Analysis of HA gene sequence of a subtype H1N1 swine influenza virus isolated from Guangxi strains.

[Objective]This study was to determine molecular biology information of HA gene of H1N1 swine influenza virus isolated from Guangxi strains to provide references for monitoring swine flu in Guangxi. [Method]To analyze HA gene of H1N1 from Genbank, the primer was designed, and then HA genes of A / swine/Guangxi/1/2011 (H1N1) influenza virus were cloned, sequenced and compared via DNASTAR software. A phylogenetic tree was made using MEGA 4.0. [Result]The results indicated that the length of HA gene was 1701 bp and coded for 566 amino acids. Comparing with classical swine influenza H1N1, human -like H1N1 and Eurasian avian-like H1N1, the nucleotide homologies of HA genes were from 88.0% to 99.6%, from 76.3% to 77.3% and from 72.9% to 75.4%,respectively. Phylogenetic analysis revealed that the strain of A / swine/Guangxi/1/2011(H1N1) belonged to classical swine influenza H1N1 lineage and was similar to the strain A/California/04/2009 (H1N1), while it did not resemble human-like H1N1 and bird-like H1N1 at all. Amino acid sequence at the HA cleavage site was IPSIQSR↓G, which had characteristics of low-pathogenic influenza viruses. Among the eight glycosylation sites, six sites were located in HAl section and the rest in HA2. Amino acid in protein RBS of Guangxi strains possessed characteristics of both human and swine influenza virus. [Conclusion]This strain was pandemic(H1N1) 2009 virus and first isolated in Guangxi.