Ruggiero Eliana, Bona Roberta, Muratori Claudia, Federico Maurizio
Division of Pathogenesis of Retroviruses, National AIDS Center, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy.
J Virol. 2008 Aug;82(16):7773-89. doi: 10.1128/JVI.00695-08. Epub 2008 May 28.
Human immunodeficiency virus type 1 (HIV-1)-infected cells transmit viral products to uninfected CD4(+) cells very rapidly. However, the natures of the transmitted viral products and the mechanism of transmission, as well as the relative virological consequences, have not yet been fully clarified. We studied the virological events occurring a few hours after contact between HIV-1-infected and uninfected CD4(+) cells using a coculture cell system in which the virus expression in target cells could be monitored through the induction of a green fluorescent protein reporter gene driven by HIV-1 long terminal repeats. Within 16 h of coculture, we observed two phenomena not related to the cell-free virus infection, i.e., the formation of donor-target cell fusions and a fusion-independent internalization of viral particles likely occurring at least in part through intercellular connections. Both events depended on the expression of Env and CD4 in donor and target cells, respectively, whereas the HIV-1 internalization required clathrin activity in target cells. Importantly, both phenomena were also observed in cocultures of primary CD4(+) lymphocytes, while primary macrophages supported only HIV-1 endocytosis. By investigating the virological consequences of these events, we noticed that while fused cells released infectious HIV-1 particles, albeit with reduced efficiency compared with donor cells, no virus expression was detectable upon HIV-1 endocytosis in target cells. In sum, the HIV-1 transmission following contact between an HIV-1-infected and an uninfected CD4(+) cell can occur through different mechanisms, leading to distinguishable virological outcomes.
1型人类免疫缺陷病毒（HIV-1）感染的细胞会非常迅速地将病毒产物传递给未感染的CD4(+)细胞。然而，所传递的病毒产物的性质、传递机制以及相关的病毒学后果尚未完全阐明。我们使用一种共培养细胞系统研究了HIV-1感染细胞与未感染的CD4(+)细胞接触后数小时内发生的病毒学事件，在该系统中，可通过由HIV-1长末端重复序列驱动的绿色荧光蛋白报告基因的诱导来监测靶细胞中的病毒表达。在共培养的16小时内，我们观察到两种与无细胞病毒感染无关的现象，即供体-靶细胞融合的形成以及病毒颗粒的不依赖融合的内化，这种内化可能至少部分通过细胞间连接发生。这两种事件分别依赖于供体细胞和靶细胞中Env和CD4的表达，而HIV-1的内化需要靶细胞中的网格蛋白活性。重要的是，在原代CD4(+)淋巴细胞的共培养中也观察到了这两种现象，而原代巨噬细胞仅支持HIV-1的内吞作用。通过研究这些事件的病毒学后果，我们注意到虽然融合细胞释放出有感染性的HIV-1颗粒，尽管与供体细胞相比效率有所降低，但在靶细胞中HIV-1内吞后未检测到病毒表达。总之，HIV-1感染的CD4(+)细胞与未感染的CD4(+)细胞接触后的HIV-1传递可通过不同机制发生，导致可区分的病毒学结果。
