Role of HLA-G on HIV Evasion of NK Cells

描述(申请人提供)：HIV-1通过减少细胞表面人类白细胞抗原A和B的表达来避免HIV抗原特异性细胞毒性T淋巴细胞(CTL)的破坏，这是触发CTL所必需的。然而，自然杀伤(NK)细胞可以摧毁缺乏MHC I类分子的细胞，因为这些分子抑制NK细胞的杀伤。尽管如此，NK细胞无法杀死感染艾滋病毒的细胞。我们的长期目标是确定HIV如何阻止NK细胞破坏受感染的细胞，即使NK细胞细胞毒反应的条件似乎是最佳的。NK细胞不能杀死HIV感染细胞的一种解释是感染细胞表面存在人类白细胞抗原-C和人类白细胞抗原E。然而，人类白细胞抗原-C和人类白细胞抗原-E只能阻止一部分NK细胞杀死感染艾滋病毒的细胞。缺乏NK细胞杀伤的另一种解释是HIV-1诱导活化的CD4+T细胞表达HLA-G。HL A-G可抑制NK细胞的细胞毒反应。这一建议的中心假设是，艾滋病毒通过诱导人类白细胞抗原G的表达来阻止NK杀死感染细胞和控制病毒复制。为了评估我们的目标，我们将确定在HIV感染的背景下，人类白细胞抗原-G细胞表面表达在丧失NK细胞功能中的作用，并剖析所需的信号事件。这将通过将小干扰(Si)RNA定向到HIV感染细胞中的HLA-G，并确定NK细胞被激活并在HLA-G表面表达减少的情况下杀死HIV感染细胞的能力来实现。我们还将确定HIV感染CD4+细胞诱导表面表达人类白细胞抗原-G的机制。最后，我们将确定HIV感染细胞分泌的可溶性HLA-G对NK细胞细胞毒反应的影响。这项研究的总体意义在于提供了对允许HIV对抗由MHC I类分子差异调节的细胞免疫反应的重要机制的洞察。

DESCRIPTION (provided by applicant): HIV-1 avoids destruction by HIV-antigen specific cytotoxic T-lymphocytes (CTL) by decreasing the cell surface expression of human leukocyte antigen (HLA)-A and HLA-B, which are needed to trigger CTL. Natural killer (NK) cells, however, can destroy cells lacking MHC class I molecules since these molecules inhibit NK cell killing. Despite this fact, NK cells are unable to kill HIV-infected cells. Our long-term objective is to determine how HIV prevents NK cells from destroying the infected cells, even though the conditions for the NK cell cytotoxic response appear optimal. One explanation for the inability of NK cells to kill HIV- infected cell is the presence of HLA-C and HLA-E on the infected cell surface. However, HLA-C and HLA-E only prevent a subset of NK cells from killing HIV-infected cells. Another explanation for the lack of NK cell killing is that HIV-1 induces the expression of HLA-G on activated CD4+ T-cells. HLA-G inhibits NK cell cytotoxic responses. The central hypothesis of this proposal is that HIV prevents NK from killing infected cells and controlling viral replication by inducing the expression of HLA-G. To evaluate our objective, we will determine the role of HLA-G cell surface expression, in the context of HIV infection, in disabling NK cell function, and to dissect the required signaling events. This will be accomplished by directing small interfering (si)RNA to HLA-G in HIV-infected cells, and determining the ability of NK cells to become activated and kill HIV-infected cells with decreased HLA-G surface expression. We will also determine the mechanisms by which HIV infection of CD4+ cells induces surface expression of HLA-G. Finally, we will determine the effect of soluble HLA-G secreted by HIV-infected cells on NK cell cytotoxic responses. The overall significance of this study is to provide insight into the mechanism important for allowing HIV to counter cellular immune responses that are differentially regulated by MHC class I molecules.