INTERVENTIONAL STRATEGIES FOR HEMORRHAGIC COLITIS

这项提议的主要目的是使用一种新的动物模型， 肠出血性大肠杆菌（EHEC）感染，以了解分子 肠出血性大肠杆菌感染的发病机制，并制定实用的干预措施 预防和治疗肠出血性大肠杆菌病的策略。 现在大家都认识到 一些产毒素的大肠杆菌菌株，最常见的血清型 O 157：H7，诱导出血性结肠炎，可能进展为致死性 溶血性尿毒症综合征 肠出血性大肠杆菌菌株产生强效毒素， 志贺样毒素（Shiga-like Toxins，SLT），因为它们与 滋贺毒素 大多数肠出血性大肠杆菌都有能力 通过粘附紧密粘附于肠上皮细胞， 消除A/E机制。 虽然肠出血性大肠杆菌的附着机制， 微绒毛的损失，可能直接导致腹泻;最严重的 肠和肾表现由毒素介导的损害引起， 血管内皮伴组织水肿，炎性浸润， 细胞因子产生和血管血栓。 A/E可能有 对向宿主输送毒素有深远的影响，但这 没有得到充分的研究。 目前，没有有效的 预防或接受EHEC疾病的治疗。 该提案的具体目标是使用肠出血性大肠杆菌动物模型 感染： 1.使用突变体检查A/E粘附对细菌毒性的影响 肠上皮细胞消失位点（LEE）。 2.测试被动施用的免疫球蛋白与抗- 预防肠出血性大肠杆菌病。 3.测试管腔内毒素受体类似物预防 肠出血性大肠杆菌病 4.确定抗生素治疗是否有益或有害 对病程的影响。 5.检查炎症介质，并确定是否抗- 炎症策略，特别是重组IL-1受体 拮抗剂（IL-1 ra）和重组TNF结合蛋白（TNF-BP）可 改变疾病。 6.研究针对肠出血性大肠杆菌的主动免疫策略， 毒素和肠上皮细胞消失位点基因产物 （LEE）. 将大肠杆菌菌株RDEC-H19 A感染的家兔作为动物 EHEC疾病模型。 RDEC-H19 A，由 将O26：H11肠出血性大肠杆菌的毒素转化噬菌体H19 A转移至 兔肠道致病性大肠杆菌RDEC-1是一种附着和消失的 兔子病原体 该菌株产生高水平的志贺样毒素I （SLT-I），定殖盲肠和结肠，并诱导肠道疾病， 病理变化与人类EHEC病相似的家兔。 干预措施将限制SLT与内皮的相互作用， 中和血管内的毒素; 肠腔;消除产生毒素的生物体;或抑制 促炎细胞因子的作用。

The broad aim of this proposal is to use a new animal model of enterohemorrhagic E.coli (EHEC) infection to understand the molecular pathogenesis of EHEC infection and develop practical interventional strategies to prevent and treat EHEC disease. It is now well recognized that some toxin-producing strains of E.coli, most commonly of serotype O157:H7, induce hemorrhagic colitis which may progress to fatal hemolytic-uremic syndrome. EHEC strains produce potent toxins which are referred to as Shiga-like toxins (SLTs) because of their relatedness to shiga toxin of shigella dysenteriae. Most EHEC share the ability to adhere intimately to intestinal epithelial cells by ~attaching and effacing~ (A/E) mechanisms. Although EHEC attachment mechanisms, with loss of microvilli, may contribute directly to diarrhea; the most severe intestinal and renal manifestations result from toxin-mediated damage to vascular endothelium with tissue edema, inflammatory infiltrates, cytokine production and vascular thrombi. A/E adherence may have profound influence on the delivery of toxin to the host, but this has not been adequately studied. At present, there is no effective prophylaxis or accepted treatment for EHEC disease. The specific aims of the proposal are to use an animal model of EHEC infection to: 1. Examine the influence of A/E adherence on SLT toxicity using mutants in the locus of enterocyte effacement (LEE). 2. Test the ability of passively administered immunoglobulin with anti- toxic activity to prevent EHEC disease. 3. Test the ability of intraluminal toxin-receptor analogs to prevent EHEC disease. 4. Determine whether antibiotic therapy has beneficial or harmful effects on the course of disease. 5. Examine the mediators of inflammation and determine whether anti- inflammatory strategies, in particular recombinant IL-1 receptor antagonist (IL-1ra), and recombinant TNF binding protein (TNF-BP) can alter the disease. 6. Examine strategies for active immunization against EHEC using the toxins, and products of the genes in the locus of enterocyte effacement (LEE). E.coli strain RDEC-H19A infection of rabbits will serve as the animal model of EHEC disease for these studies. RDEC-H19A, produced by the Transfer of the toxin-converting phage H19A of an O26:H11 EHEC to the rabbit entero-pathogenic E.coli RDEC-1, is an attaching and effacing rabbit pathogen. This strain produces high levels of Shiga-like toxin I (SLT-I), colonizes cecum and colon, and induces intestinal disease in rabbits with pathologic changes resembling human EHEC disease. Interventions will limit the interaction of SLTs with endothelium by neutralizing toxin within the vascular compartment; binging toxin in the gut lumen; eliminating the toxin-producing organisms; or inhibiting the action of pro-inflammatory cytokines.