Summary auto-generated
Post-streptococcal glomerulonephritis (PSGN) is an immune-mediated kidney disease associated with certain Group A Streptococcus M types. This study examined antibodies to streptococcal inhibitor of complement (SIC) proteins and M peptides in 198 serum samples from an Australian Aboriginal community endemic for PSGN. Two classes of SIC exist: closely related SIC (CRS) found in M1 and M57 strains, and distantly related SIC (DRS) found in M12 and M55 strains. Using ELISA, researchers detected antibodies to CRS in 57% of samples and DRS in 55%, with 90% showing antibodies to at least one M peptide tested. Notably, while no correlation existed between CRS seropositivity and specific M-type antibodies, a significant association emerged between DRS seropositivity and recorded PSGN history: 65% of DRS-positive subjects had PSGN compared to 46% of DRS-negative subjects. These findings suggest DRS antibodies may have predictive value for PSGN diagnosis or a role in disease pathogenesis, though further research in non-endemic populations is needed to confirm this association.
Key findings
- Antibodies to both CRS and DRS complement-inhibiting proteins are highly prevalent in the PSGN-endemic population, found in 57% and 55% of sera respectively
- DRS seropositivity showed a significant association with recorded PSGN history (65% vs 46% in seronegative subjects, p=0.009), while CRS showed no such association
- No correlation existed between CRS/DRS seropositivity and antibodies to their corresponding M-type peptides, suggesting differential antibody persistence or immune response patterns
- The majority of the study population (90%) had been exposed to multiple Group A Streptococcus serotypes based on M-peptide reactivity patterns
- DRS antibodies may serve as either a surrogate marker for PSGN diagnosis or have a direct role in PSGN pathogenesis
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Abstract
Post-streptococcal glomerulonephritis (PSGN) is an immune-mediated disease in which an immune complex containing a streptococcal antigen are deposited in affected glomeruli. Strains of only some M types are known to be associated with PSGN. A secretory protein called SIC inhibits complement function. Whereas all M1 and M57 strains express closely related SIC (CRS), all M12 and M55 strains express distantly related SIC (DRS) proteins. Strains belonging to these four M types are historically associated with PSGN. This study used ELISA to analyse 112 sera from individuals with a recorded history of PSGN and 86 sera from individuals who had no such recorded history, all from a PSGN endemic region in tropical Australia. Antibody reactions to CRS, DRS and peptides corresponding to the N-termini of M1, M5, M12, M49, M55 and M57 antigens were assessed. A large proportion of the population showed reactions to each of these antigens and there was no correlation between CRS seropositivity and antibodies to CRS-positive M types. Likewise there was no correlation between DRS seropositivity and antibodies to DRS-positive M types. Interestingly, in this community endemic for PSGN a significantly higher proportion of DRS seropositive subjects had a recorded history of PSGN than did DRS seronegative subjects. DRS may have a predictive value for PSGN diagnosis or a role in PSGN pathogenesis.