The immune response of a recombinant fowlpox virus coexpressing the HA gene of the H5N1 highly pathogenic avian influenza virus and chicken interleukin 6 gene in ducks

Ducks have played an important role in the emergence of H5N1 subtype of highly pathogenic avian influenza (HPAI), and the development of an effective vaccine against HPAI in ducks is a top priority. It has been shown that a recombinant fowlpox virus (FPV)-vectored vaccine can provide protection against HPAI in ducks. In this study, a recombinant fowlpox virus (rFPV-AIH5AIL6) coexpressing the haemagglutinin (HA) gene of the H5N1 subtype of the avian influenza virus (AIV) and chicken interleukin 6 gene was constructed and tested in Gaoyou and cherry valley ducks to evaluate the immune response in ducks. These animal studies demonstrated that rFPV-AIH5AIL6 induced a higher anti-AIV HI antibody response, an enhanced lymphocyte proliferation response, an elevated immune protection, and a reduction in virus shedding compared to a recombinant fowlpox virus expressing the HA gene alone (rFPV-SYHA). These data indicate that rFPV-AIH5AIL6 may be a potential vaccine against the H5 subtype of avian influenza in ducks and chicken interleukin 6 may be an effective adjuvant for increasing the immunogenicity of FPV-vectored AIV vaccines in ducks.