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

摘要：慢性免疫激活，即使抗逆转录病毒治疗也能持续，是HIV感染疾病进展的最强预测因子。了解慢性免疫激活的机制可能有助于确定hiv感染治疗干预的新靶点。大量文献证据表明，HIV疾病直接或间接激活单核细胞/巨噬细胞分泌促炎细胞因子，促炎细胞因子在这种致病性免疫激活中起主要作用。已知来自HIV感染个体的单核细胞会自发分泌细胞因子，尽管其机制或所涉及的分子尚不清楚。PD-1H是新发现的共刺激和共抑制受体B7/CD28家族成员，目前尚未在人类中发现。迄今为止的数据表明，该分子可能来源于与所有其他B7家族成员不同的前体。虽然在B7/CD28家族中，PD-1H的全长序列与负调控分子PD-1的相似性最高，但与PD-1不同的是，PD-1H的胞质结构域不包含免疫受体酪氨酸基抑制基序（ITIM）或免疫受体酪氨酸基开关基序（ITSM）。我们的初步数据显示，PD- 1H在造血细胞上广泛表达，在单核细胞上表达水平较高。PD-1H在人单核细胞中的强制过表达足以诱导多种细胞因子的自发分泌。此外，来自hiv感染者的单核细胞过表达PD-1H， PD-1H与单核细胞中的细胞因子基因表达和T细胞上的免疫激活标记相关，但与病毒载量无关。基于这些数据，我们假设PD-1H作为单核细胞激活分子在HIV发病机制中起主要作用。在本提案中，我们将测试这一假设，并评估ART如何影响这一过程，使用来自HIV疾病定义阶段的pbmc和人源化BLT模型，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)利用确定的HIV感染者群体，表征PD-1h过表达的进化与免疫激活、血浆促炎细胞因子水平、CD4 T细胞耗竭和血浆病毒血症的关系。2)通过观察病毒载量、CD4 T细胞计数和单核细胞相关生物标志物/细胞因子和T细胞活化标志物定义的免疫激活，表征人源化BLT小鼠HIV感染过程中不同时间点PD-1H的表达。我们还将测试PD-1H表达在ART后与其他参数的关系。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HIV感染的其他参数，无论是否使用ART。

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.