Whole-genome evolution of influenza B viruses prevalent in Qingdao from 2006 to 2011 / 中华微生物学和免疫学杂志

ABSTRACT

Objective To study the whole-genome evolution of influenza B viruses prevalent in Qingdao from 2006 to 2011 .Methods RNA was extracted from influenza B viruses isolated in Qingdao from 2006 to 2011 .Each gene segment was amplified by reverse transcription polymerase chain reaction ( RT-PCR) and then sequenced .Gene sequences of each virus were determined and assembled by using Sequench -er software .A phylogenetic analysis for each gene segment was conducted by using MEGA 5.0 software pack-age.Results The phylogenetic tree of hemagglutinin ( HA) gene showed that 13 strains from 2006 to 2009 belonging to V1 clade of Victoria lineage were B/Malaysia/2506/2004-like viruses,and 12 strains from 2009 to 2011 belonging to the V2 clade of Victoria lineage were B/Brisbane/60/2008-like viruses.Moreover, strains of Yamagata lineage were all B/Florida/4/2006-like viruses including 5 strains of Y1 clade circulated from 2006 to 2008 and 7 strains of Y2 clade circulated from 2010 to 2011, respectively.The analysis of whole-genome evolution showed that 3 viruses of V2 clade presented 5+3 reassortment and 1 virus presented 1+7 reassortment.All reassortant strains matched with the vaccine strains of the present and previous season . The Yamagata and Victoria lineage strains belonged to genotype 2 and genotype 15,respectively.Compared with vaccine strains , the HA1 protein of Victoria lineage strains showed mutations at amino acid sites of H14Q, L58P, N129S, I146V, N171D and R279K, while R48K, K88R, P108A, N116K, S150I, N165Y, D196N,N202S and S229G amino acid mutations were mainly detected in Yamagata lineage strains .The sites 116 and 129,150,165,196 and 202 located in the 120,150,160 and 190 loops,respectively,which had been previously determined to be the hotspots under positive selection .Conclusion Both Yamagata and Victoria lineages of influenza B viruses were prevalent in Qingdao and evolved continuously from 2006 to 2011 .The selective pressure that a vaccine would provide was only to virus strains belonging to the same lineage ,sug-gesting a bivalent vaccine may be better for the induction of protective immunity .