Enhanced CD4 down-modulation by late stage HIV-1 nef alleles is associated with increased env incorporation and viral replication
Enhanced CD4 down-modulation by late stage HIV-1 nef alleles is associated with increased env incorporation and viral replication
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DOI：
10.1074/jbc.m303679200
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发表时间：
2003-09-05
影响因子：
4.8
通讯作者：
Lama, J
中科院分区：
文献类型：
--
作者：
Argañaraz, ER;Schindler, M;Lama, J
三种病毒蛋白参与人类免疫缺陷病毒1型（HIV-1）感染细胞中CD4的下调。其潜在机制已被广泛研究。然而，这一现象的生理学相关性仍然知之甚少。为了解决CD4下调在体内HIV-1发病机制中的作用，我们对从7名HIV-1感染患者中分离的nef等位基因的功能特性进行了表征，这些患者要么处于艾滋病阶段（晚期等位基因），要么处于感染的无症状阶段（早期等位基因）。携带这些nef等位基因的HIV-1变异在CD4下调、病毒传染性和复制特性方面表现出显著差异。与携带早期nef等位基因的变异相比，携带晚期菌株的T细胞感染导致产生具有增强感染性的病毒颗粒。只有当病毒在具有高水平病毒受体的细胞中产生时，才能观察到这些传染性差异，这表明在CD4水平和Nef下调CD4并增强病毒传染性的能力之间存在功能联系。同样，在高CD4阳性细胞（包括原发性淋巴细胞）中，晚期nef等位基因在刺激HIV-1复制方面比早期nef等位基因明显更活跃，但在表达低水平CD4受体的细胞中则没有。单轮试验表明，在CD4水平高的靶细胞中评估时，晚期和早期菌株之间的传染性差异大大降低，这表明抑制作用发生在进入步骤。支持这一点的是，晚期神经等位基因增强的CD4下调调节与病毒颗粒中更高水平的包膜结合有关，这一现象可能解释了增强的传染性。我们的数据表明，在nef介导的CD4下调和CD4阳性淋巴细胞的复制增强之间存在机制联系。随着疾病的进展，选择具有增强下调CD4能力的HIV-1 Nef变异体。这些菌株有效地克服了CD4的有害影响，并在CD4阳性的原发性淋巴细胞中更积极地复制。这些结果强调了病毒诱导的CD4下调在HIV-1发病机制中的重要性。
Three viral proteins participate in the down-modulation of CD4 in human immunodeficiency virus type 1 (HIV-1)-infected cells. The underlying mechanisms have been extensively investigated. However, the physiological relevance of this phenomenon remains poorly understood. To address the role of CD4 down-modulation in HIV-1 pathogenesis in vivo, we have characterized the functional properties of nef alleles isolated from seven HIV-1-infected patients at either the stage of AIDS (late alleles) or during the asymptomatic phase of infection (early alleles). HIV-1 variants carrying these nef alleles showed striking differences in CD4 down-modulation, virus infectivity, and replication properties. Infection of T cells with late strains resulted in production of viral particles with enhanced infectivity, as compared with variants carrying early nef alleles. These differences in infectivity were observed only when viruses were produced in cells with high levels of the viral receptor, suggesting a functional link between CD4 levels and the ability of Nef to down-modulate CD4 and to enhance viral infectivity. Similarly, late nef alleles were substantially more active than early nef genes in stimulating HIV-1 replication in high CD4-positive cells, including primary lymphocytes, but not in cells expressing low levels of the CD4 receptor. Single-round assays showed that differences in infectivity between late and early strains are largely reduced when evaluated in target cells with high levels of CD4, suggesting that the inhibitory effect occurs at the entry step. Supporting this, enhanced CD4 down-modulation by late nef alleles was associated with higher levels of envelope incorporation into viral particles, a phenomenon that likely accounted for the augmented infectivity. Our data suggest a mechanistic link between the Nef-mediated CD4 down-modulation and the enhancement of replication in CD4-positive lymphocytes. As progression to disease occurs, HIV-1 Nef variants with enhanced ability to down-modulate CD4 are selected. These strains efficiently overcome the deleterious effects of CD4 and replicate more aggressively in CD4-positive primary lymphocytes. These results highlight the importance of the virus-induced CD4 down-modulation in HIV-1 pathogenesis.