Purification and characterization of CS2, a sialic acid-specific haemagglutinin of enterotoxigenic Escherichia coli.

CS2 fimbriae of enterotoxigenic Escherichia coli were purified and characterized. The surface haemagglutinins (fimbriae) were detached by sonication from a strain producing only the CS2 fimbriae. Isolation was carried out by gel filtration on a Sepharose 4B column. After depolymerization, the fimbriae subunits were purified on a Sephacryl S-300 column in 8.0 M-guanidinium chloride. From 1 litre of medium, 4-6 mg of purified fimbriae was obtained. We found that CS2 fimbriae were completely dissociated by saturated guanidinium chloride into subunits with a molecular mass of 16.5 kDa. CS2 fimbriae was sialic acid-specific, since sialic acids were the most potent inhibitors, and neuraminidase treatment of erythrocytes abolished haemagglutination. Both fimbriae and fimbrial subunits were found to bind to bovine erythrocytes. The binding of subunits to erythrocytes could be inhibited with low concentrations of sialyl-lactose.