DIFFERENTIAL INTERACTION OF ESCHERICHIA-COLI HEAT-LABILE TOXIN AND CHOLERA-TOXIN WITH PIG INTESTINAL BRUSH-BORDER GLYCOPROTEINS DEPENDING ON THEIR ABH AND RELATED BLOOD-GROUP ANTIGENIC DETERMINANTS

The ability of glycoproteins from pig intestinal brush border membrane s (BBM) to bind cholera toxin (CT) or heat-labile toxins from strains of Escherichia coli isolated from human (LTh) or pig (LTp) intestines was studied. Glycoproteins capable of binding the toxins are also reco gnized by antibodies or lectins specific for ABO(H) blood group and re lated antigens. Pigs expressing A, H, or I antigenic determinants were used for comparison. The toxin-binding capacity of a glycoprotein dep ends on the toxin type and the blood group epitope borne by the glycop rotein. LTh and LTp preferably bound to several blood group A-active g lycoproteins rather than II-active glycoproteins. By contrast, CT prac tically did not recognize either blood group A- or blood group II-acti ve glycoproteins, while glycoproteins from pigs expressing I antigenic determinants were able to interact with LTh, LTp, and CT. LTh, LTp, o r CT glycoprotein binding was selectively inhibited by specific lectin s or monosaccharides. Affinity purification of the toxin binding brush border glycoproteins on the basis of their blood group reactivity sug gests that such glycoproteins are hydrolytic enzymes. BBM from A(+) pi gs contain about 27 times more LTh binding sites, in addition to those recognized by CT, than an equivalent membrane preparation from HC pig s. The present findings may help clarify some previous unclear results on LTh binding to intestinal BBM glycoproteins obtained by use of ani mals not typed by their ABO(H) blood group phenotype.