The adenosine system in viral reservoir persistence

描述(申请人提供)：尽管接受了抗逆转录病毒治疗，但中枢神经系统的艾滋病毒感染仍然存在，这是治疗神经疾病的一个挑战，也是根除接受治疗的患者中艾滋病毒的一个重大障碍。要消除大脑中感染艾滋病毒的蓄水池，可能需要采取干预措施，以刺激对感染艾滋病毒的细胞的免疫识别和/或绕过免疫抑制机制。三磷酸腺苷(ATP)是一种有效的免疫刺激剂，通过P2受体作用于免疫细胞。相反，腺苷通过P1型受体对T细胞和巨噬细胞/树突状细胞具有强大的免疫抑制活性。在中枢神经系统的小胶质细胞中，类似于调节性T细胞的作用，表达胞外核苷酸酶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)，提供了一个潜在的重要机制来介导免疫调节。在我们对感染SIV的恒河猴中枢神经系统组织的初步研究中，CD39和CD73都显示出相对于未感染的对照脑组织的表达增加。在SIV感染的脑内，即使在没有脑炎的情况下，实质小胶质细胞上这两种胞外酶的表达也显著增加。此外，在SIV脑炎中，中枢神经系统血管周围巨噬细胞和小胶质细胞结节内的细胞高度表达这些酶。在我们拟议的研究中，我们将检验这一假说，即在SIV感染的猕猴中，通过小胶质细胞上CD39和CD73表达的酶活性，促进了中枢神经系统的ATP代谢，有助于感染细胞的存活，并损害了病毒特异性免疫反应。在特定的目标I中，我们将检验在SIV感染中小胶质细胞上CD39和CD73表达增加的假设，并确定CART治疗对表达和酶活性的影响。在这项研究中，我们将进一步评估脑脊液中作为生物标志物的ATP代谢物，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、中枢神经系统CD39和CD73的表达以及对CART治疗的反应有关。我们将验证在SIV感染中脑源性小胶质细胞表达CD39和CD73增加的假说有助于ATP代谢，抑制T细胞反应，并在体外提高小胶质细胞的存活率。我们将使用未感染对照、SIV感染和经CART治疗的SIV感染猕猴的中枢神经系统来源的小胶质细胞，测量和比较ECTs活性、抑制自体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。我们预计，我们提出的研究将为治疗提供一种新的途径，以增强免疫介导的艾滋病毒和其他中枢神经系统病原体的清除。

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.