Role of PD-1H mediated monocyte activation in HIV pathogenesis

描述(申请人提供)：摘要：慢性免疫激活即使在抗逆转录病毒治疗的情况下也能持续，是艾滋病毒感染中疾病进展的最强预测因素。了解慢性免疫激活的机制可能有助于确定艾滋病毒感染治疗干预的新靶点。大量的文献证据表明，HIV疾病直接或间接地激活单核/巨噬细胞分泌促炎细胞因子，这些细胞因子在这种致病免疫激活中起着重要作用。已知HIV感染者的单核细胞会自发分泌细胞因子，尽管其机制或涉及的分子尚不清楚。PD-1H是新发现的B7/CD28共刺激和共抑制受体家族的成员，目前还没有在人类身上发现这种受体的特征。到目前为止的数据表明，该分子可能来自不同于所有其他B7家族成员的前体。尽管在B7/CD28家族中，PD-1H的全长序列与负调控分子PD-1具有最高的相似性，但与PD-1不同的是，PD-1H的细胞质结构域不包含基于免疫受体酪氨酸的抑制基序(ITIM)或基于免疫受体酪氨酸的开关基序(ITSM)。我们的初步数据显示，PD-1H在造血细胞上广泛表达，在单核细胞上的表达水平较高。在人单核细胞中强制过表达PD-1H足以诱导多种细胞因子的自发分泌。此外，HIV感染者的单核细胞过度表达PD-1H，PD-1H与单核细胞中细胞因子基因表达和T细胞上的免疫激活标志相关，而与病毒载量无关。基于这些数据，我们假设PD-1H作为单核细胞激活分子在HIV的发病机制中发挥重要作用。在这项提案中，我们将测试这一假设，并使用HIV疾病定义阶段的PBMC和人源化BLT模型来评估ART如何影响这一过程，该模型概括了HIV发病机制的关键特征，包括免疫激活。我们的具体目标是：1)利用特定的HIV感染者组，研究PD-1h过度表达的演变与免疫激活、血浆促炎细胞因子水平、CD4T细胞耗竭和血浆病毒血症的关系。2)以病毒载量、CD4T细胞计数和T细胞表面单核细胞相关生物标志物/细胞因子及活化标志物为指标，研究人源化BLT小鼠感染�过程中不同时间点PD-1H的表达。我们还将测试抗逆转录病毒治疗后PD-1H的表达与其他参数的关系，以及3)测试在人源化小鼠中沉默PD-1H或相关分子是否会逆转免疫激活或影响使用或不使用抗逆转录病毒技术的HIV感染的其他参数。

DESCRIPTION (provided by applicant): Abstract: Chronic immune activation, which can persist even with antiretroviral therapy, is the strongest predictor of disease progression in HIV infection. Understanding the mechanism of chronic immune activation may help identify novel targets for therapeutic interventions in HIV-infection. Extensive evidence from literature suggests that HIV disease directly or indirectly activates monocyte/macrophages to secrete proinflammatory cytokines which play a major role in this pathogenic immune activation. Monocytes from HIV infected individuals are known to secrete cytokines spontaneously, although the mechanism for this or the molecules involved are not known. PD-1H is a newly discovered member of the B7/CD28 family of costimulatory and coinhibitory receptors, which has not been characterized in humans so far. Data to date suggest that the molecule may be derived from a different precursor than all other B7 family members. Although, amongst the B7/CD28 family, the full length sequence of PD-1H has the highest similarity to the negative regulatory molecule PD-1, unlike PD-1, the cytoplasmic domain of PD-1H does not contain the immunoreceptor tyrosine-based inhibitory motif (ITIM) or the immunoreceptor tyrosine-based switch motif (ITSM). Our preliminary data shows that PD- 1H is broadly expressed on hematopoietic cells with higher levels of expression on monocytes. Enforced overexpression of PD-1H in human monocytes is sufficient to induce spontaneous secretion of multiple cytokines. Further, monocytes from HIV-infected individuals overexpress PD-1H which correlates with cytokine gene expression in monocytes and immune activation markers on T cells but not with viral load. Based on these data, we hypothesize that PD-1H acts as a monocyte activation molecule that plays a major role in HIV pathogenesis. In this proposal we will test this hypothesis and evaluate how ART influences this process using PBMCs from defined stages of HIV disease and humanized BLT model which recapitulates key features of HIV pathogenesis, including immune activation. Our specific aims are to: 1) To characterize the evolution of PD-1h over expression in relation to immune activation, plasma proinflammatory cytokine levels, CD4 T cell depletion and plasma viremia using defined groups of HIV infected individuals. 2) Characterize PD-1H expression at different time points during the course of HIV infection in humanized BLT mice vis-�-vis viral load, CD4 T cell counts and immune activation defined by monocyte associated biomarkers/cytokines and activation markers on T cells. We will also test how PD-1H expression changes after ART, in relation to other parameters and 3) Test if silencing PD-1H or related molecules in humanized mice reverses immune activation or affects other parameters of HIV infection with or without ART.