A reverse genetics-based NS1-truncated live attenuated vaccine confers broad heterologous protection against swine influenza viruses

Swine influenza A viruses (swIAVs) undergo frequent reassortment and evolution, posing significant threats to both animal and human health. In this study, we employed reverse genetics to generate five recombinant viruses and evaluated their potential as vaccine candidates. Through pathogenicity evaluation in mice, we identified two promising candidates: an inactivated vaccine (rPR8-JGL16+2) and a live-attenuated vaccine (rPR8-JGL15+3). Both vaccines induced robust hemagglutination inhibition (HI) antibody responses and specific IgG levels against homologous strains. Notably, the attenuated rPR8-JGL15+3 vaccine provided complete protection against both homologous (H1N1) and heterologous (H3N2) viral challenges, with no detectable viral loads in the lungs or nasal turbinate. Although the inactivated rPR8-JGL16+2 vaccine exhibited effective protective efficacy against influenza viruses, it did not fully inhibit the replication of heterologous viruses in mice. Histopathological assessment revealed that rPR8-JGL15+3 immunization prevented significant lung damage, contrasting with the mild pathology observed in rPR8-JGL16+2-vaccinated animals. These findings demonstrate the successful development of novel vaccine candidates against avian-like H1N1 swIAV, with the attenuated vaccine showing promise for broad protection against circulating strains.