Identification of Streptococcus pyogenes proteins that bind to rabbit kidney in vitro and in vivo

Proteins were extracted from the surface of a nephritogenic strain of Streptococcus pyogenes M12 and tested for binding to rabbit kidney using indirect immunofluorescence and enzymelinked immunoassays. Streptococcal antigens bound in vitro in a fine linear pattern to basal laminae of glomeruli, Bowman's capsule, and tubules. Perfusion of rabbit kidney in vivo with Streptococcal components resulted in focal and segmental fine granular staining of glomerular capillaries. Three Streptococcal proteins (43, 31 and 9 kDa) were recovered from renal tissue that was pretreated in vitro with S. pyogenes extract. Streptococcal components bound in vitro to heparan sulfate, heparin, laminin and collagen IV but only weakly or not at all to fibronectin, bovine serum albumin or dextran sulfate. Affinity chromatography of bacterial extracts on heparin-agarose produced a 9 kDa Streptococcal protein (pl 9.5) which bound to kidney basement membranes in vitro and in isolated perfused kidneys. Several additional strains of group A streptococci were found to contain the 9 kDa cationic protein. This bacterial protein, when released into the blood by the bacterium during infection, may contribute to the Pathogenesis of streptococcus-associated nephritides in man.