Persistent norovirus infection impairs protective immunity

描述(申请人提供)：杯状病毒科中的人类诺如病毒是全球非细菌性流行性胃肠炎的主要原因。原发人类诺沃克病毒感染不会引起持久的保护性免疫，这一事实可能会极大地影响疫苗接种策略的效果。我们的长期目标是阐明诺如病毒避免诱导保护性免疫的机制，最终将这一知识转化为成功的疫苗接种方法。关于人类诺如病毒的发病机制或控制它们的免疫反应知之甚少，因为以前还没有小动物模型或细胞培养系统的感染。我们实验室的数据定义了第一个诺沃克病毒感染的小动物模型：我们发现了第一个小鼠诺沃克病毒(MNV)MNV-1，并在体外证明了它在巨噬细胞和树突状细胞中的培养。我们现在已经使用这些独特的模型来研究诺沃克病毒的发病机制和免疫。我们已经确定MNV-1具有口服传染性，并与多种免疫活性小鼠品系的胃肠炎诱导有关，证实了该病毒作为研究人类诺沃克病毒致病机制的模型的实用性。重要的是，我们还确定，MNV-1的原发感染不能提供与同源病毒重新挑战的保护。因此，MNV-1代表了一个有价值的模型，可以用来剖析缺乏对人类诺沃克病毒感染的持久保护的病理生理学基础。有趣的是，老鼠和人类诺如病毒似乎持续感染它们的宿主。对于小鼠诺如病毒，持续病毒可以在免疫诱导部位检测到，包括肠系膜淋巴结和脾。我们的特定假设是，持续的诺沃克病毒感染免疫诱导部位，特别是这些部位内的抗原提呈细胞，损害了保护性免疫的发展。我们现在已经确定，由MNV-1原发感染引起的记忆免疫反应的大小与接种剂量呈负相关。因此，为了验证我们的假设，我们将(I)确定MNV-1持续感染与接种剂量之间是否存在直接相关性；(Ii)表征接种剂量对初次MNV-1感染后粘膜记忆免疫反应的影响；以及(Iii)确定免疫诱导部位的树突状细胞和巨噬细胞是否持续感染MNV-1。我们的最终目标是了解诺如病毒如何损害抗原提呈细胞的功能，从而不能诱导和/或维持保护性诺如病毒免疫，并将这一信息转化为有效的疫苗设计。 公共卫生相关性：杯状病毒科中的人类诺如病毒是全世界非细菌性流行性胃肠炎的主要原因，但感染不会产生持久的保护作用。我们的长期目标是阐明诺沃克病毒感染避免诱导保护性免疫的机制，最终将这一知识转化为成功的疫苗接种策略。我们的具体假设是，持续感染免疫细胞的诺沃克病毒抑制了保护性免疫的发展。

DESCRIPTION (provided by applicant): Human noroviruses in the Caliciviridae family are the major cause of non-bacterial epidemic gastroenteritis worldwide. Primary human norovirus infection does not elicit lasting protective immunity, a fact that could greatly affect the efficacy of vaccination strategies. Our long term goal is to elucidate the mechanisms by which noroviruses avoid the induction of protective immunity, ultimately translating this knowledge into successful vaccination approaches. Little is known regarding the pathogenesis of human noroviruses or the immune responses that control them because there has previously been no small animal model or cell culture system of infection. Data from our laboratory has defined the first small animal model of norovirus infection: We discovered the first murine norovirus (MNV), MNV-1, and demonstrated its cultivation in macrophages and dendritic cells in vitro. We have now used these unique models to examine norovirus pathogenesis and immunity. We have determined that MNV-1 is infectious orally and is associated with the induction of gastroenteritis in multiple immunocompetent mouse strains, confirming the utility of this virus as a model to study human norovirus pathogenesis. Importantly, we have also determined that primary MNV-1 infection fails to afford protection to re-challenge with homologous virus. Thus, MNV-1 represents a valuable model with which to dissect the pathophysiological basis for the lack of lasting protection to human norovirus infection. Interestingly, murine and human noroviruses appear to persistently infect their hosts. For murine noroviruses, persistent virus can be detected in immune-inductive sites including the mesenteric lymph nodes and the spleen. Our specific hypothesis is that persistent norovirus infection of immune- inductive sites, and specifically of antigen presenting cells within these sites, impairs the development of protective immunity. We have now determined that the magnitude of memory immune responses elicited by primary MNV-1 infection inversely correlates with inoculum dose. Thus, to test our hypothesis, we will (i) determine whether there is a direct correlation between persistent MNV-1 infection and inoculum dose; (ii) characterize the effect of inoculum dose on mucosal memory immune responses to primary MNV-1 infection; and (iii) determine whether dendritic cells and macrophages in immune-inductive sites are persistently infected with MNV-1. Our ultimate goal is to understand how noroviruses impair the functioning of antigen presenting cells such that protective norovirus immunity is not elicited and/or maintained, and to translate this information into effective vaccine design. PUBLIC HEALTH RELEVANCE: Human noroviruses in the Caliciviridae family are the major cause of non-bacterial epidemic gastroenteritis worldwide but infection does not induce lasting protection. Our long term goal is to elucidate the mechanisms by which norovirus infection avoids the induction of protective immunity, ultimately translating this knowledge into successful vaccination strategies. Our specific hypothesis is that persistent norovirus infection of immune cells inhibits the development of protective immunity.