Gut Homing Cells in SIV infection

描述(由申请人提供)：在急性HIV/SIV期间肠道相关淋巴组织(GALT)内的CD4+T细胞大量耗尽，随后在慢性感染期间持续的CD4+T细胞丢失导致GALT和覆盖的粘膜上皮的进行性损害。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。T细胞通过GALT内产生的信号运输到GALT，这些信号包括维甲酸的释放，这反过来又导致细胞表面α4？7整合素和CCR9上调。通过与肠壁上皮细胞表达的同源受体α和CCL25相互作用，表达CCR9和MADCAM的细胞选择性地定位于GalT。最近的数据表明，α4？7除了作为归巢受体外，还可以作为许多HIV和SIV毒株的替代受体，它们的V1/V2包膜片段对α4？7具有类似于其天然配体的识别‘基序’。此外，定位于V1/V2和V3/C4包膜区的序列含有残基，如果去糖基化，可以显著增强病毒与α4？7的亲和力。这种高亲和力结合α-1被认为是优先通过粘膜途径传播的。我们的实验室最近显示，在急性IV和直肠内SIV感染之前和期间，注射一种主要的抗α4？7单抗，可以显著降低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。本文建议的研究目的是：1)通过确定α4？7给药是否能有效地降低动物体内的GALT病毒载量来确定这些先前发现的临床实用性：a)阴道内感染，b)SIV感染后，c)低重复剂量阴道内感染以模拟自然传播，以及d)如果单独或与α4？7单抗一起注射CCR9小分子抑制剂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，重点描述参与维持肠道组织完整性的蛋白质的作用，确定细菌转运的动力学和肠道组织通透性的生理测量；以及3)确定α4？7诱导其作用的机制a)通过确定α4？7单抗是否通过阻断α4？7的受体功能或通过使用与α4？7结合或不与α4？7结合的重组复制能力SIVenv构建物来阻断α4？7表达细胞的转运而介导其作用；b)通过使用W.T.和用低v/S高亲和力结合α4？7的重组env脱糖基化SIV‘s来确定抗α4？7治疗的体内效应是否受环境糖基化水平的影响，C)使用我们实验室开发的最新优化的实时“实时”正电子发射计算机断层扫描技术，确定病毒和α+细胞在对照组和CD47组动物体内的组织/器官定位。认识到有效的艾滋病毒疫苗不仅需要诱导广泛的中和抗体和有效的病毒特异性CTL，而且还需要防止与疾病进展密切相关的GALT损伤，这突显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.