title: [Analysis of genetic variation of hemagglutinin and three internal genes of influenza B virus isolated in Zhejiang province from 1999 to 2012].
abstract: OBJECTIVE
  To explore the characteristics of the genetic variation of hemagglutinin( HA) and three internal genes coding for the nucleoprotein ( NP) , matrix protein ( M) and nonstructural protein ( NS) of influenza B virus.
  
  
  METHODS
  A total of 31 strains of influenza B virus were isolated in Zhejiang province from 1999 to 2012, and then were amplified and sequenced the genes of HAl , NP, M and NS. The phylogenetic tree was constructed, the nucleotide substitution rate of the above individual gene was estimated and the variation sites of amino acids were analyzed.
  
  
  RESULTS
  The 31 isolated strains of influenza B virus were divided into two distinct lineages Victoria and Yamagata in the phylogenetic tree of HAl gene,represented by B/Victoria/2/87 and B/Yamagata/16/88. Phylogenetic analysis of the NP gene showed that the NP gene of Victoria-like influenza B strains which were isolated after 2010 was highly homologous with Yamagata-like isolates, and thereby they were found to be on the same branch of the phylogenetic tree of the NP gene. Nucleotide substitution rates of HAl , NP, M and NS genes were estimated to be 2. 29 x 10 -3 ,1. 39 X 10-3 ,1. 78 X 10-3 ,1. 30 X 10-3 /site per year, respectively. Variations of amino acid of HAl domain of Victoria-like isolates mainly included K48E ,L58P ,N75K,K80R,K129N/S,N165K,S172P ,Sl97N/D and A202V; while those in Yamagata-like isolates were R48K, S1501, N166Y, N203S, G230D and D233N. Determined amino acid sequences of NP of Victoria-like influenza B isolates were similar to Yamagata-like isolates after 2010 and variations happened on four characteristic amino acid sites, naming A60D, I233V, N513S and V5341, compared with previous Victoria-like influenza B isolates.
  
  
  CONCLUSIONS
  Significant variation was found among influenza B strains isolated in Zhejiang province from 1999 to 2012. The surface HAl gene evolved more rapidly than internal genes. Gene reassortment and gene mutation were the main evolutionary mechanism of influenza B virus.
authors: Microbiology Institute of Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, China. luyiyuzjh@yahoo.com.cn
authors: Hai-yan
authors: HY
authors: Mao
authors: Yi
authors: Y
authors: Sun
authors: Yan-jun
authors: YJ
authors: Zhang
authors: Min
authors: M
authors: Zhou
authors: Yin
authors: Y
authors: Chen
authors: Zhen
authors: Z
authors: Li
authors: Yi-yu
authors: YY
authors: Lu
mesh_terms: D002681:China / Q000453:epidemiology; D019143:Evolution, Molecular; D005814:Genes, Viral; D014644:Genetic Variation; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics*; D006801:Humans; D009981:Influenza B virus / Q000235:genetics*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D019590:Nucleocapsid Proteins; D010802:Phylogeny; D016865:Reassortant Viruses / Q000235:genetics; D014758:Viral Core Proteins / Q000235:genetics; D014763:Viral Matrix Proteins / Q000235:genetics; D017361:Viral Nonstructural Proteins / Q000235:genetics
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; C545845:M1 matrix protein, influenza B virus; D019590:Nucleocapsid Proteins; D014758:Viral Core Proteins; D014763:Viral Matrix Proteins; D017361:Viral Nonstructural Proteins; C588186:nucleoprotein, influenza B virus