GAS virulence factors

The arsenal of virulence factors expressed by GAS to thwart the host innate immune response. The secreted proteases SpyCEP/ScpC and ScpA degrade the chemokines IL-8 and C5a, respectively, hindering phagocyte recruitment to the site of infection. Surface-associated M protein binds Fc domains of Ig and the complement-regulatory proteins C4BP and factor H to interfere with complement deposition. Mac-1/2 degrades Ig and binds phagocyte Fc receptors to block phagocytosis. Antimicrobial peptide resistance is mediated by hyaluronic acid capsule, D-alanylation of surface lipoteichoic acid by DltABCD, inactivation though SIC binding, and degradation by the cysteine protease SpeB. Ig and antimicrobial peptides are degraded by SpeB to facilitate the establishment of GAS infection in vivo. Secreted Sda1 DNase activity degrades NETs to promote neutrophil survival. The cytolysins SLS and SLO mediate lysis and apoptosis of neutrophils and macrophages.