Efficacy of a high-growth reassortant H1N1 influenza virus vaccine against the classical swine H1N1 subtype influenza virus in mice and pigs.

Swine influenza (SI) is an acute, highly contagious respiratory disease caused by swine influenza A viruses (SwIVs), and it poses a potential global threat to human health. Classical H1N1 (cH1N1) SwIVs are still circulating and remain the predominant subtype in the swine population in China. In this study, a high-growth reassortant virus (GD/PR8) harboring the hemagglutinin (HA) and neuraminidase (NA) genes from a novel cH1N1 isolate in China, A/Swine/Guangdong/1/2011 (GD/11) and six internal genes from the high-growth A/Puerto Rico/8/34(PR8) virus was generated by plasmid-based reverse genetics and tested as a candidate seed virus for the preparation of an inactivated vaccine. The protective efficacy of this vaccine was evaluated in mice and pigs challenged with GD/11 virus. Prime and boost inoculation of GD/PR8 vaccine yielded high-titer serum hemagglutination inhibiting (HI) antibodies and IgG antibodies for GD/11 in both mice and pigs. Complete protection of mice and pigs against cH1N1 SIV challenge was observed, with significantly fewer lung lesions and reduced viral shedding in vaccine-inoculated animals compared with unvaccinated control animals. Our data demonstrated that the GD/PR8 may serve as the seed virus for a promising SwIVs vaccine to protect the swine population.