Gut Homing Cells in SIV infection

描述（由申请人提供）：急性HIV/SIV期间，肠道相关淋巴组织（GALT）内CD4+ T细胞大量耗损，随后慢性感染期间持续CD4+ T细胞损失，导致GALT和上覆粘膜上皮的进行性损伤。随着时间的推移，这些事件会导致免疫功能障碍、病毒载量和疾病进展速度。CD4+ T细胞通过GALT内产生的信号转运到GALT，其中包括视黄酸的释放，这反过来又导致了？4?的上调。7整合素和CCR9在细胞表面。表达？4？7和CCR9通过与它们的同源受体MAdCAM和CCL25相互作用选择性地回到GALT上，这些受体由肠壁上皮细胞表达。最近的数据显示？7除了作为归巢受体外，还作为许多HIV和SIV毒株的替代受体，这些毒株的V1/V2 env片段具有识别4？7 .类似于MAdCAM的天然配体。此外，位于V1/V2和V3/C4 env区域的序列含有残基，如果去糖基化，可以显著增强病毒与病毒结合的亲和力。这样4 ?高亲和力结合HIV-1被认为优先通过粘膜途径传播。我们的实验室最近表明，给药一种初始化的抗？？7 mAb，在急性静脉和直肠内SIV感染之前和期间，导致GALT中的病毒载量显著降低，并首次提供了详细检查急性感染期间发生的事件的工具。本文提出的研究旨在：1)通过确定是否？a)经阴道感染的动物，b) SIV感染后，c)低重复剂量经阴道感染以模拟自然传播，d) CCR9的小分子抑制剂单独使用或与？7单抗治疗可更有效、更持久地控制高尔特病毒血症；2)定义肠道组织的组织病理学分析，重点描述蛋白质在维持肠道组织完整性中的作用，定义细菌易位动力学和肠道组织通透性的生理测量；3)确定所涉及的机制？a)通过决定是否？7 mAb通过阻断？4?受体功能介导其作用。或者通过阻止？4？通过使用重组复制的SIV环境构建物来表达细胞，这些构建物可以结合或不结合？7、b)通过测定体内抗- 4？使用wt和重组env去糖基化SHIV结合的方法对env糖基化水平有影响。7低v/s高亲和力，c)确定病毒和CD4+细胞的组织/器官定位；使用我们实验室开发的最新优化的实时“LIVE”PET-CT扫描技术管理7只动物。认识到有效的HIV疫苗不仅需要引起广泛的中和抗体和有效的病毒特异性CTL，而且意味着预防与疾病进展密切相关的GALT损伤，突出了这些研究的重要性。

DESCRIPTION (provided by applicant): The massive depletion of CD4+ T cells within the gut associated lymphoid tissues (GALT) during acute HIV/SIV followed by sustained CD4+ T cell loss during chronic infection leads to progressive damage to the GALT and the overlying mucosal epithelium. These events contribute to immune dysfunction, viral loads and the rate of disease progression over time. The CD4+ T cells traffic to the GALT by signals generated within the GALT which include the release of retinoic acid which in turn leads to upregulation of the ?4?7 integrin and CCR9 on the cell surface. Cells expressing ?4?7 and CCR9 selectively home to the GALT by interacting with their cognate receptors MAdCAM and CCL25 expressed by epithelial cells lining the intestinal wall. Recent data show that ?4?7, besides serving as the homing receptor, also serves as an alternate receptor for many strains of HIV and SIV whose V1/V2 env segments have recognition 'motifs' for ?4?7 similar to MAdCAM its natural ligand. In addition, sequences localized to the V1/V2 and V3/C4 env region contain residues which, if deglycosylated, markedly enhance the affinity of the virus to bind ?4?7. Such ?4?7 high affinity binding HIV-1 is thought to be preferentially transmitted via the mucosal route. Our lab has recently shown that the administration of a primatized anti??4?7 mAb, just prior to and during acute IV and intra-rectal SIV infection, leads to markedly reduced viral loads in the GALT and provides, for the first time, tools to examine in detail the events that occur during acute infection. The studies proposed herein are aimed at: 1) determining the clinical utility of these previous findings by determining if ?4?7 administration is effective in lowering GALT viral loads in animals a) infected intravaginally, b) post SIV infection, c) infected with low repeated doses intravaginally to mimic natural transmission, and d) if a small molecule inhibitor of CCR9 alone or with ?4?7 mAb administration leads to more effective and prolonged control of GALT viremia; 2) defining the histopathological analysis of the gut tissues with a focus on delineating the role of proteins involved in maintaining gut tissue integrity, defining the kinetics of bacteril translocation and the physiologic measurement of gut tissue permeability; and 3) determining the mechanisms involved by which ?4?7 induces its effect a) by determining whether ?4?7 mAb mediates its effect via blocking the receptor function of the ?4?7 or by blocking the trafficking of ?4?7 expressing cells by using recombinant replication competent SIV env constructs that do or do not bind ?4?7, b) by determining whether the in vivo effect of anti-??4?7 treatment is influenced by the level of env glycosylation using W.T. & recombinant env deglycosylated SHIV's that bind ?4?7 with low v/s high affinity, c) determine the tissue/organ localization of virus and CD4+ cells in the control and ?4?7 administered animals using a newly optimized real time "LIVE" PET-CT scanning technique developed by our lab. The realization that effective HIV vaccines require to elicit not only broad neutralizing Abs and effective virus specific CTL's but also means to prevent GALT injury which is intimately associated with disease progression, highlight the importance of these studies. PUBLIC HEALTH RELEVANCE: Both the HIV/SIV appear to use ?4?7, a molecule expressed by CD4+ T cells as an alternate co- receptor. Our lab has used a monoclonal antibody against the ?4?7 molecule and shown that treatment of monkeys prior to and during the acute intravenous infection period with the monoclonal antibody leads to a marked reduction in viral loads in the gastrointestinal tract. We propose to carry out more detailed studies aimed at defining the clinical use of these initial findings to determine if we can "blunt" the initial gastrointestinal tract pathology which will greatly enhance our understanding of the pathogenic mechanisms involved during acute infection.