The K88 fimbrial adhesin of enterotoxigenic Escherichia coli binds to beta 1-linked galactosyl residues in glycosphingolipids

Abstract

The K88 fimbrial adhesin enables certain strains of enterotoxigenic Escherichia coli to adhere to the porcine small intestine. In this study, the ability of the K88 adhesin to bind to glycosphingolipids was monitored by modified enzyme-linked immunosorbent assay and thin-layer chromatography overlay binding analysis. The binding of the K88 adhesin to glycosphingolipid-coated microtiter plates was saturable, with 50% maximal binding occurring with gangliotriaosylceramide, gangliotetraosylceramide, and lactosylceramide at 67 +/- 21, 117 +/- 21, and 73 +/- 22 pM, respectively. Thin-layer chromatography overlay binding analysis demonstrated that serotype O8:K87:K88ab:H19 E. coli bound to hydroxylated galactosylceramide, gangliotriaocylceramide, gangliotetraosylceramide, and lactosylceramide but not to globotriaosylceramide, nonhydroxylated galactosylceramide, glucosides, glucosylceramide, or a mixture of ceramides. The K88 adhesin did not bind by either assay to globoside, the Forssman glycolipid, GM1, GM2, GM3, GD1a, GD2, GD3, GQ1b, or GT1b. The binding pattern observed with the K88 adhesin suggests that beta 1-linked galactosyl residues are the minimum determinant required for binding, provided they are presented correctly. It is suggested that beta 1-linked galactose residues may form the molecular basis of both glycoprotein and glycolipid receptors for the K88 fimbrial adhesin in the porcine small intestine.