FIG 2.

Examples of immune subversion by streptococcal effectors. Host phagocytes are debilitated by streptolysin O (SLO) (70), streptolysin S (SLS) (294, 295), and secreted phospholipase A2 (Sla) (296). Neutrophil extracellular traps (NETs) are countered by the Sda1 and SpnA nucleases (264, 265). Antimicrobial peptides are inactivated by the secreted streptococcal inhibitor of complement (Sic) and SpeB proteases (200, 201). M-like proteins bind host factor H and plasminogen/plasmin, which inactivate host complement components to protect the bacterium (297). Sic protects streptococci from phagocytosis by neutrophils, resists the host complement membrane attack complex (MAC) (70), and counters the antibacterial actions of the host secretory leukocyte proteinase inhibitor (SLPI) (200, 201). Host antibodies are destroyed by membrane-associated ZmpC (226) and the secreted IdeS proteases (222) and inactivated by sugar-cleaving EndoS (223). The group B Streptococcus C5a peptidase ScpB is a serine protease and surface invasin (298) that reduces the neutrophil response and bacterial clearance by cutting the chemoattractant C5a (299). The streptococcal complement protector ScpA helps the bacterium resist phagocytosis (183) and also inactivates C5a (300). SpyCEP eliminates the neutrophil chemoattractant IL-8 (230) and other chemokines (225). Note that this figure depicts SoCs found in both group A and group B streptococci for illustrative purposes, but they would not naturally occur together.