Defining the Pathogenesis of Immune Deficiency in Chronic HIV Infection

描述（由申请人提供）：本项目申请由克利夫兰免疫发病机制联盟（CLIC）的成员提交，该联盟由代表美国和加拿大10个学术和研究机构的一组研究人员组成，他们从事了三年多的协调研究工作，旨在揭示HIV感染导致进行性免疫缺陷的机制。这群经验丰富、杰出的研究人员利用互补的研究技能和资源，提出了一个跨学科的项目，包括四个项目，由两个核心协调和支持：行政核心，负责项目的整体协调和管理；标本采集核心，艾伦·兰迪，PI，负责确保肠道和淋巴结临床标本的持续供应，以支持项目研究者。这些项目包括一系列相互作用的研究平台，从基础实验室研究到实验动物模型再到转化项目，每个项目都旨在探索免疫激活驱动CD4+ T细胞耗竭和慢性HIV感染功能障碍的决定因素和机制。项目#1：旁观者激活驱动慢性HIV感染中的T细胞损失- pi: Michael M. Lederman, m.d., Scott F. Sieg博士- Case将验证在慢性HIV感染中，继发性淋巴组织中微生物TLR配体和常见γ链细胞因子的系统水平增加驱动中央记忆T细胞激活和周转的假设。项目#2:HIV感染中肠道屏障功能的丧失- Alan Levine博士将研究HIV感染中肠道粘膜的完整性，以记录微生物产物通过受损肠道增强易位的机制细节，我们认为这有助于慢性HIV感染中细胞损失的发病机制。项目#3:SIV感染的非人灵长类动物的免疫激活和艾滋病发病机制——宾夕法尼亚大学的Guido Silvestri医学博士将尝试通过激活先天免疫系统在非致病性SIV感染的黑白鹭中诱导疾病，并将测试阻断先天免疫激活是否会减轻感染的恒河猴的疾病发病机制。Rafick Pierre Sekaly博士-蒙特利尔大学，将通过HIV rna和TLR7/8之间的相互作用来研究先天免疫系统激活对PDL-1和2表达的作用及其对HIV反应性T细胞功能和存活的影响。

DESCRIPTION (provided by applicant): This program project application is submitted by the members of the Cleveland Immunopathogenesis Consortium (CLIC) a group of investigators representing 10 academic and research institutions in the United States and Canada who have engaged for more than three years in a coordinated research effort aimed at unraveling the mechanisms whereby HIV infection results in progressive immune deficiency. This group of experienced, outstanding investigators capitalizes on complementary research skills and resources and proposes an interdisciplinary program comprising 4 projects that are coordinated and supported by two cores: Administrative Core, charged with overall coordination and administration of the program and Specimen Acquisition Core, Alan Landay, PI, charged with assuring a sustained supply of clinical specimens of gut and lymph nodes to support project investigators. The projects comprise a series of interacting research platforms from basic laboratory research to experimental animal models to translational projects, each designed to explore the determinants and mechanisms whereby immune activation drives CD4+ T cell depletion and dysfunction in chronic HIV infection. Project #1: Bystander activation drives T cell losses in chronic HIV infection - PIs: Michael M. Lederman, M.D., Scott F. Sieg Ph.D. - Case, will test the hypothesis that increased systemic levels of microbial TLR ligands and common gamma chain cytokines in secondary lymphoid tissues drive central memory T cell activation and turnover in chronic HIV infection. Project #2: Loss of intestinal barrier function in HIV infection - Alan Levine, Ph.D. Case, will examine the integrity of the intestinal mucosa in HIV infection to document the mechanistic details underlying the enhanced translocation of microbial products through the damaged gut that we propose contributes to the pathogenesis of cell loss in chronic HIV infection. Project #3: Immune activation and AIDS pathogenesis in SIV-infected non-human primates - Guido Silvestri, M.D., Univ of Pennsylvania, will attempt to induce disease in non-pathogenic SIV infection of sooty mangabeys by activation of the innate immune system and will test whether blocking innate immune activation will attenuate disease pathogenesis in infected rhesus macaques. Project #4: Immune activation promotes PD1 expression and immune dysfunction in chronic HIV infection - Rafick Pierre Sekaly Ph.D. - Univ of Montreal, will examine the role of innate immune system activation through the interaction between HIV RNAs and TLR7/8 on the expression of PDL-1 and 2 and their effects on the function and survival of HIV reactive T cells. PROJECT 1: Bystander activation drives T cell losses in chronic HIV infection (Michael Lederman) PROJECT 1 DESCRIPTION (provided by applicant): Recent data from our collaborative group provide background for a new model of HIV pathogenesis that will be tested here. In this model, turnover of central memory (CM) CD4+ T cells is central to progressive cell losses of HIV infection. We propose that this is driven by interplay between indirect effects of HIV replication on the cytokine environment of secondary lymphoid tissues and in situ exposure to microbial TLR ligands translocated from the damaged gut. HIV replication is necessary but not sufficient to promote T cell turnover; microbial TLR ligands provide additional signals via two distinct mechanisms. First, they promote enhanced non-specific retention of effector CD8+ T cells in secondary lymphoid tissues by increasing expression of the C-type lectin CD69 that interferes with surface expression of sphingosine-1 phosphate receptors needed to permit exit of activated cells from lymph nodes. Sequestration of effector cells intensifies the cytokine "storm" in these tissues that results in explosive levels of common gamma chain receptor cytokines IL-2 and IL-15 that we have quantified at these sites. TLR ligands also activate CM T cells to lose characteristic resistance to death signals a resistance that is due to FOXO3a phosphorylation and inactivation. This results in heightened turnover and selective death of CM CD4+ T cells that drives the immune deficiency of HIV infection. Our aims are: 1) To characterize the intercellular interactions and mechanisms whereby selected TLR ligands and common gamma chain receptor cytokines promote activation of central memory CD4+ and CD8+ T cells. This will be achieved by detailing the specific ARC requirements for T cell activation, by exploring selected gene expression patterns for signals characteristic of cell cycle progression, apoptosis and survival and to use these results to identify the pathways that render CM T cells in HIV infection more susceptible to death signals. 2) To establish in vitro models for bystander T cell activation and sequestration after exposure to TLR ligands and common gamma chain receptor cytokines in secondary lymphoid tissues. This will be accomplished first by defining the model using peripheral blood mononuclear cells in suspension and then confirming the model in lymph node histoculture experiments. 3) To identify the proximate causes of immune activation in chronic HIV infection. We will determine the levels of selected microbial TLR agonists, HIV RNA and bacterial PGN, LPS and DNA in the plasma of chronically HIV infected persons. Based upon the results of SpAim 1 experiments, we will develop a panel of flow based reagents that will characterize the signatures of bystander T cell activation that will be applied to ex vivo analyses of blood, lymph node and gut lymphocytes in chronic HIV infection.