Comparative study of the immunogenicity and immunoenhancing effects of two hepatitis B core antigen variants in mice by nasal administration.

The hepatitis B virus (HBV) core antigen (HBcAg) is a potent immunogen in animal models and humans and has been used as a carrier for several antigens; however, the mucosal immunogenicity of HBcAg has been poorly studied. In this study, we explored the immunogenicity and the immunoenhancing effect elicited by two different variants of the recombinant complete nucleocapside of HBV in mice by intranasal route. For this purpose, we used as co-administered antigen, the HBV surface protein (HBsAg) and the antibody response in sera was evaluated after each dose. To analyze the specificity of the generated antibody response, the recognition of lineal epitopes was evaluated on a cellulose membrane bearing 12 mer peptides covering the HBcAg sequence. The obtained results evidenced that the intranasal immunogenicity of both variants of HBcAg was similar and high, developing early responses of IgG. The immunoenhancing effect on the HBsAg-specific antibody response was also similar for both variants. The results of the recognition of lineal epitopes study evidenced a similar recognition pattern to all sera and vaginal lavages samples generated by the immunization of mice with the two variants of HBcAg, and also similar to a pool of human anti-HBcAg positive sera samples.