Evolutionary Characterization of Human H1N1 Influenza Virus Hemagglutinin Genes Isolated from 1947 to 2009 in China

Abstract

Objective: Our aim was to reveal the molecular characteristics of human H1N1 influenza virus hemagglutinin (HA) genes from 1947 to 2009 in China. Methods: 129 HA gene sequences were downloaded from NCBI’s GenBank and analyzed by DNASTAR software. Additionally, the three-dimensional structure of HA protein was predicted by the SWISS-MODEL service. Results: First, 2009 Chinese HA genes were 99% identical to those of Mexican and American ones; their key sites remained highly conserved. Second, 50 Chinese strains from 1947 to 2009 clustered by the year of isolation, and 2009 strains had only 70% identity to 1947–2008 ones. Third, over the past 60 years, 3 receptor-binding (RB) sites and 2 of the 8 glycosylation sites (amino acids 279 and 290) underwent considerable changes while the cleavage sites remained stable. Fourth, the human HA sequences differed completely from swine and avian isolates. Finally, the mutation of cleavage sites can change the three-dimensional structures, but single mutations cannot. Conclusions: Thus, in the past 60 years, Chinese H1N1 influenza HA genes kept stable with high affinity and low pathogenicity to human except changes in 2 glycosylation and 3 RB sites which were associated with the pandemic strength, range and host specificity of viruses.