Gut microbiome influences on autoimmune disease

描述(申请人提供)：人类物种在数十万年的时间里与一系列共生微生物共同进化，这种共生关系现在被生活方式、卫生或抗生素广泛使用的深刻变化所改变，这些变化可能与过敏或自身免疫性疾病的发病率增加有关。肠道微生物强烈影响免疫细胞分化，节段性丝状细菌(SFB)是一种驻留在肠道的厌氧菌，它促进产生IL17的“Th17”细胞的分化，进而引发依赖Th17的自身免疫性疾病。本项目将分析SFB&GT；Th17轴的机制，这是一个定义明确且易于处理的微生物对免疫功能影响的模型系统。SFB诱导的小肠变化的基因表达谱带来了几个有趣的候选基因，我们已经获得了正式证据，其中之一，血清淀粉样蛋白SAA3，构成了级联反应中的一个重要继电器。我们将在这些结果的基础上分析SFB和Th17分化之间的相互作用，以及SFB的影响如何与其他微生物或环境影响相结合。1.确定SFB在体内诱导Th17分化的细胞和分子序列。我们推测，三七在与其相互作用的上皮细胞中启动了一系列反应级联反应，并通过树突状细胞的巨噬细胞传递，最终促进了CD_4+αβT细胞的Th17分化。基因组图谱显示，SFB诱导了一些基因的表达，这些基因的产物可能是级联反应的中间产物：我们已经开始确定其重要性的血清淀粉样蛋白SAA3，以及其他候选基因(SAA1，iNOS，Resisin-β)。我们将绘制事件的顺序：(I)确定这些假定的中间体被诱导的细胞类型；(Ii)用可诱导的转基因和基因敲除小鼠评估每个中间体下游的反应图的哪一段。2.SAA3是如何诱导αβT细胞产生Th17的。重组SAA3只能在髓系CD11b+和CD11c+细胞存在的情况下才能诱导Th17分化。我们将通过确定哪个髓样细胞(S)可以作为基本辅助因子，分析哪些信号通路是由SAA3触发的，以及测试哪些中间细胞因子可能被诱导和需要来建立发挥作用的机制。3.SFB效应是否受其他微生物或环境辅助因素的调节。SFB的影响很可能受到其他肠道共生因素或饮食因素的影响。我们将通过将SFB作用中的微观异质性与其他细菌家族的丰富程度相关联来测试这一概念，这是由微生物群落遗传图谱确定的，并测试SFB诱导的Th17细胞和关节炎表现如何受到饮食元素(AhR配体、氯化钠)的影响。这些研究应该为肠道微生物区系如何改变宿主的免疫系统和调节自身免疫性疾病的风险提供新的机械性见解，这些机械性信息可能会为解决人类自身免疫性疾病提供新的策略。

DESCRIPTION (provided by applicant): The human species has co-evolved over hundreds of millennia with an array of commensal microbes, a symbiotic relationship now altered by profound changes in lifestyle, hygiene, or widespread antibiotic use, changes that may be linked to the increasing incidence of allergy or autoimmune diseases. Intestinal microbes strongly influence immune cell differentiation, as exemplified by Segmented Filamentous Bacteria (SFB), a gut- resident anaerobe which promotes the differentiation of IL17-producing "Th17" cells, which in turn unleash Th17-dependent autoimmune diseases. This project will analyze the mechanisms of the SFB>Th17 axis, a well-defined and tractable model system of the microbial influence on immune function. Gene expression profiling of changes induced by SFB in the small intestine brought forth several intriguing candidates, and we have obtained formal evidence that one of them, the serum amyloid protein SAA3, constitutes an essential relay in the cascade. We will build on these results to analyze the interplay between SFB and Th17 differentiation, and how the effects of SFB are influenced and integrated within other microbial or environmental influences. 1. Identify the sequence of cells and molecules through which SFB induces Th17 differentiation in vivo. We hypothesize that SFB elicits a response cascade, initiated in the epithelial cells with which SFB interacts, transmitted via macrophages of dendriti cells, which ultimately promotes the Th17 differentiation of CD4+ αβT cells. Genomic profiling show that SFB induces the expression of a number of genes whose products may function as intermediates in the cascade: the serum amyloid SAA3 whose importance we have begun to establish, and other candidates (SAA1, iNOS, Resistin-β). We will chart the sequence of events: (i) identify the cell-types in which these putative intermediates are induced; (ii) assess with inducible transgenesis and knockout mice which segment of the response maps downstream of each intermediate. 2. How SAA3 induces the Th17 in αβT cells. Recombinant SAA3 can induce Th17 differentiation but only in the presence of myeloid CD11b+ od CD11c+ cells. We will establish the mechanism at play by establishing which myeloid cell(s) can serve as the essential cofactor, analyzing which signaling pathways are triggered by SAA3, and testing which intermediate cytokines may be induced and required. 3. Are SFB effects modulated by, other microbes or environmental cofactors. It is likely that SFB's influence is modulated by other gut commensals, or by dietary factors. We will test this notion by correlating the micro- heterogeneity in SFB's effects with the abundance of other bacterial families, determined by microbial community genetic profiling, and by testing how SFB-induced Th17 cells and arthritis manifestations are influenced by dietary elements (Ahr ligands, NaCl). These studies should provide novel mechanistic insights into how the gut microbiota alters the host's immune system and modulate the risk of autoimmune diseases, mechanistic information which may suggest new strategies for addressing human autoimmune disease.