Binding of human enterotoxigenic Escherichia coli expressing coli surface antigen 6 to rabbit intestinal enterocytes and glycoproteins.

Abstract

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and in travelers to developing countries. Binding to and colonization of the small intestinal mucosa, which is medicated by different colonization factors, is considered an important early event in the development of diarrheal disease. Coli surface antigen 6 (CS6), a non-fimbrial subcomponent of the colonization factor antigen (CFA) IV complex, is expressed on the surface of human ETEC strains either alone or together with other colonization factors. Strains expressing only CS6 have been isolated from patients with diarrhea but hitherto it has not been possible to demonstrate the binding of such strains to human intestinal enterocytes or to mucosal tissue in vitro. However, CS6-only strains have been shown to colonize rabbit small intestine in vivo. The difference between the in vivo and in vitro situation might be due to that binding components on the surface of the enterocyte/mucosa, e.g. in the glycocalyx or mucus layer, are lost during the washing and isolation/cultivation procedures. In the present study, we have evaluated the binding capability of ETEC-strains expressing only CS6 to rabbit small intestinal enterocytes, isolated either with the standard approach using an EDTA-containing buffer or with a gentler method using saline, as well as to fractionated intestinal glycoproteins.