Immunological characterization of two hepatitis B core antigen variants and their immunoenhancing effect on co-delivered hepatitis B surface antigen.

The hepatitis B virus (HBV) core and surface antigens are potent immunogens in animal models and humans. They have been used in vaccine studies for prevention or therapy of HBV diseases and also as carrier molecules in new developments. In this study we explored the nasal immunogenicity of two different variants of the recombinant complete nucleocapsid (HBcAg) as well as their adjuvant effect on hepatitis B surface antigen (HBsAg). To characterize the immune response, the serum IgG antibody response was tested during one year against both antigens, and the serum and vaginal secretions were tested for recognition of linear epitopes of HBcAg for both HBcAg variants. The results obtained evidenced that the intranasal immunogenicity of both HBcAg variants was similar and high, developing early and long lasting IgG responses. A similar recognition pattern to all sera and vaginal washes samples was generated by the two variants of HBcAg, also similar to a pool of human anti-HBcAg positive sera. A synergistic effect in the enhancement of the immunogenicity for both antigens was evidenced in the combined formulation after nasal administration. Taken together, these results would be of interest in the design of more potent therapeutic and preventive vaccines complementing systemic and mucosal responses.