Different contribution of co-stimulatory molecules B7.1 and B7.2 to the immune response to recombinant modified vaccinia virus Ankara vaccine expressing prM/E proteins of Japanese encephalitis virus and two hepatitis B virus vaccines

This study clarifies the role of co-stimulatory molecules B7.1 and B7.2 in the immune response to 3 types of vaccines: a/ recombinant modified Vaccinia virus Ankara (MVA) (vJH9) expressing prM/E proteins of Japanese encephalitis virus (JEV), b/ recombinant yeast-expressed Hepatitis B virus (YHBV), c/ human plasmaderived Hepatitis B virus (PHBV). We constructed plasmids expressing B7.1 and B7.2 molecules and found that the expression level of B7.2 protein in transfected CHO-k1 cells was higher than that of B7.1 protein. Mice were co-injected with vaccines vJH9, YHBV and PHBV and plasmids expressing B7.1 or B7.2, respectively, and specific antibody titers for each vaccine were monitored at days 7, 14 and 28 post injection (p.i.). In mice injected with vJH9 vaccine and both B7 plasmids, plasmid B7.2 induced a higher anti-JEV immune response than plasmid B7.1. This implies that the stimulation of the B7.2 immune pathway may be a feasible method of boosting protective immunity against a recombinant viral vaccine. Both B7 molecules were able to induce a specific anti-HBV immune response using YHBV vaccine. On the other hand, B7 molecules had little effect to the specific antibody induction in PHBV vaccination. These results suggested that the contribution of B7.1 and B7.2 molecules in an immune response depended on the character and status of the presenting antigen.