Abstract: To investigate the prevalence and biological characteristics of swine influenza virus (SIV) in Jilin,the nasal swab samples were collected from swine farm in Jilin and inoculated into SPF chicken embryos for virus isolation. The isolated virus was identified using hemagglutination test and RT-PCR. Whole genome amplification, genetic evolutionary analysis, analysis of functional amino acid mutations, and selection pressure analysis were performed on the isolated strain. RT-PCR analysis confirmed that the isolated strain belonged to the H1N1 subtype of SIV. Genetic evolutionary analysis revealed that all eight gene segments of the strain belonged to the classical lineage of SIV H1N1. No gene rearrangements among different genotypes of influenza viruses were observed. Analysis of functional amino acid sites indicated that the strain had mutations at sites associated with increased pathogenicity, virulence, and replicability of SIV. Mutations in the NA gene were found at sites associated with resistance to neuraminidase inhibitors. Moreover, the HA and NA genes of SIV in Jilin province displayed evidence of autonomous mutations, with higher mutation rates observed in the NA gene compared to the HA gene. Whole genome sequence analysis of the H1N1 subtype SIV isolates in this study provides valuable insights for epidemiological investigations of SIV and future vaccine development.

Key words: swine influenza virus, H1N1 subtype, isolation and identification, phylogenetic analysis, selection pressure analysis