Control of Viral Pathogenesis by Regulation of 2-5A Levels

描述（由申请人提供）：病毒逃避或对抗宿主I型IFN反应的能力在病毒的趋向性和疾病发病机制中起着重要作用。然而，病毒阻碍组织特异性宿主防御导致病毒诱导病理的精确细胞和分子机制仍然难以捉摸。冠状病毒小鼠肝炎病毒（MHV）在其自然宿主中引起急性肝炎，并为了解病毒与肝细胞的相互作用提供了有用的模型。MHV蛋白ns2阻断巨噬细胞中ifn诱导的强效抗病毒2',5'-寡聚腺苷酸（2- 5a）合成酶(OAS)-RNase L途径，促进肝炎的发展。ns2蛋白及其相关病毒（轮状病毒VP3）和哺乳动物（AKAP7）蛋白是具有2',5'-磷酸二酯酶（PDE）活性的2H磷酸酯酶，可降解RNase l的激活剂2- 5a。我们的长期目标是探讨病毒和宿主2',5'-PDE在抗病毒先天免疫中的作用及其对病毒发病机制的影响。我们在此的总体假设是巨噬细胞中的OAS-RNase L通路在保护宿主免受病毒性肝炎的侵害方面至关重要。我们的具体目标是：(1)为了确定肝巨噬细胞（Kupffer细胞，KC）中的RNase L信号传导是否限制病毒进入肝实质并诱导肝炎，我们将比较KC、肝内皮细胞和肝细胞原代培养中MHV的复制和OAS-RNase L途径的激活，产生具有细胞类型特异性缺失的RNase L基因的小鼠，并使用野生型和ns2突变型MHV评估肝炎的发展。(2)为了确定ns2相关病毒和宿主2',5'- pdes的作用，我们将研究它们对2- 5a水平、病毒复制、细胞凋亡和IFN-¿诱导的影响；并确定小分子抑制剂

DESCRIPTION (provided by applicant): The ability of viruses to evade or antagonize the host type I IFN response plays an important role in viral tropism and disease pathogenesis. However, the precise cellular and molecular mechanisms by which viruses impede tissue specific host defenses leading to virus-induced pathology remain elusive. The coronavirus, mouse hepatitis virus (MHV), causes acute hepatitis in its natural host and provides a useful model for understanding virus interaction with liver cells. The MHV protein ns2 blocks the IFN-inducible and potent antiviral 2',5'-oligoadenylate (2-5A) synthetase (OAS)-RNase L pathway in macrophages and facilitates the development of hepatitis. The ns2 protein and related viral (rotavirus VP3) and mammalian (AKAP7) proteins are 2H phosphoesterases with 2',5'-phosphodiesterase (PDE) activities that degrade 2-5A, the activator of RNase L. Our long-term objective is to probe the role of viral and host 2',5'-PDEs in antiviral innate immunity and its effect on viral pathogenesis. Our overall hypothesis herein is that the OAS-RNase L pathway in macrophages is critical in protecting the host from developing viral hepatitis. Our Specific Aims are: (1) To determine if RNase L signaling in liver macrophages (Kupffer cells, KC) restricts virus from entering the liver parenchyma and inducing hepatitis, we will compare MHV replication and activation of the OAS-RNase L pathway in primary cultures of KC, liver endothelial cells and hepatocytes, generate mice with cell type specific deletions of the RNase L gene and assess the development of hepatitis using wild type and ns2 mutant MHV. (2) To determine the roles of ns2 related viral and host 2',5'-PDEs, we will study their effects on 2-5A levels, viral replication, apoptosis and IFN-¿ induction; and identify small molecule inhibitors of viral 2',5'-PDEs (ns2 and VP3) and cellular 2',5'-PDE (AKAP 7) by high throughput screening. (3) To determine and compare the "proviral" and RNase L "antagonist" activities of cellular and viral 2',5'-PDEs, we will investigate the mechanisms underlying 2',5'-PDE mediated protection to MHV by determining subcellular location of MHV replication complexes and ns2 and cellular AKAP7; generate chimeric viruses expressing different viral and cellular 2',5'-PDEs and determine their ability to antagonize RNase L and induce hepatitis. In addition, to determine effects of controlling 2-5A levels on viral pathogenesis during ongoing infections, virus-infected mice will be treated with inhibitors of 2',5'-PDEs. Our proposed studies will investigate a novel mode of regulation of the IFN antiviral response with broad implications for the control of viral infections that extend beyond hepatitis to virus mediated pathologies in other organ systems. Expected results include defining the role of KC as "gatekeeper" that prevents viruses from entering into the liver parenchyma and defining proviral and RNase L antagonist roles of diverse viral and cellular 2',5'-PDEs. It is anticipated that further understanding of the competition between virus and type I IFN signaling, particularly the OAS-RNase L pathway, will aid in the development or refinement of therapeutic strategies for human viral hepatitis and other viral diseases.