immunogenicity assessment of hepatitis a-vp1 and hepatitis b surface antigen (hbsag) fusion protein: a novel bivalent vaccine candidate

Background and objectives: subunit vaccines have the privilege of utilizing immunogenic parts of the variable viruses. the current preventive vaccines against hepatitis a are based on live-attenuated virus or wild-type growth in cell culture, which is a time-consuming and costly procedure. thus, the investigation of immunogenic hepatitis a virus (hav) regions seems to be a rational priority. we aimed to evaluate a novel chimeric protein composed of truncated hav-vp1 and hepatitis b surface antigen (hbsag) as a bivalent vaccine candidate in balb/c mice.materials and methods: the hav-vp1 (amino acids 99 to 259) and hbsag fusion protein were applied as a bivalent vaccine in combination with adjuvants. the purified protein was administered through different regimens via subcutaneous injection. two weeks following the final immunization, serum samples were gathered to assess the humoral responses. moreover, splenocytes were investigated and assessed for il-5 and ifn-γ secretion.results: the immunized mice with recombinant truncated hav-vp1-aay-hbsag showed a significant immune response, especially in combination with the m720 adjuvant. humoral immune response results indicated th1 switching by igg2a and igg2b dominancy. moreover, ifn-γ secretion reached the highest rate in the truncated hav-vp1-aay-hbsag+m720 recipients (p<0.0001).conclusion: the hav-vp1-aay-hbsag protein subunit vaccine could help the immune system fight hav and hbv by stimulating both the humoral and cellular immune systems. the formula proposed in this study has the potential to produce an endemic vaccine based on the circulating hav viruses in iran.