Cardiac Myosin Epitopes Recognized by Autoantibody in Acute and Convalescent Rheumatic Fever.

BACKGROUND: Acute rheumatic fever (ARF) is an autoimmune disorder associated with Streptococcus pyogenes infection. A prevailing hypothesis to account for this disease is that epitopes of self-antigens, such as cardiac myosin react to antibodies against S. pyogenes. The goal of our study was to confirm disease epitopes of cardiac myosin, identify immunodominant epitopes and to monitor the epitope response pattern in acute and convalescent rheumatic fever. METHODS: Enzyme-linked immunosorbant assays were used to determine epitopes immunodominant in acute disease and to track the immune response longitudinally to document any changes in the epitope pattern in convalescent sera. Multiplex fluorescence immunoassay was used to correlate anti-streptolysin O (ASO) and anti-human cardiac myosin antibodies. RESULTS: Disease-specific epitopes in rheumatic fever were identified as S2-1, 4 and 8. Epitopes S2-1, 4, 8 and 9 were found to be immunodominant in acute sera and S2-1, 8, 9, 29 and 30 in the convalescent sera. Frequency analysis showed that 50% of the ARF subjects responded to S2-8. S2-8 responders tended to maintain their epitope pattern throughout the convalescent period, whereas the S2-8 nonresponders tended to spread their responses to other epitopes later in the immune response. There was a significant correlation between anti-cardiac myosin and ASO titers. In addition, S2-8 responders showed elevated ASO titers compared with S2-8 non responders. CONCLUSION: Our studies confirm the existence of S2-1, 4 and 8 as disease-specific epitopes. We provide evidence that cardiac myosin S2-8 responders remain epitope stable in convalescence, whereas S2-8 nonresponders shift to neoepitopes. Multiplex data indicated a correlation between elevated ASO and anti-human cardiac myosin antibody titers. Mapping of cardiac myosin epitopes recognized in rheumatic fever sera may identify immunophenotypes of rheumatic fever.

An insert in the covS gene distinguishes a pharyngeal and a blood isolate of Streptococcus pyogenes found in the same individual.

Expression of the extensive arsenal of virulence factors by Streptococcus pyogenes is controlled by many regulators, of which CovRS is one of the best characterized and can influence ∼15 % of the genome. Animal models have established that mutants of covRS arise spontaneously in vivo resulting in highly invasive organisms. We analysed a pharyngeal and a blood isolate of S. pyogenes recovered from the same individual 13 days apart. The two isolates varied in many phenotypic properties including SpeB production, which were reflected in transcriptomic analyses. PFGE, multilocus sequence typing and partial sequencing of some key genes failed to show any differences except for an 11 bp insert in the covS gene in the blood isolate which caused a premature termination of transcription. Complementation of a fully functional covS gene into the blood isolate resulted in high expression of CovS and expression of speB. These results, showing a pharyngeal and a blood isolate from a single individual differing by a simple insertion, provide evidence for the model that regulatory gene mutations allow S. pyogenes to invade different niches in the body.