We have previously demonstrated the preferential secretion of streptococcal proteinase or streptococcal pyrogenic exotoxin B (SPEB) by nephritic strains of Group A streptococci isolated from the skin or throat of patients with acute poststreptococcal glomerulonephritis (APSGN).
To further explore the possible role of SPEB in APSGN, we performed ELISA studies to detect anti-SPEB antibodies in the sera of patients with APSGN, acute rheumatic fever (ARF), scarlet fever (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 kidney biopsies to probe for the presence and localization of SPEB.
Our data show that anti-SPEB antibodies are present in APSGN sera and antibody titers are significantly higher than in ARF, SF and normal sera. Anti-SPEB titers tend to rise acutely and decrease with time but do not reach baseline after one year. When kidney biopsies were probed with rabbit anti-SPEB antibody, 12 of 18 (67%) of the APSGN cases were positive while only 4 of 25 (16%) of the non-APSGN cases were positive.
In summary, we were able to demonstrate unique reactivity to SPEB in human sera and kidney biopsies of APSGN suggesting a significant role of this toxin in the pathogenesis of acute post-streptococcal glomerulonephritis.