Mucosal dendritic cell function following enteric virus infection

描述(申请人提供)：粘膜免疫系统必须保持对共生细菌和食物抗原的耐受性，同时仍保持对致病微生物的炎症反应的能力。肠道粘膜中多种树突状细胞(DC)控制着对感染的炎性适应性免疫反应的启动过程。虽然微生物病原体相关的分子模式触发DC上的模式识别受体(PRRs)已被广泛接受，但究竟是什么因素迫使树突状细胞启动炎症反应，目前还没有一个清晰的图景。了解树突状细胞如何对肠道病毒感染启动炎症反应的过程将有助于成功开发粘膜疫苗，这直接解决了题为黏膜免疫防御机制的RFA的目的。 肠内呼肠孤病毒感染可在肠道诱导强大的Th1型免疫反应，其特征是产生干扰素-β，激活病毒特异性CD8+细胞毒性T细胞，并产生丰富的IgG2a亚类抗原特异性血清抗体。这些观察结果以及其他初步数据支持该项目的中心假设，即呼肠孤病毒的Th1促进佐剂作用是由于无细胞或细胞相关病毒粒子激活树突状细胞，需要瞬时病毒基因转录才能充分发挥作用。病毒基因转录通过细胞内PRRs RIG-1/MDA-5介导的信号通路激活DC，诱导粘膜DC产生IL-12等Th1极化细胞因子。该项目的总体目标是更清楚地了解肠道病毒是如何刺激粘膜树突状细胞的，从而为推进粘膜疫苗开发领域提供机会。中心假说的检验有以下具体目的：1)比较复制能力和复制能力不强的病毒通过细胞内抗病毒PRR信号激活粘膜DC和巨噬细胞的能力；2)评估粘膜DC对游离呼肠孤病毒和呼肠孤病毒感染的IECs的反应；3)展示病毒感染的粘膜DC将幼稚细胞极化为Th1表型的能力，并确定IL-12在这一反应中的作用。 相关性：全世界每年有多达250万人死于食物和水传播的腹泻疾病，据估计，美国近80%的食物传播疾病是由肠道病毒引起的。除了胃肠炎，其他由肠道病毒引起的疾病包括肝炎、心肌炎和中枢神经系统炎症。该项目将提高有关肠道免疫系统最初如何对肠道病毒做出反应的知识，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.