Protection efficacy of the H1 and H3 bivalent virus-like particle vaccine against swine influenza virus infection.

Swine influenza (SI) is widely prevalent in pig herds worldwide, causing huge economic losses to the pig industry and public health risks. The traditional inactivated swine influenza virus (SIV) vaccines are produced in chicken embryos, and egg-adaptive substitutions that occur during production process can impact vaccine effectiveness. Thus, developing an SI vaccine that can decrease the dependence on chicken embryos with a high immunogenicity is urgently needed. In this study, the utility of insect cell-derived SIV H1 and H3 bivalent virus-like particle (VLP) vaccines containing HA and M1 proteins of Eurasian avian-like (EA) H1N1 SIV and recent human-like H3N2 SIV were assessed in piglets. Antibody levels were monitored, and the protection efficacy of the vaccine after viral challenge was evaluated and compared with the inactivated vaccine. Results show that piglets produced high hemagglutination inhibition (HI) titers of antibodies against H1 and H3 SIV after immunization with SIV VLP vaccine. The neutralizing antibody level was significantly higher in SIV VLP vaccine than in the inactivated vaccine at 6 weeks post vaccination (p < 0.05). Furthermore, piglets immunized with the SIV VLP vaccine were protected against the challenge of H1 and H3 SIV, displaying inhibition of viral replication in piglets, and reduced lung damage. These results show that SIV VLP vaccine has good application prospects, thus laying the foundation for further research and commercialization of SIV VLP vaccine.