Novel Mechanism of Immune Evasion by Arenaviral Nucleoproteins

沙粒病毒核蛋白免疫逃避的新机制

• 批准号: 8824864
• 负责人: Hinh Ly
• 金额: $ 38万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2016-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8824864
• 关键词: 5' -exoribonuclease; Accounting; Africa; Amino Acids; Animal Model; Antiviral Agents; Area; Arenavirus; Arenavirus Infections; Binding; Biochemical; Biological; Biological Assay; Cavia; Cell Culture Techniques; Cells; Clinical; Collaborations; Complement; Detection; Development; Disease; Disease Outbreaks; Exonuclease; Exoribonucleases; Goals; Human; Immune; Immune response; Immunity; Immunology; Immunosuppression; In Vitro; Infection; Interferon Suppression; Interferon Type I; Interferons; Knowledge; Lassa Fever; Lassa fever virus; Lassa virus; Lead; Learning; Ligands; Measures; Mediating; Molecular; Molecular and Cellular Biology; Mutagenesis; Natural Immunity; Nature; Nucleoproteins; Pathogenesis; Pathology; Patients; Pattern; Pattern recognition receptor; Pharmaceutical Preparations; Pichinde virus; Preventive; Process; Proteins; RNA; Reporting; Ribonucleases; Role; Structural Biochemistry; Structural Biologist; Structural Models; Structure; Substrate Specificity; System; Testing; Therapeutic; Therapeutic Intervention; Time; Vaccines; Viral; Viral Hemorrhagic Fevers; Virulence; Virus; Virus Diseases; Zinc; adaptive immunity; base; cell type; in vitro activity; in vivo; insight; novel; novel strategies; pathogen; prophylactic; response; reverse genetics; virus host interaction

DESCRIPTION (provided by applicant): Arenaviruses such as Lassa fever virus (LASV) are known to cause deadly hemorrhagic fever diseases in human with little preventive or prophylactic measures. A hallmark of arenavirus-induced hemorrhagic fevers is the general immune suppression in severe and lethally infected patients. The current lack of knowledge on how arenaviral infections lead to host immune suppression is a major barrier to understanding the virulence nature and disease pathogenesis of these human pathogens and has hindered the development of effective vaccine and therapeutic intervention. Arenavirus nucleoprotein (NP) has been shown to suppress the interferon (IFN) induction, the mechanism of which, however, remains elusive. We have recently reported the first crystal structure of the LASV NP protein (Qi, et al, Dec 2010, Nature). An unexpected finding from our structural and functional analyses is that the C domain of NP folds into a functional 3'-5' exoribonuclease (RNase) that degrades various types of RNA substrates and is essential for the NP's ability to suppress the IFN induction. As IFNs are induced by the cellular pattern recognition receptors (PRRs) that recognize viral pathogen-associated molecular patterns (PAMP) RNAs, we hypothesize that arenaviral NP proteins evade host innate immunity by specifically degrading these PAMP RNA ligands via its exoribonuclease activity. LASV NP is the first virally encoded RNase that uses exoribonuclease activity to block the IFN induction, which represents a novel mechanism of viral immune evasion. The goal of this proposal therefore is to provide mechanistic insights into this novel approach of viral immune evasion by arenavirus NP exoribonuclease activity. Specifically, we will define the structural basis of LASV NP in mediating IFN suppression and exoribonuclease activities (Aim #1) and determine its RNA substrate specificity (Aim #2). Finally, we will complement and extend biochemical and cell-based studies outlined in Aims #1 and #2 to determine the role of NP RNase in mediating host immune suppression and pathogenesis using a disease-relevant small animal model (Aim #3). The novelties of the study are defined not only by the unique concept of how virally encoded RNase mediates the IFN suppression but also by a combination of unique experimental systems that integrate protein structural biochemistry, molecular and cellular biology, infectious virus, and a pertinent animal model for understanding human hemorrhagic fever diseases. The proposed study is highly significant as it will reveal for the first time a novel molecular mechanism of immune evasion mediated by arenaviral NP protein that may offer opportunities for development of effective therapeutics and/or vaccines against lethal arenaviral hemorrhagic fever infections in humans. As LASV NP is the first identified viral RNase with IFN suppression function, this study has a broaden significance in understanding the virus-host interactions, in particular, on how viral pathogens employ various ingenious strategies to evade host immunity.

描述（由申请人提供）：已知诸如拉沙热病毒（LASV）之类的沙粒病毒会在人类中引起致命的出血热疾病，而几乎没有预防或预防措施。沙粒病毒引起的出血热的一个特点是严重和致命感染患者的普遍免疫抑制。目前缺乏关于沙粒病毒感染如何导致宿主免疫抑制的知识，这是了解这些人类病原体的毒力性质和疾病发病机制的主要障碍，并阻碍了有效疫苗和治疗干预措施的开发。沙粒病毒核蛋白 (NP) 已被证明可以抑制干扰素 (IFN) 诱导，但其机制仍不清楚。我们最近报道了 LASV NP 蛋白的第一个晶体结构（Qi 等人，2010 年 12 月，Nature）。我们的结构和功能分析中的一个意外发现是，NP 的 C 结构域折叠成功能性 3'-5' 核糖核酸酶 (RNase)，该酶可降解各种类型的 RNA 底物，并且对于 NP 抑制 IFN 诱导的能力至关重要。由于 IFN 是由识别病毒病原体相关分子模式 (PAMP) RNA 的细胞模式识别受体 (PRR) 诱导的，因此我们假设沙粒病毒 NP 蛋白通过其外核糖核酸酶活性特异性降解这些 PAMP RNA 配体，从而逃避宿主先天免疫。 LASV NP 是第一个病毒编码的 RNase，它利用外切核糖核酸酶活性来阻断 IFN 诱导，这代表了病毒免疫逃避的一种新机制。因此，该提案的目标是为这种通过沙粒病毒 NP 外核糖核酸酶活性逃避病毒免疫的新方法提供机制见解。具体来说，我们将定义 LASV NP 在介导 IFN 抑制和核糖核酸外切酶活性中的结构基础（目标#1），并确定其 RNA 底物特异性（目标#2）。最后，我们将补充和扩展目标#1和#2中概述的生化和细胞研究，以确定 NP RNase 使用疾病相关小动物模型介导宿主免疫抑制和发病机制的作用（目标#3）。该研究的新颖性不仅在于病毒编码的核糖核酸酶如何介导干扰素抑制的独特概念，还在于整合了蛋白质结构生物化学、分子和细胞生物学、感染性病毒和相关动物模型的独特实验系统的组合了解人类出血热疾病。这项拟议的研究具有非常重要的意义，因为它将首次揭示由沙粒病毒 NP 蛋白介导的免疫逃避的新分子机制，这可能为开发针对人类致命的沙粒病毒出血热感染的有效疗法和/或疫苗提供机会。由于LASV NP是第一个被鉴定的具有IFN抑制功能的病毒RNase，因此这项研究对于理解病毒与宿主的相互作用，特别是病毒病原体如何利用各种巧妙的策略来逃避宿主免疫具有广泛的意义。