Isolation of a sialic acid-specific surface haemagglutinin of Helicobacter pylori strain NCTC 11637.

A deionized water extract of Helicobacter pylori NCTC 11637 contained haemagglutinin activity that was (i) soluble (i.e., not associated with particulate material sedimented by centrifugation at 100,000 x g for 1 h), (ii) stable to lyophilization, (iii) heat-labile, (iv) chymotrypsin-sensitive, (v) inhibited by fetuin, orosomucoid, and NANLac, but not by asialofetuin and (vi) inactive against guinea pig erythrocytes incubated with Clostridium perfringens neuraminidase, but active against untreated guinea pig erythrocytes. The data support the idea that the haemagglutinin is a protein which recognizes the alpha-(2-3) structure of sialylated glycoconjugates. Fractionation of the extract by isoelectric focusing and by gel filtration with Sephacryl S-400 indicated that the haemagglutinin has a pI of 3.7 and consist of high molecular-weight-protein aggregates. SDS-PAGE analysis of the preparation purified by gel filtration showed 3 protein bands at ca. 64 kD, 56 kD and 20 kD. Electron microscopy of H. pylori incubated with gold-labelled fetuin indicated that the haemagglutinin was associated with loosely adherent material on the bacterial surface, and that the purified haemagglutinin did not reveal a fimbrial structure. The ability to bind to sialoglycoconjugates on the erythrocyte membrane suggests that the haemagglutinin may be an important colonization factor enabling H. pylori to bind to similar saccharide structures on epithelial cells.