Epidemiological and evolutionary characteristics of influenza B viruses in Hubei, 2010-2015

Objective To understand the epidemiological and evolutionary characteristics of influenza B viruses in Hubei during 2010-2015. Methods The sequences of HA and NA genes of influenza B viruses isolated in Hubei during this period were obtained from sequencing and GISAID's database. Then the phylogenetic trees and amino acid mutations of HA and NA proteins were analyzed respectively. Moreover, the homology modeling structures of the NA proteins were constructed and analyzed. The epidemiological dynamics of influenza B virus was described by using phylogenetic data. Results After the intra-lineage and inter-lineage reassortments of influenza B viruses, predominant circulation of the viruses would occur in Hubei during this period. Amino acid substitutions of the viruses, such as N116K, N129S, A146T, K162R and N197S, were detected on four major epitopes of HA protein. D197N substitution was found on the enzyme active locus of NA protein, which was not directly in contact with substrate or neuraminidase inhibitors on homology modeling structure. Conclusion There was a close relationship between epidemiological dynamics and gene evolution of influenza B viruses in Hubei during 2010-2015. It would facilitate the understanding of the evolutionary characteristics of influenza B viruses by monitoring amino acid substitutions on the epitopes of HA protein and drug resistance loci.