Evolution analysis of hemagglutinin gene of novel influenza virus A/H1N1 in 2009 pandemic

Abstract

Objective:To investigate the evolutionary relationship of the hemagglutinin(HA)gene of novel influenza virus A/H1N1 in 2009 pandemic with the HA genes of A/H1N1 viruses isolated in different parts of the world previously.Methods:The sequences of the HA gene of the novel A/H1N1 strain and the reference sequences of human,swine,and avian influenza A viruses were retrieved from NCBI.MEGA 4.0 software was employed to align,blunt nucleotide sequences,and construct phylogenetic tree.The deduced amino acid sequences of the HA genes of novel influenza virus A/H1N1 were compared with those of the A/H1N1 isolates in North America,Europe,and Asia.Results:Phylogenetic tree of the HA genes of A/H1N1 strains worldwide showed that the HA genes of novel influenza virus A/H1N1 in 2009 shared a high homology with those of the 7 human A/H1N1 influenza viruses isolated in North America during 1976 to 2007,and shared a low homology with those of the human influenza viruses A/H1N1 isolated in Europe and Asia.Phylogenetic tree of the HA gene between different species showed that the HA genes of novel influenza virus A/H1N1 in 2009 had a close evolutionary relationship with those of the two swine A/H1N1 strains isolated in 1998 and 2007 in North America,but a distant evolutionary relationship with those of swine and avian A/H1N1 isolated in Europe and Asia.Alignment of amino acid at important antigenic sites showed that the HA gene of the novel A/H1N1 strains shared important antigen sites with the swine A/H1N1 influenza viruses isolated in North America,and did not share with the swine A/H1N1 influenza viruses isolated in Europe and Asia or the human A/H1N1 influenza vaccine strains.Conclusion:The HA genes of the novel influenza virus A/H1N1 might originate from swine A/H1N1 influenza viruses in North America after a long time evolution and the reassortment with fragments of human A/H1N1 in the area,and the current A/human/H1N1 influenza vaccine may not be effective for the novel A/H1N1 virus.