Shiga Toxin Production and Role in Pathogenesis

描述（由申请人提供）：E。大肠杆菌O 157：H7是一种重要的新型病原体。由E.大肠杆菌O 157：H7的特征是腹泻、出血性结肠炎和潜在的致命并发症溶血性尿毒综合征（HUS）。滋贺毒素（Stx）是大肠杆菌的主要毒力因子。coli O157：H7。滋贺毒素的两种主要抗原变体Stx 1和Stx 2具有55%的氨基酸同源性，然而Stx 2的产生与包括HUS在内的严重疾病的进展相关。我们建议检查滋贺毒素在由大肠杆菌引起的疾病的发病机制中的两个方面。大肠杆菌O 157：H7 -肠内滋贺毒素产生的调节以及Stx 1和Stx 2之间效力差异的分子基础。滋贺毒素的基因由细菌病毒编码。毒素产生的调节与影响病毒生命周期的因素密切相关，特别是诱导病毒裂解周期的因素，例如抗生素如环丙沙星。在具体目标1中，我们将表征影响Stx 2在体外和体内表达的因素。除了毒素产生的量之外，在感染期间产生的滋贺毒素的类型可以影响疾病的严重程度，其中Stx 2是迄今为止更有效的毒素。虽然很明显Stx 2可以诱导细胞死亡，但尚不清楚细胞死亡是HUS发展所必需的，毒性可能发生在生物体水平。在具体目标2中，我们将使用体外细胞培养模型表征Stx 2/Stx 1杂合突变体，以确定为什么Stx 2比Stx 1更有效。在具体目标3中，我们将使用疾病的小鼠模型确定杂交突变体的体内效力。了解影响滋贺毒素产生和效力的病毒、细菌和宿主因素可能会导致降低致命疾病发生率的治疗。

DESCRIPTION (provided by applicant): E. coli O157:H7 is an emerging pathogen of major importance. Disease caused by E. coli O157:H7 is characterized by diarrhea, hemorrhagic colitis, and the potentially fatal complication, hemolytic uremic syndrome (HUS). Shiga toxin (Stx) is a major virulence factor of E. coli O157:H7. Two major antigenic variants of Shiga toxin, Stx1 and Stx2, share 55% amino acid homology, however Stx2 production has been associated with progression to severe disease, including HUS. We propose to examine two aspects of Shiga toxin in the pathogenesis of disease caused by E. coli O157:H7 - regulation of Shiga toxin production in the intestine and the molecular basis for the difference in potency between Stx1 and Stx2. The genes for Shiga toxin are encoded on bacterial viruses. Regulation of toxin production is strongly linked to factors that affect the virus life cycle, specifically factors that induce the viral lytic cycle, for example antibiotics such as ciprofloxicin. In Specific Aim 1 we will characterize factors that influence Stx2 expression in vitro and in vivo. In addition to amount of toxin production, the type of Shiga toxin produced during infection can influence the severity of disease, with Stx2 being by far the more potent toxin. While it is clear that Stx2 can induce cellular death, it is not clear that cellular death is required for development of HUS, and toxicity may occur at the organismal level. In Specific Aim 2 we will characterize hybrid Stx2/Stx1 mutants to determine why Stx2 is more potent than Stx1 using in vitro cell culture models. In Specific Aim 3 we will determine the potency of the hybrid mutants in vivo using a mouse model of disease. Understanding the viral, bacterial and host factors that influence Shiga toxin production and potency could lead to treatments that reduce the incidence of fatal disease.