我国部分地区HIV-1流行毒株亚型分布及gag基因变异特征研究

Subtype and characterization of gag gene of HIV-1 strains prevalent in some areas of China

目的:分析我国4个地区的人免疫缺陷病毒1型(HIV-1)主要流行毒株的亚型分布,以及在宿主免疫压力下的基因变异和抗原表位的变化情况,初步探讨这些地区HIV-1gag基因的分子进化特征。方法:从来自河南、广东、四川、北京的HIV-1感染者血浆样本中提取基因组RNA,经逆转录-聚合酶链反应(RT-PCR)扩增部分gag基因,用扩增产物直接进行测序;使用Genotyping Tool软件进行亚型分析,使用MEGA4.1软件绘制系统进化树;用Distance工具计算各个亚型序列的基因离散率;用SNAP程序分析同义替换率与非同义替换率的比值(Ks/Ka),并对各亚型中我国人群中较常见的HLA-Ⅰ型限制的CTL抗原表位的突变情况进行分析。结果:这些地区HIV-1主要流行毒株gag基因亚型主要是B′、CRF07_BC、CRF01_AE、B、CRF08_BC和CRF02_AG。各亚型内的基因离散率不同,由大到小排列为CRF01_AE>B>CRF08_BC>CRF07_BC>B′,Ks/Ka为CRF01_AE>B>CRF08_BC>B′>CRF07_BC。p17区段的CTL抗原表位变异远大于p24区段。各个亚型共享序列中存在的突变位点由多到少排列为CRF01_AE>B>B′>CRF07_BC。结论:我国HIV-1流行毒株的gag基因序列中,CRF01_AE亚型受到的选择压力最大,基因离散率也最大,且CTL抗原表位的变异亦最大,其次是B和B′亚型,CRF07_BC亚型变异最小。各亚型间CTL抗原表位变异的差异明显。

Objective：To investigate the subtype distribution of HIV-1 strains prevalent in four areas of China,and to study the characteristics of gag gene variation and changes in antigen epitopes under the host immune pressures.Methods：The plasma of HIV-1 infected people from Henan,Guangdong,Sichuan and Beijing in China were collected.Virion RNA was extracted directly from plasma after the virion was condensed.The gag gene was amplified by RT-PCR and nested-PCR.Sequences were subtyped by Genotyping Tool software, and phylogenetic analysis of gag gene were performed using the MEGA 4.1 software. The gene distances intra each subtype were calculated by Distance program. The Ks/Ka ratios were calculated using SNAP program. The variation analysis of CTL antigen epitopes restricted by main HLA- I specifici- ties in China was performed. Results：Six subtypes or circulating recombinant forms （CRFs）of HIV-1, including B＇, CRF07_ BC, CRF01_AE, B, CRF08_BC and CRF02_AG,were identified in four areas of China. The gene distances intra each sub- type were CRF01_AE 〉 B 〉 CRF08_BC 〉 CRF07_BC 〉 B＇ listed in order of size, meanwhile the order of Ks/Ka ratios was CRF01_AE 〉 B 〉 CRF08 BC 〉 B＇ 〉 CRF07_BC. Far more diversity of antigen epitopes in P17 region was observed than that in P2d. Epitope mutations intra subtypes were CRF01_AE 〉 B 〉 B＇ 〉 CRFO7_BC listed in order of size. Conclusion：It seems that CRF01_AE is under the strongest immune pressures, and displays the most diversity of gene and variation of epitopes intra subtypes prevalent in China, followed by subtype B, B＇ and CRF07_BC. The discrepancy of epitope mutations intra the subtypes is significant.