HOST DEFENSES AGAINST PATHOGENIC E. coli

描述(由申请人提供)：致病性(腹泻)大肠杆菌是美国和发展中国家食源性疾病的重要原因。大多数致病性大肠杆菌菌株，如EPEC和EHEC，可引起粘膜炎症和疾病，但不会深入肠道粘膜或全身传播。虽然在理解致病性大肠杆菌致病机制(如毒素)方面取得了很大进展，但对寄主对这些病原体的防御机制知之甚少。基于缺乏深层组织侵袭，我们假设在肠腔或粘膜表面工作的宿主防御是控制和根除大多数致病性大肠杆菌感染的关键。我们的初步数据强烈支持这一观点，因为我们发现在感染的小鼠模型中，B细胞是清除EPEC菌株所绝对需要的。这项拟议的研究将建立在这一观察的基础上，并使用小鼠感染模型来确定B细胞依赖的宿主对致病性大肠杆菌的防御机制。我们将特别关注分泌型抗体作为B细胞免疫效应器的重要性。这些对特定免疫效应机制的研究将与对致病性大肠杆菌的粘膜免疫防御调节的功能研究相辅相成，特别是免疫调节细胞因子IL-6的功能。此外，我们将开始确定肠道上皮细胞在协调对致病性大肠杆菌的免疫防御中的重要性，因为上皮细胞是宿主和大多数致病性大肠杆菌菌株之间相互作用的焦点。这些实验将特别关注转录因子NF-kappaB在肠上皮细胞中的生理功能，使用我们建立的一种新的小鼠模型，在该模型中，有选择地从肠上皮细胞中删除NF-kB信号通路的关键成分。本研究的主要目的如下：目的1.明确B细胞依赖宿主对致病性大肠杆菌的防御机制。目的2.探讨IL-6在致病性大肠杆菌宿主防御中的作用。目的3.明确上皮细胞核因子-kappaB在宿主防御致病性E.coll中的重要性。总之，这些研究将为宿主根除致病性大肠杆菌感染的关键宿主防御系统提供重要的新见解，从而为设计针对这些病原体的免疫策略提供重要的基础。

DESCRIPTION (provided by applicant): Pathogenic (diarrheagenic) Escherichia coli are an important cause of food-borne disease in the U.S. and developing countries. Most pathogenic E. coli strains, e.g. EPEC and EHEC, cause mucosal inflammation and disease without deep invasion into the intestinal mucosa or systemic spread. Although much progress has been made in understanding the mechanisms by which pathogenic E. coli cause disease (e.g. toxins), relatively little is known about the host defenses against these pathogens. Based on the lack of deep tissue invasion, we hypothesize that host defenses that operate in the intestinal lumen or at the mucosal surface are key for controlling and eradicating infections with most strains of pathogenic E. coil. Our preliminary data strongly support this notion since we found that B cells are absolutely required for clearance of an EPEC strain in a mouse model of infection. The proposed studies will build on this observation and define the mechanisms of B cell-dependent host defense against pathogenic E. coli, using murine infection models. We will focus specifically on the importance of secretory antibodies as immune effectors of B cells. These studies on specific immune effector mechanisms will be complemented with functional investigations on the regulation of mucosal immune defenses against pathogenic E. coli, with a particular focus on the functions of the immunoregulatory cytokine, IL-6. In addition, we will begin to determine the importance of the intestinal epithelium in orchestrating immune defenses against pathogenic E. coli, as epithelial cells are a focal point of interaction between host and most strains of pathogenic E. coll. These experiments will focus particularly on the physiologic functions of the transcription factor, NF-kappaB, in the intestinal epithelium, using a novel murine model we have developed in which a key component of the NF-kB signaling pathway is deleted selectively from intestinal epithelial cells. The proposed studies have the following Specific Aims: AIM 1. To define the mechanisms of B cell-dependent host defense against pathogenic E. coli. AIM 2. To determine the functions of IL-6 in host defense against pathogenic E. coli. AIM 3. To define the importance of epithelial cell NF-kappaB in host defense against pathogenic E. coll. Together, these studies will provide significant new insights into the key host defenses by which the host can eradicate infection with pathogenic E. coli, thus providing an important basis for designing immunization strategies against these pathogens.