In 2013, three reassortant swine influenza viruses (SIVs), two H1N2 and one H3N2, were isolated from symptomatic pigs in Japan. Each contained genes from the pandemic A(H1N1)2009 virus and endemic SIVs. Phylogenetic analysis revealed that the two H1N2 viruses were reassortants that contained genes from three distinct lineages: 1) H1 and NP genes derived from a classical swine H1 HA lineage uniquely circulating among Japanese SIVs; 2) NA genes from human- like H1N2 swine viruses; and 3) other genes from pandemic A(H1N1)2009 viruses. The H3N2 virus comprised genes from two sources: 1) HA and NA genes derived from human and human-like H3N2 swine viruses; and 2) other genes from pandemic A(H1N1)2009 viruses. Phylogenetic analysis also indicated that each reassortant may have arisen independently in Japanese pigs. The antigenic reactivities of these reassortant SIVs with antisera against both vaccine strains of SIV and some seasonal human-lineage viruses were low. These findings indicate that the emergence and spread of these reassortant swine influenza viruses are a potential threat to livestock production and public health.
(Influenza and Prion Disease Research Center)
References:
Kanehira K. et al (2014) Microbiol. Immunol. 58(6):327-341
