Anti-phagocytotic protein

Group B streptococci (GBS) are the most common cause of sepsis and pneumonia in newborns. One effective antibacterial strategy in immunodeficient hosts is phagocytosis, but how virulent Gram-positive bacteria evade phagocytosis has been unclear. In the January 1 Journal of Clinical Investigation, Theresa O. Harris and colleagues at the University of Washington, Seattle, USA, show that a novel streptococcal surface protease promotes virulence, resistance to opsonophagocytosis, and cleavage of human fibrinogen (Journal of Clinical Investigation, 111:61-70, January 1, 2003).

Harris et al. screened numerous GBSs and isolated the cspA gene from a highly virulent strain. They observed that cspA encoded a surface-localized protein that promoted GBS survival through evasion of opsonophagocytosis. The cspA sequence indicated that it is a subtilisin-like extracellular serine protease, homologous to the streptococcal C5a peptidases and caseinases of lactic acid bacteria. In addition, they showed that cspA was required for GBS cleavage of human fibrinogen. A ...