Immune stimulating activity of two new chitosan containing adjuvant formulations

Recombinant proteins have potential as both human and veterinary vaccine antigens, but they are often weakly immunogenic and immunization with recombinant proteins may not elicit a significant immune response that recognizes the native protein. This report describes the immune stimulating activity of two new adjuvant formulations, a zinc-chitosan particle formulation designed to bind to histidine tagged recombinant proteins; and an emulsion formulation containing chitosan. BALB/c mice vaccinated with formulations comprising recombinant beta-human chorionic gonadotropin (βhCG) and each adjuvant had prolonged high titer antibodies that recognized both the recombinant βhCG and native hCG. βhCG is an established target for immunocontraceptive vaccines and a potential target for tumor immunotherapy. Isotype analysis of these antibodies revealed an IgG1 response in mice immunized with zinc-chitosan particles and a mixed IgG1, IgG2a and IgG2b response with the emulsion. These chitosan based adjuvant formulations were effective in sensitizing mice and guinea pigs for antigen specific DTH responses, indicating that these adjuvants stimulate both B and T lymphocytes. The ability of these adjuvants to stimulate significant responses with a poorly immunogenic recombinant protein suggests that they may have potential in developing vaccines based on synthetic peptides and subunit antigens.