The adenosine system in viral reservoir persistence

描述（由申请人提供）：尽管抗逆转录病毒治疗，中枢神经系统的HIV感染仍然存在，这是神经系统疾病治疗的挑战，也是治疗患者根除HIV的重大障碍。很可能，消除大脑中受HIV感染的储存库将需要旨在刺激对HIV感染细胞的免疫识别和/或规避免疫抑制机制的干预措施。三磷酸腺苷（ATP）是一种有效的免疫兴奋剂，通过p2型受体作用于免疫细胞。相比之下，腺苷通过p1型受体对T细胞和巨噬细胞/树突状细胞具有有效的免疫抑制活性。中枢神经系统中的小胶质细胞，类似于调节性T细胞的作用，表达外核苷酶CD39和CD73，将ATP和ADP转化为AMP（通过CD39），并进一步代谢为腺苷（通过CD73），提供了介导免疫调节的潜在重要机制。在我们对SIV感染的恒河猴中枢神经系统组织的初步研究中，CD39和CD73相对于未感染的对照脑组织表现出更高的表达。即使在没有脑炎的情况下，SIV感染的脑实质小胶质细胞上这两种外切酶的表达也显著增加。此外，在SIV脑炎的背景下，中枢神经系统血管周围巨噬细胞和小胶质结节内的细胞高度表达这些酶。在我们提出的研究中，我们将验证ATP代谢，通过CD39和CD73在小胶质细胞上表达的酶活性，在SIV感染的恒河猴中枢神经系统中增加，有助于感染细胞的存活，并损害病毒特异性免疫反应的假设。在Specific Aim I中，我们将验证小胶质细胞上CD39和CD73表达在SIV感染中增加的假设，并确定cART治疗对表达和酶活性的影响。在本研究过程中，我们将进一步评估ATP代谢物作为脑脊液中的生物标志物，并确定其值是否与SIV感染状态、发病机制的生物学和病毒学标志物、CNS中CD39和CD73的表达以及对cART治疗的反应相关。我们将在体外验证SIV感染时脑源性小胶质细胞中CD39和CD73表达增加有助于ATP代谢，抑制T细胞反应，并增加小胶质细胞存活率的假设。我们将测量和比较外核苷酸酶活性、抑制自身SIV特异性免疫反应的能力以及对ATP诱导的细胞死亡的敏感性，使用来自未感染对照、SIV感染和经cART治疗的SIV感染恒河猴的CNS衍生小胶质细胞。我们预计我们提出的研究将为增强免疫介导的HIV和其他CNS病原体清除的治疗方法提供新的途径。

DESCRIPTION (provided by applicant): HIV infection of the CNS persists despite antiretroviral treatment, representing a challenge for treatment of neurologic disorders and a significant hurdle for the eradication of HIV in treated patients. It is likely that elimination ofHIV infected reservoirs in the brain will require interventions designed to stimulate immune recognition of HIV infected cells and/or circumvent immune suppressive mechanisms. Adenosine triphosphate (ATP) is a potent immune stimulant, acting via P2-type receptors on immune cells. Adenosine, in contrast, has potent immune suppressive activities on T cells and macrophages/dendritic cells via P1-type receptors. Microglia in CNS, similar to an action of regulatory T cells, express ectonucleotidases CD39 and CD73, which convert ATP and ADP to AMP (via CD39), with further metabolism to adenosine (via CD73), providing a potentially important mechanism mediating immune modulation. In our preliminary studies in CNS tissues from SIV infected rhesus macaques, both CD39 and CD73 exhibit increased expression relative to uninfected control brain tissue. The expression of both ectoenzymes is markedly increased on parenchymal microglia in SIV infected brain, even in the absence of encephalitis. In addition, CNS perivascular macrophages and cells within microglial nodules, highly express these enzymes in the setting of SIV encephalitis In our proposed studies, we will test the hypothesis that ATP metabolism, via the enzymatic activities of CD39 and CD73 expression on microglia, is increased in the CNS in SIV infected rhesus macaques, contributes to the survival of infected cells, and impairs virus specific immune responses. In Specific Aim I, we will test the hypothesis that CD39 and CD73 expression on microglia, is increased in SIV infection and determine the impact of cART treatment on expression and enzymatic activity. We will further evaluate ATP metabolites as biomarkers in CSF during the course of this study and determine if values correlate with SIV infection status, biologic and virologic markers for pathogenesis, CD39 and CD73 expression in CNS, and the response to cART treatment. We will test the hypothesis increased CD39 and CD73 expressed on brain derived microglia in SIV infection contributes to ATP metabolism, suppresses T cell responses, and increase survival of microglia in vitro. We will measure and compare ectonucleotidase activities, the ability to suppress autologous SIV specific immune responses, and the sensitivity to ATP induced cell death, using CNS derived microglia from uninfected controls, SIV infected, and SIV infected rhesus macaques treated with cART. We anticipate that our proposed studies will provide a novel avenue for therapeutics to augment immune mediated clearance of HIV and other CNS pathogens.