DEFINING HOST-MICROBIAL INTERACTIONS THAT TRIGGER INFLAMMATORY BOWEL DISEASE

描述（由申请人提供）：炎症性肠病（IBD）以肠道炎症复发/缓解为特征。遗传和环境因素在IBD易感性中起作用。本地微生物是可能在遗传易感宿主中引发IBD的环境因素之一。我们之前通过抗生素预处理小鼠的定植，在dnKO小鼠结肠炎模型中建立了特定细菌物种，拟杆菌（B. theta）的Koch假设。该模型包含两种抑制性细胞因子的信号缺失：IL-10和TGF？在CD4+ T细胞中，这两种细胞在一部分人IBD病例中具有同源遗传缺陷。现在需要的是确定B. theta在这种基因易感的小鼠中引发结肠炎的分子机制。我们有初步的数据表明，B. theta中一个控制28种磺胺酶（厌氧磺胺酶成熟酶anSME）活性的基因的缺失完全抑制定植dnKO小鼠的结肠炎。重要的是，这种突变B. theta在dnKO小鼠中的定殖水平与野生型B. theta相似。这一发现创造了一个整体假设，即B. theta可以引发结肠炎，因为它能够降解宿主硫酸粘液并进入粘膜。我们将使用这个独特的功能系统来执行分子科赫假设，并更精确地确定B θ中的细菌硫酸盐酶，这是其结肠炎活性所必需的。我们还将测试宿主硫酸酸化粘液的作用以及它的产生和分泌。最终，在这个模型中，T细胞绝对是产生结肠炎所必需的。令人惊讶的是，在B. theta定植之前，CD4+ T细胞被激活并产生炎症细胞因子，但不会引起疾病。因此，B. theta作为结肠炎细菌的鉴定也为确定CD4+ T细胞如何被触发成为致病性提供了独特的机会。我们还发现了人类B. theta特有的tcr。该工具对于确定B. theta定植的dnKO小鼠结肠炎发生的机制至关重要。我们组建了一个多学科的小组来处理这个项目。我们将从三个具体目标来研究这个问题。特异性目的1：确定B. theta粘液脱硫在dnKO结肠炎中的作用。特异性目的2：确定肠道粘液在dnKO小鼠中作为B. theta的功能性屏障的作用。特异性目的3：确定CD4+ T细胞如何引发dnKO结肠炎。如果有竞争，这些研究将建立新的范例，了解结肠菌如何在遗传易感宿主中引发疾病，并应应用于了解人类IBD的发病机制以及设计新的治疗方法。

DESCRIPTION (provided by applicant): Inflammatory bowel disease (IBD) is characterized by relapsing/remitting inflammation of the intestinal tract. Genetics and environmental factors play a role in IBD susceptibility. Indigenous microbes are one of the environmental factors that can trigger IBD in a genetically susceptible host. We previously established Koch's postulates for a specific bacterial species, Bacteroides thetaiotaomicron (B. theta) in the dnKO mouse model of colitis, by colonization of antibiotic pre-treated mice. This model contains loss of signaling for two inhibitory cytokines: IL-10 globally and TGF? in CD4+ T cells, both of which have homologous genetic defects in a subset of cases of human IBD. What is now needed is to determine the molecular mechanism by which B. theta can trigger colitis in this genetically susceptible mouse. We have preliminary data to show that deletion of a single gene in B. theta that controls the activity of 28 sulfatases (anSME for anaerobic sulfatase maturating enzyme) completely inhibits colitis in colonized dnKO mice. Importantly, this mutant B. theta colonizes dnKO mice to similar levels as wild- type B. theta. This finding created the overall hypothesis that B. theta can trigger colitis due to its ability to degrade host sulfated-mucus and access the mucosa. We will use this unique functional system to perform molecular Koch's postulates and determine with more precision, the bacterial sulfatase enzymes in B theta that are required for its colitogenic activity. We will also test the role of host sulfation of mucus as well as its production and secretion. Ultimately in this model, T cells are absolutely required to generate colitis. Surprisingly, prior to colonization with B. theta, the CD4+ T cells are activated and produce inflammatory cytokines, but cause no disease. Thus, the identification of B. theta as the colitogenic bacterium also provides the unique opportunity to determine how CD4+ T cells are triggered into becoming pathogenic. We have also identified TCRs that are specific for human B. theta. This tool will be critical to determine the mechanism by which colitis develops in B. theta colonized dnKO mice. We have assembled a multi-disciplinary team to tackle this project. We will investigate this question in three specific aims. Specific Aim 1: Determine the role of B. theta mucus desulfation in dnKO colitis. Specific Aim 2: Determine the role of intestinal mucus as a functional barrier to B. theta in dnKO mice. Specific Aim 3: Determine how CD4+ T cells initiate dnKO colitis. If competed, these studies will establish new paradigms for how colitogenic microbes trigger disease in a genetically susceptible host and should have application to understanding the pathogenesis of, as well as engineering new treatments for, human IBD.