Streptococcus pyogenes speB

Streptococcus pyogenes speB is a cysteine protease produced by most strains of Streptococcus pyogenes (Group A Streptococcus, GAS), not limited to serotype M28. Its core function is to degrade host proteins, enabling GAS to invade tissues, evade immunity, and cause disease. By breaking down extracellular matrix proteins, speB helps GAS spread through connective tissue; by cleaving immunoglobulins and complement factors, it blocks immune recognition and phagocytosis; and by processing cytokines, it modulates inflammation-sometimes increasing tissue damage. SpeB also plays a role in GAS colonization of the pharynx, as it can degrade mucus proteins. The protease is immunogenic, and antibodies against speB can neutralize its activity, providing some protection against GAS infections. Given its widespread presence in pathogenic GAS strains and role in multiple virulence processes, speB is a candidate for GAS vaccines. A speB-based vaccine could provide broad protection against various GAS serotypes, reducing the incidence of both mild (e.g., pharyngitis) and severe (e.g., necrotizing fasciitis) infections.