Characterization of innate immune response stimulation by Sin Nombre virus

描述（由申请人提供）：由sinnombre病毒（SNV）引起的汉坦病毒心肺综合征（HCPS）是一种通常致命的疾病，目前尚无特异性治疗方法。与暴露于SNV颗粒相关的活跃的先天免疫反应可能在导致毛细血管泄漏和HCPS的致病过程中起着重要的作用，但尚未被认识到。人类先天免疫系统通过模式识别受体（PRR）识别多种病原体相关分子模式（PAMPs） （LPS, ssRNA， dsRNA等），包括膜结合toll样受体（TLR）和细胞质PRRs，如rig - 1和MDA-5。因此，人类对病毒感染的免疫反应可能因不同的病毒而有很大差异，因此了解这些反应机制的范围非常重要。先天免疫对病毒RNA的反应已被广泛研究，但对病毒蛋白的反应的信息较少。我们选择关注SNV不仅是因为全球健康威胁，而且因为SNV作为生物武器的潜在用途突出了确定HCPS特定治疗靶点的必要性，还因为干预先天免疫反应可能提供针对多种具有相关致病机制的生物体的治疗选择。为了实现这一目标，有必要阐明SNV感染触发先天免疫系统的机制。由于病毒RNA （vRNA）被紫外线照射严重破坏，我们使用紫外线杀死的SNV来证明，即使在没有完整病毒RNA的情况下，对SNV的先天免疫反应也会发生，干扰素相关基因ISG56和MxA的诱导证明了这一点。因此，我们提出UV-SNV的初始基因诱导是由于宿主对病毒颗粒的一种或多种成分的反应，而不是对核酸片段的反应，因此不依赖于传统的RNA识别受体TLR3、TLR7/8、MDA-5或rig - 1。先天免疫诱导至少部分是由暴露在SNV病毒粒子表面的分子（如g1和/或G2糖蛋白）驱动的，与膜封闭的核酸相比，这种可能性提供了更容易获得的治疗靶点。因此，本项目的具体目的是：1)研究TLRs、RIG-I和MDA-5等常规先天免疫受体在诱导SNV初始先天免疫应答中的作用；2)研究SNV糖蛋白G1/G2在诱导SNV初始先天免疫应答中的作用。总之，这些实验的结果将确定致病性汉坦病毒SNV触发先天免疫反应所需的病毒成分和宿主细胞受体，并将是确定对抗这种病原体的特定治疗靶点的关键一步。

DESCRIPTION (provided by applicant): Hantavirus cardiopulmonary syndrome (HCPS) caused by Sin Nombre virus (SNV) is an often lethal condition for which there is no specific therapy. The brisk innate immune responses associated with exposure to the SNV particle may play a significant and as yet unappreciated role in the pathogenic process that leads to capillary leak and HCPS. The human innate immune system recognizes a variety of pathogen associated molecular patterns (PAMPs) (LPS, ssRNA, dsRNA, etc.) via pattern recognition receptors (PRR) including membrane bound Toll-like receptors (TLR) and cytoplasmic PRRs such as RIG-I and MDA-5. Hence the human immune response to viral infection can vary widely with different viruses, making it important to understand the scope of these response mechanisms. The innate immune response to viral RNA has been extensively studied, with less information available on the response to viral protein. We have chosen to focus on SNV not only because of the global health threat and because the potential use of SNV as a bio-weapon highlights the need to identify specific therapeutic targets for HCPS, but also because intervening in innate immune responses may offer therapeutic options against a variety of organisms with related pathogenic mechanisms. Towards this goal, there is a need to elucidate the mechanism(s) by which SNV infection triggers the innate immune system. Since viral RNA (vRNA) is severely damaged by UV exposure, we used UV-killed SNV to demonstrate that the innate immune response to SNV, as evidenced by induction of interferon-related genes ISG56 and MxA, occurs even in the absence of intact viral RNA. Accordingly, we propose that initial gene induction by UV-SNV is due to the host response to one or more components of the viral particle, rather than to a nucleic acid moiety, and is therefore independent of the conventional RNA recognition receptors, TLR3, TLR7/8, MDA-5 or RIG-I. The possibility that innate immune induction is driven, at least in part, by molecules exposed on the surface of the SNV virion, such as G1and/or G2 glycoproteins, provides a more readily accessible therapeutic target compared to membrane enclosed nucleic acid. Therefore, the specific aims of this project are 1) to examine the role of conventional innate immune receptors, including TLRs, RIG-I and MDA-5, in induction of the initial innate immune response to SNV, and 2) to examine the role of SNV glycoproteins G1/G2 in induction of the initial innate immune response to SNV. Together, the results from these experiments will identify the viral component(s) and host cell receptor(s) required for the pathogenic hantavirus SNV to trigger the innate immune response, and will be a crucial step towards identifying specific therapeutic targets to combat this pathogen.