The Pathogenesis of Enteric Fever

项目摘要/摘要 由伤寒沙门氏菌和副伤寒沙门氏菌引起的肠热病占近1500万 每年有13.6万人感染和死亡。我们开发了一种新的致死小动物肠道动物模型。 使用植入有功能的人类造血系统的人源化小鼠发烧。伤寒沙门氏菌的能力 和甲型副伤寒沙门氏菌对植入人造血细胞的人源化小鼠造成致死性感染 提示人类巨噬细胞在肠热病的发病机制中是必需的，并可能提供 持续感染的蓄水池。在人源化小鼠中进行的伤寒沙门氏菌全基因组分析证实了一些 疑似基本毒力决定因素，但也揭示了伤寒沙门氏菌和 非伤寒沙门氏菌血清型。此外，我们还发现伤寒沙门氏菌在培养的人体内持续存在。 由于缺乏多种SPI-2 III型分泌系统，巨噬细胞通过防止细胞凋亡而死亡 在非伤寒沙门氏菌发病机制中发挥核心作用的效应器。抑制核因子-κB选择性地杀死S. 伤寒杆菌感染的巨噬细胞，提示了一种治疗慢性肠热病的新策略。最近 我们还发现，肠热病和非伤寒沙门氏菌对 缺铁，观察到肠道微生物区系对抗伤寒沙门氏菌的肠道定植，以及 甲型副伤寒沙门氏菌和伤寒沙门氏菌在与人类的相互作用中显示出重要的相似性 巨噬细胞和人源化小鼠。 我们的中心假设是，肠道热沙门氏菌血清型的毒力取决于 巨噬细胞对先天免疫的逃避和持久性。研究计划将审查三个方面 具体目标： 1.避免肠道热沙门氏菌引起的巨噬细胞死亡。遗传和生化 方法将阐明伤寒沙门氏菌促进巨噬细胞存活和 在人源化小鼠中评估巨噬细胞存活与伤寒沙门氏菌毒力的相关性。 2.伤寒沙门氏菌与肠道微生物区系的相互作用胞外应激的作用 伤寒沙门氏菌对巨噬细胞毒性的反应、微生物区系拮抗和避免 将对持续定植于肠道的细菌进行调查。 3.甲型副伤寒沙门氏菌A毒力甲型副伤寒沙门氏菌毒力决定因素及其系统分析 将进行血清抵抗、铁摄取和巨噬细胞持久性的机制研究。 建议的研究将促进我们对肠热病发病机制的理解，并导致新的 预防和治疗的策略。

PROJECT SUMMARY/ABSTRACT Enteric fever, caused by the Salmonella serovars S. Typhi and S. Paratyphi, accounts for nearly 15 million infections and 136,000 deaths each year. We have developed a novel lethal small animal model for enteric fever using humanized mice engrafted with a functional human hematopoietic system. The ability of S. Typhi and S. Paratyphi A to cause lethal infections in humanized mice engrafted with human hematopoietic cells suggests that human macrophages are required for the pathogenesis of enteric fever and may provide a reservoir for persistent infection. A genome-wide analysis of S. Typhi in humanized mice confirms some suspected essential virulence determinants but also reveals unexpected differences between S. Typhi and non-typhoidal Salmonella serovars. Moreover, we have discovered that S. Typhi persists in cultured human macrophages by preventing apoptotic cell death, due to the absence of multiple SPI-2 type III secretion system effectors that play a central role in non-typhoidal Salmonella pathogenesis. NF-κB inhibition selectively kill S. Typhi-infected macrophages, suggesting a novel strategy for the treatment of chronic enteric fever. Recently we have also found significant differences in the responses of enteric fever and non-typhoidal Salmonella to iron deprivation, observed that the gut microbiota antagonizes S. Typhi intestinal colonization, and demonstrated important parallels between S. Paratyphi A and S. Typhi in their interactions with human macrophages and humanized mice. Our central hypothesis is that the virulence of enteric fever Salmonella serovars depends on the evasion of innate immunity and persistence in macrophages. The research plan will examine three specific aims: 1. Avoidance of Macrophage Cell Death by Enteric Fever Salmonella Serovars. Genetic and biochemical approaches will elucidate the molecular mechanisms by which S. Typhi promotes macrophage survival and assess the relevance of macrophage survival to S. Typhi virulence in humanized mice. 2. Interactions of Salmonella Typhi with the Gut Microbiota. The contributions of extracytoplasmic stress responses, microbiota antagonism and avoidance of macrophage cytotoxicity to the ability of S. Typhi to persistently colonize the intestinal tract will be investigated. 3. Salmonella Paratyphi A Virulence. A systematic analysis of S. Paratyphi A virulence determinants and its mechanisms of serum resistance, iron acquisition and macrophage persistence will be performed. The proposed studies will advance our understanding of enteric fever pathogenesis and lead to novel strategies for its prevention and treatment.