The role of norovirus capsid flexibility in infection and pathogenesis

标题：诺如病毒衣壳柔性在感染和发病机制中的作用 摘要 病毒衣壳是在环境中的稳定形式和环境中的稳定形式之间转变的亚稳态结构。 在宿主体内形成不稳定的形态特定的线索，通常被认为发生在细胞内或细胞内， 引发这种变化。衣壳的这种柔性能力是病毒粒子的基本特征，对于病毒粒子的形成至关重要。 成功感染病毒。然而，在我们理解衣壳的灵活性如何 影响诺如病毒感染和发病机制。诺如病毒是引起肠道疾病的常见肠道病原体， 世界范围内发病率和死亡率都很高。然而，没有直接的抗病毒策略被批准使用， 部分原因是我们对它们生物学的基本方面了解有限。因此，这一目标 应用是研究衣壳动力学在病毒生物学中的作用，使用鼠诺如病毒（MNV）作为一种 非常易于处理的诺如病毒生物学研究模型。我们和其他人最近的研究已经确定了 人和鼠诺如病毒衣壳的灵活性模式，突出了它们的动态性质。不同于任何 迄今为止，诺如病毒的衣壳在细胞外以两种状态存在，一种是膨胀的， 突出（P）结构域从壳（S）结构域升起的构象，以及收缩的构象 构象，其中P结构域位于S结构域的顶部。这两种状态之间的转换是 由环境因素介导，包括胆汁酸，肠腔中的关键成分，管腔pH值和 亲液离子，如Ca2+。针对人诺如病毒的多种抗体结合至仅在细胞中可接近的表位。 扩张构象，而受体结合占有率在收缩构象中增加。一 第二层灵活性位于P结构域内，在含有中和表位的外部环中 抗体的逃避抗体中和和胆汁酸与衣壳的结合影响了 这些循环。已发表的和初步的研究结果提出了一个模型， 与免疫系统相互作用，而收缩形式则针对细胞/病毒相互作用进行了优化。到 为了研究这一假设，我们将在体外和体内追求以下目标：1）确定 P和S结构域之间的柔性接头介导诺如病毒衣壳对感染性的收缩，以及 2)确定衣壳蛋白环柔性对MNV感染性的重要性。为此，我们将测试 通过改变接头长度而具有不同水平柔性的病毒突变体，以及缺乏胆汁的病毒突变体， 酸结合位点这些概念上创新的研究有望产生很大的影响，因为它们将定义 诺如病毒衣壳动力学的基本特征及其在感染和发病机制中的作用。等 信息对于诺如病毒疫苗设计是重要的。

Title: The role of norovirus capsid flexibility in infection and pathogenesis Abstract Virus capsids are metastable structures that transition between a stable form in the environment and an unstable form inside the host. Specific cues, generally thought to occur at or inside the cell, are required to elicit this change. This ability of capsids to be flexible is a fundamental feature of virions that is critical for the success of a virus infection. However, there is a fundamental gap in our understanding how capsid flexibility influences norovirus infection and pathogenesis. Noroviruses are prevalent enteric pathogens that cause significant morbidity and mortality worldwide. However, no directed antiviral strategies are approved for use, in part due to our limited understanding of fundamental aspects of their biology. Therefore, the objective of this application is to investigate the role of capsid dynamics in virus biology using murine norovirus (MNV) as a highly tractable model for studies of norovirus biology. Recent studies from us and others have identified key modes of flexibility in the human and murine norovirus capsid that highlight their dynamic nature. Unlike any other virus structure to date, the norovirus capsid exists in two states outside the cell, an expanded conformation where the protruding (P) domain is raised up off the shell (S) domain, and a contracted conformation, where the P domain rests on top of the S domain. The transition between these two states is mediated by environmental cues, including bile acids, a key constituent in the intestinal lumen, luminal pH and kosmotropic ions, like Ca2+. Multiple antibodies against human norovirus bind to epitopes accessible only in the expanded conformation, while receptor binding occupancy is increased in the contracted conformation. A second layer of flexibility lies within the P domain, in external loops that contain epitopes for neutralizing antibodies. Escape from antibody neutralization and bile acid binding to the capsid influence the positioning of these loops. Published and preliminary findings suggest a model whereby the expanded conformation interfaces with the immune system, while the contracted form is optimized for cell/virus interactions. To investigate this hypothesis, we will pursue the following aims in vitro and in vivo: 1) Determine the importance of the flexible linker between P and S domain mediating contraction of the norovirus capsid on infectivity, and 2) Determine the importance of capsid protein loop flexibility on MNV infectivity. Towards that end, we will test viral mutants with varying levels of flexibility by changing the linker length, and viral mutants lacking the bile acid binding site. These conceptually innovative studies promise to be of high impact, because they will define fundamental features of norovirus capsid dynamics and their role in infection and pathogenesis. Such information is important for norovirus vaccine design.