Virological surveillance and analysis of HA1 gene of influenza B viruses in Jiaxing City from 2011 to 2012

[Objective] To study the variation and genetic characteristics of hemagglutinin gene HA1 of influenza virus B strains isolated in Jiaxing City since 2011,and evaluate the protective effect of the influenza vaccine strains recommended by WHO.[Methods] The influenza viruses were isolated by using MDCK cell culture from specimens of the influenza-like cases in Jiaxing City,and further identified by serological test and reverse-transcription polymerase chain reaction(RT-PCR).Six isolated strains were selected randomly and their sequences of the HA1 genes were analyzed by the software DNAStar.[Results] The viruses of Yamagata lineage and Victoria lineage were both found to be existent.The 4 strains of selected strains were Victoria lineage,whose homologies of nucleotide acids were 98.6% to 99.7% and those of amino acids were 98.8% to 100.0%,of which,as compared with vaccine strains of 2009-2012,two of them appeared 4 amino acids substitutions at the sites of L58P,N129S,I146V and N171D in HA1 respectively.The 2 strains of selected strains were Yamagata lineage,with the homologies of nucleotide acids and amino acids of 99.4%,and a high similarity to the vaccine strains of 2012 to 2013 recommended by WHO.[Conclusion] The vaccines recommended by WHO from 2009 to 2012,be-longed to Victoria lineage,with a certain protective effect against Victoria lineage strains of influenza B vi-rus,but were unable to provide optimum prevention from Yamagata lineage strains,which also simultane-ously prevailed in Jiaxing City during this period.