A Preliminary Study On The Induction Of Immune Response In Mice By A Novel Recombinant Baculovirus Vector Vaccine Expressing H5N1 Highly Pathogenic Avian Influenza Hemagglutinin (HA) In Mice

The baculovirus Autographa californica multiple Nucleopolyhedrovirus (AcMNPV) have been traditionally and widely used to overexpress recombinant proteins in insect cells, due to the high levels of expression, proper post-translational modification, and biosafety to human, animal, and plants. Recent studies indicate that recombinant baculovirus can elicit immune responses against target antigen in vivo. There has been an increased interest to develop baculovirus as a novel vector for gene therapy and vaccination.The H5N1avian influenza virus is a highly contagious virus that causes acute respiratory disease with significant morbidity and mortality worldwide each year. These viruses have infected not only avian species but also over440humans, of which262cases proved to be fatal. New prophylactic and therapeutic strategies to combat human infections by H5N1viruses are essential for influenza pandemic preparedness. Hemagglutinin (HA), the principal antigen on the viral surface is responsible for viral binding to host receptors, enabling entry into the host cell through endocytosis and subsequent membrane fusion. It is also the primary target for neutralizing antibodies andIn this study, base on bioinformatics analyse we selected typical HA sequence (A/Vietnam/1203/2004) and synthesize by PCR. We also constructed two pseudtyped baculovirus viruses, vAc-HA and vAc-HA-DUAL carrying HA on their virion envelope. Meanwhile, the vAc-HA-DUAL could express HA gene in mammalian cells (BHK and MDCK) by adding a mammalian compatible CMV promoter. The production and application of baculovirus was not affected by the display of HA protein on the virion envelope. The displayed HA protein showed the hemagglutination activity and increase the infection efficiency of the pseudtyped baculovirus, which indicated that the display of HA protein did not affect the native function of HA. The results also show that both constructs can induce HA-specific humoral and cellular immune responses in subcutaneously and intraperitoneally immunized mice.Interestingly, the level of IFN-y and IL-2secreted by the spleen cells from vAc-HA-DUAL immunized mice upon specific antigen stimulation was significantly higher than that of IL-4and IL-6, suggesting a Th1-dominant immune response.We here demonstrated that pseudotyped baculovirus can mediate efficient expression of avian influenza HA protein in vitro and are able to induce significant humoral and cellular immune responses after vaccination in mice by direct injection. Moreover, our results indicate that different pseudotype baculovirus can induced different immune responses to balance between Th1or Th2dominant immune response in mouse model. This strategy is considered to be safe, since baculoviruses do not replicate in mammalian cells and do not induce a cytopathic effect.These results showed that pseudotyped baculovirus can serve as a potential new vaccine by not only displaying antigens on envelop but also functioning as a DNA vaccine against H5N1highly pathogenic avian influenza viruses infection. Future studies will be done to improve the protective range of this system using appropriate selection of pseudotype baculovirus strains for the composition of the vaccine.