preparing the PHK cell that can be used as a cell substrate in various vaccine preparations.
In connection with this, after carrying out many studies to develop a hamster which can be safely used for the preparation of the biological products for human beings, the present inventors established the SPF hamster group which is free of many parasites, bacteria, and endogenous- and exogenous viruses that have a potency to cause diseases. Further, by verifying the safety of the PHK cell originated from said SPF hamster and the biological products prepared using the PHK cells, the present invention was completed.
DISCLOSURE OF THE INVENTION
Therefore, the purpose of the present invention is to provide a method of producing a hamster colony that can be safely used for the preparation of biological products.

In order to achieve the above-described purpose of invention, the present invention provides a method of producing a SPF hamster for the preparation of biological products, comprising the steps of:
(a) Firstly, selecting hamsters which are free of infection by carrying out contamination test for parasites, bacteria and hamster viruses, propagating the selected hamsters by sister-brother mating, and then secondly, selecting hamsters not infected with said microorganisms from the propagated hamsters;
(b) mating the selected hamsters, obtaining uterus from the female hamster on the 12th to 14th day after pregnancy, introducing the resulting uterus into an isolator, obtaining embryos by C-section, and then breeding the embryos with a surrogate mother inside the barrier area with a class of less than 10,000; and
(c) propagating the hamsters bred in the above step (b) by sister-brother mating, carrying out microbiological contamination test for parasites, bacteria, hamster viruses, mouse viruses, endogenous hamster retroviruses, hamster polyoma virus (HPyV), hamster lymphoma virus and unknown hamster viruses, and then selecting the hamsters not infected with said microorganisms from the above-propagated hamsters.
In the present invention, the term 'biological products' (or, 'biologicals') refer to vaccines, cultures, and other preparations which are made from living organisms or their products and are intended for use in diagnosing, immunizing, or treating humans or animals, or in related researches.
The present invention is described in detail herein below.
The present invention is characterized in that it provides a method of producing

the SPF hamster which can be safely used for the preparation of biological products for human and animals. In addition, the present invention is characterized in that, in order to stably and consistently provide primary cells for the preparation of said biological products, a germ-free hamster group which is free of microbiological contaminants such parasites, bacteria, and endogenous or exogenous viruses, etc, is established and the standard and the method for determining the safety of said hamster are provided.
The hamsters of the present invention include every kind of hamsters which are used for preparing biological products. Preferably, it is golden syrian hamster. Specifically in the present invention, the golden hamster group that has been used in Chengdu Institute of Biological Products, China as an animal source for the cell substrate of the vaccine preparation is selected and served to provide original embryo to be transferred to a clean surrogate mother.
In one embodiment of the present invention, microbiological contamination test was carried out for the above-described golden hamster group against parasites, bacteria and hamster viruses, and a hamster group free of microbial contamination was selected firstly. The selected hamsters were allowed to propagate in a breeding room for laboratory animals, and said microbiological contamination test was carried out again. Consequently, a hamster group free of microbial contamination was selected for a second time. For said microbiological contamination test, any methods publicly known in the pertinent art can be used. Specifically, the present inventors carried out the microbiological contamination test for 6 endogenous- and exogenous parasites, 11 bacteria, and 7 hamster viruses listed in the following Table 1, using the method described in Reference Example 1.

Table 1
Subject for the microbiological contamination test to select a pregnant mother
(Table Removed)

In another embodiment of the present invention, in order to select a pregnant mother (a female hamster which becomes pregnant with an embryo that is later transferred to a surrogate mother), two female hamsters with experience of at least one previous parturition were put together in a single cage with a male hamster with mating experience. Subsequently, the vaginal plug-developed female hamster was selected and treated to have the first day of the pregnancy and kept being fed. In addition, the above-described microbiological contamination test was carried out for a VAF hamster obtained from Charles River Lab. Inc. The hamster confirmed to be free of the contamination was used as a surrogate mother (a female hamster that receives the embryo from the pregnant mother and nurses it until the weaning period).
Figure 1 illustrates a brief diagram for producing a SPF hamster of the present invention. Some uterus was taken out from the pregnant mother by C-section on the 12th to 14lh day of pregnancy, and it was introduced into the inside of the isolator via dipping bath full of aseptic solution. The proper moment for carrying out C-section can be decided depending on the abdominal distension, congestion- and relaxation degree of vaginal orfice of the pregnant mother. For said aseptic solution, peracetic acid solution, 2% Mikro-quat solution, or iodine solution can be used. Preferably, peracetic acid solution is used. Moreover, the concentration of said peracetic acid solution is preferably between 0.1 and 0.2%.
After obtaining the embryo from the uterus, it is bred with the surrogate mother. The breeding is preferably carried out in the SPF barrier area with class less than 10,000, in accordance with the guide for animal experiment (edited by KAMS, Korean Academy of Medical Science). Specifically, the present inventors carried out the breeding in the SPF barrier area provided by Department of Laboratory Animal Medicine, Medical Research Center, Yonsei University College of Medicine, Korea, which is adjusted with the conditions of: temperature of 22-26°C, relative humidity of

45-55%, ventilation frequency of 8-12 times per hour, light intensity of more than 25 lux, and a class less than 10,000. The animals were allowed to propagate based on sister-brother mating.
Yet in another embodiment of the present invention, in order to select a SPF hamster group from the propagated hamsters, microbiological contamination test was carried out for various kinds of parasites, bacteria, and viruses, as listed in Tables 2, 3 and 4. In Tables 2, 3 and 4 described below, the subject for the microbiological contamination test of the present invention in order to select the SPF hamster is compared to the test subject to the existing VAF hamster from Charles River Laboratories, Inc. or Harlan Sprague Dawley, Inc.
Table 2
Subject for the microbiological contamination test to select a SPF hamster group of the present invention: bacteria
(Table Removed)
Table 3
Subject for the microbiological contamination test to select the SPF hamster group of the present invention: parasites
(Table Removed)

Table 4

Subject for the microbiological contamination test to select the SPF hamster group of the present invention: viruses
(Table Removed)
First of all, the present inventors carried out the microbiological contamination test for the bacteria and parasites described in the above Table 2 and Table 3, and 10 specified hamster viruses and 16 specified mouse viruses described in Table 4. As a result, a SPF hamster group which was confirmed to be free of microbial contamination was selected (see. Table 5 to Table 9). The microbiological contamination test for the bacteria and the parasites were requested to the Department of Laboratory Animal Medicine, Medical Research Center. Yonsei University College of Medicine, Korea,
and the microbiological contamination test for the specified hamster- and mouse viruses were requested to Q-One Biotech Ltd., Glasgow, of the United Kingdom.
With respect to the test for said hamster viruses, in addition to the serological test, hamster antibody production test (HAP test) against the 10 specified exogenous viruses described in Table 4 was carried out using the PHK cells isolated from the hamster.
The HAP test is a modification of the Mouse Antibody Production test (MAP test), first developed by Rove and co-workers (Rowe WP et al, J. Exp. Med., 109:379-391,1959; and Rowe WP et al, Virology 11:645-649, 1960). It is a sensitive, specific and comprehensive method for detecting viruses that are shown to infect hamster tissues. It involves inoculation of highly susceptible host-hamsters, free of the 10 specified exogenous viruses - followed by sensitive and specific serological assays for detection of viral antibodies.
3 routes of inoculation are used to assure the maximum opportunity for any adventitious viruses to infect the test animal. The per os inocuclum provides enteric viruses with access to the alimentary canal. The intranasal inoculum provides respiratory viruses with entry into the respiratory system. The intraperitoneal inoculum provides the viruses an acceptable route to the internal organs, while by passing the mucous membranes of the alimentary canal.
With respect to the test for said mouse viruses, mouse antibody production test (MAP test) against the 16 specified viruses described in Table 4 was carried out (Rowe WP., et al, J. Exp. Med., 109:379-391, 1959; Rowe WP., et al., In, The Problems of Laboratory Animal Disease, pp 132-141. ed. RC Harris. Academic Press Inc., New York, 1962; Smith AL., In, Viral and Mycoplasmal Infections of Laboratory Rodents.
pp 731-750 eds PN Bhatt, RO Jacoby, MC Morse and AE New. Academic Press Inc., New York, 1986).
The MAP test has been used extensively for more than 20 years as the primary method for detecting adventitious murine viruses in cell and/or tumor lines. The test is based on production of antibodies in inoculated mice against any murine viruses that are present in the test material.
4 routes of inoculation are used to assure the maximum opportunity for any adventitious viruses to infect the test animal. The per os inoculum provides enteric viruses (MHV & GDVII) with access to the alimentary canal. The intranasal inoculum provides respiratory viruses (PVM & SEND) with entry into the respiratory system. The intraperitoneal inoculum provides the viruses with an acceptable route to the internal organs, while bypassing the mucous membranes of the alimentary canal. The puncture site also serves as an entry route for ectromelia. The intracerebral inoculum provides LCMV with a direct route to the meninges of the brain.
In the LCM challenge experiment, mice are challenged with a known lethal strain of virus and observed each working day for up to 12 days for morbidity and mortality. If an avirulent strain of LCMV is present in the test article, it will render theses mice immune to challenge and they will survive. If the test article is free of such an avirulent strain, the mice will die from the challenge dose in 4-12 days.
Whether infection of the test animal has occurred and therefore, whether the test material contained virus, is determined by various techniques for different possible viruses. The serological techniques that can be used in the present invention include indirect fluorescent antibody (IFA), enzyme linked immunosorbent assay (ELISA), complement fixation (CFA), immuno-electron microscopy (IEM) and haemagglutination inhibition (HAI).

Thereafter, in order to examine whether or not a latent virus that may cause an opportunistic infection is present in the selected SPF hamster group, the infection test with hamster polyoma virus (hereinafter, referred to 'HPyV'), was examined. Syrian hamsters are susceptible to infection by HPyV which can induce hair follicle epitheliomas. The viral genome consists of double stranded DNA of approximately 5.3 kb and the organization of the open reading frames is typical of polyomaviruses (Delmas V, et al., EMBO Journal, 4:1279-1286, 1985).
The use of real time PCR detection allows the quantitative determination of the copy number of a nucleic acid target molecule. Real time PCR detection utilizes the 5' exonuclease activity of Taq polymerase to hydrolyze an internal Taq Man probe labeled with fluorescent reporter and quencher dye (Lee LG, et al., Nucleic Acids Research 21:3761-3766, 1993). Calculation of the copy number is based on when amplification of a target is first detected on an ABI 7700 sequence detection system. The 7700 system determines the threshold cycle (CT), which is the fractional cycle number at which fluorescence passes above a fixed threshold baseline. • Absolute quantitation is performed by comparing the standard curve generated by known numbers of target molecule with unknown samples (PE Applied Biosystems, 1997, Relative quantitation of gene expression, User Bulletin # 2. ABI PRISM 7700 Sequence detection system). The amount of HPyV genomic DNA present in the test sample is determined by comparing test sample CT values to those obtained from a known amount of recombinant plasmid molecules containing HPyV DNA used to produce a standard curve. Under the conditions used the assay routinely detects 100 pHPyV genomes.
As a result, no HPyV-specific sequences were detected in any tissue of the SPF hamster of the present invention (see, Table 10).
Cell lines used for the preparation of the biological products may produce

retrovirus with an extended host range. Therefore, it is determined as to whether or not the SPF hamster of the present invention is infected with the endogenous hamster retrovirus (endogenous hamster leukemia virus). If the infection is confirmed for the SPF hamster, it is also determined as to whether or not human cells can be infected with the retro virus present in the SPF hamster. The following detector cell lines can be used to determine whether retrovirus capable of infecting human or primate cells is present in the test article cell line; human diploid cell line MRC-5, Burkitt's lymphoma cell line Raji, African green monkey kidney cell line Vero, baby hamster kidney cell line BHK, etc. MRC-5 and Raji cells are used to determine whether retrovirus capable of infecting human cells is present. C-type retrovirus replicates in MRC-5 cells while Raji cells are also permissive for D-type retrovirus (including Squirrel monkey retrovirus). Co-cultivation with Vero cells indicates the presence of retrovirus capable of infecting primates, while BHK cells represent a cell line of hamster cell line. The reason of using such a variety of the detector cells is that the expression opportunity for the unknown viruses that may be latent in the test article cells can be increased by co-cultivating the test article cells with various host cells.
For such a test, the test article cells are co-cultivated with the detector cells and, at passage 1, the test article cells are removed. The detector cells are maintained over at least 5 passages in order to amplify a low-level infectious virus. Post passage 5 of culture (or at a later passage if appropriate) the supernatant is harvested from the cultures and tested for the presence of retrovirus by product enhanced reverse transcriptase (PERT) assay. The PERT assay is an extremely sensitive assay for the detection of reverse transcriptase (RT) activity and has been reported to be up to 106-fold more sensitive than conventional RT assays (Silver J, et al.. Nucleic Acids Research, 21: 3593-3594, 1993; and Pyra H, et al.. PNAS, U.S.A., 91:1544-1548, 1994). Due to the fact that BHK cells have an endogenous retrovirus and, as a result, generate a

positive result by PERT assay, supematants harvested from the BHK culture are tested for the presence of retrovirus by RT assay.
Specifically, in the present invention, the PHK cells isolated from SPF hamster according to the present invention are co-cultivated with MRC-5 and Raji cells, respectively. As a result, reverse transcriptase (RT) activity, which is an indicator for the retrovirus activity, was not found for the human cell lines co-cultivated with the PHK cells (see, Table 11 and Table 12).
As a third test, the SPF hamster of the present invention was examined for the infection with unknown viral contaminants. For this, the detector cells that are co-cultivated with the PHK cells originated from the SPF hamster of the present invention are examined microscopically for evidence of CPE over the culture period. In addition, the detector cells are haemadsorbed using red blood cells (rbcs) originated from various animals, i.e., guinea pig, chicken, human, etc. Specifically, in the present invention, the PHK cells isolated from the SPF hamster according to the present invention are co-cultivated with MRC-5, Raji and Vero cells, respectively. The detector cells are also haemadsorbed with a mixture of guinea pig rbcs, chiken rbcs and human type 'O' rbcs. As a result, no cytophathic effect (CPE) or haemadsorption was observed for said different kinds of the detector cells that were co-cultivated with the PHK cells of the present invention.
As a final test, the SPF hamster produced according to the present invention was examined for the infection with an unknown lymphoma-causing virus, using an immuno-suppressant drug, cyclosporin. The SPF hamster group of the present invention showed no tumor development or other tumor-like symptoms for a period of 100 days after the hamster's immunological function was suppressed.

As it has been described above, the SPF hamster of the present invention and the PHK cells originated therefrom are proved to be free of bacteria, parasites, 10 specified hamster viruses, 16 specified mouse viruses, hamster polyoma virus, endogenous retroviruses (hamster leukemia viruses), unknown hamster lymphoma viruses that may have a potential to induce malignant lymphoma, and other unknown hamsters. Meanwhile, for the VAF series hamsters developed by Charles River Laboratory Inc. or by Harlan Sprague Dawley, Inc., the absence of only a few bacteria, parasites and 4-5 specific hamster viruses were confirmed, and an extensive safety verification as in the present invention has not been carried out (see, Tables 2, 3, and 4). Therefore, the SPF hamster produced according to the present invention is superior in its safety to the existing VAF or other SPF hamsters. As such, it is evident that the primary cells, preferably PHK cells, originated from the SPF hamster according to the present invention can be advantageously used as a cell substrate for the preparation of the biological products.
Said biological products include vaccines against all the viruses that are able to proliferate in the primary cells originated from a SPF hamster as a host cell (cell substrate). Specific examples include the live attenuated vaccine against Japanese encephalitis as prepared in the present invention (Tsai et al., Japanese encephalitis vaccine. 3rd ed. Vaccines, ed. S.A. Plotkin and W. Orenstein., 1999, Philadelphia: WB Saunders, 672-710), inactivated vaccine against Japanese encephalitis (Lu et al., Japanese encephalitis vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 528), Rabies vaccine (Plotkin SA, et al., Rabies vaccine, In Plotkin SA, Orenstein WA, eds. (1999) Vaccines (3rd ed.), Philadelphia, PA: WB Saunders company, 743-766; Lu et al, Rabies vaccine. 1st ed. Medical

Biological Products. 1995, Beijing: Peoples Medical Publishing House, 552), vaccine for Dengue fever, vaccine against hemorrhage fever with renal syndrome (Lu et al., Hemorrhagic fever vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 652), and vaccine against tick-borne encephalitis (Lu et al., Tick-borne encephalitis vaccine. 1st ed. Medical Biological Products. 1995, Beijing: Peoples Medical Publishing House, 540), etc.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates a brief diagram showing the process of producing a SPF hamster of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will hereinafter be described in further detail by examples. It should, however, be borne in mind that the present invention is not limited to or by the examples.
Microbiological Contamination Test 1-1) Examination for parasites
Presence of any exogenous parasites was determined using light microscopic examination with specimen picked up by a tape. Meanwhile, in order to examine presence of any endogenous parasites, test animals were sacrificed and cut open, and then tissue specimens of stomach, small intestine, and large intestine were prepared. Specimens obtained so were dyed with hematoxylin and eosin, and men examined under a light microscope.

1-2) Examination for bacteria
Presence of bacteria was examined based on the following three methods.
a. Culture method - for all of the bacteria except Helicobacter spp..
Mycoplasma pulmonis, and Clostridium piliforme
Using a sterile swab, materials in the trachea, nasal cavity and intestinal tract were collected and spread over the culture plate for bacteriological examination. Consequently, it was treated in accordance with the SOP(Standard Operating Procedure).
b. PCR method - for Heliecobacter spp.
PCR was carried out using the forward primer of-SEQ ID NO. 1 and the reverse primer of SEQ ID NO. 2 (J. Clin. Microbiol., 35(6): 1620-1623, 1997; J. Clin. Microbiol., 39(11): 3920-3926, 2001). The PCR reaction was carried out under the operating condition of denaturation (94 °C, 30 seconds), annealing (55 °C, 30 seconds), and extension (72 "C, 2 minutes), amplified for 30 cycle, and the final step was performed at 72*0 for 5 minutes. The resulting PCR products were identified by an electrophoresis, which is based on 1.5% NuSieve agarose gel (FMC BioProducts, Rockland, Maine).
c. ELISA method - for Mycoplasma pulmonis and Clostridium piliforme
The examination was carried out using Monilisa kit (ICLAS, Main Research Center for Test Animals, Japan) and Murin antigen kit (Intracel, USA) in accordance with the manufacturer's protocols.
1-3) Examination for viruses
Viruses were examined based on ELISA method. The ELISA was carried out

using Monilisa kit (ICLAS, Main Research Center for Test Animals, Japan) and Murin antigen kit (Intracel, USA) in accordance with the manufacturer's protocols. Especially, the examination for the seven hamster viruses listed in the above-described Table 1 was carried out in accordance with a method of Smith (Smith AL. (1986) Serologic tests for detection of antibody to rodent viruses. In, Viral and Mycoplasmal Infections of Laboratory Rodents, pp 731-750. eds. PN Bhatt, RO Jacoby, MC Morse and AE New. Academic Press Inc., Orlando) and a method of Lewis et al. (Lewis AM, Rowe WP, Turner HC and Heubner RJ. (1965) Lymphocytic choriomeningitis virus in hamster rumor: spread to hamsters and humans. Science, 150, 363-364). Examinations for other viruses except the hamster viruses are described in detail in the corresponding examples.
Preparation of a surgical isolator
Inside of a surgical isolator (Daehan Biolink Co. Ltd., Korea) was sterilized with alcohol and Hibiclean solution, and then the positive pressure was maintained by operating airflow. A dipping bath was filled with 0.2% peracetic acid solution. Operational tools and other necessaries were placed inside the isolator for a surgical operation, and a blood agar plate (SIGMA) was also prepared for the examination of microbiological contaminants that can be present in a specimen obtained immediately from the embryo.

Selection of hamsters for the production of the SPF hamsters
1-1) First selection of the hamster group
For the Golden syrian hamsters obtained from Chengdu Institute of Biological

Products, China, the microbiological contamination test of Table 1 was carried out in accordance with the method described in Reference Example 1. As a result, the hamster group with no contaminants was selected first.
1-2) Propagation of the first-selected hamster group and the second selection
The hamsters selected first in the above Example 1 -1) were propagated in the breeding room for laboratory animals more than 3 generations by sister-brother mating. The microbiological contamination test described in the above-described Example 1-1) was carried out again and the animal with no contaminants was secondly selected. Thereafter, the selected animals were allocated into new groups and then propagated.

Production and propagation of the SPF hamster
2-1) Selections of a pregnant mother and a surrogate mother
In order to select a pregnant mother which can provide an embryo via C-section, two female hamsters with experience of at least one previous parturition were selected from the hamster group of the Example 1-2) and then put together in a single cage with a male hamster with mating experience. Next day, the female hamster developing vaginal plug was selected and treated to have the first day of the pregnancy, and kept being fed. In addition, for the VAF Golden Syrian hamsters (Harlan, USA) obtained from Charles River Lab. Inc., the microbiological contamination test described in the above Example 1-1) was carried out, and the hamsters confirmed to be free of contaminants were mated using the same method as above for the pregnant mother. The surrogate mother was therefore obtained. The mating for the surrogate mother was carried out one day ahead of the pregnant mother. The animals, which gave birth

one day before the expected birth date of the pregnant mother, were selected and used as a surrogate mother for an embryo of the pregnant mother.
2-2) Production of the embryo by C-section
Suitable time for carrying out C-section was determined based on the abdominal distension and congestion- and relaxation degree of vaginal orfice of the pregnant mother. On the 13.5* day after the pregnancy, C-section was carried out. First, the pregnant mother was sacrificed with CO2 gas injection, and the outside of the dead body was cleaned with a disinfection soap (Iodex Hand Soap, QUIP LABORATORIES INC., USA) and disinfected with alcoholic gauze. Iodine solution was also used for further disinfection. For the disinfection, the vaginal opening area and the genital area of the pregnant mother were thoroughly cleaned with extra caution. The abdomen of the dead animal was cut open and its uterus was taken out. Regions flanking each ovary were ligated with a forcep and cut out with a surgical scissors. The cervical region of the uterus was ligated again with the forcep and cut with the scissors. The incised area was disinfected with the iodine solution and, with the uterine cornu headed downward, the uterus was passed through the dipping bath of the isolator prepared in the above Reference Example 2 and introduced into the inside of the isolator (see, Figure 1). Thereafter, the disinfection solution on the surface of the uterus was removed as fast as possible using disinfected gauze and cotton balls, and then the uterus was cut open to obtain the embryo. The embryos obtained therefrom were then transferred to an operating table that was previously prepared and warmed. Caution has to be taken not to have the embryo in a contact with the chemical solution such as the disinfection solution, etc. About half an hour iater, the condition of the embryos was checked out and the embryos capable of managing self-breathing were selected. Then, the surrogate mother's excreta were applied to the embryos and eight

embryos were assigned to each of the surrogate mothers. Using the placenta, etc., which was isolated during the operation, the microbiological contamination test for the embryos was carried out.

Breeding and propagation of the embryo in a sterile environment
The embryos obtained from the above Example 2 were bred in the SPF barrier area provided by Department of Laboratory Animal Medicine, Medical Research Center, Yonsei University College of Medicine, Korea. The condition for said barrier region is adjusted as follows; temperature of 22-26'C, relative humidity of 45-55%, ventilation frequency of 8-12 times per hour, light intensity of more than 25 lux, and class less than 10,000. For drinking water, ionized drinking water that is supplemented with chloride of below 2% concentration was provided. For feeding stock, rodent general diet (Lab Diet Co., USA), which is sterilized by irradiation, was provided. For organization of hamster generation, the bred hamsters were grouped so that more than 8 propagating groups are present in each of the generations. In order to achieve the propagation via inbreeding, the sister-brother mating method was adopted, in which the mating is carried out within the same litter.

Selection of the SPF hamsters
4-1) Bacterial and parasitic contamination test
For each of the hamsters selected from the propagated group of Example 3, the microbiological contamination test was carried out for the bacteria and parasites listed in Table 2 and Table 3. The test was carried out according to the method described in the above Reference Example 1. As described in Table 5 below, it was confirmed that

the parasites and bacteria were not detected in the selected hamster groups.
Table 5
Bacterial- and parasitic contamination test result
(Table Removed)

-: Not detected
4-2) Viral contamination test
For the hamsters selected in accordance with Example 4-1), microbiological contamination test was carried out for various kinds of viruses. All viral contamination tests were requested to Q-One Biotech Ltd., Glasgow, United Kingdom.
4-2-1) Test for 10 specified hamster viruses
a. Serological test
ELISA analysis was carried out for the serum obtained from the 5 animals of each test group which has been selected in Example 4-1) (Smith AL., Viral and Mycoplasmal Infections of Laboratory Rodents. 731-750, 1986; Lewis AM et ai. Science, 150: 363-364, 1965; Baum SG et ai, N. Eng. Med, 274: 934-936, 1966). First, the microtiter plates were pre-coated with antibody against the 10 specified hamster viruses of Table 4. The prepared serum samples were added to the each well and the plates were incubated at room temperature for 1 hour. The serum of VAF LVG Syrian hamsters, 3-4 weeks old (female), bread in barrier-maintained colonies, was used as a negative control. The serum of the hamsters previously exposed to the antigen of each virus was used as a positive control. The plates were then washed 3 times with PBS/0.05% Tween 20 and peroxidase-conjugated anti-species IgG was added to the each well of the plates. The plates were again incubated at room temperature for 1 hour, and then they were washed 3 times with PBS/0.05% Tween 20. Subsequently, o-Phenylenediamine and urea/F^O? substrate were added into each well of the plates. The plates were then incubated at the room temperature in the dark for 20 minutes. After the incubation, the absorbance was read at 490nm to detect the

presence of the specified hamster viruses. As a result, the hamster group, which is completely free of any of the hamster viruses, was selected. The test results for the selected hamsters are summarized in Table 6 described below.
Table 6
Serological test results for the hamster viruses
(Table Removed)

*NC: Negative control
PC: Positive control -: Not detected "+: Detected
b. Hamster antibody production test (HAP test)
In order to examine more precisely as to whether the above-described 10 specified viruses, known to infect hamster tissues, have been present in the hamster group selected in the above Step a., HAP test was carried out. The HAP test employed in the present invention is a slight modification of the MAP test, first developed by Rowe, et al. (Rowe WP et ai, J. Exp. Med., 109:379-391, 1959; and Rowe WP et ai. Virology 11:645-649, 1960). The PHK cells isolated from the hamster selected in the

above Step a. were inoculated into the female VAF LVG Syrian hamster, 3-4 weeks old (female). During the test period, the inoculated hamsters were maintained in autoclaved microisolation units containing bedding, water and feed, to preclude infection with viruses other than those contaminating the PHK cells. On the 28th day after the inoculation, serum samples were collected from all animals. All serum samples were assayed for 10 different viral antibodies using serological assays. The antibody for HANT was determined by carrying out IFA (indirect immunofluorescence assay) in accordance with the method of Hartley et al. (Hartley JW et al, Virology, 11:645-649, 1960). The antibodies for the rest of other 9 viruses were determined by EL1SA assay. As shown in Table 7 below, it was confirmed that no antibodies were produced against any of the tested hamster viruses. These results were consistent with those of the above step a.
Table 7
HAP test results
(Table Removed)

-: Not detected
4-2-2) Test for 16 specified mouse viruses
In order to confirm as to whether the hamster group selected in the above Example 4-2-1) has been infected with the mouse viruses or not, MAP test was carried out for the PHK cells isolated from said hamsters (Rowe WP., el al, J. Exp. Med., 109:379-391, 1959; Rowe WP., et al., In, The Problems of Laboratory Animal Disease. pp 132-141. ed. RC Harris. Academic Press Inc., New York, 1962; Smith AL., In, Viral and Mycoplasmal Infections of Laboratory Rodents, pp 731-750 eds PN Bhan, RO Jacoby, MC Morse and AE New. Academic Press Inc., New York, 1986).
First of all, 20 VAF mice (strain CD 1, obtained from Harlan UK Ltd.) were inoculated with the PHK cells obtained from the hamsters of the above Step a. On the 4th day after the inoculation, 4 mice were sacrificed and their plasmas were isolated. Using the spectrophotometric assay, the level of LDH (lactate dehydrogenase) activity was measured to examine the presence of LDV (Lactate dehydrogenase-elevating virus). As a result, it was confirmed that the LDH activity of the mouse inoculated with the PHK cells of the present invention was the same as that of the negative control (see, the following Table 8). Such results suggest that the hamsters selected in the above 4-2-1) are free of LDV.
Table 8
LDV infection test results
(Table Removed)

On the 23rd day after the inoculation, 4 mice were challenged to a known lethal strain of LCMV (Lymphocytic choriomeningitis virus, Armstrong stains) and observed each working day for up to 12 days for morbidity and mortality. If the above-described PHK cells are not infected with LCMV, the animals will die within 4 to 12 days. The 4 mice inoculated with the hamster PHK cells of the present invention died within 12th day after the LCMV inoculation. This result suggests that the hamsters produced according to the present invention are free of LCMV.
On the 31s' day after the inoculation, serum samples were isolated from the remaining mice and assayed for the presence of antibody against the mouse viruses by the serological test. As described in Table 9 below, the mouse viruses of 15 different kinds were not detected in the serum of the mouse inoculated with the PHK cells of the present invention.
Table 9
MAP test results
(Table Removed)

-: Not detected
With the tests as described in the above, the present inventors established the SPF hamster group which are confirmed to be free of any contamination with 19 kinds of bacteria, 6 kinds of parasites as well as 10 kinds of the hamster viruses, and 16 kinds of the mouse viruses.

Additional test for the infection with various kinds of viruses
The present inventors carried out further experiments for the SPF hamster group selected in Example 4 to determine the endogenous or exogenous viral infection.
5-1) Test for hamster polyoma virus (HPyV) infection
From one test animal obtained from the selected SPF hamster group of Example 4, liver-, spleen-, lymph node-, lung- and kidney tissues were isolated according to the known method. Then, using the ABI 7700 sequence detection system (PE Applied Biosystems, 1997, Relative quantitation of gene expression, User Bulletin #2), the presence of HPyV-specific sequences was determined for the tissues obtained. PCR reactions were carried out in single well of 96 well reaction plates. The DNA isolated from said tissues was used as a template. The TaqMan PCR reagent mix (containing TagMan buffer A, Mg'T, dNTPs, AmpErase UNG, AmpliTaq Gold DNA polymerase, TaqMan HPyV-specific primers and fluorescent probe) was placed into the reaction. The reaction plate was placed into the ABI 7700 instrument where AmpErase, and AmpliTaq activation and amplification reactions were carried out. Said AmpErase reaction was carried out at 50C for 2 minutes, and subsequently, AmpliTaq Gold activation reaction was carried out at 95C0 for 10 min. In addition, the PCR reaction conditions were as follows: 40 cycles consisting of denaturation at 95C for 15 seconds and annealing/extension at 60C for 1 minute. For the control, the negative control and the positive control were prepared in which PCR was carried out without a template and the recombinant pHaPV containing HPyV target gene was used as a template, respectively. The results are shown in Table 10 below. Accordingly, it is confirmed that no HpyV-specific sequences were detected in all tissues of the SPF hamster according to the present invention.
Table 10
Test results for the hamster polyoma virus
(Table Removed)

-: Not detected
+: Detected
5-2) Test for the retrovirus infection
The PHK cells isolated from the SPF hamster of Example 4 were co-cultivated with human diploid cell line MRC-5 and human Burkitts lymphoma cell line Raji, respectively, and then the production of the retrovirus was examined. First, the PHK cells isolated from the SPF hamster of the present invention were co-cultivated with the detector cells, MRC-5 or Raji cells, for 4-5 days. The detector cell lines were obtained from the American Type Culture Collection (ATCC). At passage 1, the PHK cells were removed and the detector cells cultured over 5 passages. In order to minimize false positive signals from reverse transcriptase (RT) -like activity of DNA polymerase, CT NEAT (activated calf-thymus DNA) that interferes with RT-like activity of DNA polymerase was added. For positive control, virus like particles (VLPs) were treated in. Consequently, supernatant was harvested from the detector cells post passage 5 of culture. These were tested for the presence of retrovirus by PERT assay (product

enhanced reverse transcriptase assay), in accordance with the publicly known method (Lugert R, et al, Biotechniques, 20(2):210-217, 1996; Pyra H, et al, PNAS. U.S.A., 91:1544-1548, 1994). The detector cells inoculated onto the base of duplicate transwell plates. As a result, no RT activity was detected in the PHK cells inoculated cultures (see, Table 11 and Table 12 in this regard). Such results indicate that the PHK cells of the SPF hamster of the present invention are not contaminated with the retrovirus that can infect a human.
Table 11
Test results tor the retroviruses: MRC-5 cell line
(Table Removed)

d: threshold cycle
+ : positive -: negative
Table 12

Test results for the retroviruses: Raji cell line
(Table Removed)

Cj: threshold cycle
+ : positive -: negative
5-3) Test for the unknown hamster viral infection
The presence of possible unknown hamster viral contamination that can induce the opportunistic infection of various detector cells in the SPF hamster of the present invention was also examined. For the detector cells, the human diploid cell line MRC-5, the human Burkitt's lymphoma cell line Raji, and the African green monkey kidney cell line Vero were used and the detector cells were obtained form the ATCC. The detector cells, MRC-5, Raji or Vero cells, were co-cultivated with the PHK cells isolated from the SPF hamster of the present invention for 4-5 days. At passage 1, the PHK cells were removed and the detector cells cultured over 5 passages. Then, the detector cells were examined microscopically for evidence of CPE over the culture period. As a result, no CPE was observed in the inoculated cultures throughout the culture period.
In addition, the detector cells were tested for the ability to haemadsorb the mixture of guinea pig rbcs. chicken rbcs and human type 'O' rbcs. The PHK cells of

the SPF hamster of the present invention were subjected to hameadsorption with the mixture of guinea pig rbcs, chicken rbcs and human type 'O' rbcs at 4C for at least 30 minutes. The negative controls were detector cells inoculated with culture medium and the postivie controls were MRC-5 cells inoculated with Influenza A virus. As a result, hameadsorption with human type 'O', chiken and guinea pig rbcs was not observed in the negative control and the PHK cells inoculated cultures at post passage 5. On the other hand, the haemadsorption was observed in the positive control.
Considering that CPE and hameadsorption were not observed for the PHK cells which have been the co-cultured with various kinds of detector cells for a long period of time, it can be said mat unknown viral contaminants with the hamster origin are noi present in the PHK cells of the SPF hamster of the present invention.
5-4) Test for the unknown hamster lymphoma virus infection
To the 20 newborn SPF hamster babies, an immunosuppressant drug, cyclosporin was administered in order to suppress their immunoactivity. After having confirmed the decreased immunoreactivity, the animals were used as the test group. The hamsters of the test group were bred for more than 100 days and the development of malignant lymphoma or other tumor was monitored every week. For the positive control, 20 hamsters inoculated with HeLa tumor cells (ATCC) were prepared. For the negative control, 10 healthy hamsters not administered with said immunosuppressant drug were prepared. After 100 days, the test animals which have been determined to be free of malignant lymphoma or other tumor were sacrificed and subjected to an autopsy. For each of the sacrificed animals, traces of tumors in lymph node, spleen, pancreas, kidney, lung and liver, etc. were exmained. Other abnormality was also examined. The result shows that tumor or other tumor-like lesion was not found for the SPF hamster of the present invention for 100 days after the immunosuppression.

BP), for approximately 1 hour. The cells were incubated for an additional 3-4 days to propagate the virus after replacing the medium containing the virus. After having observed the CPE of 75% or more, the virus containing suspension was harvested, clarified & sterile filtered and stored at 2-81 for QC testing. Then, final formulation (adding stabilizer), filling and lyophilization was performed.
Experimental example 1>
Safety test for the live attenuated JE vaccine of the present invention
In order to confirm the human safety of the live attenuated JE vaccine, which has been prepared using the PHK cells of the SPF hamster according to the present invention (Example 5), the safety test was carried out.
1-1) Examination for HPyV
In order to determine as to whether or not HpyV is present in the live attenuated JE vaccine of the present invention, the presence of HpyV specific sequences was determined using ABI 7700 sequence probe system and the method as described in Example 5-1). The results are summarized in the following Table 13.
Table 13
Test results for the hamster polyoma viruses
(Table Removed)

-: Not detected

*+: Detected
1-2) HAP test
In order to determine as to whether or not the hamster viruses are present in the live attenuated JE vaccine of the present invention, HAP test was carried out using the method as described in Step b. of Example 4-2-1). The results are summarized in the following Table 14, and as obvious as it is, none of the hamster viruses were detected in the live attenuated JE vaccine of the present invention.
Table 14
HAP test results
(Table Removed)

*-: Not detected
1-3) MAP test with LCM challenge
In order to examine as to whether or not the mouse viruses are present in the live attenuated JE vaccine of the present invention. MAP test was carried out using the method as described in Example 4-2-2). The live attenuated JE vaccine of the Example 6 was resuspended in 1.5 mℓ DMEM medium per vial. The neutralizing

antiserum was diluted 1 in 10 using DMEM medium. Then, said vaccine and the diluted neutralizing antiserum were mixed in the ratio of 1:1 and incubated at 37C for 1 hour to produce the test samples. 20 SPF mice (strain CD1, Harlan UK Ltd.) were inoculated with the samples. On the 13th day after the inoculation, 4 mice were sacrificed and their plasma were assayed for the level of LDH activity using a spectrophotometric assay. As described in Table 15 below, LDH activity for the mouse inoculated with the PHK cells of the present invention is slightly lower than that of the negative control.
Table 15
LDV infection test results
(Table Removed)

On the 14th day after the inoculation, 4 mice were challenged with LCM virus (Amstrong strain) and observed each working day for up to 12 days for morbidity and mortality. 7 days later, all of the mice were dead. From this result, it is confirmed that the live attenuated JE vaccine, which has been prepared using the PHK cells of the present invention, carries no LCM virus.
In addition, on the 34th day after the inoculation, the remaining mice were bled and their sera were subjected to the serological test. As indicated in the following Table 16, none of the 1 5 kinds of the mouse viruses were detected.

Table 16
MAP test results
(Table Removed)

'-: Not detected
1-4) PERT assay
For the live attenuated JE vaccine of the present invention, the presence of retrovirus was determined. The present inventors performed the PERT assay that is useful to detect particles of reverse transcriptase with enzymatic activity, in very high sensitivitN. First. 3 ml of the live vaccine as prepared in Example 6 were clarified by
centrifugation at approximately ll,000g for 10 minutes, and passed through 0.45 µm sterile filter to remove remaining debris. Then, the resulting vaccine was pelleted by ultracentrifugation at l00.000g for 60 minutes. Each pellet was resuspended in 100 µℓ of disruption buffer solution to release RT activity. The PERT assay was then carried out using the method disclosed by Pyra, et al. (Pyra H, et ai, Proc. Nat. Acad. Sci., 91:1544-1548, 1994). As a result, the live attenuated JE vaccine of the present invention was confirmed to be negative for RT activity. Such result suggests that no retrovirus is present in the live attenuated JE vaccine of the present invention.
1-5) In vitro assay for unknown viral contaminants
The present inventors identified the presence of viral contaminations in the live attenuated JE vaccine of the present invention by co-cultivating it with a detector cell line. The human near-triploid cell line H9 (ATCC) was used as a detector cell. First, seed stock of the live attenuated JE vaccine of the present invention was cultivated with H9 cell line. At passage 1, the seed stock was removed. The detector cells were maintained over at least 5 passages. The detector cells were examined microscopically for evidence of CPE over the culture period. No CPE was observed in the H9 cultures.
Post passage 5 of culture, the supernatant was harvested from H9 cultures and tested for the presence of retrovirus by PERT assay (Pyra H. et ai, Proc. Natl. Acad. Sci. USA, 9:1544-1548, 1994). RT activity was not detected in seed stock inoculated H9 cultures.
In addition, the H9 cells inoculated with the live attenuated JE vaccine of the present invention were haemadsorbed using the mixture of guinea pig rbcs, chicken rbcs and human type 'O' rbcs at 4°C for at least 30 min. As a result, no haemadsorption
was observed in the H9 cells. Because CPE, RT activity and haemadsorption were not detected in the H9 cells inoculated with the live attenuated JE vaccine of the present invention, it can be said that the live attenuated JE vaccine of the present invention carries no viral contaminants.
1-6) In vivo assay for unknown viral contaminants
To detect the adventitious viral agents in the live attenuated JE vaccine of the present invention by inoculation of embryonated eggs, suckling mice, adult mice, and guinea pigs, according to CPMP and FDA requirements (Committee for Proprietary Medicinal Products: Ad Hoc Working Party on Biotechnology/Pharmacy. J. Biol. Stand., 17:213-222, 1989; and Points to consider in characterization of cell lines used to produce biologicals, 1993. Center for Biologies Evaluation and Research. Food and Drug Administration, Gethesda MD 20205, USA), the present invention performed the following in vivo assay.
(1) Sample preparation
The live attenuated JE vaccine of the present invention, which has been prepared in Example 6, was resuspended in 1.5 µℓ DMEM medium per vial. The neutralizing antiserum was diluted 1 in 10 using DMEM medium. Said vaccine was mixed with the diluted antiserum in the ratio of 1:1 and incubated at 3712 for 1 hour.
(2) Animal test
a. Test with suckling mice
First of all, safety of the vaccine prepared according to the present invention was determined for the suckling mice. Minimum of 20 suckling mice (SPF. strain CD 1), from 2 or more litters were inoculated with the sample prepared in the above step (1)

by the intramuscular (0.01 mℓ), intraperitoneal (0.1 mℓ) and intracerebral (0.01 mℓ) routes (1st inoculation). Another set of the suckling mice was inoculated similarly with DMEM medium and served as the negative controls. The mice were observed for a period of 14 days for any ill effects such as weakness, tremors, paralysis or death. 14 days later, the mice were sacrificed. The organs of the mice were isolated, dissolved, and homogenized. The organ suspension was administered to a new set of suckling mice by the same method as in the First Inoculation (2nd inoculation). The mice were also observed for 14 days. For the lst inoculation, 19 out of 20 mice survived 24 hours after the inoculation (95% survival). No evidence of viral infection was observed following post mortem examination in the suckling dead mouse. For the 2"" inoculation, all of the mice survived 24 hours after the inoculation (100% survival).
b. Test with adult mice
10 adult mice (SPF, strain CD 1) were inoculated with the sample by the intramuscular (0.1 mℓ), intraperitoneal (0.5 mℓ) and intracerebral (0.03 mℓ) routes. The negative control mice were inoculated similarly with DMEM medium. Then, the mice were observed for 28 days for any ill effects. As a result, all of the mice survived 24 hours after the inoculation (100% survival).
c. Test with a guinea pig
As a final test, 5 adult guinea pigs (SPF. strain Duncan Hartley) were inoculated with the sample by intramuscular injection (0.5 ml). For the negative control. 5 guinea pigs were inoculated similarly with DMEM medium. The guinea pigs were observed for a period of 28 days for any ill effects. As a result, it was found that all of the guinea pigs survived 24 hours after the inoculation (100% survival).

(3) Test with embryonated eggs
a. Amniotic inoculation
For amniotic inoculation, 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the amniotic cavity. Another 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of DMEM medium into the amniotic cavity and served as the negative controls. A third set of 10, ten to eleven-day old embryonated hens' eggs were inoculated with 0.1 ml of Influenza-A virus into the amniotic cavity and served as the positive controls. After the inoculation, the eggs were incubated at 35-36 X: for 5 days. The amniotic fluids were harvested and pooled. The pooled amniotic fluids were assayed for haemagglutination (HA) activity. The HA assay was performed in microtiter plates by making serial 2-fold dilutions of the amniotic fluids. The erythrocytes obtained from washed chicken and guinea pig were added separately as 0.5% suspensions and replicate plates were observed for HA activity after incubation for 1-2 hours at 2-8°C and after 1-2 hours at 17-20°C. The result shows that, the levels of HA activity in the amniotic fluid of the test eggs are similar to those of the negative control. In addition, according to the viability test 24 hours after the inoculation, 8 out of the 9 test eggs remained viable (89% viability).
b. Allantoic inoculations
For allantoic inoculations, 10, ten to eleven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the allantoic cavity (1st passage). Another 10, ten to eleven-day old SPF embryonated hens" eggs were inoculated with 0.1 ml of DMEM medium into the allantoic cavity and served as the negative controls. A third set of 10, ten to eleven-day old embryonated hens' eggs were inoculated with 0.1 ml of Influenza-A virus (ATCC VR-547) into the allantoic cavity and served as the

positive controls. After the inoculation, the eggs were incubated at 35-36C for 3 days. The allantoic fluids were harvested and pooled. A portion of the pooled fluids was frozen and stored at or below -70C until either assayed for HA activity or subpassaged into a new set of embryonated eggs.
The pooled allantoic fluids, derived from embryonated eggs initially inoculated with the sample via the allantoic route, were passaged by inoculation of 0.2 ml into each of 7, ten to eleven-day old eggs (2nd passage). The allantoic fluids derived from eggs initially inoculated with DMEM medium were similarly passaged into a new wet of 7, ten to eleven-day old eggs. The allantoic fluids derived from eggs initially inoculated with Influenza-A were similarly passaged into a new set of 7, ten to eleven-day old eggs. 3 days later, the allantoic fluids were harversted, pooled and assayed for HA activity. The HA assays were performed according to the same method as described in the amniotic test.
The assay result shows that, the levels of HA in the allantoic fluid of the test eggs are similar to those of the negative control. In addition, according to the viability test 24 hours after the inoculation, all of the embryonated hen's eggs remained viable for the Is' passage (100% viability), and 5 out of the 7 embryonated hen's eggs remained viable for the 2nd passage (71% viability).
c. Yolk sac inoculations
For yolk sac inoculations, 10, six to seven-day old SPF embryonated hens' eggs were inoculated with 0.1 ml of the sample into the yolk sac (1st passage). Another 10, six to seven-day old SPF embryonated hen's eggs were inoculated with 0.1 ml of DMEM medium and served as the negative controls. The eggs were incubated at 35-36°C for 9 days. Later, the embryos were then examined for viability. The yolk sacs were harvested, washed and pooled. A 10% suspension was prepared and subpassaged

into a new set of 7, six to seven-day old SPF embryonated eggs (2nd passage). A 10% yolk sac suspension was also prepared from the DMEM injected eggs, subpassaged into a new set of 7, six to seven-day eggs and served as the negative controls. All embryos were examined 9 days later for viability.
The result shows that, all of the 10 test eggs remained viable 24 hours after the inoculation for the 1st passage (100% viability), and all out of 7 test eggs remained viable for the 2nd passage (100% viability).
With the above experimental results taken together, it is confirmed that the live attenuated JE vaccine, which is prepared by using the PHK cells originated from the SPF hamster of the present invention is free of any viral contaminants.
INDUSTRIAL APPLICABILITY
As described in the above, the SPF hamster produced according to the method of the present invention does not carry any parasites, bacteria, or other various endogenous or exogenous viral contaminants. Therefore, the primary cells originated form the SPF hamster and the biological products prepared using the same will not cause the opportunistic infection by microbial contaminants that can be present in the animal cells used for the preparation of the existing biological products such as vaccine, etc. Accordingly, the SPF hamster of the present invention, hamster tissues originated therefrom and their culture supematants can be safely used for the preparation of diverse biological products intended for human use.

WHAT IS CLAIMED IS:
1. A method of producing a SPF (specific pathogen free) hamster for the preparation of
biological products, comprising the steps of:
(a) firstly, selecting the hamsters which are free of infection by carrying out
contamination test for parasites, bacteria and hamster viruses, propagating
the selected hamsters by sister-brother mating, and then secondly, selecting
the hamsters not infected with said microorganisms from the propagated
hamsters;
(b) mating the selected hamsters, obtaining uterus from the female hamster on the
12th to 14th day after pregnancy, introducing the resulting uterus into an isolator, obtaining embryos by C-section, and then breeding the embryos with a surrogate mother inside the barrier area with class of less than 10,000; and
(c) propagating the hamsters bred in the above step (b) by sister-brother mating,
carrying out the microbiological contamination test for parasites, bacteria, hamster viruses, mouse liruses, endogenous hamster retroviruses, hamster polyoma virus (HPyV), hamster lymphoma virus and unknown hamster viruses, and then selecting the hamsters not infected with said microorganisms from the above-propagated hamsters.
2. The method according to claim 1, wherein said SPF hamster for the preparation of biological products is used for preparing primary hamster kidney cell (PHK cell).
3. The method according to claim 1, wherein said hamster of the step (a) is golden Syrian hamster.

4. The method according to claim 1, wherein said parasites of the steps (a) or (c) consist of endoparasites and ectoparasites.
5. The method according to claim 4, wherein said endoparasites consist of Capillaria hepatica, Hymenolepsis spp., Encephalitozoon cuniculi, Girdia muris, Spironucleus muris and Syphacia spp.
6. The method according to claim 1, wherein said bacteria of the step (a) consist of Bordetella bronchiseptica, Corynebactehum kutscheri, Helicobacter spp., Mycoplasma pulmonis, Salmonella spp., Salmonella typhimurium, Streptococcus pneumoniae, Pseudomonas aeruginosa, Pasteurella pneumotropica, Staphylococcus aureus and Clostridium piliforme.
7. The method according to claim 1, wherein said hamster viruses of the step (a) consist of Sendai (SEND), Pneumoina virus of mice (PVM). Minute virus of mice (MVM), Kilham rat virus (KRV), Reovirus type 3 (Reo-3), Lymphocytic choriomeningitis virus (LCMV) and Toolans H-l virus (H-l).
8. The method according to claim 1, wherein said surrogate mother of the step (b) is a viral antigen free (VAF) hamster.
9. The method according to claim 1, wherein said bacteria of the step (c) further comprise Pseudomonas spp., Pasteurella spp.. Klebsiella oxytoca, Pasteurella multocida, Klebsiella pneumoniae, Beta Streptococcus group B, Beta Streptococcus group G, and Beta Streptococcus spp.. in addition to the bacteria of

the step (a).
10. The method according to claim 1, wherein the hamster viruses of the step (c) further comprise Theilers mouse encephalomyelitis virus (GD-7), Simian virus 5 (SV5), and Hantaan virus (HANT), in addition to the hamster viruses of the step (a).
11. The method according to claim 1, wherein said mouse viruses of the step (c) consist of Lymphocytic choriomeningitis virus (LCMV), Mouse hepatitis virus (MHV), Pneumoina virus of mice (PVM), Minute virus of mice (MVM), Sendai (SEND), Ectromelia (ECTRO), Epizootic diarrhea of infant mice (EDIM), Reovirus type 3 (Reo-3), Mouse encephalomyelitis (GDVII), Mouse adenovirus (MAD), Polyoma viurs (POLY), Hantaan virus (HANT), Mouse thymic virus (MTV), Mouse cytomegalovirus (MCMV), Mouse, pneumonitis virus (K) and Lactate dehydrogenase-elevating virus (LDV).
12. The method according to claim 1, wherein said biological products are selected from a group consisting of the live attenuated vaccine against Japanese encephalitis, inactivated vaccine against Japanese encephalitis, Rabies vaccine, vaccine against Dengue fever, vaccine against hemorrhage fever with renal syndrome, and vaccine against tick-borne encephalitis.

13. A method of producing a SPF (Specific Pathogen Free) hamster substantially as herein described with reference to the foregoing description and the accompanying drawings.

Documents:

1227-del-2003-abstract.pdf

1227-del-2003-assignment.pdf

1227-del-2003-claims.pdf

1227-del-2003-correspondence-others.pdf

1227-del-2003-correspondence-po.pdf

1227-del-2003-description (complete).pdf

1227-del-2003-drawings.pdf

1227-del-2003-form-1.pdf

1227-del-2003-form-19.pdf

1227-del-2003-form-2.pdf

1227-del-2003-form-3.pdf

1227-del-2003-form-5.pdf

1227-del-2003-gpa.pdf

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Patent Number

226936

Indian Patent Application Number

1227/DEL/2003

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

30-Dec-2008

Date of Filing

01-Oct-2003

Name of Patentee

GLOVAX COMPANY LIMITED

Applicant Address

3F KORYO ACADEMYTEL, 437-3 AHYUN-DONG, MAPO-GU, SEOUL 121-010, REPUBLIC OF KOREA

Inventors:

#	Inventor's Name	Inventor's Address
1	SEONG, JE KYUNG	GYOSU APT NA-205, #244, BONGEHON-7-DONG, GWANAK-GU, SEOUL 151-818, REPUBLIC OF KOREA
2	OH, SEUNG HYUN	BLDG.NO.85, RM NO.612, SAN 56-1, SHILLIM-9-DONG, GWANAK-GU, SEOUL, 150-742, REPUBLIC OF KOREA
3	SHIN, SUN HEANG	38 SIDNEY STREET, CAMBRIDGE, MA 02139, U.S.A

PCT International Classification Number

A01K 67/027

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	KR 10-2003-1698	2003-01-10	Republic of Korea