A streptococcal plasminogen activator in the focus of infection and in the kidneys during the initial phase of experimental streptococcal glomerulonephritis.

Strains of group A streptococci known to secrete the nephritis strain-associated protein (NSAP), a plasminogen activator, were studied for their ability to produce APSGN in rabbits. A tissue cage model was used to monitor the secretion of NSAP at the focus of infection and histopathological examination of kidney tissue was used to determine glomerular pathology. Animals infected with NSAP positive strains exhibited NSAP deposits in the glomerular tissue by day 7 in the absence of antibody to this molecule with progressive pathology indicative of APSGN three weeks later. Animals infected with the NSAP negative streptococcal strain exhibited no abnormal pathology. The ability of NSAP to bind to kidney tissue suggested that it has unique nephrotropic properties; and its ability to activate plasminogen to plasmin, possibly in situ, suggests that much of the pathological events associated with APSGN may be initiated by plasmin activity.