Immune responses to commensal bacterial spores in the intestinal mucosa

项目总结/摘要 厚壁菌门中的许多细菌物种产生孢子。真菌和病原菌的孢子 细菌在进入宿主和与免疫系统的最初接触中起着至关重要的作用。有多细菌 然而，孢子与宿主免疫的相互作用仍然知之甚少。在研究项目中，我们 研究孢子-免疫相互作用及其对炎症和组织稳态的影响， 肠粘膜我们发现，小鼠体内的RNA敏感Toll样受体（TLR）-TLR 7和TLR 13， 它们的人类对应物-在检测和触发对孢子的免疫反应方面发挥了至关重要的作用， 炭疽杆菌（BA），炭疽病的病原体。BA孢子携带大量的RNA，其TLR- 提取和纯化后保留了刺激活性。这种RNA主要位于最外层 孢子的外层，或者说孢子外壁。TLR 7/13感应BA孢子导致I型干扰素（IFN-I）的产生 从宿主细胞。这些发现促使我们在细菌孢子中寻找类似的结构 特征和功能特性。为了这项研究，我们设计了一个新的协议， 从粪便样品或肠腔内容物中分离而不进行离体培养。该协议使我们能够 检测具有高RNA含量和IFN-I诱导能力的肠道微生物群来源的孢子。这些发现，在 与新出现的证据相结合，“滋补”IFN-I信号传导可以预防结肠炎，结肠癌， 肠道病毒感染，使我们制定了中心假设，TLR传感孢子相关的RNA是一个重要的机制。 寄生细菌孢子诱导IFN-Ⅰ依赖性组织保护反应的关键机制 在肠粘膜中。在拟议的研究中，我们将通过追求 以下具体目的：鉴定小鼠和人肠道中的肠道细菌种类，其孢子 具有RNA负载的外孢壁和IFN-1诱导活性（目的#1）;并确定 芽孢杆菌芽孢和芽孢敏感TLR诱导IFN-1产生和抑制IFN-1表达的研究 肠粘膜中的炎性损伤（目标#2）。我们的研究将促进我们对粘膜 通过鉴定肠道细菌孢子作为肠道IFN-Ⅰ的主要诱导物， 生产和展示其在免疫调节和组织保护中的作用。

PROJECT SUMMARY/ABSTRACT Many bacterial species in the phylum Firmicutes produce spores. The spores of commensal and pathogenic bacteria play a crucial role in host entry and the initial encounter with the immune system. How bacterial spores interact with host immunity, however, remains poorly understood. In the proposed research project, we investigate spore-immune interactions and their impact on inflammation and tissue homeostasis in the intestinal mucosa. We discovered that RNA-sensing toll-like receptors (TLRs)—TLR7 and TLR13 in mice and their human counterparts—played a crucial role in detecting and triggering immune responses to the spores of Bacillus anthracis (BA), the etiologic agent of anthrax. BA spores harbored high amounts of RNA whose TLR- stimulating activity was retained after extraction and purification. This RNA was mainly located in the outermost layer of the spore, or the exosporium. TLR7/13 sensing of BA spores led to type I interferon (IFN-I) production from host cells. These findings prompted us to search commensal bacterial spores for similar structural features and functional properties. For this investigation, we devised a novel protocol that enabled spore isolation from fecal samples or intestinal luminal contents without ex vivo culture. This protocol allowed us to detect gut microbiota-derived spores with high RNA content and IFN-I-inducing capacity. These findings, in conjunction with the emerging evidence that "tonic" IFN-I signaling protects against colitis, colon cancer, and enteric viral infection, led us to formulate the central hypothesis that TLR sensing of spore-associated RNA is a pivotal mechanism by which commensal bacterial spores induce IFN-I-dependent tissue-protective responses in the intestinal mucosa. In the proposed research, we will verify the central hypothesis by pursuing the following specific aims: to identify the commensal bacterial species in the mouse and human gut whose spores possess an RNA-laden exosporium and IFN-I-inducing activity (Aim #1); and to establish the role of commensal bacterial spores and spore-sensing TLRs in inducing IFN-I production and suppressing inflammatory damage in the intestinal mucosa (Aim #2). Our study will advance our understanding of mucosal physiology and pathology by identifying commensal bacterial spores as major inducers of intestinal IFN-I production and demonstrating their role in immune regulation and tissue protection.