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 了解肠出血性大肠杆菌(EHEC)感染的分子机制 肠出血性肠杆菌感染的发病机制及实用干预研究进展 预防和治疗EHEC疾病的策略。它现在已经被公认为 一些产毒素的大肠杆菌，最常见的血清型 O157：H7，导致出血性结肠炎，可能进展至致命 溶血性尿毒症综合征。EHEC菌株产生强烈的毒素，这些毒素是 称为志贺样毒素(SLT)，因为它们与 志贺氏痢疾杆菌志贺毒素。大多数EHEC都有能力 通过与肠上皮细胞贴附和贴附 消除~(A/E)机制。虽然EHEC的附着机制， 微绒毛的丢失，可能直接导致腹泻；最严重的 肠道和肾脏的表现是由毒素介导的损害引起的 血管内皮细胞有组织水肿，炎性浸润物， 细胞因子的产生与血管血栓。遵守A/E可能会 对毒素向宿主的传递产生了深远的影响，但这对 没有得到充分的研究。目前，还没有一种有效的 预防或接受肠出血性大肠杆菌病的治疗。 该提案的具体目的是使用EHEC的动物模型 感染： 1.利用突变体检测A/E黏附对SLT毒性的影响 在肠上皮细胞消失点(Lee)。 2.检测被动免疫球蛋白对小鼠免疫功能的影响 具有预防EHEC疾病的毒性活性。 3.检测腔内毒素受体类似物预防 肠出血性肠出血性疾病。 4.确定抗生素治疗是有益还是有害 对病程的影响。 5.检查炎症介质，确定是否有抗炎作用 炎症策略，特别是重组IL-1受体 拮抗剂(IL-1ra)和重组肿瘤坏死因子结合蛋白(TNF-BP)可以 改变疾病。 6.研究针对EHEC的主动免疫策略 毒素和肠细胞消失点基因的产物 (李)。 以大肠杆菌RDEC-H19A株感染兔为实验动物 用于这些研究的EHEC疾病模型。RDEC-H19A，由 O26：H11 EHEC的毒素转化噬菌体H19A转移到 兔肠道致病性大肠杆菌RDEC-1，是一种附着和清除 兔疫病原体。该菌株产生高水平的志贺样毒素I。 (SLT-I)，在盲肠和结肠定植，并在 兔的病理变化类似于人的EHEC疾病。 干预措施将通过以下方式限制SLT与内皮的相互作用 中和血管腔内毒素；结合血管腔内毒素 肠腔；清除产生毒素的微生物；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.