中国艾滋病病毒1型AE循环重组型毒株env基因的变异和进化分析

目的　研究中国艾滋病病毒 1型 (HIV 1)AE循环重组型 (CRF0 1 AE)毒株env不同基因区序列变异的特点及其与进化压力的关系。方法　应用巢式聚合酶链反应 (nested PCR)对从全国部分省收集来的HIV 1感染者血液样本中的HIV 1外膜蛋白 (env)基因进行扩增和亚型鉴定后 ,选择 3 4份CRF0 1 AE重组型HIV 1毒株env基因V3～V4区及其邻近区域的序列进行系统进化树和氨基酸变异分析 ,并计算和分析氨基酸同义替换 (Ks)值和非同义替换 (Ka)值及Ks Ka比值。结果基因系统树显示中国的 3 4份样本CRF0 1 AE重组型毒株与我国代表株AE .97CNGX2F和泰国代表株AE .CM 2 40、AE .93TH2 53聚集在一起。氨基酸替换主要发生在C3和V4区 ,而V3区和V3上游区氨基酸序列相对保守 ,糖基化位点也比较保守。V 3环顶端四肽以GPGQ为主 (87.50 % )。大部分毒株的第 3 0 6和 3 2 0位点上没有出现带正电荷的氨基酸。整个V 3～V4区的Ks值显著高于Ka值(P <0 .0 0 1) ,且Ks Ka比值显著高于 1(P <0 .0 0 1) ,只有V4区Ks Ka比值显著低于 1(P <0 .0 1)。结论　目前多数流行于中国的CRF0 1 AE重组型HIV 1毒株具有较高的同源性 ,在进化上关系密切。氨基酸替换主要发生在C3和V4区 ,而不是V3区。由于大部分毒株的第 3 0 6和 3 2 0位点上没有出现带正电荷的

Study on the evolutionary pressure on the env gene of the human immunodeficiency virus type 1 CRF01-AE strains circulating in China

ObjectiveTo identify variations in the e nv gene of human immunodeficiency virus type 1(HIV-1) subtype CRF01-AE strains circulating in China and to elucidate the potential relationship between genetic variation and evolutionary pressure. Methods Fragments of the HIV-1 env gene were amplifie d by nested-polymerase chain reaction(n-PCR) from the whole blood of HIV-1 in fected individuals from four provinces in Southeast China (Guangdong, Hunan, Jia ngsu and Jiangxi). The PCR products were then directly sequenced by ABI 377 DN A sequencers. The sequences covering the env V3-V4 region of 34 HIV-1 subtype CRF01-AE strains were selected to analyse phylogenetic trees and amino acid mu tations. The accumulation of synonymous (Ks) and antonymous (Ka) substitutions a s well as Ks/Ka ratios were calculated using DIVERGE. Results Phylogenetic trees showed that the 34 HIV-1 s ubtype CRF01-AE strains from China clustered with the Chinese AE reference stra in (AE.97CNGX2F), as well as with the reference strains from Thailand (AE.CM240 and AE.93TH253). The amino acid sequences of the env V4 and C3 regions in the sa mples were highly variable, compared with those of V3 and V3-downstream regions . The V3 loop central motif in the majority ( 87.5 %) of the strains was GPGQ. The majority of strains did not contain positively charged amino acids at posit ions 306 and 320 in V3 loop. The N-linked glycosylation sites in the V3-V4 reg ion and flanking regions in these strains were relatively conserved. Analysis of the entire region showed that the mean Ks values were significantly higher tha n that of the Ka values ( P< 0.001 ), with the Ks/Ka significantly hig her than 1.0 ( P< 0.001 ).In contrast,the Ks/Ka ratio in the V4 region was significantly lower than 1.0 ( P< 0.01 ). ConclusionsOur study indicated that the majority of HIV -1 subtype CRF01-AE strains circulating in China were highly homogeneous. The amino acid sequences of the V4 and C3 regions were significantly more variable than those of the V3 loop. Our analysis also suggested that the phenotype of nea rly all strains was likely to be non-syncytium inducing (NSI). Finally, the var iation found in the V3-V4 sequence was significantly influenced by functional c onstraints as opposed to positive selective pressure, while the variability of t he lone V4 region was strongly related to positive selective pressure.