2013-2014年南宁市A(H3N2)亚型流感病毒病原学特征分析

Virological characterization of influenza A(H3N2)virus in Nanning from 2013-2014

目的分析南宁市2013-2014年A(H3N2)亚型流感病毒的病原学特征及流行趋势。方法通过RT-PCR扩增毒株A(H3N2)病毒血凝素(HA)基因和神经氨酸酶(NA)并进行同源比对,采用Mega5.1(N-J法)构建系统进化树,统计氨基酸位点的差异,同源建模后分析蛋白结构的变化。结果构建系统进化树,20株毒株HA基因与NA基因均分为4个类群,呈多侧支流行;部分毒株的HA蛋白A抗原决定簇144位点及B抗原决定簇156和158位点发生突变,二硫键和糖基化位点高度保守,未发生变化;NA蛋白抗原基本稳定,只有A/Nanning/43/2014(H3N2)毒株抗原决定簇312位点发生突变,二硫键、酶活性位点、糖基化位点及耐药性位点均未发生变化;HA和NA蛋白晶体结构分析显示氨基酸突变位点主要发生在β折叠部位和无规则卷曲处。结论南宁市A(H3N2)亚型流感病毒株变异活跃,在HA基因和NA基因进化树上疫苗株明显滞后于南宁市流行株,抗原决定簇位点出现氨基酸的替换,但关于疫苗的预防效果尚需进一步验证。

Objectives To analyze the spectrum of influenza viruses in Nanning from 2013--2014 by bioinformatically studying genetic variation of the hemagglutinin （HA） and neuraminidase （NA） genes of influenza A（H3N2）. Methods Sequences of both the HA and NA genes were amplified using RT-PCR and differences in their amino acids were statis- tically analyzed. Mega5.1 （N-J method） was used to create a phylogenetic tree. Homology modeling of the sequences was performed and changes in protein structures were analyzed. Results The phylogenetic tree indicated that the HA gene and the NA gene of 20 strains belonged to four groups with numerous branches. Disulfide bonds and glycosylation sites of the HA protein were highly conserved among all strains and had not changed. There were mutations in the HA protein of some of the strains at the A antigenic determinant site at amino acid 144 and the B antigenic determinant site at amino acids 156 and 158. The NA protein was stable. There was a mutation in the NA protein at an antigenic determinant site at amino acid 312, but this was only found in the A / Nanning / 43/2014 （H3N2） strain. Disulfide bonds, the enzyme ac tive site, glycosylation sites, and drug resistance sites were unchanged. Analysis of the crystal structure of the HA and NA proteins indicated that mutations mainly occurred at β-folds and random coils. Conclusion The Nanning A（H3N2） subtype of the influenza virus is actively mutating. Based on the phylogenetic tree for the HA gene and the NA gene, the vaccine strain lags far behind the strains prevalent in Nanning. Amino acids of antigenic determinant sites have been sub- stituted, but the prophylactic effect of the vaccine still needs to be verified further.