[S6-3] アンギノーサスグループレンサ球菌のフィブロネクチン結合タンパク質
Anginosus group of streptococci (AGS) are causative agent of infective endocarditis and abscesses of the brain or liver. Although bacterial adhesion to host tissues is a critical step in infection, the mechanisms of AGS have not been clarified. We have identified fibronectin-binding protein (FBP) in AGS that could mediate adhesion to host cells. The FBP of Streptococcus anginosus and S. intermedius does not contain the transmembrane motifs or a leader peptide, suggesting this it is an atypical FBP. The antigenic similarity of FBP was recognized among oral streptococci with anti-S. intermedius FBP antiserum. The recombinant FBP bound to immobilized fibronectin in a dose-dependent manner. In addition, the adherence of the isogenic mutant (Δfbp) to immobilized fibronectin and epithelial cells was reduced compared with that of the wild-type. Western blotting and immunofluorescence analysis revealed that FBP localized to the bacterial cell surface. Furthermore, the binding domain of FBP molecule was revealed in the C-terminal using recombinant N-terminal (amino acid residues 1–265) and C-terminal (amino acid residues 266–549) constructs. The Δfbp was less pathogenic compared to the wild-type, in the mouse infection model. Taken together, FBP of AGS play a role of adherence to host cells and may be an important virulence factor in these bacterial infections.