Acute rheumatic fever (ARF) and associated rheumatic heart disease (RHD) are serious sequelae of Group A Streptococcus (GAS) infection. Rates of ARF/RHD remain unacceptably high in Indigenous Aboriginal children in Australia and Māori and Pacific children in New Zealand. Pathogenesis remains poorly understood, with the current prevailing hypothesis based on molecular mimicry and the notion that antibodies generated in response to GAS infection cross-react with cardiac proteins such as myosin. Specific laboratory tests for ARF are lacking, with diagnosis relying on presentation of a set of clinical symptoms. This presents a major hurdle in disease control efforts, with an accurate diagnosis requiring a series of assessments over a period of days. The aim of this study is to map autoantigens targeted by serological antibodies in ARF patients using a multi-platform approach to both inform pathogenesis models and identify new biomarkers for the disease.
Sera from patients with ARF, matched healthy controls and patients with uncomplicated GAS pharyngitis was analysed for autoreactivity using high content protein arrays (Protoarray, 9000 autoantigens). Autoantigens were validated using a second high content protein array (HuProt Array, 16,000 autoantigens) and 2-D gel electrophoresis using human heart lysate with LC-MS/MS mass spectrometry. Individual autoantigens were further validated using conventional immunoassays using sera from a nationwide case-control study of ARF conducted in New Zealand (RF RISK Study). Disease pathway analysis revealed several auto-antigens within pathways linked to arthritic and myocardial disease. Notably autoantigen profiling revealed known disease-associated autoantibodies (anti-Myosin and anti-collagen antibodies) as well as novel candidates. These novel candidates are potential ARF biomarkers and provide new insight into disease pathogenesis.