IMMUNOHISTOCHEMICAL AND SEROLOGICAL EVIDENCE FOR THE ROLE OF STREPTOCOCCAL PROTEINASE IN ACUTE POSTSTREPTOCOCCAL GLOMERULONEPHRITIS

Background. We have previously demonstrated the preferential secretion of streptococcal proteinase or streptococcal pyrogenic exotoxin B (SP EB) by nephritic strains of Group A streptococci isolated from the ski n or throat of patients with acute poststreptococcal glomerulonephriti s (APSGN). Methods. To further explore the possible role of SPEB in AP SGN, we performed ELISA studies to detect anti-SPEB antibodies in the sera of patients with APSGN, acute rheumatic fever (ARF), scarlet feve r (SF) and normal children. Using ELISA, anti-SPEB titers on acute and convalescent APSGN sera were measured to determine immunity to APSGN. We also performed immunofluorescence studies on APSGN and non-APSGN k idney biopsies to probe for the presence and localization of SPEB. Res ults. Our data show that anti-SPEB antibodies are present in APSGN ser a and antibody titers are significantly higher than in ARF, SF and nor mal sera. Anti-SPEB titers tend to rise acutely and decrease with time but do not reach baseline after one year. When kidney biopsies were p robed with rabbit anti-SPEB antibody, 12 of 18 (67%) of the APSGN case s were positive while only 4 of 25 (16%) of the non-APSGN cases were p ositive. Conclusions. In summary, we were able to demonstrate unique r eactivity to SPEB in human sera and kidney biopsies of APSGN suggestin g a significant role of this toxin in the pathogenesis of acute post-s treptococcal glomerulonephritis.