title: [Analysis of evolution features of whole genome of influenza virus H3N2 in Qingdao between year 2007 and 2011].
abstract: OBJECTIVE
  To investigate the evolution features of whole-genome of influenza virus H3N2 prevalent in Qingdao from year 2007 to 2011.
  
  
  METHODS
  The RNA of 58 strains of influenza virus H3N2 prevalent in Qingdao between 2007 and 2011 was extracted and all segments amplified by RT-PCR. The sequence was then detected and assembled by software Sequencer. A total of 589 strains of influenza virus H3N2 with more than 300 amino acid recorded by GenBank were selected. The phylogeny and molecular features of all gene segments were analyzed by software Mega 5.0, referred by the heavy chain of hemagglutinin (HA1).
  
  
  RESULTS
  Hemagglutinin (HA) genes of influenza virus H3N2 prevalent in Qingdao between year 2007 and 2011 formed a single trunk of phylogenetic tree. Every prevalent strain originated in last season. The analysis of the evolution of whole genome found that reassortment virus strains were prevalent between year 2009 and 2010, but between 2010 and 2011 there were two series of prevalent strains, which showed complicated reassortment. Compared with the vaccine strains, the variant amino acids of protein of virus HA1 between year 2007 and 2011 were 8, 6, 6, 8 and 11, involving 13 antigenic sites. The sequence analysis of M2 protein showed that the isolated influenza virus H3N2 mutated in amino acid site 31, from serine to asparagine (S31N). HA1 gene of influenza virus H3N2 isolated in Qingdao between 2007 and 2011 shared the similar phylogenetic tree with the globally prevalent strain. The comparison of the sequence and the analysis of the antigenicity found co-infection between H3N2 and A/H1N1 in the strain A/Qingdao/F521/2011.
  
  
  CONCLUSIONS
  The evolution features of all segments of influenza virus H3N2 prevalent in Qingdao between year 2007 and 2011 were complicated.
authors.affiliation: Department of Microorganism and Parasite Test, Qingdao Municipal Center for Disease Prevention and Control, Qingdao 266033, China.
authors.forename: Zhao-guo
authors.initials: ZG
authors.lastname: Wang
authors.forename: Ting-ting
authors.initials: TT
authors.lastname: Yang
authors.forename: Qing
authors.initials: Q
authors.lastname: Chai
authors.forename: Xiao-lin
authors.initials: XL
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Yi
authors.forename: Yu
authors.initials: Y
authors.lastname: Yang
authors.forename: Ping
authors.initials: P
authors.lastname: Yu
authors.forename: Zhi-yu
authors.initials: ZY
authors.lastname: Wang
mesh_terms: D002681:China; D019143:Evolution, Molecular; D016679:Genome, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics*; D010802:Phylogeny; D012367:RNA, Viral; D016865:Reassortant Viruses / Q000235:genetics; D017421:Sequence Analysis; D014763:Viral Matrix Proteins / Q000235:genetics; D000086082:Viroporin Proteins
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D014763:Viral Matrix Proteins; C488937:M2 protein, Influenza A virus; D000086082:Viroporin Proteins