Toxin a from Clostridium difficile binds to rabbit erythrocyte glycolipids with therminal Galα1-3Galβ1-4GlcNaC sequences

Toxin A is one of two clostridial toxins implicated as the causative agent of pseudomembranous colitis in patients undergoing postoperative antibiotic therapy. Evidence that the carbohydrate binding determinant for this toxin is a glycoconjugate(s) with non-reducing Galα1-3Galβ1-4GlcNAc has recently been reported. Specific agglutination of rabbit erythrocytes by Toxin A is inhibited by bovine thyroglobulin and prevented by pretreatment of cells with α-galactosidase. Total lipid extracts from rabbit erythrocytes were subjected to thin layer chromatography and the chromatogram overlaid with purified 125I-labeled Toxin A. Two major and several minor toxin-binding glycolipids were detected following autoradiography. The major toxin-binding glycolipids were identified as pentasaccharide- and decasaccharide-ceramides expressing terminal Galα1-3Galβ1-4GlcNAc sequences. Treatment of the toxin-binding glycolipids with α-galactosidase abolished binding. Forsmann glycolipid, globoside, Galα1-4 Galβ1-4Glc-cer, and Galα1-3Galβ1-4Glc-cer did not bind the toxin. These observations are consistent with the proposed carbohydrate specificity of the toxin for the non-reducing terminal sequence, Galα1-3Galβ1-4GlcNAc