Immunoregulatory networks and HIV pathogenesis

描述（由申请人提供）：缺陷性CD 4 T细胞应答与HIV感染者的疾病进展相关，并且对这种功能障碍的机制知之甚少。一个基本的问题是CD 4 T细胞损伤是否是由于功能的不可逆丧失或抑制机制的控制下，可以通过操纵调节途径恢复。最近的研究结果提供了证据表明，HIV+受试者中CD 4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细胞功能障碍中起着关键作用，并且在HIV感染者中，CD 4 T细胞上的PD-1表达与疾病进展相关。我们发表的报告（PI是其共同第一作者）和本申请的初步数据表明，CD 4 T细胞增殖能力可以通过阻断PD-1与其配体PD-L1的相互作用来恢复。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CD 4 T细胞功能障碍的标志物。在本申请中，我们建议阐明PD-1在HIV+受试者中HIV特异性CD 4 T细胞增殖受损中的作用。在目的1中，基于先前将CD 4 T细胞的PD-1表达与CD 4计数和病毒载量相关联的结果，我们将首先评估HIV+受试者在不同疾病阶段的PD-1和CTLA-4的CD 4 T细胞表达。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CD 4 T细胞群来确定PD-1 low和PD-1high病毒特异性CD 4 T细胞的表型和功能特征。鉴于肠道相关淋巴组织（GALT）的参与是HIV发病机制的核心，我们还将评估PD-1及其配体在肠道相关淋巴组织活检中的表达，并在各种细胞群和HIV感染细胞上鉴定这些分子。在目标2中，我们将确定CD 4 T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，其中一些PD-L1+ APC亚群摄取HIV抗原并以抑制有效增殖的方式将其呈递给HIV特异性T细胞。在目的3中，使用选择性去除，我们将鉴定HIV+受试者外周血中通过PD-1抑制CD 4 T细胞增殖的APC亚群，并确定PD 1配体是否可以改变HIV特异性CD 4 T细胞功能，当其存在于非抗原负载细胞上时（反式）或仅当其作为抗原肽存在于同一细胞上时（顺式）。 我们以前的研究表明，感染艾滋病毒的人的免疫系统细胞变得“疲惫不堪”。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.