HIV PATHOGENESIS: DIFFERENTIAL EFFECTS ON LYMPHOCYTE SUBSETS

人类免疫缺陷病毒(HIV)在Th2和Th0细胞中优先于Th1细胞复制的现象最近被认为发生在艾滋病的发生发展过程中。为了解决这个问题，我们用不同的HIV分离株感染了来自不同正常献血者的人类T辅助(Th)克隆，并检查了HIV融合、进入和传染性方面的所有差异。我们的研究表明，人类T细胞和抗原特异的T细胞克隆在其表面表达多种趋化因子受体，这些受体介导T细胞的运输、脱颗粒和细胞内钙动员，并作为辅助受体介导HIV-1进入这些细胞群。然而，尽管趋化因子受体的表达存在这些差异，我们的研究表明，人类Th0、Th1和Th2克隆都能够感染不同的T-、M-和双嗜性HIV-1毒株。感染HIV-1的Th1克隆在体外表现出快速(1-5天)的Fas介导的细胞凋亡，而感染Th2克隆(4-21天)。HIV-1感染后Th1细胞表面Fas配体表达增加，而Th2细胞表面Fas配体表达增加，这可能是导致这一CD4+T细胞亚群更替较快的原因。进一步研究人类Th1和Th2克隆之间的各种凋亡信号差异，发现大多数人Th1而不是Th2细胞对激活诱导的细胞死亡(AICD)敏感。此外，大多数人类Th1克隆几乎不表达bcl2和bclxl(抗凋亡蛋白)，这使得它们更容易受到各种凋亡刺激以及HIV-1介导的细胞死亡。相比之下，人类Th2克隆表达更高水平的bcl2和bclxl，并被发现较不容易受到细胞凋亡和HIV-1介导的细胞病变的影响。因此，对表达bclT细胞免受HIV诱导的细胞死亡的保护表明，细胞凋亡不仅有助于HIV感染导致细胞死亡，而且可能允许选择性地破坏外周Th1细胞，导致循环中Th2样淋巴细胞的增加。Th1克隆对HIV介导的细胞死亡的易感性增加，这表明HIV诱导艾滋病免疫抑制的一个主要机制。我们的研究发现，Th1和Th2克隆在某些细胞表面趋化因子受体的表达上也存在差异，这可能是Th亚群易感性增加的原因。我们认为Th0-Th1向Th2的转换发生在许多慢性炎症性疾病以及衰老过程中。我们认为，与来自年轻捐献者的淋巴细胞相比，来自老年人外周血的CD4+T辅助细胞和克隆在没有任何外源性细胞因子影响的情况下，可能更容易发生嗜T细胞的HIV-1感染。临床免疫科将尝试直接研究这一问题。该项目的目标是进一步确定T细胞、单核细胞和双嗜性HIV-1在来自年轻和老年捐赠者的T细胞以及人类Th1和Th2克隆中的复制差异。T细胞对HIV-1感染性的易感性与细胞凋亡之间的关系将通过使用各种细胞因子(如IGF1、IL-4)和信号抑制剂(如caspase和激酶抑制剂)来阻止HIV-1的感染性而进一步研究。最后，我们将研究HIV-1及其糖蛋白对病毒相互作用和T淋巴细胞感染性的信号和基因表达要求。-艾滋病毒、趋化因子、老年人、T细胞、Th1、Th2、辅受体

The preferential replication of HIV in Th2 and Th0 cells over Th1 cells has been recently proposed to occur during the development of AIDS. To address this question, we have infected human T helper (Th) clones, developed from different normal donors, with different HIV isolates and examined all differences in HIV fusion, entry, and infectivity. Our studies has demonstrated that human T cells and antigen-specific T cell clones express significant levels of several chemokine receptors on their surface which mediate T-cell trafficking, degranulation, and intracellular calcium mobilization as well as serving as co-receptors mediating HIV-1 entry into these cell populations. However, despite these differences in chemokine receptor expression, our studies have demonstrated that human Th0, Th1, and Th2 clones are all capable of being infected with the various T-, M-, and dual-tropic HIV-1 strains. HIV-1-infected Th1 clones exhibit a rapid (1-5 day) Fas-mediated apoptosis in vitro compared to infected Th2 clones (4-21 days). The increased expression of Fas ligand on the surface of Th1 but not Th2 clones post HIV-1 infection may possibly explain the more rapid turnover of this CD4+ T cell subset. Further examination of the various apoptotic-signaling differences between human Th1 and Th2 clones revealed that the majority of human Th1 but not Th2 cells are susceptible to activation-induced cell death (AICD). In addition, the majority of human Th1 clones expressed little to no bcl-2 and bcl-xl (anti-apoptotic proteins) making them more susceptible to various apoptotic stimuli as well as HIV-1-mediated cell death. In contrast, human Th2 clones express higher levels of bcl-2 and bcl-xl and were found to be less susceptible to apoptosis and HIV-1-mediated cytopathic effects. Thus, the protection of bcl-expressing T cells from HIV- induced cell death suggests that apoptosis not only contributes to cell killing by HIV infection but may also permit the selective destruction of Th1 cells in the periphery leading to an increase in circulating Th2-like lymphocytes. This increased susceptibility of Th1 clones to HIV-mediated cell death suggests a major mechanism for HIV-induced immunosuppression in AIDS. Our findings that Th1 and Th2 clones also differ in the expression of certain cell surface chemokine receptor may account for the increased susceptibility of Th subsets. We believe that a Th0-Th1 to Th2 switch occurs during many chronic inflammatory disease as well as aging. We propose that CD4+ T helper cells and clones, without any exogenous influence from cytokines, derived from the peripheral blood of older individuals may be more permissive to T cell tropic HIV-1 infections compared to lymphocytes derived from younger donors. The Clinical Immunology Section will attempt to directly examine this question. The objective of the proposed project is to further define the differences in T cell-, monocyte-, and dual-tropic HIV-1 replication in T cells derived from young and old donors as well as in human Th1 and Th2 clones. The relationship between T cell susceptibility to HIV-1 infectivity and apoptosis will be further examined using various cytokines (i.e. IgF1, IL-4) and signaling inhibitor agents (ie caspase and kinase inhibitors) to hinder HIV-1 infectivity. Finally, we will examine the signaling and gene expression requirements of HIV-1 and its glycoproteins for virus interactions and infectivity of T lymphocytes. - HIV, Chemokines, Elderly, T cells, Th1, Th2, Co-Receptors