Screening, Identification And Immunogenicity Of A Novel Rabies Virus Epitope Compound Vaccine

Rabies, caused by rabies virus, is a kind of worldwide severe zoonosis. The infection induced by rabies results in a death toll of55,000in the world every year, and China is among one of the high-prevalence countries. When animals or human beings are infected with rabies virus, the virus will enter the central nervous system and cause neurocyte disorders. If animals or human beings show the symptoms of rabies, there is no method to cure this disease. Up to now, using the rabies vaccine is the only way to prevent this disease.It has been120years since people developed the first rabies vaccine. In China, the current rabies vaccine is developed based on the inactivated strain of rabies virus, and there is no adjuvant in the vaccine from2005.So there are some shortcomings of the current vaccine, such as poor immunogenicity, slow production of antibodies and complicated immune procedures. In some cases of severe exposure, rabies vaccines should be applied with expensive rabies virus-specific immunoglobulin (RIG) to prevent infection. However, the shortest incubation of rabies virus may be less than one week. Therefore, there exists risks that the current rabies vaccine could not elicit strong humoral and cellular immune responses in a short time to clear virus infection, thus causing severe consequences. Hence, developing a new rabies vaccine is an effective way to avoid the defects of the current vaccines. But there are few reports about developing new rabies vaccines and current papers only focus on improving the immune procedures or designing DNA vaccines, not to mention prospective results.In this study, we have successfully developed a kind of new rabies vaccine which combined the technology of vaccine adjuvants and epitope vaccine. We did experiments in vitro and vivo to screen and verify the effects of the new vaccines, and we also studied its mechanisms. The main research findings are as follows:Firstly, we studied the mechanisms of MPLA, which could improve the immune responses. The results showed that MPLA accelerated the antibody production, as well as it could induced the proliferation of mice Tc cells and Th2cellular immune responses, which was marked by producing cytokine IFN-y and IL-4.Secondly, we successfully identified the epitopes of rabies virus. We predicted12cell epitopes from the glycoprotein and nucleoprotein of rabies virus using bioinformatics softwares based on the model of BALB/c mice. Then we screened out4from these epitopes through immunologic techniques, such as ELISPOT and flow cytometry. These cell epitopes were G367-381、G333-341、N92-106and N409-423, and they all could induce the proliferation of lymphocytes and the production of IFN-y and IL-4. Among them, G367-381could be the CTL epitope, and G367-381、N92-106and N409-423could be the Th epitopes.Finally, we synthetized four different polypeptide with palmic acid groups, and added MPLA to develop new lipopeptide vaccines. We did preliminary experiments in the animals through examining some indexes of immune responses, such as the proliferation of lymphocytes and the secretion of cytokines. The results showed that peptide C could prominently enhance the Th1cellular immune responses and peptide B and D could partially enhance the Thl/Th2immune responses.In conclusion, this study proved the fact that the combination of MPLA and lipopeptides could enhance the Thl/Th2cellular immune responses through the technology of vaccine adjuvants and epitope vaccines, which could be significant in clearing the infection of rabies virus. This result was conducive to avoiding the defects of the current rabies vaccines, as well as provided experiment basis and new ideas for further developing new generations of rabies vaccines.