Immunoregulatory networks and HIV pathogenesis

描述(申请人提供)：缺陷的CD4T细胞反应与HIV感染者的疾病进展有关，而导致这种功能障碍的机制尚不清楚。一个基本的问题是，CD4T细胞损伤是由于不可逆转的功能丧失，还是在抑制机制的控制下，这些抑制机制可能通过操纵调节通路而逆转。最近的发现提供了证据表明，HIV+受试者CD4功能的主要缺陷可能是可逆的：我们和其他人表明，程序性死亡1(PD-1)途径在体外T细胞功能障碍中发挥关键作用，并且在HIV感染者中，CD4T细胞上PD-1的表达与疾病进展有关。我们发表的报告(PI是第一作者之一)和本申请的初步数据表明，通过阻断PD-1与其配体PD-L1的相互作用，可以恢复CD4T细胞的增殖能力。此外，我们的初步数据显示，另一种抑制性受体CTLA-4的表达也是可逆性CD4T细胞功能障碍的标志。在这一应用中，我们建议阐明PD-1在HIV+受试者中HIV特异性CD4T细胞增殖受损中的作用。在目标1中，基于先前将CD4T细胞表达PD-1与CD4计数和病毒载量相关的结果，我们将首先评估HIV+受试者在疾病不同阶段CD4T细胞表达PD-1和CTLA-4的情况。为了确定不同水平的抑制分子表达对T细胞功能的影响，我们将使用定量RT-PCR和分选的HIV特异性CD4T细胞群来确定PD-1low和PD-1High病毒特异性CD4T细胞的表型和功能。鉴于肠道相关淋巴组织(GALT)的参与是HIV发病的核心，我们还将评估PD-1及其配体在肠道相关淋巴组织活检组织中的表达，并确定这些分子在不同细胞群和HIV感染细胞上的表达。在目标2中，我们将确定CD4T细胞功能障碍的逆转程度与两个参数之间是否存在相关性：疾病状态和抑制性受体的表达水平。初步数据与一个模型一致，在该模型中，一些PD-L1+APC亚群会吸收HIV抗原，并以一种抑制有效增殖的方式将其呈递给HIV特异性T细胞。在目标3中，我们将使用选择性耗尽法，确定HIV+受试者外周血中通过PD-1抑制CD4T细胞增殖的APC亚群，并确定当PD1配体存在于非抗原负载细胞(反式)或仅当其与抗原肽(在顺式)出现在同一细胞上时，PD1配体是否可以改变HIV特异性CD4T细胞的功能。我们之前的研究表明，在感染艾滋病毒的人中，免疫系统的细胞变得“筋疲力尽”。我们正在研究造成这种衰竭的机制，并寻找恢复艾滋病毒感染者正常免疫功能的方法。

DESCRIPTION (provided by applicant): Defective CD4 T cell responses are associated with disease progression in HIV-infected persons, and the mechanisms responsible for this dysfunction are poorly understood. A fundamental question is whether CD4 T cell impairment is due to an irreversible loss of functions or under control of inhibitory mechanisms that may be reverted by manipulation of regulatory pathways. Recent findings provide evidence that major defects in CD4 function in HIV+ subjects may be reversible: we and others showed that the Programmed Death 1 (PD-1) pathway plays a key role in T cell dysfunction in vitro, and that in persons with HIV infection, PD-1 expression on CD4 T cells is associated with disease progression. Our published report, for which the PI is the co-first author, and preliminary data in this application demonstrate that CD4 T cell proliferative capacity can be restored by blocking the interaction of PD-1 with its ligand PD-L1. In addition, our preliminary data show that expression of another inhibitory receptor, CTLA-4, is also a marker for reversible CD4 T cell dysfunction. In this application, we propose to elucidate the role of PD-1 in the impairment of HIV-specific CD4 T cell proliferation in HIV+ subjects. In Aim 1, building on previous results correlating PD-1 expression by CD4 T cells with CD4 count and viral load, we will first assess expression by CD4 T cells of PD-1 and CTLA-4 in HIV+ subjects at various stages of disease. To determine the effect of varying levels of inhibitory molecule expression on T cell function, we will use quantitative RT-PCR and sorted HIV-specific CD4 T cell populations to define the phenotypic and functional profile of PD-1low and PD-1high virus-specific CD4 T cells. Given that involvement of gut-associated lymphoid tissue (GALT) is central to HIV pathogenesis, we will also assess the expression of PD-1 and its ligands in biopsies of gut-associated lymphoid tissue, and identify these molecules on various cell populations and on HIV-infected cells. In Aim 2, we will determine whether there is a correlation between the degree to which CD4 T cell dysfunction can be reversed and two parameters: disease status, and level of expression of inhibitory receptors. Preliminary data are consistent with a model in which some PD-L1+ subsets of APCs take up HIV antigen and present it to HIV-specific T cells in a manner that inhibits efficient proliferation. In Aim 3, using selective depletion, we will identify APC subsets in peripheral blood of HIV+ subjects that inhibit CD4 T cell proliferation via PD-1, and determine whether PD1 ligand can alter HIV-specific CD4 T cell function when present on non-antigen-loaded cells (in trans) or only if presented on the same cell as antigenic peptide (in cis). Our previous studies have shown that cells of the immune system become "exhausted" in people infected with HIV. We are studying the mechanisms responsible for this exhaustion and looking for ways to restore normal immune function in HIV-infected persons.