The Microvesicle Component of HIV-1 Inocula Modulates Dendritic Cell Infection and Maturation and Enhances Adhesion to and Activation of T Lymphocytes

HIV-1 is taken up by immature monocyte derived dendritic cells (iMDDCs) into tetraspanin rich caves from which the virus can either be transferred to T lymphocytes or enter into endosomes resulting in degradation. HIV-1 binding and fusion with the DC membrane results in low level de novo infection that can also be transferred to T lymphocytes at a later stage. We have previously reported that HIV-1 can induce partial maturation of iMDDCs at both stages of trafficking. Here we show that CD45+ microvesicles (MV) which contaminate purified HIV-1 inocula due to similar size and density, affect DC maturation, de novo HIV-1 infection and transfer to T lymphocytes. Comparing iMDDCs infected with CD45-depleted HIV-1BaL or matched non-depleted preparations, the presence of CD45+ MVs was shown to enhance DC maturation and ICAM-1 (CD54) expression, which is involved in DC∶T lymphocyte interactions, while restricting HIV-1 infection of MDDCs. Furthermore, in the DC culture HIV-1 infected (p24+) MDDCs were more mature than bystander cells. Depletion of MVs from the HIV-1 inoculum markedly inhibited DC∶T lymphocyte clustering and the induction of alloproliferation as well as limiting HIV-1 transfer from DCs to T lymphocytes. The effects of MV depletion on these functions were reversed by the re-addition of purified MVs from activated but not non-activated SUPT1.CCR5-CL.30 or primary T cells. Analysis of the protein complement of these MVs and of these HIV-1 inocula before and after MV depletion showed that Heat Shock Proteins (HSPs) and nef were the likely DC maturation candidates. Recombinant HSP90α and β and nef all induced DC maturation and ICAM-1 expression, greater when combined. These results suggest that MVs contaminating HIV-1 released from infected T lymphocytes may be biologically important, especially in enhancing T cell activation, during uptake by DCs in vitro and in vivo, particularly as MVs have been detected in the circulation of HIV-1 infected subjects.

HIV-1可被未成熟单核细胞衍生树突状细胞（immature monocyte derived dendritic cells, iMDDCs）通过富含四跨膜蛋白的膜窖摄取，病毒可从此处转移至T淋巴细胞，或进入内体后被降解。HIV-1结合并融合DC细胞膜可引发低水平的从头感染（de novo infection），该感染也可在后续阶段转移至T淋巴细胞。本团队此前曾报道，HIV-1在转运的两个阶段均可诱导iMDDCs发生部分成熟。本研究显示，因尺寸与密度相似而污染纯化HIV-1接种物的CD45+微囊泡（microvesicles, MV），会对DC成熟、HIV-1从头感染以及向T淋巴细胞的转移产生影响。对比用CD45耗竭的HIV-1BaL与匹配的未耗竭制备物感染的iMDDCs，结果证实CD45+ MVs的存在可增强DC成熟与细胞间黏附分子-1（intercellular adhesion molecule 1, ICAM-1, CD54）的表达——后者参与DC与T淋巴细胞的相互作用——同时抑制MDDCs的HIV-1感染。此外，在DC培养体系中，被HIV-1感染（p24阳性）的MDDCs较旁观者细胞更为成熟。从HIV-1接种物中耗竭MV可显著抑制DC与T淋巴细胞的聚集以及同种增殖反应的诱导，同时限制HIV-1从DC向T淋巴细胞的转移。向耗竭了MV的体系中重新添加从活化而非非活化的SUPT1.CCR5-CL.30细胞或原代T细胞中纯化得到的MV，可逆转MV耗竭对上述功能的影响。对这些MV以及MV耗竭前后的HIV-1接种物的蛋白质组分进行分析后发现，热休克蛋白（Heat Shock Proteins, HSPs）与Nef可能是介导DC成熟的候选因子。重组HSP90α、HSP90β以及Nef均可诱导DC成熟与ICAM-1的表达，联合使用时诱导效果更强。上述结果表明，从受感染T淋巴细胞中释放的、污染HIV-1的MV可能具有重要的生物学功能，尤其是在DC体外与体内摄取过程中可增强T细胞活化；鉴于已在HIV-1感染受试者的循环系统中检测到MV，该效应的生理意义尤为突出。