The role of norovirus capsid flexibility in infection and pathogenesis

诺如病毒衣壳柔韧性在感染和发病机制中的作用 摘要 病毒衣壳是一种亚稳态结构，它在环境中的稳定形式和 宿主内部的不稳定形式。通常认为发生在细胞内或细胞内的特定提示需要 引发这一变化。衣壳的这种柔韧性是病毒粒子的一个基本特征，这对 病毒感染的成功。然而，我们对灵活性的理解存在一个根本性的差距。 影响诺如病毒感染和发病机制。诺如病毒是一种流行的肠道病原体，可引起 世界范围内的严重发病率和死亡率。然而，没有定向抗病毒策略被批准使用，在 部分原因是我们对它们生物学的基本方面了解有限。因此，这样做的目的是 目的是以小鼠诺如病毒(MNV)为研究对象，研究衣壳蛋白在病毒生物学中的作用 用于诺沃克病毒生物学研究的高度易处理的模型。我们和其他人最近的研究发现了关键 人类和小鼠诺沃克病毒衣壳的灵活性模式，突出了它们的动态性质。不像任何人 其他病毒结构到目前为止，诺如病毒衣壳存在于细胞外的两种状态，一种是扩张的 其中突出的(P)结构域从壳(S)结构域向上抬起，并且收缩的 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 由环境信号调节，包括胆汁酸，肠腔的关键成分，腔内pH和 粘性离子，如钙离子。多个抗人诺沃克病毒抗体结合到只能在 扩张构象，而收缩构象中受体结合占有率增加。一个 第二层灵活性存在于P结构域中，在包含中和表位的外部环中 抗体。逃避抗体中和和胆汁酸与衣壳结合影响定位 这些循环。已发表的和初步的发现表明，扩展的构象 与免疫系统对接，而收缩形式针对细胞/病毒相互作用进行了优化。至 研究这一假说，我们将在体外和体内追求以下目标：1)确定重要性 P和S结构域之间的柔性连接子介导诺如病毒衣壳的收缩对感染性的影响 2)确定衣壳蛋白环灵活性对MNV感染性的重要性。为此，我们将测试 通过改变连接子长度具有不同程度灵活性的病毒突变体，以及缺乏胆汁的病毒突变体 酸结合部位。这些概念上的创新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。是这样的 信息对诺沃克病毒疫苗的设计很重要。

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.