Sterjovski Jasminka, Churchill Melissa J, Ellett Anne, Gray Lachlan R, Roche Michael J, Dunfee Rebecca L, Purcell Damian F J, Saksena Nitin, Wang Bin, Sonza Secondo, Wesselingh Steven L, Karlsson Ingrid, Fenyo Eva-Maria, Gabuzda Dana, Cunningham Anthony L, Gorry Paul R
Macfarlane Burnet Institute for Medical Research & Public Health, Melbourne, Victoria, Australia.
Retrovirology. 2007 Dec 12;4:89. doi: 10.1186/1742-4690-4-89.
CCR5-restricted (R5) human immunodeficiency virus type 1 (HIV-1) variants cause CD4+ T-cell loss in the majority of individuals who progress to AIDS, but mechanisms underlying the pathogenicity of R5 strains are poorly understood. To better understand envelope glycoprotein (Env) determinants contributing to pathogenicity of R5 viruses, we characterized 37 full-length R5 Envs from cross-sectional and longitudinal R5 viruses isolated from blood of patients with asymptomatic infection or AIDS, referred to as pre-AIDS (PA) and AIDS (A) R5 Envs, respectively.
Compared to PA-R5 Envs, A-R5 Envs had enhanced fusogenicity in quantitative cell-cell fusion assays, and reduced sensitivity to inhibition by the fusion inhibitor T-20. Sequence analysis identified the presence of Asn 362 (N362), a potential N-linked glycosylation site immediately N-terminal to CD4-binding site (CD4bs) residues in the C3 region of gp120, more frequently in A-R5 Envs than PA-R5 Envs. N362 was associated with enhanced fusogenicity, faster entry kinetics, and increased sensitivity of Env-pseudotyped reporter viruses to neutralization by the CD4bs-directed Env mAb IgG1b12. Mutagenesis studies showed N362 contributes to enhanced fusogenicity of most A-R5 Envs. Molecular models indicate N362 is located adjacent to the CD4 binding loop of gp120, and suggest N362 may enhance fusogenicity by promoting greater exposure of the CD4bs and/or stabilizing the CD4-bound Env structure.
Enhanced fusogenicity is a phenotype of the A-R5 Envs studied, which was associated with the presence of N362, enhanced HIV-1 entry kinetics and increased CD4bs exposure in gp120. N362 contributes to fusogenicity of R5 Envs in a strain dependent manner. Our studies suggest enhanced fusogenicity of A-R5 Envs may contribute to CD4+ T-cell loss in subjects who progress to AIDS whilst harbouring R5 HIV-1 variants. N362 may contribute to this effect in some individuals.
CCR5限制型（R5）1型人类免疫缺陷病毒（HIV-1）变体在大多数进展为艾滋病的个体中导致CD4+T细胞损失，但R5毒株致病性的潜在机制仍知之甚少。为了更好地理解包膜糖蛋白（Env）决定因素对R5病毒致病性的影响，我们对37种全长R5 Env进行了特征分析，这些R5 Env分别来自无症状感染患者或艾滋病患者血液中分离出的横断面和纵向R5病毒，分别称为艾滋病前期（PA）和艾滋病期（A）R5 Env。
与PA-R5 Env相比，A-R5 Env在定量细胞-细胞融合试验中具有增强的融合活性，并且对融合抑制剂T-20抑制作用的敏感性降低。序列分析发现在gp120的C3区域中，紧邻CD4结合位点（CD4bs）残基N端的潜在N-糖基化位点Asn 362（N362）在A-R5 Env中比在PA-R5 Env中更频繁出现。N362与增强的融合活性、更快的进入动力学以及Env假型报告病毒对CD4bs导向的Env单克隆抗体IgG1b12中和作用的敏感性增加有关。诱变研究表明N362有助于大多数A-R5 Env增强融合活性。分子模型表明N362位于gp120的CD4结合环附近，并提示N362可能通过促进CD4bs更大程度的暴露和/或稳定CD4结合的Env结构来增强融合活性。
增强的融合活性是所研究的A-R5 Env的一种表型，这与N362的存在、HIV-1进入动力学增强以及gp120中CD4bs暴露增加有关。N362以毒株依赖的方式促进R5 Env的融合活性。我们的研究表明，A-R5 Env融合活性增强可能导致携带R5 HIV-1变体并进展为艾滋病的个体中CD4+T细胞损失。N362可能在某些个体中导致这种效应。
