Analysis of the molecular evolutionary characteristics of neuraminidases in influenza B virus strains isolated in Jiangsu province from 2010 to 2012 / 中华微生物学和免疫学杂志

ABSTRACT

Objective To analyze the substitutions at amino acid residues of neuraminidases ( NAs) in influenza B virus strains isolated in Jiangsu province from 2010 to 2012 and to further understand the genetic evolution of NAs in those influenza B virus strains .Methods Forty strains of influenza B virus isolated in Jiangsu province from 2010 to 2012 were screened out for this study .A two-step reverse transcrip-tion PCR ( RT-PCR) was performed to amply the gene fragments encoding the neuraminidases of influenza B virus strains.The PCR products were purified and then sequenced in an ABI 3730XL Genetic Analyzer.The evolutionary characteristics of NA gene were analyzed by using DNAStar , Bioedit, MEGA 5.0 and BEAST 1.8.0 softwares.Results The phylogenetic tree analysis of the NA genes showed that the NAs of 28 Vic-toria strains were derived from the Yamagata lineage .There were reassortments between the Victoria lineage-HA and theYamagata lineage-NA.Some of the strains added a glycosylation site at position 462.No substitu-tion was found in important enzyme active sites and neuraminidase inhibitor resistant sites .The Bayesian MCMC analysis showed that the estimated mean evolutionary rate for NA gene was 1.74×10-3(95%HPD1.46×10-3-2.06×10-3) substitutions/site/year.The dN/dS ratio (ω), an indicator of selective pressure, was 0.24.Conclusion The important amino acid sites of NA were relatively conservative and the evolution -ary rate for NA gene was low .The dN/dS ratio was less than one , indicating that the NA gene was under pu-rifying selection .