Intestinal granuloma formation during Yersinia pseudotuberculosis infection

项目总结/摘要 在各种感染性和非感染性情况下，慢性免疫刺激诱导免疫球蛋白的形成。 肉芽肿：募集的免疫细胞的聚集，被认为是包裹病原体并阻止其 传播。尽管这是许多感染的一个突出特征，但我们知识中的关键差距是 肉芽肿形成的机制和这些结构在控制炎症中的功能作用 传染病耶尔森氏菌是一种细菌病原体，可阻断免疫细胞功能并诱发肉芽肿 在淋巴组织中形成。假结核耶尔森氏菌（Yptb）引起自限性胃肠炎， 粪-口传播后免疫活性宿主的淋巴结炎。YPTB破坏免疫反应 通过注射耶尔森氏菌外部蛋白（Yops）到附近的免疫细胞通过针样III型， 分泌系统，阻断功能，如吞噬作用和促炎基因表达。而 肉芽肿在耶尔森氏菌感染淋巴组织期间得到了很好的描述，但对早期肉芽肿的了解相对较少。 肠道感染在这一建议中，我们描述了，第一次，小鼠模型的肉芽肿形成 在急性Yptb感染期间的肠粘膜中。重要的是，体内有大量的活细菌， 肉芽肿，但在周围的非肉芽肿肠组织中基本上没有，这表明肉芽肿 在肠粘膜中起着以前没有特征的作用，肠粘膜是一种免疫屏障， 耶尔森氏菌传播。有趣的是，缺乏Yops的Yptb不诱导肠肉芽肿形成， 这表明这些结构的形成是对细菌毒力特征的响应。此外，肠 肉芽肿高度富集嗜中性粒细胞和炎性单核细胞。引人注目的是，单核细胞缺乏型Ccr 2- /-小鼠在限制细菌传播方面表现出缺陷，屈服于急性感染。同样，老鼠 缺乏肿瘤坏死因子（TNF）信号传导，一种增强吞噬细胞杀微生物功能的细胞因子， 在细菌限制方面表现出缺陷。因此，我假设Yop对免疫细胞功能的阻断 效应蛋白诱导肠道肉芽肿的形成，通过 单核细胞衍生的TNF介导的细菌限制。在这个建议中，我将调查形成和 从细菌和宿主两方面探讨了肠道肉芽肿的功能。首先，我将揭开耶尔森菌 通过检测一组Yop突变株，毒力因子诱导肠肉芽肿形成， 使用注射报告菌株（Aim 1）。其次，我将剖析免疫细胞的功能， 通过嵌合体互补机制研究肠肉芽肿对耶尔森氏菌的限制 动物和基因消融系统（目标2）。这项工作将机械地定义一个以前不被欣赏的 宿主对耶尔森氏菌感染的免疫反应。来自这种新型肠肉芽肿模型的发现 形成将提供深入了解未来的工作，研究不足的肉芽肿性疾病，并强调 治疗慢性疾病的潜在治疗靶点。

Project Summary/Abstract In various infectious and non-infectious contexts, chronic immune stimulation induces the formation of granulomas: aggregations of recruited immune cells that are thought to encapsulate pathogens and prevent their dissemination. Despite being a prominent feature of numerous infections, key gaps in our knowledge are the mechanisms of granuloma formation and the functional role of these structures in controlling infectious disease. Yersinia are bacterial pathogens that block immune cell function and induce granuloma formation in lymphoid tissues. Yersinia pseudotuberculosis (Yptb) causes self-limiting gastroenteritis and lymphadenitis in immunocompetent hosts following fecal-oral transmission. Yptb subverts the immune response through the injection of Yersinia outer proteins (Yops) into nearby immune cells through a needle-like type III secretion system, blocking functions such as phagocytosis and pro-inflammatory gene expression. While granulomas are well-described during Yersinia infection of lymphatic tissue, relatively little is known about early intestinal infection. In this proposal, we describe, for the first time, a murine model of granuloma formation in the intestinal mucosa during acute Yptb infection. Importantly, live bacteria are abundant within granulomas but are largely absent from surrounding non-granuloma intestinal tissue, suggesting that granulomas play a previously uncharacterized role at the intestinal mucosa, an immunological barrier that bottlenecks Yersinia dissemination. Interestingly, Yptb lacking Yops does not induce intestinal granuloma formation, suggesting that these structures form in response to features of bacterial virulence. Further, intestinal granulomas are highly enriched in neutrophils and inflammatory monocytes. Strikingly, monocyte-deficient Ccr2- /- mice show defects in restriction of bacterial dissemination, succumbing to acute infection. Similarly, mice deficient in tumor necrosis factor (TNF) signaling, a cytokine that enhances phagocyte microbicidal function, exhibit defects in bacterial restriction. I therefore hypothesize that blockade of immune cell function by Yop effector proteins induces the formation of intestinal granulomas, which protect the host through bacterial restriction mediated by monocyte-derived TNF. In this proposal, I will investigate the formation and function of intestinal granulomas from both the bacterial and host sides. First, I will uncover how Yersinia virulence factors induce intestinal granuloma formation by testing a panel of Yop mutant strains, in addition to using an injection reporter strain (Aim 1). Second, I will dissect immune cell functions that are necessary for restriction of Yersinia by intestinal granulomas through complementary mechanistic studies using chimeric animals and genetic ablation systems (Aim 2). This work will mechanistically define a previously unappreciated facet of the host immune response to Yersinia infection. Findings from this novel model of intestinal granuloma formation will provide insight into future work on poorly-studied granulomatous disorders and underscore potential therapeutic targets for the treatment of chronic disease.