Abstract: 【Objective】 The objective of this study is to understand the molecular epidemiology of swine influenza virus, to provide scientific references for prevention of animal influenza in China. 【Method】Nasal swab samples collected from pigs were inoculated into SPF chicken embryos for virus isolation. The HA positive samples were further purified and proliferated in SPF chicken embryos. Eight gene fragments of the isolated virus were amplified by RT-PCR and then sequenced by Applied Biosystems 3500xL Genetic Analyzer. Nucleotide homology was analyzed by using DNASTAR. The phylogenetic trees of the genes were constructed using MEGA 6.0. 【Result】 The isolated virus was identified as an H1N1 subtype influenza virus, designated as A/swine/Zhejiang/245/2013(H1N1). Nucleotide homology analysis showed that eight gene fragments of this strain were highly homologous with the respective gene of the viruses recently isolated from China. Phylogenetic analysis revealed that the strain belonged to the avian-like swine H1N1 lineage, no gene reassortment occurred. Amino acid sequence at the HA cleavage site was IPSIQSR↓G, which had characteristics of low-pathogenic influenza viruses. And its receptor-binding sites contained 190D and 225E, which prefer sialic acid (SA)-2,6-Gal-terminated saccharides that are abundant in mammal upper respiratory epithelium. Among the six glycosylation sites, four sites were located in HA1 section and the rest in HA2. The isolates contained 271T, 627E and 701N in the polymerase subunit PB2, which had been shown to be determinants of virulence and host adaptation. The M2 proteins of the isolates have the mutation (S31N), a characteristic marker which may confer resistance to amantadine and rimantadine antivirals.【Conclusion】The sustained existence and continual mutation of avian-like swine H1N1 influenza virus suggested that intensive swine influenza surveillance should be carried out in the future.

Key words: swine influenza virus')">