CLOSTRIDIUM-DIFFICILE TOXIN-A BINDING TO HUMAN INTESTINAL EPITHELIAL-CELLS

Clostridium difficile radiolabelled toxin A ([H-3]-toxin A) bound to h uman duodenal and colonic epithelial cells isolated from endoscopic bi opsies, Binding was greater at 4 degrees C than 37 degrees C, consiste nt with the thermal binding characteristic of toxin A to a carbohydrat e moiety, At 37 degrees C colonic cells bound significantly more [H-3] -toxin A than duodenal cells, The amount of [H-3]-toxin A binding vari ed considerably between individuals, [H-3]-toxin A was displaced by un labelled toxin A by 50% for duodenal cells and 70% for colonic cells w ith 94.3 nM unlabelled toxin A, Low non-displacable binding was observ ed in some samples at 4 degrees C and 37 degrees C, suggesting that th ese cells came from individuals incapable of specifically binding toxi n, Pre-treating cells with alpha- or beta-galactosidases to cleave ter minal alpha- and beta-galactose residues reduced [H-3]-toxin A binding , There was also a reduction in [H-3]-toxin A binding after heat treat ing cells, which is suggestive of protein binding, The reduction in bi nding varied between individuals, The reduction of [H-3]-toxin A bindi ng, after the removal of beta-linked galactose units, implicates these as components of the receptor and adds credence to the idea that the Lewis X, Y and I antigens may be involved in toxin A binding to human intestinal epithelial cells, However, because the Lewis antigens do no t possess terminal alpha-galactose units, the reduction in binding aft er alpha-galactosidase treatment suggests that other receptors may be involved in toxin A binding to some human intestinal cells, These data are the first demonstration of direct toxin A binding to human intest inal epithelial cells.