Antiviral Therapy for Polyomavirus Infection

描述(申请人提供)：多瘤病毒是在包括人类在内的各种脊椎动物宿主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，几乎所有的人类都感染了两种已知的多瘤病毒，BKV和JCV。BKV的重新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重新激活会导致进行性致命的中枢神经系统(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一起发生。最近，几名接受Tysabri治疗的患者出现了PML。Tysabri是一种人源化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。目前还没有针对多瘤病毒感染或重新激活的后果的临床有效的抗病毒疗法。持续感染期间重复的抗原遭遇会导致病毒特异性T细胞的功能衰弱，克隆性缺失是慢性TCR参与的最终后果。持续病毒感染的持续时间和大小决定了记忆T细胞的生存及其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的抗病毒T细胞记忆的产生。由于该病毒家族宿主范围狭窄，小鼠多瘤病毒(PYV)系统提供了唯一简便的模型来评估这个临床重要病毒家族的致病机制和免疫力，并开发和测试新的治疗药物。我们最近发现，PYV的复制需要Abl家族的酪氨酸激酶，而这些酶的抑制剂(例如诺华的Gleevec)合理地设计用于控制特定的人类癌症(例如，费城染色体+慢性粒细胞白血病)，在体外和小鼠中都能阻止PYV的复制。在这一探索性应用中，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Daniel Kalman博士(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、去卷积荧光显微镜)的专业知识，研究了这些化合物在体外抑制PYV感染的机制(S)及其在体内抑制PYV感染的能力。在特定的目标1中，我们将检验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CD8T细胞在多瘤病毒感染细胞的免疫监控中的重要性，以及持续病毒感染对记忆性T细胞生存和功能的不利影响，我们进一步假设，Ab1家族激酶抑制剂介导的病毒载量的减少将改善记忆性多瘤病毒特异性CD8T细胞的反应，并进一步抑制多瘤病毒的重新激活(特异性目标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，将为它们在高危人群中用于抗多瘤病毒再激活的治疗提供原则证据。项目简介：几乎所有的人终生感染两种人类多瘤病毒，否则就是沉默的感染，对免疫抑制的人(例如，肾移植接受者、艾滋病毒/艾滋病)会造成虚弱的、潜在的致命后果。目前还没有有效的抗病毒疗法来治疗多瘤病毒感染。在这项应用中，有人建议进行研究，以探索这一新观察结果的机制，即抑制Abl家族酪氨酸激酶的化合物(例如，FDA批准的Gleevec)可以限制多瘤病毒的感染，这是它们潜在治疗用途防止免疫抑制患者多瘤病毒重新激活的关键前奏。

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.