Streptococcus pyogenes serotype M28 speB

Streptococcus pyogenes serotype M28 speB (Streptococcal Pyrogenic Exotoxin B) is a cysteine protease produced by Streptococcus pyogenes serotype M28-a strain of Group A Streptococcus (GAS) associated with severe infections like necrotizing fasciitis ("flesh-eating disease") and streptococcal toxic shock syndrome. SpeB acts by degrading a wide range of host proteins, including extracellular matrix components (e.g., collagen, fibronectin), immune proteins (e.g., immunoglobulins, complement factors), and cytokines. This degradation facilitates bacterial invasion through tissue barriers, evades immune clearance, and disrupts the host's inflammatory response-all of which contribute to the severity of infection. SpeB also processes other GAS virulence factors, enhancing their activity. The gene encoding speB is regulated by environmental signals, and its expression is highest during the later stages of infection, when tissue destruction and spread are critical. Due to its role in severe GAS infections, speB is a potential target for therapeutic interventions: inhibiting its protease activity or inducing neutralizing antibodies could reduce tissue damage and improve outcomes for patients with invasive serotype M28 infections.