2010—2012 年江苏省乙型流感病毒神经氨酸酶分子进化特征分析

Analysis of the molecular evolutionary characteristics of neuraminidases in influenza B virus strains isolated in Jiangsu province from 2010 to 2012

目的 分析江苏省乙型流感病毒神经氨酸酶（ NA）蛋白特征性氨基酸位点的变化,掌握江苏省乙型流感病毒NA分子进化特征. 方法 选择2010—2012年40株乙型流感毒株,两步法扩增NA基因片段,3730XL测序仪进行测序;利用DNAStar、Bioedit、MEGA5.0和BEAST 1.8.0等软件分析NA基因进化特征. 结果 从NA进化树可以看出,28株Victoria系的分离株NA来源于Yamagata系,发生了基因的重配;部分分离毒株在462位增加了一个糖基化位点;重要的酶活性位点及耐药位点氨基酸未发生变化;2010—2012 年江苏省乙型流感病毒NA基因核苷酸平均碱基替代率每年为1.74×10-3[95%HPD（最高后验密度区间）：1.46×10-3 -2.06×10-3]替换/位点;整体选择压力ω（ω=dN/dS）值为0.24. 结论 2010—2012年江苏省乙型流感病毒NA重要的氨基酸位点相对保守,基因速率缓慢,尚未受到明显的正向选择压力.

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＆#215;10-3（95%HPD：1.46＆#215;10-3-2.06＆#215;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 .