Efficacy of avridine and liposomes as adjuvants for avian influenza virus antigens in turkeys.

Four-week-old turkeys were vaccinated with H4N8, H5N2 and H7N3 inactivated avian influenza viruses (AIV) in one of the following adjuvants: avridine, positively charged liposomal avridine, liposomal avridine with covalent attachment to the AIV antigens and oil-emulsion; and without any adjuvant. Two vaccinations were given at a 4-week interval. Antibody concentrations in sera and in respiratory lavages were measured over a period of 8 weeks. The turkeys responded with high cumulative geometric mean HI titres to the H4N8, H5N2 and H7N3 components of the vaccines, while the cumulative geometric mean HI titres for the antigens without adjuvant were significantly (P < 0.05) lower. The most efficacious adjuvant, positively charged liposomal avridine, gave the highest local immune response as measured by total antibody specific to AIV in respiratory lavages. The difference in weight gains between vaccinated and non-vaccinated turkeys was significant (P<0.05). Virus isolations 2 weeks post-challenge decreased in vaccinated turkeys.