Interaction of verotoxin 2e with pig intestine

In pigs with edema disease, verotoxin 2e (VT2e) is produced in the intestine and transported to tissues, but neither the mechanism by which toxin passes through the intestine nor its failure to induce an enterotoxic reaction is understood. Binding of VT2e to pig intestine was examined by enzyme-linked immunosorbent assay involving microvillus membranes (MVM) and crude mucus; thin-layer chromatographic overlay immunoassay with total lipids extracted from MVM; and indirect immunofluorescence of toxin bound to thin sections of jejunum, ileum, and colon. VT2e bound significantly to MVM from pig jejunum and ileum but not to crude mucus. Verotoxin 2e-binding glycolipids, globotetraosylceramide and globotriaosylceramide, were detected by thin-layer chromatographic overlay immunoassay in extracts of MVM from jejunum and ileum. Indirect immunofluorescence showed that VT2e bound to vessels within the submucosa and muscularis mucosa of the jejunum, ileum, and colon and to enterocytes at the lower portion but not at the tips of villi in the jejunum and ileum. Receptors for VT2e are therefore present in the intestine of the pig, but their role in absorption of VT2e is unclear since intraintestinal inoculation of pigs with large quantities of VT2e does not result in edema disease. Previously reported lack of enterotoxicity of verotoxins in pig intestine may be explained by the absence of toxin receptors in the villus absorptive enterocytes.