The Biological Characteristics Of Different Strains Of Rabies Virus And The Animal Model Of Rabies Exposure After Exposure

Rabies is a kind of zoonosis which is caused by rabies virus. Human who gotinfected by RV were usually caused by bites or scratches of domestic animals orwildlife which was infected by RV. Until now there is no therapeutic method on rabies,and the mortality is nearly100%.Vaccination is the most effective means to prevent human and animals fromrabies. Rabies virus strains used for producing human and veterinary vaccines arevarious. In this part of study we choose6rabies fixed virus strains:2strains ofchallenge virus standard（CVS、CVS-11）and4strains for production of human rabiesvaccine （PV、4aG、Flury-LEP、CTN-1）. We studied the pathogenicity to laboratoryanimals and the infectivity by different methods with6rabies fixed virus strains.Mice (10-12g) were inoculated intracerebrally (i.c.) or intramuscularly (i.m.)with six fixed virus strains, and observed their mortality for14days. Studied andestablished HEPES enhancing plaque assay for measuring virus plaque forming unit(PFU), and the CPE stained assay for measuring CCID50made in BHK-21and Verocells. The two new methods were used for comparison of virus infectivity with routinedFA assay.The result showed that the6strains were highly pathogenic to the mice by i.c.inoculation but lower pathogenic by i.m. inoculation. The pathogenic of i.c.inoculation was3.0-5.0lgLD50higher than i.m. inoculation.The result of dFA assaywas comparable to that of the mouse inoculation method routine used for titration ofvirus content in the vaccine production. The infectivity tested with the both newmethods, PFU and CPE, were comparable to the routine dFA method. For example,titers of CVS-11、4aG、PV tested by different methods ranged from7.1to7.9lg.The conclusion is that the dFA method can be used for titration of virus contentinstead of the i.c. mouse inoculation in the vaccine quality control. As the two newmethods were technically simplicity, no need of expensive instruments and reagents,they can be used more popularly for the investigation (virus titers) of rabies virus and rabies virus vaccine development. This study also lay the foundation for the researchof RV pathogenic and RV vaccine quality control. To understand the possibility of Syria Hamster used as an animal model forevalution potency of rabies vaccine in post-exposure prophylasis (PEP).Syria Hamsters infected by intramuscular (i.m.) route with rabes virus (CVS andCTN-1strains) developed rabies symptoms after7days of inoculation. The infectivity(LD50) in infected hamsters was higher (6.4-8.0lgLD50/ml) than that of mice (3.4-6.5lgLD50/ml), no difference between the3-week old and8-week old hamsters. Rabiesvirus was found in the brains of infected hamsters after5-6days of inoculation andneutralizing antibodies were detected beginning at day6after inoculation.The Syria Hamster was used as an animal modle for evaluation of the protectiveeffects in rabies PEP with inactivated rabies vaccine, adjuvant rabies vaccine and liveattenuated rabies vaccine. Hamster was i.m. infected with CVS strain virus(approximately3.7-4.2lg MICLD50), vaccine was administered6hours lateraccording to the WHO regime (0、3、7、14).The results demonstrated that the undiluted original vaccine with high antigenvalue (≥5.0IU/dose) resulted in higher rate of protection (50%-70%) than that of thevaccine diluted1-4fold (<3.0IU/dose) with PBS (20%-30%). However when thevaccine was same diluted with PIKA adjuvant, the protection increased to60%-80%,and when the vaccine was combined administration with rabies immunoglobulin allthe animals got protection (100%).Interestingly, when the infected hamsters were vaccinated with live attenuatedrabies vaccine, only one dose at the first day (day0),77%animals were protected or2doses at day0and day3, all animals could be protected.This study demonstrated that high antigen value of rabies vaccine is importantfor protection in the PEP vaccine treatment. Combined administration with rabiesHRIG is critical important. PIKA adjuvant has enhancing effect on immunogenicity ofrabies vaccine.However, we found that the antibody levels beginning at4days after vaccination was no correlation with protection effects.