Staphylococcus aureus fibronectin-binding proteins (FnBPs). Identification of antigenic epitopes using polyclonal antibodies.

Polyclonal antibodies against recombinant fibronectin-binding proteins (gal-FnBP A and ZZ-FnBP B) of Staphylococcus aureus were analyzed by both solid-phase and solution-phase methods. These antibodies were found to bind homologous antigen and to cross-react with heterologous antigen. It was also found that antibodies recognize native FnBP on the cell surface. It has been shown, by the inhibition assay, that the majority of antibodies recognize a fibronectin-binding D1-D2 sequence of FnBP A. Anti-FnBP A Fab fails to bind the D3 sequence, though this peptide used in a solution inhibits binding of fibronectin to immobilized FnBP A, similarly to D1 and D2 peptides. Since the anti-FnBP A antibodies are able to block fibronectin binding to staphylococci by about 50%, it is reasonable to assume that the bacterial receptor has additional binding sites outside the D domain.