PROTEIN F1 IS REQUIRED FOR EFFICIENT ENTRY OF STREPTOCOCCUS-PYOGENES INTO EPITHELIAL-CELLS

It was recently reported that strains of Streptococcus pyogenes are ca pable of inducing entry of the bacterium into epithelial cells; howeve r, nothing is known regarding the gene(s) and the underlying mechanism (s) involved, Using isogenic mutants of S. pyogenes JRS4 strain that a re defective in the expression of each of the surface proteins F1 and M6, it was demonstrated that both are required for efficient internali zation. Expression of F1 on the surface of a poorly invading S, pyogen es strain significantly enhances its internalization efficiency, Prote in F1-mediated internalization is inhibited by UR, the nonrepetitive f ibronectin-binding domain of this protein, and to a lesser extent, by the repetitive fibronectin-binding domain, RD2, Polyclonal anti-human fibronectin antibodies completely abolish F1-mediated internalization; increasing fibronectin concentrations result in a significant enhance ment of bacterial uptake. The findings shown here suggest that protein F1 mediates streptococcal internalization and that the M6 protein is required for more efficient entry of the bacterium.