Genetic characteristic of haemagglutinin of influenza B virus in Guiyang, 2012-2015

Objective To understand the genetic variation and epidemiological characteristics of influenza B virus in Guiyang, Guizhou province, in 2012-2015, and to evaluate the matching situation of epidemic strains and the influenza vaccine strains recommended by WHO and China. Methods The haemagglutinin segment 1(HA1) nucleotide sequences of 19 strains and 2 positive specimens of influenza B viruses were determined by Sanger dideoxy sequencing, the sequencing products were analyzed by bioinformatics software DNAStar version 7.1. Results Both BY and BV lineage of influenza B viruses were found to co-circulate in Guiyang.Results of homology analysis revealed that there were 97.8%~99.3% homology in nucleotide between BV lineage viruses and vaccine strain B/Brisbane/60/2008. However, vaccine strain B/Massachusetts/02/2012 showed a lower homology (96.2%-96.5%) to BY lineage viruses than previous vaccine strain B/Wisconsin/01/2010 did (99.0%-99.3%). BY lineage viruses had a high homology to vaccine strain B/PHUKET/3073/2013 recommended by WHO in 2015, with homology ranged from 99.2% to 99.5%. During 2012-2015, Chinese representative strain B/Chongqing-Yuzhong/1384/2010 had 96.8%-99.0% homology to BV lineage viruses, meanwhile, another Chinese vaccine seed strain B/Hubei-Wujiagang/158/2009 had 98.2%-99.2% homology. Compared to the current vaccine strain recommended by WHO, amino acid sequence alignment analysis showed there were 9 amino acid mutations in HA1 fragment of BY lineage strains in 2013-2014, the mutation of A134P was related to antigenic determinant site A, N142K was related to site B. There was a new amino acid mutation of L198Q relating to antigenic determinant site D in HA1 fragment of BY lineage strains in 2015. There were different kinds of amino acid mutations in HA1 fragment of BV lineage strains, which were rarely related to antigenic determinant site. Conclusions Genetic characteristic of influenza B virus was constantly changing in Guiyang in 2012-2015. Overall, the predominant circulating influenza B viruses in 2013-2014 in Guiyang could be not provided a good protection by current influenza vaccine, but the rest years of influenza B viruses were matched by current influenza vaccines with a good protective effect.