Antiviral Therapy for Polyomavirus Infection

描述（由申请方提供）：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病原体。到青春期早期，几乎所有的人类都被两种已知的多瘤病毒BKV和JCV感染。BKV再活化是肾移植排斥反应的主要原因，在老年人和AIDS患者中，JCV再活化导致进行性致死性中枢神经系统（CNS）脱髓鞘疾病，称为进行性多灶性白质脑病（PML）。PML也与免疫抑制药物方案联合发生。最近，几个用Tysabri治疗的患者，Tysabri是一种人源化VLA-4抗体，通过限制T细胞迁移到CNS来控制多发性硬化症患者的复发，发展为PML。目前没有临床上有效的抗病毒治疗多瘤病毒感染，或重新激活的后果。持续感染期间的重复抗原遭遇导致病毒特异性T细胞的功能衰弱，其中克隆缺失是慢性TCR接合的最终结果。持续性病毒感染的持续时间和程度决定了记忆T细胞的存活及其限制病毒复制的能力。因此，降低病毒载量的治疗剂将促进有效的抗病毒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）系统提供了唯一易于处理的模型来评估该临床重要病毒家族的发病机制和免疫力，以及开发和测试新型治疗化合物。我们最近发现，PyV的复制需要β-家族酪氨酸激酶，并且这些激酶的抑制剂（例如诺华的格列卫）被合理地设计以控制特定的人类癌症（例如，Philadelphia染色体+慢性骨髓性白血病），在体外和小鼠中阻断PyV复制。在该探索性应用中，我们结合了Aron Lukacher博士（小鼠多瘤病毒发病机制和病毒免疫学）和丹尼尔卡尔曼（酪氨酸激酶、β-家族抑制性化合物、病毒体-宿主细胞相互作用、去卷积荧光显微镜）的专业知识，以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。在具体目标1中，我们将检验以下假设：β-家族酪氨酸激酶参与PyV细胞摄取和细胞内运输以及复制的早期步骤。由于CD 8 T细胞在多瘤病毒感染细胞的免疫监视中的重要性，以及持续性病毒感染对记忆T细胞存活和功能的不利影响，我们进一步假设，由β-家族激酶抑制剂介导的病毒载量减少将改善记忆性多瘤病毒特异性CD 8 T细胞应答，并进一步减少多瘤病毒再活化（特异性目的2）。研究这些化合物的抑制机制及其在体内限制PyV感染的能力将为其在高危人群中对抗多瘤病毒再活化的治疗用途提供原理证明。项目叙述：几乎所有个体都终身感染两种人多瘤病毒，否则在免疫抑制个体中具有使人衰弱的、潜在致命的后果的沉默感染（例如，肾移植受者，艾滋病毒/艾滋病）。多瘤病毒感染尚无有效的抗病毒治疗。在本申请中，提出了研究以探索新观察的机制，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，这是其潜在治疗用途的关键前奏，以防止免疫抑制个体中的多瘤病毒再活化。

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.