RAPID DETECTION AND CHARACTERIZATION OF SIALIC ACID-SPECIFIC LECTINS OF HELICOBACTER-PYLORI

A particle agglutination assay (PAA) using fetuin (Ft) covalently coup led to carboxylate-modified latex (CML) particles was evaluated for ra pid detection of sialic acid-specific haemagglutinins/lectins (SALs) o f Helicobacter pylori isolates which bind sialoglycoconjugates. Sixty- three percent (20/32) of the isolates examined gave a positive PAA tes t. Cell-bound SALs were extracted by washing the bacteria with deioniz ed water or isotonic saline, and their expression was influenced by pH and culture conditions. The Ft-CML reactivity of the PAA-positive iso lates was inhibited by bovine submaxillary mucin, transferrin, fetuin. orosomucoid, vitronectin and lactoferrin in a manner which suggested that the isolates contain a lectin recognizing the alpha-(2-6) linkage of terminal sialic acid. Western blots of strain NCTC 11637 SALs prob ed with horseradish peroxidase (HRP)-labelled Ft identified three band s (MW 64 kD, 62 kD, 56 kD) which also reacted with HRP-labelled mucin, transferrin, lactoferrin, orosomucoid, vitronectin and laminin. Sera from patients with a H. pylori infection and one polyclonal rabbit ant iserum (strain NCTC 11637) also reacted with the SALs. Immunogold labe lling of a polyclonal rabbit antiserum raised against the 64 kD protei n of strain NCTC 11637 that reacted strongly with Ft-CML showed that a bundant SALs were loosely cell-associated with the cell surface of bot h spiral and coccoidal forms of H. pylori. SALs were also present in l ow amounts on the surface of strain NCTC 11638 and 66, a clinical isol ate that did not react with Ft-CML.