Immune responses to commensal bacterial spores in the intestinal mucosa

项目摘要/摘要 毛藻门中的许多细菌都能产生孢子。共生孢子和致病孢子 细菌在宿主进入和与免疫系统的最初接触中起着至关重要的作用。细菌有多多 然而，孢子与宿主免疫的相互作用仍然知之甚少。在建议的研究项目中，我们 研究孢子-免疫相互作用及其对炎症和组织动态平衡的影响 肠粘膜。我们在小鼠和小鼠体内发现了RNA感测Toll样受体(TLRs)-TLR7和TLR13 它们在检测和触发对沙门氏菌孢子的免疫反应方面发挥了关键作用 炭疽芽孢杆菌是炭疽病的病原菌。BA孢子含有大量的RNA，其TLR- 提取纯化后仍保留刺激活性。该RNA主要位于最外层 孢子层，或外孢子层。TLR7/13对BA孢子的感应导致I型干扰素(IFN-I)的产生 来自宿主细胞。这些发现促使我们在共生细菌孢子中寻找类似的结构 特征和功能特性。为了这次调查，我们设计了一种新的协议，使孢子 未经体外培养从粪便样本或肠腔内容物中分离。这份协议允许我们 检测肠道微生物区系衍生的孢子，具有高RNA含量和诱导干扰素-I的能力。这些发现，在 与新出现的证据相结合的“强效”干扰素-I信号可预防结肠炎、结肠癌和 肠道病毒感染，导致我们形成一个中心假设，即TLR对孢子相关RNA的感知是一种 共生细菌孢子诱导干扰素-I依赖的组织保护反应的关键机制 在肠粘膜中。在拟议的研究中，我们将通过以下方式验证中心假设 以下具体目标：鉴定小鼠和人类肠道中的共生细菌种类，其孢子 具有携带RNA的外孢子菌和干扰素-I诱导活性(目标1)；并确定 共生细菌孢子和孢子感应TLR在诱导干扰素-I产生和抑制中的作用 肠黏膜的炎性损伤(目标2)。我们的研究将促进我们对粘膜的理解 确定共生细菌孢子为肠道干扰素-I的主要诱导物的生理和病理学 并展示了它们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.