Mechanisms of HIV-associated Gut T Cell Depletion

描述(由申请人提供)：HIV-1在感染早期在肠道相关淋巴组织(GALT)中复制导致粘膜效应CD4+T细胞，特别是产生IL-17的CD4+T细胞(Th17)大量耗尽。Th17细胞的耗尽会导致细菌从管腔移位到固有层(LP)，随后导致循环，这一过程与免疫激活和炎症有关。因此，了解HIV-1如何诱导GalT CD4+T细胞死亡可能是预防HIV-1感染的炎性后遗症的关键。然而，HIV-1杀死CD4+T细胞的机制仍然是基础HIV/AIDS研究中最关键的未解问题之一。尽管已发表了大量关于这一主题的研究，但大多数先前的CD4+T细胞杀伤研究使用的是X4嗜性HIV-1毒株和细胞类型，这些毒株和细胞类型与了解粘膜间隔中的CD4+T细胞耗尽没有直接关系。为了解决这个问题，我们最近开发了一个新的实验系统，使用原代肠道粘膜细胞来模拟R5嗜性HIV-1、微生物物种和LP CD4+Th细胞亚群之间的相互作用。因此，我们的合作团队处于独特的位置来解决HIV-1粘膜免疫发病机制中的以下关键知识空白：1.R5嗜性HIV-1如何导致GalT CD4+T细胞死亡？2.肠道细菌移位如何影响HIV介导的GalT CD4+T细胞杀伤？3.哪些病毒决定因素介导了传播/创始HIV-1毒株的GalT CD4+T细胞死亡？使用我们的动态体外LP感染模型，我们提出了三个具体目标来解决这些重要问题。在目标1中，我们将利用差异标记的HIV-1感染和未感染细胞来研究PCD通路在HIV-1介导的CD4+T细胞死亡中的作用，方法是抑制caspase活性，在其生命周期的不同阶段抑制HIV-1，并使用无偏见的基因表达谱。在目标2中，我们将确定具有代表性的肠道细菌单独和联合对HIV-1介导的LP CD4+T细胞死亡的生物学影响，并确定影响CD4+T细胞耗竭的细菌的免疫调节特性。在目标3中，我们将记录一组40个传播/创建者和慢性HIV-1 B和C亚型感染性分子克隆的复制和杀伤特征，以确定导致LP CD4+T细胞死亡的病毒特征。这些研究的结果可能最终提供对途径的洞察，这些途径可以有针对性地维持或恢复艾滋病毒感染患者的粘膜免疫系统的完整性，从而限制全身炎症及其下游后果。

DESCRIPTION (provided by applicant): HIV-1 replication in gut-associated lymphoid tissue (GALT) in the early stages of infection results in massive depletion of mucosal effector CD4+ T cells, in particular IL-17-producing CD4+ T cells (Th17). Depletion of Th17 cells leads to bacterial translocation from the lumen into the lamina propria (LP) and subsequently the circulation, a process associated with increased immune activation and inflammation. Thus, understanding how HIV-1 induces GALT CD4+ T cell death may be key to preventing the inflammatory sequelae of HIV- 1 infection. However, the mechanism by which HIV-1 kills CD4+ T cells remains one of the most critical unanswered questions in basic HIV/AIDS research. Despite extensive published studies on the subject, most prior CD4+ T cell killing studies utilized X4-tropic HIV-1 strains and cell types that are not directly relevant to understanding CD4+ T cell depletion in mucosal compartments. To address this issue, we recently developed a novel experimental system to model the interactions between R5-tropic HIV-1, microbial species and LP CD4+ Th cell subsets ex vivo using primary intestinal mucosal cells. Thus, our collaborative team is in a unique position to address the following critical knowledge gaps in HIV-1 mucosal immunopathogenesis: 1. How does R5-tropic HIV-1 cause GALT CD4+ T cell death? 2. How do translocating enteric bacteria influence HIV-mediated GALT CD4+ T cell killing? 3. Which viral determinants mediate GALT CD4+ T death by transmitted/founder HIV-1 strains? Using our dynamic ex vivo LP infection model, we propose three specific aims to address these important questions. In Aim 1, we will utilize differentially-labeled HIV-1 infected and uninfected cells to investigate the role of PCD pathways in HIV-1 mediated CD4+ T cell death by counteracting caspase activity, inhibiting HIV-1 at discrete steps in its life cycle, and using non-biased gene expression profiling. In Aim 2, we will determine the biological impact of representative gut bacterial species individually, and in combination, on HIV-1 mediated LP CD4+ T cell death and identify the immunomodulatory properties of bacteria that influence CD4+ T cell depletion. In Aim 3, we will document the replication and killing characteristics of a panel of 40 Transmitted/Founder and chronic HIV-1 Subtype B and C infectious molecular clones, to define the viral characteristics responsible for LP CD4+ T cell death. The results of these studies may ultimately provide insight into pathways that can be targeted to preserve or restore the integrity of the mucosal immune system in HIV- infected patients and thereby limit systemic inflammation and its downstream consequences.