DIFFERENTIAL-EFFECTS OF THE STREPTOCOCCAL FIBRONECTIN-BINDING PROTEIN, FBP54, ON ADHESION OF GROUP-A STREPTOCOCCI TO HUMAN BUCCAL CELLS ANDHEP-2 TISSUE-CULTURE CELLS

We have previously demonstrated that fibronectin mediates streptococca l adhesion to host cells and that streptococci interact primarily with the N-terminal domain of fibronectin. FBP54 is a 54-kDa protein from group A streptococci that binds fibronectin. In this report, we show t hat the N-terminal domain of fibronectin reacts with FBP54 and prefere ntially blocks streptococcal adhesion to buccal epithelial cells. FBP5 4 blocked adhesion to human buccal epithelial cells by 80% in a dose-r elated fashion. In contrast, FBP54 had little effect on adhesion of gr oup A streptococci to HEp-2 tissue culture cells. The fibronectin-bind ing domain of FBP54 has been localized to the first 89 N-terminal resi dues of the protein. Experiments using affinity-purified antibodies to this region indicated that the N terminus of FBP54 is exposed on the surface of streptococci in a manner that can interact with immobilized receptors. Analysis of sera from patients with post-streptococcal glo merulonephritis and acute rheumatic fever indicated that FBP54 is expr essed in vivo and is immunogenic in the human host. These data indicat e that FBP54 is a streptococcal adhesin that is expressed in the human host and that preferentially mediates adhesion to certain types of hu man cells.