Mucosal dendritic cell function following enteric virus infection

描述（由申请方提供）：粘膜免疫系统必须对肠道细菌和食物抗原保持耐受性，但仍保持对病原微生物引发炎症反应的能力。肠粘膜中的树突状细胞（DC）群体控制启动针对感染的炎症适应性免疫应答的过程。虽然微生物病原体相关的分子模式触发DC中的模式识别受体（PRR）被广泛接受，但是关于什么因素迫使树突状细胞启动炎症反应的清晰画面尚未出现。了解DC如何启动肠道病毒感染的炎症反应的过程将提高开发粘膜疫苗的成功率，这直接解决了RFA题为粘膜免疫防御机制的目的。 肠道呼肠孤病毒感染诱导肠道中强烈的Th 1型免疫应答，其特征在于产生IFN-γ，病毒特异性CD 8+细胞毒性T细胞的活化，以及IgG 2a亚类的丰富的抗原特异性血清抗体的出现。这些观察结果，连同沿着额外的初步数据支持了该项目的中心假设，即呼肠孤病毒的Th 1促进佐剂效应是由于无细胞或细胞相关病毒体激活树突状细胞，并且需要瞬时病毒基因转录以获得完全活性。病毒基因转录通过由细胞内PRRs RIG-1/MDA-5介导的信号传导导致DC活化，其诱导粘膜DC产生Th 1极化细胞因子如IL-12。该项目的总体目标是更清楚地了解肠道病毒如何刺激粘膜DC，从而为推进粘膜疫苗开发领域提供机会。中心假设将通过以下特定目的进行检验：1）比较有复制能力和无复制能力的病毒由于通过细胞内抗病毒PRR的信号传导而激活粘膜DC和巨噬细胞的能力，2）评价粘膜DC对无细胞呼肠孤病毒和呼肠孤病毒感染的IEC的应答，和3）证明病毒感染的粘膜DC将初始细胞活化为Th 1表型的能力，并确定IL-12在该应答中的作用。 相关性：全世界每年有多达250万人死于食源性和水源性腹泻病，据估计，美国近80%的食源性疾病是由肠道病毒引起的。除了肠胃炎，肠道病毒引起的其他疾病包括肝炎、心肌炎和中枢神经系统炎症。该项目将提高肠道免疫系统最初如何对肠道病毒作出反应的知识，这些信息将有助于开发针对通过胃肠道入侵的病毒的疫苗。

DESCRIPTION (provided by applicant): The mucosal immune system must remain tolerant to commensal bacteria and food antigens, yet still maintain the capacity to trigger inflammatory responses to pathogenic microorganisms. The process of initiating inflammatory adaptive immune responses to infection is controlled by multiple populations of dendritic cells (DCs) in the intestinal mucosa. Although it is widely accepted that microbial pathogen associated molecular patterns trigger pattern recognition receptors (PRRs) in DCs, a clear picture as to what factors force dendritic cells into initiating inflammatory responses has not yet emerged. Understanding the processes of how DCs initiate inflammatory responses to enteric virus infection will enhance success in developing mucosal vaccines, which directly addresses the purpose of the RFA entitled Immune Defense Mechanisms at the Mucosa. Enteric reovirus infection induces robust Th1- type immune responses in the intestine that is characterized by production of IFN-?, activation of virus-specific CD8+ cytotoxic T-cells, and appearance of abundant antigen-specific serum antibody of the IgG2a subclass. These observations, along with additional preliminary data support the central hypothesis of this project that the Th1-promoting adjuvant effect of reovirus is due to activation of dendritic cells by cell-free or cell-associated virions, and requires transient viral gene transcription for full activity. Viral gene transcription leads to DC activation through signaling mediated by the intracellular PRRs RIG-1/MDA-5, which induces mucosal DCs to produce Th1 polarizing cytokines such as IL-12. The overall goal of this project is to produce a clearer understanding of how mucosal DCs are stimulated by enteric viruses, thus providing opportunities for advancing the field of mucosal vaccine development. The central hypothesis will be tested with the following Specific Aims: 1) Compare the capacities of replication competent and replication incompetent virus to activate mucosal DCs and macrophages as a result of signaling through intracellular antiviral PRRs, 2) Evaluate the responses of mucosal DCs to cell free reovirus and reovirus-infected IECs, and 3) Demonstrate the capacity of virus-infected mucosal DCs to polarize naive cells to a Th1 phenotype, and determine the role of IL-12 in this response. RELEVANCE: There are up to 2.5 million deaths per year worldwide from food and water-borne diarrheal disease, and it has been estimated that nearly 80% of food-borne illnesses in the United States are due to enteric viruses. Besides gastroenteritis, other diseases caused by enteric viruses include hepatitis, myocarditis, and inflammation of the central nervous system. This project will improve knowledge of how the intestinal immune system initially responds to enteric viruses, and this information will aid in development of vaccines against viruses that invade through the gastrointestinal tract.