Which of the following is a virulence factor for streptococci?

The cell wall antigens include capsular polysaccharide (C-substance), peptidoglycan and lipoteichoic acid (LTA), R and T proteins, and various surface proteins, including M protein, fimbrial proteins, fibronectin-binding proteins (eg, protein F), and cell-bound streptokinase. The C-substance may have a role in increased invasive capacity. The R and T proteins are used as epidemiologic markers and have no known role in virulence. Another virulence factor, C5A peptidase, destroys the chemotactic signals by cleaving the complement component of C5A. M protein, the major virulence factor, is a macromolecule incorporated in fimbriae present on the cell membrane projecting on the bacterial cell wall. It is the primary cause of antigenic shift and antigenic drift among group A streptococci.