And Partial Characterization of the Nephritis Strain-associated Protein From

Numerous investigators, most notably Rammelkamp (1) and Stollerman (2), have established that acute poststreptococcal glomerulonephritis (APSGN) ~ results from infection with a limited number of serological types of group A streptococci. However, even within a given nephritogenic type, it has been noted that not all strains cause nephritis, thereby suggesting that only certain strains of these nephritogenic types elaborate a streptococcal product that may be responsible for the initiation of APSGN. Histological data, in association with immunofluorescent studies of a large number of glomerular biopsies in APSGN have demonstrated the presence of streptococcal antigen(s) in the glomeruli. Seegai et al. (3) have suggested that antigen(s) localized in the glomerular wall of APSGN patients were part of the streptococcal cell wall; whereas Lange et al. (4) have suggested that a cytoplasmic entity known as endostreptosin was the antigen in question. In a similar approach, Ahmed et al. (5) suggested that the putative agent resides also within the streptococcal cell and could be detected only in the supernatant of disrupted streptococci. Vogt et al. (6, 7) reported that cationic, extracellular streptococcal antigens were observed in 8 out of 18 renal biopsies from patients with APSGN and suggested that APSGN was initiated by in situ immune complex formation with these cationic antigens. ViUareal et al. (8) reported that group A streptococci isolated from patients diagnosed as having developed APSGN secreted an extracellular protein that had a subunit of Mr 46,000 as determined by SDS-PAGE. This protein was generally not secreted by streptococcal strains isolated from patients who were diagnosed as not having APSGN. Because of this association between isolate and disease, this protein was called the nephritis strain-associated protein (NSAP). Villareal et al. (8) also showed that several M types of group A streptococci representing both the classical skin and throat strains elaborated this protein. Polyclonal rabbit antibody prepared to this extracellular protein and used as a