Marine gastropod hemocyanins as adjuvants of non-conjugated bacterial and viral proteins

Killed viral vaccines and bacterial toxoids are weakly immunogenic. Numerous compounds are under evaluation as immunological adjuvants and peptide-carriers to improve the immune response. The hemocyanins, giant extracellular copper proteins in the blood of many mollusks, are widely used as immune stimulants. In the present study we investigated the adjuvant properties of hemocyanins isolated from marine gastropods Rapana thomasiana and Megathura crenulata. An immunization with Influenza vaccine or tetanus toxoid combined with Rapana thomasiana hemocyanin (RtH) and Keyhole limpet hemocyanin (KLH) in mice induced an anti-influenza cytotoxic response lasting at least 5 months and an antibody response to viral proteins. The IgG antibody response to the tetanus toxoid (TT) combined with RtH or KLH was comparable to the response of the toxoid in complete Freund's adjuvant. The results obtained demonstrate that the both hemocyanins are acceptable as potential bio-adjuvants for subunit vaccines.