Date of Award
Master of Science
Theses & dissertations (Interdisciplinary)
Shiga toxin (Stx)-producing Escherichia coli (STEC) cause severe disease in humans and pigs. STEC characteristically produce one or more Stx types (Stxl, Stx2), virulence factors that mediate development of systemic STEC disease. Stxs recognize membrane glycolipids called globotriaosylceramide (Gb3) and mediate damage in the kidney, colon and central nervous system. The mechanisms of Stx-mediated damage are poorly understood. Stxs are directly cytotoxic for vascular endothelial and renal epithelial cells and may be indirectly cytotoxic through interactions with other cell types, such as leukocytes. The identification of tissue and cell types to which Stx binds is an important step toward identification of mechanisms of Stx-mediated damage. The susceptibility of pigs to natural STEC infection (edema disease) and experimental infection with human STEC strains make pigs an ideal model for Stx binding studies. In one study, an immunohistochemical Stx overlay assay for analysis of bovine tissues was modified for use with porcine tissues and leukocytes to identify Stx binding sites and localize Gb3 distribution. Stxl and Stx2 binding sites were identified in all tissues evaluated (kidney, intestine, cerebellum and liver from neonatal pigs) and on leukocytes (alveolar macrophages and peripheral blood monocytes and polymorphonuclear leukocytes [PMN] from pigs [greater than or equal to]4-weeks-old). We identified some Stx binding sites that had not been previously reported in pigs including kidney tubules, intestinal lymphoid aggregates, sinusoidal cells in the liver and isolated leukocytes. Gb3 was localized to all sites where Stx bound. In another study, rapid, multi-color flow cytometric assays were developed to monitor Stx2 binding and Gb3 expression on viable, isolated porcine peripheral blood PMN. These assays were used to demonstrate that crude Stx2 preparations bind to porcine PMN. Our findings support further use of porcine models to study STEC disease and Stx-mediated tissue damage. The immunohistochemical and flow cytometric assays will be useful tools for studying Stx binding and to evaluate the roles of PMN in the pathogenesis of STEC disease. The relevance of in vitro findings can be tested using available porcine STEC infection models. The results of such studies may facilitate the development of measures to treat human and porcine STEC disease.
Winter, Kellie, "Identification of Shiga toxin binding sites in porcine tissues and to porcine leukocytes" (2005). Retrospective Theses and Dissertations. 17525.