Protective efficacy of a bivalent inactivated reassortant H1N1 influenza virus vaccine against European avian-like and classical swine influenza H1N1 viruses in mice

The classical swine (CS) H1N1 swine influenza virus (SIVs) emerged in humans as a reassortant virus that caused the H1N1 influenza virus pandemic in 2009, and the European avian-like (EA) H1N1 SIVs has caused several human infections in European and Asian countries. Development of the influenza vaccines that could provide effective protective efficacy against SIVs remains a challenge. In this study, the bivalent reassortant inactivated vaccine comprised of SH1/PR8 and G11/PR8 arboring the hemagglutinin (HA) and neuraminidase (NA) genes from prevalent CS and EA H1N1 SIVs and six internal genes from the A/Puerto Rico/8/34(PR8) virus was developed. The protective efficacy of this bivalent vaccine was evaluated in mice challenged with the lethal doses of CS and EA H1N1 SIVs. The result showed that univalent inactivated vaccine elicited high-level antibody against homologous H1N1 viruses while cross-reactive antibody responses to heterologous H1N1 viruses were not fully effective. In a mouse model, the bivalent inactivated vaccine conferred complete protection against lethal challenge doses of EA SH1 virus or CS G11 virus, whereas the univalent inactivated vaccine only produced insufficient protection against heterologous SIVs. In conclusion, our data demonstrated that the reassortant bivalent inactivated vaccine comprised of SH1/PR8 and G11/PR8 could provide effective protection against the prevalent EA and CS H1N1 subtype SIVs in mice.