F18-fimbriated Escherichia coli are associated with porcine postweaning diarrhea and edema disease. Adhesion of F18-fimbriated bacteria to the small intestine of susceptible pigs is mediated by the minor fimbrial subunit FedF. However, the target cell receptor for FedF has remained unidentified. Here we report that F18-fimbriated E. coli selectively interact with glycosphingolipids having blood group ABH determinants on type 1 core, and blood group A type 4 heptaglycosylceramide. The minimal binding epitope was identified as the blood group H type 1 determinant (Fuc␣2Gal3GlcNAc), while an optimal binding epitope was created by addition of the terminal ␣3-linked galactose or N-acetylgalactosamine of the blood group B type 1 determinant (Gal␣3(Fuc␣2)Gal3GlcNAc) and the blood group A type 1 determinant (GalNAc␣3(Fuc␣2)-Gal3GlcNAc). To assess the role of glycosphingolipid recognition by F18-fimbriated E. coli in target tissue adherence, F18-binding glycosphingolipids were isolated from the small intestinal epithelium of blood group O and A pigs and characterized by mass spectrometry and proton NMR. The only glycosphingolipid with F18-binding activity of the blood group O pig was an H type 1 pentaglycosylceramide (Fuc␣2Gal3GlcNAc-3Gal4Glc1Cer). In contrast, the blood group A pig had a number of F18-binding glycosphingolipids, characterized as A type 1 hexaglycosylceramide (GalNAc␣3(Fuc␣2)Gal3Glc-NAc3Gal4Glc1Cer), A type 4 heptaglycosylceramide (GalNAc␣3(Fuc␣2)Gal3GalNAc3Gal␣4Gal4Glc1Cer), A type 1 octaglycosylceramide (GalNAc␣3(Fuc␣2)Gal3GlcNAc3-Gal3GlcNAc3Gal4Glc1Cer), and repetitive A type 1 nonaglycosylceramide (GalNAc␣3(Fuc␣2)Gal3GalNAc␣3-(Fuc␣2)Gal3GlcNAc3Gal4Glc1Cer). No blood group antigen-carrying glycosphingolipids were recognized by a mutant E. coli strain with deletion of the FedF adhesin, demonstrating that FedF is the structural element mediating binding of F18-fimbriated bacteria to blood group ABH determinants.
Enterotoxigenic (ETEC)4 and verotoxigenic Escherichia coli are important causes of disease in man and animal (1, 2). In newly weaned pigs, F18-fimbriated E. coli producing enteroand/or Shiga-like toxins induce diarrhea and/or edema disease, which accounts for substantial economical losses in the pig industry (3). Two virulence factors are of major importance, namely the F18 fimbriae, the adhesive polymeric protein surface appendages of F18-fimbriated E. coli, and the Shiga-like toxin (SLT-IIv), or enterotoxins (STa or STb), that are produced by the bacterium. F18 fimbriae are expressed by the fed (fimbriae associated with edema disease) gene cluster, with fedA encoding the major subunit, fedB the outer membrane usher, fedC the periplasmic chaperone, whereas fedE and fedF encode minor subunits (4). FedF is the adhesive subunit and is presumably located at the tip of the fimbrial structure (5, 6). Typically, tip adhesins consist of two domains: an N-terminal carbohydrate-specific lectin domain and a C-terminal pilin domain (7), which needs to be donor-strand-complemented ...