Antiviral Therapy for Polyomavirus Infection

描述（由申请人提供）：多瘤病毒是多种脊椎动物宿主（包括人类）中普遍存在的沉默病原体，但在免疫功能低下的情况下成为机会性病原体。到青春期早期，几乎所有人都感染了两种已知的多瘤病毒，BKV和JCV。BKV再激活是肾移植排斥反应的主要原因，在老年人和艾滋病患者中，JCV再激活导致进行性致命性中枢神经系统（CNS）脱髓鞘疾病，称为进行性多灶性脑白质病（PML）。PML也与免疫抑制药物方案一起发生。最近，一些接受Tysabri治疗的患者发展为PML。Tysabri是一种人源化的VLA-4抗体，通过限制T细胞向中枢神经系统的迁移来控制多发性硬化症患者的复发。目前尚无临床有效的抗病毒治疗多瘤病毒感染或再激活的后果。在持续感染期间遇到重复抗原会导致病毒特异性T细胞的功能衰弱，慢性TCR接合的最终结果是克隆缺失。持续病毒感染的持续时间和程度决定记忆T细胞的存活和它们限制病毒复制的能力。因此，降低病毒载量的治疗方法将促进有效抗病毒T细胞记忆的产生。由于该病毒家族的宿主范围狭窄，小鼠多瘤病毒（PyV）系统提供了唯一可处理的模型来评估这一临床重要病毒家族的发病机制和免疫，并开发和测试新的治疗化合物。我们最近发现，abl家族酪氨酸激酶是PyV复制所必需的，这些激酶的抑制剂（如诺华公司的格列卫）被合理设计用于控制特定的人类癌症（如费城染色体+慢性髓性白血病），在体外和小鼠中阻断PyV复制。在这个探索性的应用程序中，我们结合了博士的专业知识。Aron Lukacher（小鼠多瘤病毒发病机制和病毒免疫学）和Daniel Kalman（酪氨酸激酶，abl家族抑制化合物，病毒粒子-宿主细胞相互作用，反褶积荧光显微镜）研究这些化合物的体外抑制机制及其在体内限制PyV感染的能力。在Specific Aim 1中，我们将验证abl家族酪氨酸激酶参与PyV细胞摄取、细胞内运输和复制的早期步骤的假设。由于CD8 T细胞在多瘤病毒感染细胞的免疫监视中的重要性，以及持续病毒感染对记忆T细胞存活和功能的有害影响，我们进一步假设，由abl家族激酶抑制剂介导的病毒载量的减少将改善记忆多瘤病毒特异性CD8 T细胞反应，并进一步减少多瘤病毒的再激活（Specific Aim 2）。研究这些化合物的抑制机制及其在体内限制PyV感染的能力，将为它们在高风险人群中用于治疗多瘤病毒再激活提供原理证明。项目描述：几乎所有的人都终身感染两种人类多瘤病毒，否则无声的感染对免疫抑制的个体（如肾移植受者、艾滋病毒/艾滋病）具有使人衰弱甚至可能致命的后果。多瘤病毒感染没有有效的抗病毒治疗。在这项应用中，研究人员提出了探索新观察机制的研究，即抑制Abl-家族酪氨酸激酶的化合物（例如fda批准的格列卫）限制多瘤病毒感染，这是其潜在的治疗用途，以防止免疫抑制个体中多瘤病毒的再激活。

DESCRIPTION (provided by applicant): Polyomaviruses are ubiquitous silent pathogens in a variety of vertebrate hosts, including humans, but become opportunistic pathogens in the setting of depressed immune function. By early adolescence, nearly all humans are infected by both of the two known polyomaviruses, BKV and JCV. Reactivation of BKV is a leading cause of kidney transplant rejection and, in the elderly and AIDS patients, JCV reactivation causes the progressive fatal central nervous system (CNS) demyelinating disease called Progressive Multifocal Leukoencephalopathy (PML). PML also occurs in conjunction with immunosuppressant drug regimens. Recently, several patients treated with Tysabri, a humanized VLA-4 antibody that controls relapses in multiple sclerosis patients by restricting T cell immigration to the CNS, developed PML. There is currently no clinically effective antiviral therapy for polyomavirus infection, or the consequences of reactivation. Repetitive antigen encounter during persistent infection causes functional debilitation of virus-specific T cells, with clonal deletion the eventual consequence of chronic TCR engagement. The duration and magnitude of persistent viral infection govern the survival of memory T cells and their ability to limit viral replication. Thus, therapeutics that lower viral load will promote generation of effective antiviral T cell memory. Because of the narrow host range of this virus family, the mouse-polyoma virus (PyV) system provides the only tractable model to evaluate pathogenesis of and immunity to this clinically important virus family, and to develop and test novel therapeutic compounds. We recently found that Abl-family tyrosine kinases are required for replication of PyV and that inhibitors of these kinases (e.g. Novartis' Gleevec), rationally designed to control specific human cancers (e.g., Philadelphia chromosome+ chronic myelogenous leukemia), block PyV replication both in vitro and in mice. In this exploratory application application, we have combined the expertise of the Drs. Aron Lukacher (mouse polyoma virus pathogenesis and viral immunology) and Daniel Kalman (tyrosine kinases, Abl-family inhibitory compounds, virion-host cell interaction, deconvolution fluorescence microscopy) to investigate mechanism(s) of inhibition by these compounds in vitro and their capacity to limit PyV infection in vivo. In Specific Aim 1, we will test the hypothesis that Abl-family tyrosine kinases are involved in early steps in PyV cell uptake and intracellular trafficking and in replication. Because of the importance of CD8 T cells in immunosurveillance for polyomavirus-infected cells, and the detrimental effect of persistent viral infections on memory T cell survival and function, we further hypothesize that reductions in viral load mediated by the Abl-family kinase inhibitors will improve memory polyomavirus-specific CD8 T cell responses and further curtail polyomavirus reactivation (Specific Aim 2). Investigation of the mechanism of inhibition by these compounds and their capacity to limit PyV infection in vivo will provide proof-of-principle for their therapeutic use to counter polyomavirus reactivation in high-risk populations. Project Narrative: Nearly all individuals are infected lifelong by two human polyomaviruses, otherwise silent infections that have debilitating, potentially fatal, consequences in immunosuppressed individuals (e.g., kidney transplant recipients, HIV/AIDS). There is no effective antiviral therapy for polyomavirus infection. In this application, studies are proposed to explore the mechanism for the novel observation that compounds that inhibit Abl- family tyrosine kinases (e.g., FDA-approved Gleevec) limit polyomavirus infection, a critical prelude for their potential therapeutic use to prevent polyomavirus reactivation in immunosuppressed individuals.