The impact of Helicobacter pylori infection on inflammatory bowel disease suscept

描述(由申请人提供)： 幽门螺杆菌在世界上超过一半的人口的胃粘膜中定居。大约10%-15%的感染者将继续发展为胃十二指肠溃疡，3%的人将发展为胃癌。已经提出了普遍接种疫苗的建议，但在85%-90%的无症状个体中根除幽门螺杆菌的影响尚未得到强调。一个潜在的负面影响是幽门螺杆菌可能对炎症性肠病(IBD)的发展起到保护作用，IBD是一种由于宿主对肠道内微生物的免疫反应失调而导致的胃肠道慢性衰弱炎症状况。这项提议的广泛的长期目标是阐明幽门螺杆菌如何有助于预防IBD的机制。一些报告表明，感染幽门螺杆菌的患者患IBD的风险较低，并指出在幽门螺杆菌感染的地方性地区，IBD的发病率上升。这种联系的机制对于确定根除幽门螺杆菌和增加IBD风险之间的因果关系非常重要，目前尚不清楚。这项研究背后的中心假设是幽门螺杆菌的定植通过维持髓系树突状细胞(DC)的耐受表型来诱导调节性T细胞(Tregs)，从而降低宿主对IBD的易感性。这一假设的理论基础是基于以下观察结果。首先，幽门螺杆菌感染患者的Treg反应比未感染的患者高。Tregs的耗尽逆转了幽门螺杆菌感染者记忆T细胞的免疫抑制。其次，Tregs被证明在抑制小鼠结肠炎方面起到了作用。第三，我们的初步结果表明，在体外，幽门螺杆菌维持半成熟树突状细胞的耐受表型，在体内，幽门螺杆菌冲击的髓系树突状细胞诱导幽门螺杆菌特异性Tregs。因此，这项建议的总体目标是研究幽门螺杆菌感染在调节IBD易感性中的作用。 具体目标： 1.研究幽门螺杆菌维持DC耐受表型的机制。1.1.目的：研究幽门螺杆菌基因敲除株在维持DC耐受性中的作用。将C57BL/6骨髓来源的树突状细胞与幽门螺杆菌突变株共培养，比较其转化生长因子-2的产生和Tregs的诱导。1.2.研究TLR-2信号和IRAK-M的作用。使用TLR-2空或IRAK-M siRNA来评估这两条通路在幽门螺杆菌诱导的DC耐受中的作用。 2.研究幽门螺杆菌诱导的Tregs对小鼠慢性葡聚糖硫酸钠结肠炎易感性的影响。2.1.目的：证明幽门螺杆菌诱导的胃外特异性Tregs反应的存在(口服幽门螺杆菌与幽门螺杆菌冲击的DC转移加口服幽门螺杆菌)。小鼠将被过继转移到PBS处理的树突状细胞或幽门螺杆菌致敏的树突状细胞，随后幽门螺杆菌感染。胃外幽门螺杆菌特异性Tregs的存在将被评估。2.2.目的：探讨幽门螺杆菌Treg诱导治疗慢性DSS结肠炎的疗效。过继转移PBS处理的树突状细胞或幽门螺杆菌致敏的树突状细胞后感染幽门螺杆菌的小鼠将被DSS治疗以诱导慢性结肠炎。将比较结肠炎的程度，以确定幽门螺杆菌特异性Tregs对宿主结肠炎易感性的影响。该项目与健康相关的是了解根除幽门螺杆菌对宿主对IBD易感性的影响。该项目的完成还将提供一种潜在的机制，通过这种机制，有益的细菌(例如益生菌)可以帮助预防IBD暴发。幽门螺杆菌在世界上超过一半的人口的胃粘膜中定居。大约10%-15%的感染者将继续发展为胃十二指肠溃疡，3%的人将发展为胃癌。已经提出了普遍接种疫苗的建议，但在85%-90%的无症状个体中根除幽门螺杆菌的影响尚未得到强调。一些报告表明，感染幽门螺杆菌的患者患炎症性肠病的风险较低，并指出在幽门螺杆菌感染的地方性地区，炎症性肠病的发病率上升。这种联系的机制对于确定根除幽门螺杆菌和增加IBD风险之间的因果关系非常重要，目前尚不清楚。这项建议的目标是研究幽门螺杆菌如何通过诱导宿主中的抑制性T细胞来影响个体的免疫系统，并在结肠炎的动物模型中展示幽门螺杆菌感染如何预防IBD。该项目与健康相关的是了解根除幽门螺杆菌对宿主对IBD易感性的影响。该项目的完成还将提供一种潜在的机制，通过这种机制，有益的细菌(例如益生菌)可以帮助预防IBD暴发。

DESCRIPTION (provided by applicant): Helicobacter pylori colonizes the gastric mucosa of more than half of the world's population. Approximately 10-15% of the infected individuals will go on to develop gastroduodenal ulcers and <3% will develop gastric cancer. Universal vaccination has been proposed and yet the impact of eradicating H. pylori in the 85-90% of otherwise asymptomatic individuals has not been emphasized. One potential negative impact is the possible protective role of H. pylori against the development of inflammatory bowel disease (IBD), a chronic debilitating inflammatory condition of the gastrointestinal tract resulting from a dysregulation of host immune response to resident gut microbes. The broad long-term objective of this proposal is to elucidate the mechanisms of how H. pylori may aid in the prevention of IBD. Several reports indicated lower risk of IBD in patients infected with H. pylori and noted a rising incidence of IBD in regions endemic for H. pylori infection. The mechanism of this association, which is important for defining a causal relationship between H. pylori eradication and increased risk of IBD, is currently unknown. The central hypothesis behind the proposed research is that H. pylori colonization induces regulatory T cells (Tregs) by maintaining toleragenic phenotype of myeloid dendritic cells (DCs) thus decreases host susceptibility to the development of IBD. The rationale for this hypothesis is based on the following observations. First, patients with H. pylori infection were found to have higher Treg response than uninfected individuals. Depletion of Tregs reversed the immunosuppression on memory T cells in those infected with H. pylori. Second, Tregs were shown to play a role in suppressing colitis in mice. Third, our preliminary results show that in vitro, H. pylori maintains the toleragenic phenotype of semi-mature DCs and that, in vivo, H. pylori-pulsed myeloid DCs induce H. pylori-specific Tregs. Thus, the overall goal of this proposal is to examine the role of H. pylori infection in modulating IBD susceptibility. Specific Aims: 1. Study the mechanism of how H. pylori maintains DC toleragenic phenotype. 1.1. To study the role of H. pylori factors (PAI, CagA, VacA) in the maintenance of DC tolerance using knockout strains of H. pylori. C57BL/6 bone marrow-derived DCs will be cocultured with H. pylori mutant strains and TGF-2 production and Tregs induction will be compared. 1.2. To examine the role of TLR-2 signaling and IRAK-M. Using TLR-2 null or IRAK-M siRNA to assess the role of these two pathways in H. pylori-induced DC tolerance. 2. To study the impact of H. pylori-induced Tregs on mouse susceptibility to chronic dextran sulfate sodium (DSS)-colitis. 2.1. To demonstrate the presence of extragastric H. pylori-specific Tregs response induced by H. pylori (oral gavaged H. pylori versus H. pylori-pulsed DC transfer plus oral H. pylori). Mice will be adoptively transferred with PBS-treated DCs or H. pylori-pulsed DCs followed by H. pylori infection. The presence of extragastric H. pylori-specific Tregs will be assessed. 2.2. To study the effect of H. pylori Treg induction on chronic DSS colitis. Mice adoptively transferred with PBS-treated DCs or H. pylori-pulsed DCs followed by H. pylori infection will be treated with DSS to induce chronic colitis. The degree of colitis will be compared to determine the effect of H. pylori-specific Tregs on host susceptibility to colitis. The health relatedness of the project is to understand the impact of H. pylori eradication on the host susceptibility to IBD. The completion of this project will also offer a potential mechanism through which beneficial bacteria (e.g., probiotics) may help to prevent IBD flares. Helicobacter pylori colonizes the gastric mucosa of more than half of the world's population. Approximately 10-15% of the infected individuals will go on to develop gastroduodenal ulcers and <3% will develop gastric cancer. Universal vaccination has been proposed and yet the impact of eradicating H. pylori in the 85-90% of otherwise asymptomatic individuals has not been emphasized. Several reports indicated lower risk of Inflammatory bowel disease (IBD) in patients infected with H. pylori and noted a rising incidence of IBD in regions endemic for H. pylori infection. The mechanism of this association, which is important for defining a causal relationship between H. pylori eradication and increased risk of IBD, is currently unknown. The goals of this proposal are to study how H. pylori may influence the immune system of an individual by inducing suppressive T cells in the host and to show in an animal model of colitis, how H. pylori infection may protect against IBD. The health relatedness of the project is to understand the impact of H. pylori eradication on the host susceptibility to IBD. The completion of this project will also offer a potential mechanism through which beneficial bacteria (e.g., probiotics) may help to prevent IBD flares.