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，其中包括维甲酸的释放，维甲酸的释放反过来导致细胞表面α4ß7整合素和CCR9的上调。表达α4ß7和CCR9的细胞通过与肠壁上皮细胞表达的同源受体MAdCAM和CCL25相互作用，选择性地返回到GALT。最近的数据表明，α4ß7除了作为归家受体外，还可以作为许多HIV和SIV毒株的替代受体，这些毒株的V1/V2 env片段具有识别α4ß7的“基元”，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，可以显著增强病毒结合α4ß7的亲和力。这种α4ß7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，在急性静脉和直肠内SIV感染之前和期间施用一种初始化的抗α4ß7单抗，可显著降低GALT中的病毒载量，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α4ß7给药是否有效降低动物体内的GALT病毒载量来确定这些先前发现的临床效用a)阴道感染，b) SIV感染，c)低重复剂量阴道感染以模拟自然传播，以及d)单独使用CCR9小分子抑制剂或与α4ß7单抗一起给药是否能更有效和更持久地控制GALT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α4ß7诱导其作用所涉及的机制a)确定α4ß7单抗是通过阻断α4ß7的受体功能，还是通过使用能够或不能够结合α4ß7的重组复制能力SIV环境构建体阻断表达α4ß7的细胞运输来介导其作用。b)利用W.T.和重组env去糖基化SHIV's以低v/s高亲和力结合α4ß7，确定抗α4ß7治疗的体内效果是否受env糖基化水平的影响；c)利用本实验室开发的最新优化的实时“LIVE”PET-CT扫描技术，确定对照组和α4ß7给药动物中病毒和CD4+细胞的组织/器官定位。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 α4ß7 integrin and CCR9 on the cell surface. Cells expressing α4ß7 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 α4ß7, 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 α4ß7 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 α4ß7. Such α4ß7 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-α4ß7 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 α4ß7 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 α4ß7 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 α4ß7 induces its effect a) by determining whether α4ß7 mAb mediates its effect via blocking the receptor function of the α4ß7 or by blocking the trafficking of α4ß7 expressing cells by using recombinant replication competent SIV env constructs that do or do not bind α4ß7, b) by determining whether the in vivo effect of anti-α4ß7 treatment is influenced by the level of env glycosylation using W.T. & recombinant env deglycosylated SHIV's that bind α4ß7 with low v/s high affinity, c) determine the tissue/organ localization of virus and CD4+ cells in the control and α4ß7 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.