streptolysin O

Streptolysin O (SLO) is a potent, oxygen-labile, cholesterol-dependent cytolysin (CDC) secreted by *Streptococcus pyogenes* (Group A Streptococcus). It functions by binding to cholesterol in the plasma membranes of target cells, such as erythrocytes and leukocytes, where it oligomerizes to form large transmembrane pores (approximately 25-30 nm in diameter). This pore formation leads to cell lysis or apoptosis, facilitating bacterial virulence and immune evasion. Beyond its role as a virulence factor, SLO is widely utilized in laboratory research as a tool for the controlled permeabilization of mammalian cell membranes, allowing the delivery of impermeable molecules into the cytosol. Clinically, SLO is the primary reagent used in the Antistreptolysin O (ASO) titer test to diagnose recent or past Group A Streptococcal infections. In pharmaceutical development, detoxified recombinant versions of SLO are being investigated as key antigens in multicomponent vaccine candidates aimed at preventing infections and associated complications like rheumatic heart disease.

Other names

Cholesterol-dependent cytolysinSLO protein