Immune responses and protection efficacy of a recombinant swinepox virus expressing HA1 against swine H3N2 influenza virus in mice and pigs

► This is the first construction of recombinant SPV expressing HA1 of H3N2 SIV. ► The recombinant rSPV-H3 can express HA1 of H3N2 SIV in vitro. ► rSPV-H3 can induce specific humoral and cell-mediated immune responses in animals. ► Administration of rSPV-H3 provides a complete protection against H3N2 SIV in pigs. Swine influenza virus (SIV) is not only an important respiratory pathogen in pigs but also a potent threat to human health. Even though immunization with recombinant vaccinia poxviruses expressing protective antigens as a vaccination strategy has been widely used for many infectious diseases, development of recombinant swinepox virus (rSPV) vector for this purpose has been less successful. Here, we report the construction of a recombinant swinepox virus (rSPV) expressing hemagglutinin (HA1) of H3N2 SIV (rSPV-H3). Immune responses and protection efficacy of the vaccination vector were assessed in both mouse and pig models. Prime and boost inoculations of rSPV-H3 yielded neutralization antibody against SIV and elicited potent H3N2 SIV-specific INF-γ response from T-lymphocytes. Complete protection of pigs against H3N2 SIV challenge was achieved. No pigs showed severe systemic and local reactions and no SIV was found shed from the pigs vaccinated with rSPV-H3 after challenge. The data suggest that the SPV-based recombinant vector expressing HA1 of H3N2 SIV might serve as a promising SIV vaccine for protection against SIV infection.