HEPARIN-INHIBITABLE LECTIN ACTIVITY OF THE FILAMENTOUS HEMAGGLUTININ ADHESIN OF BORDETELLA-PERTUSSIS

Bordetella pertussis, the etiologic agent of whooping cough, produces an outer membrane-associated filamentous hemagglutinin (FHA) which is the major adhesin of this organism. FHA exhibits a lectin-like activit y for heparin and dextran sulfate. By using in vitro adherence assays to cultured epithelial cells, the attachment of B. pertussis was reduc ed in the presence of sulfated polysaccharides such as heparin and dex tran sulfate but not in the presence of dextran, indicating the crucia l role of polysaccharide sulfation. In addition, inhibition of cellula r sulfation by chlorate treatment of the cells resulted in a reduction of B. pertussis adherence, suggesting that epithelial cell surface-ex posed sulfated glycoconjugates may serve as receptors for the microorg anism. B. pertussis mutant strains deficient in FHA production express ed residual adherence that was no longer inhibited by sulfated polysac charides. In addition, purified FHA displayed heparin-inhibitable bind ing to epithelial cells. Mapping experiments of the heparin-binding si te of FHA indicated that this site is different from the RGD site and the recently proposed carbohydrate-binding site involved in the intera ction of PHA with lactosylceramide. This result demonstrates that FHA contains at least three different binding sites, a feature unusual for bacterial adhesins but similar to features of eukaryotic adhesins and extracellular matrix proteins.