Innate Immune Defense against Clostridium Difficile Infection

描述(申请人提供)：艰难梭菌引起结肠炎后，抗生素介导的肠道微生物区系扰动。艰难梭菌每年导致500,000多例感染 据估计，美国每年有15,000人死亡。从受污染的环境中摄取具有感染性的孢子是获得这种感染的主要途径。艰难梭菌与正常肠道微生物区系或宿主天然免疫系统之间的相互作用知之甚少。本实验室对抗生素治疗的小鼠艰难梭菌感染进行了研究，结果表明，用细菌鞭毛蛋白刺激TLR-5或用Resiquimod刺激TLR7/8可显著增强对艰难梭菌感染的抵抗力。我们还证明，单剂克林霉素会延长艰难梭菌感染的易感性。该项目的目标是表征先天性免疫防御系统，包括由共生微生物群诱导的免疫系统，以保护艰难梭菌免受感染。第一个目的是研究鞭毛蛋白刺激TLR5或雷斯奎莫德刺激TLR7/8增强对艰难梭菌感染的抵抗力的机制。我们将研究IL22、ARL碳氢化合物受体以及初级和次级胆盐在TLR介导的对艰难梭菌感染的防御中的作用。第二个目标是确定肠道树突状细胞或炎性单核细胞是否有助于抵抗艰难梭菌感染。我们将使用我们实验室培育的CCR2报告基因和CCR2缺失小鼠来确定炎性单核细胞在艰难梭菌结肠炎发病机制中的作用。第三个目的是确定不同抗生素处理对肠道微生物区系组成的影响。我们将使用罗氏454大规模并行焦磷酸测序平台来确定胃肠道微生物的复杂性，并将菌群的变化与艰难梭菌感染的易感性相关联。将用分离的肠道微生物群重组小鼠，并测量对艰难梭菌感染的抵抗力。这些研究将确定抑制艰难梭菌萌发和/或营养生长的微生物种群。我们的最终目标是确定体内保护宿主免受艰难梭菌感染的机制，并发现可行的方法，如选择性TLR或细胞因子受体刺激或微生物区系操作，在脆弱的患者中重新诱导这些机制。

DESCRIPTION (provided by applicant): Clostridium difficile causes colitis following antibiotic-mediated perturbation of the intestinal microbiota. C. difficile causes over 500,000 infections per year, with an estimated 15,000 deaths annually in the United States. Ingestion of infectious spores from contaminated environments represents the major route by which this infection is acquired. Very little is known about interactions between C. difficile and the normal intestinal microbiota or with the host innate immune system. Our laboratory has investigated C. difficile infection in antibiotic treated mice and demonstrated that stimulating TLR-5 with bacterial flagellin or TLR7/8 with resiquimod markedly enhances resistance to C. difficile infection. We have also demonstrated that a single dose of clindamycin results in prolonged susceptibility to C. difficile infection. The goal of this project is to characterize innate immune defenses, includig those induced by the commensal microbial flora, in protection against C. difficile infection. The first aim is to characterize the mechanism by which stimulation of TLR5 by flagellin or TLR7/8 by resiquimod enhances resistance to C. difficile infection. We will investigate the role IL22, the arl hydrocarbon receptor and primary and secondary bile salts in TLR-mediated defense against C. difficile infection. The second aim is to determine whether intestinal dendritic cells or inflammatory monocytes contribute to resistance to C. difficile infection. We will use CCR2-reporter and CCR2-depletor mice that were generated in our laboratory to determine the impact of inflammatory monocytes on the pathogenesis of C. difficile colitis. The third aim is to determine the effect of different antibiotic treatments on the composition of the intestinal microbial flora. We will use the Roche 454 massively parallel pyrosequencing platform to determine microbial complexity in the GI tract, and to correlate changes in the flora with susceptibility to C. difficile infection. Mice will be reconstituted with fractionated intestinal microbiota and resistance to C. difficile infection will be measured. These studies will identify microbial populations that inhibit germination and/or vegetative growth of C. difficile. Our ultimate goal is to identify the in vivo mechanisms protecting the host from C. difficile infection and to discover practicable approaches, such as selective TLR or cytokine receptor stimulation or microbiota manipulation, to re-induce these mechanisms in vulnerable patients.