Immunopotentiators Improve the Efficacy of Oil-Emulsion-Inactivated Avian Influenza Vaccine in Chickens, Ducks and Geese

Combination of CVCVA5 adjuvant and commercial avian influenza (AI) vaccine has been previously demonstrated to provide good protection against different AI viruses in chickens. In this study, we further investigated the protective immunity of CVCVA5-adjuvanted oil-emulsion inactivated AI vaccine in chickens, ducks and geese. Compared to the commercial H5 inactivated vaccine, the H5-CVCVA5 vaccine induced significantly higher titers of hemaglutinin inhibitory antibodies in three lines of broiler chickens and ducks, elongated the antibody persistence periods in geese, elevated the levels of cross serum neutralization antibody against different clade and subclade H5 AI viruses in chicken embryos. High levels of mucosal antibody were detected in chickens injected with the H5 or H9-CVCA5 vaccine. Furthermore, cellular immune response was markedly improved in terms of increasing the serum levels of cytokine interferon-γ and interleukine 4, promoting proliferation of splenocytes and upregulating cytotoxicity activity in both H5- and H9-CVCVA5 vaccinated chickens. Together, these results provide evidence that AI vaccines supplemented with CVCVA5 adjuvant is a promising approach for overcoming the limitation of vaccine strain specificity of protection.