DETECTION OF ATTACHMENT OF ENTEROTOXIGENIC ESCHERICHIA-COLI (ETEC) TOHUMAN SMALL-INTESTINAL CELLS BY ENZYME-IMMUNOASSAY

Simple immunoassays were developed to study the binding between entero cytes of the small intestine and other cell types, and enterotoxigenic Escherichia coil (ETEC). CFA/I or CFA/II pilus protein or CFA-positiv e E. coil bacteria were immobilised in wells of microtitre plates and incubated with vesicles or crude mucus prepared from human brush borde r enterocytes. Binding of the cell preparations was detected by adding specific rabbit anti-brush border IgG followed by urease-labelled goa t anti-rabbit IgG and urea substrate. The binding of purified CFA/I to human or rabbit small intestine, human oral epithelial cells or Caco- 2 cells was detected with specific anti-CFA/I IgG. Both human brush bo rder and mucus-derived preparations were able to attach to ETEC. The b inding was CFA-specific and strong enough to withstand several washing s. In contrast, CFA/I did not bind to small intestinal cells of non-hu man small intestinal origin, indicating that there may be important di fferences in affinity between receptors present on human small intesti nal cells and cells of non-human small intestinal origin. Antibodies d irected against human small intestinal and non-small intestinal cells did not cross-react with either preparation, indicating that receptors between these different cell sources are different. The EIA proved us eful during the identification of a newly-recognised 15 kDa bacterial surface component of ETEC strain H10407P, which may function as a puta tive attachment factor. The EIAs developed in this study were easy to perform and multiple tests could be performed on small samples, includ ing biopsy samples obtained during endoscopy.