人类免疫缺陷病毒-1的核酸遗传学特点

Observation of gene heterogeneity and quasispecies of HIV-1

目的研究人类免疫缺陷病毒(HIV)-1膜蛋白基因(env)的准种与变异特点。方法采用套式聚合酶链反应(PCR)对5例艾滋病患者血浆HIV-1 env基因C2～V3区进行PCR扩增,产物经纯化后克隆至pMD-18T载体中,每例患者分别挑取5～8个克隆,共34株,完成阳性克隆的鉴定、抽提纯化和测序。将获得的DNA序列及核苷酸序列进行分析,并计算其核苷酸同源替换率(ds)与非同源替换率(dn)的比值。结果同一患者体内HIV准种株平均为83．5%,各克隆株之间的核苷酸同源性在88%～99%之间；不同患者之间的核苷酸同源性在75%～91%；34株序列的V3区平均变异频率明显高于C2～C3区(P＜0．05)；而V3区和C2～C3区的ds/dn比值均＞1。结论艾滋病患者体内有大量HIV准种存在．基因的变异在V3区发生较频繁,免疫选择压力在该区变异中不起主要作用。

Objective To investigate the HIV quasispeeies in the patients with AIDS. Methods Blood samples were obtained from 5 patients with AIDS, the C2～C3 region of HIV-1 envelope gene （env） was amplified by nested polymerse chain reaction（PCR） from plasma of each patient, and then subject to sequencing, clonal-quasispeeies analysis, and the accumulation of synonymous （ds） and nonsynonymous（dn） substitutions as well as ds/dn ratios were calculated. Results The average quasispeeies groups were 83.5% in each patient, the homology of the nucleic acid sequence from same patient and other patients were 88%～99% and 75%～91% respectively, further sequence analysis on env clones for each patients showed significantly greater HIV mutation frequencies in V3 than C2～C3 region（P 〈0.05） ; the ds/dn ratio in the V3 and C2～C3 region are higher than 1.0. Conclusions There are HIV quasispeeies groups in AIDS patients. The mutation always occurred in V3 region, but the variability of the V3 region may be not related to immune selective pressure.