Background
Group A Streptococcal (GAS) infections may lead to post-sequelae diseases such as acute rheumatic fever (ARF) and rheumatic heart disease (RHD). Evidence for long-term GAS antibody persistence in RHD patients is scarce, representing a critical knowledge gap. This study evaluates antibody persistence and their potential as biomarkers for identifying at-risk individuals. Developing a cost-effective point-of-care-test could improve early detection and prevention in high-burden regions with limited healthcare access.
Methods
Serum samples from a diverse African cohort (60 severe RHD cases and 60 age-matched controls) from the RHDGen Network Consortium were subjected to ELISA assays, to assess differences in antibody titres against twenty-two GAS antigens (11 shared and 11 M-peptides); results were captured as arbitrary ELISA units. Analysis incorporated the Mann-Whitney-U test for pairwise comparisons.
Results
For 4 of 11 shared GAS antigens, mean titres (cases/controls) were DNase B, 82.7/43.9, p<0.001; FHU, 37.1/27.6, p=0.04; SpyAD, 133.9/72.3 p<0.001; and SpyCEP, 114.8/93.4, p=0.018. Seven M peptides were significantly elevated in cases compared to controls (p<0.05 in all instances).
Conclusion
Our study revealed a persistence of GAS antibodies in an African RHD cohort, demonstrating a significant increase, as compared with controls, against 4/11 shared, and 7/11 M peptide antigens. Of interest, SLO, a diagnostic criterion in the Jones criteria for ARF, was not significantly elevated in this population. The increased levels of antibodies to M peptides in cases supports the notion of valve deterioration via persistent antibody-driven autoimmune responses. Further studies in this area of RHD research are warranted.