SHIGELLA TOXIN; STRUCTURE & FUNCTION RELATIONSHIPS

志贺氏菌病是一种世界性的疾病， 发展中国家是疟疾死亡率的主要原因。 的 引起最严重疾病的志贺氏菌， 抑制蛋白质合成的强效毒素分子。 该毒素由 一条A链和5条B链。 B链的功能作用是 介导毒素与真核细胞表面结合。 毒素受体 是含有末端Gal-α 1->4Gal二糖的糖脂。 滋贺 毒素现在被认为是毒素家族的原型， 被称为志贺样。 滋贺和志贺样毒素与 临床表现包括腹泻，痢疾， 出血性结肠炎和溶血性尿毒综合征。 本课题旨在研究植物蛋白质的基本结构与功能关系， 毒素B链。 与B交叉反应的单克隆抗体 将表征滋贺和志贺样毒素II的链。 由于这些 两种毒素被认为在免疫学上是不同的， 与一组相同的受体结合， 取决于该抗体是否针对结合结构域。 一 单克隆抗体和具有Gal-alpha 1->4Gal末端的糖蛋白 二糖，P1-糖蛋白，将被用作选择细菌的工具， 产生结合结构域改变的B亚基的菌株。 的 这些突变体的特征将提供对 参与受体识别的B链区域。 这些信息 这将有助于未来设计安全有效的疫苗， 治疗性干预方案的潜在设计。 另外 生物化学和遗传特性的材料，其中交叉- 与抗滋贺毒素的抗体发生反应， 强调揭示这种物质在发病机制中可能发挥的作用。 最后，由其他革兰氏阴性菌产生的未表征的细胞毒素 将分析微生物的志贺样特性。 信息作为 其他致病菌是否产生志贺样毒素将有助于 我们对与毒素相关的疾病谱的理解。

Shigellosis is a world wide disease producing significant morbidity and in developing countries, a leading cause of diarrheal disease mortality. The Shigella species which causes the severest disease, dysenteriae, produces a potent toxin molecule which inhibits protein synthesis. The toxin consists of one A chain and 5 B chains. A functional role of the B chain is to mediate toxin binding to the eukaryotic cell surface. The toxin receptors are glycolipids containing terminal Gal-alpha1->4Gal disaccharide. Shiga toxin is now considered to be the prototype of a family of toxins which have been called Shiga-like. Shiga and Shiga-like toxins are associated with many clinical manifestations including diarrhea, dysentery, hemorrhagic colitis, and the hemolytic uremic syndrome. This proposal is designed to study basic structure-function relationship of the toxin B chain. A monoclonal antibody which cross-reacts with the B chain of Shiga and Shiga-like toxin II will be characterized. Since these two toxins are thought to be immunologically distinct and since the two bind to an identical set of receptors, particular attention will be focused on whether this antibody is directed against the binding domain. A monoclonal antibody and a glycoprotein with Gal-alpha1->4Gal terminal disaccharide, P1-glycoprotein, will be used as tools to select bacterial strains which produce B subunits with binding domain alterations. The characterization of these mutants will provide an understanding of the regions of the B chain involved in receptor recognition. This information will be useful for the future design of safe and effective vaccines and for the potential design of therapeutic intervention regimens. Additionally the biochemical and genetic characterization of a material which cross- reacts with antibody against Shiga toxin will be undertaken with particular emphasis on revealing the role this material may play in pathogenesis. Finally, the uncharacterized cytotoxins produced by other Gram-negative organisms will be analyzed for their Shiga-like properties. Information as to whether other pathogenic bacteria produce Shiga-like toxins will aid in our understanding of the spectrum of disease associated with toxin.