Myers, J.; Sandel, C.; Alvarez, K.; Garman, L.; wiley, G.; Montgomery, C.; Gaffney, P.; Stavrakis, S.; Fairweather, D.; Bruno, K.; Zhao, Y. D.; Cooper, L. T.; Cunningham, M. W.

Background: Myocarditis leads to dilated cardiomyopathy (DCM) with one-third failing to recover normal ejection fraction (EF50%), and there is a critical need for prognostic biomarkers to assess risk of nonrecovery. Cardiac myosin (CM) autoantibodies (AAbs) cross-reactive with the beta-adrenergic receptor (BAR) are associated with myocarditis/DCM, but their potential for prognosis and functional relevance is not fully understood. Methods: CM AAbs and myocarditis-derived human monoclonal antibodies (mAbs) were investigated to define pathogenic mechanisms and CM epitopes of nonrecovery. Myocarditis patients who do not recover ejection fraction (EF<50%) by one year were studied in a longitudinal (n=41) cohort. Sera IgG and human mAbs were investigated for autoreactivity with CM and CM peptides by ELISA, protein kinase A (PKA) activation, and transcriptomic analysis in H9c2 heart cell line. Results: CM AAbs were significantly elevated in nonrecovered compared to recovered patients and correlated with reduced EF (<50%). CM epitopes specific to nonrecovery were identified. Transcriptomic analysis revealed serum IgG and mAb 2C.4 induced fibrosis/apoptosis pathways in vitro similar to isoproterenol treated cells. Sera IgG and 2C.4 activated PKA in an IgG and BAR-dependent manner. Endomyocardial biopsies from myocarditis/DCM revealed IgG+ trichrome+ tissues. Conclusions: CM AAbs were significantly elevated in nonrecovered patients, suggesting novel prognostic relevance. CM AAbs correlated with lower EF, and Ab-induced fibrosis/apoptosis pathways suggested a role for CM AAbs in patients who do not recover and develop irreversible heart failure. Homology between CM and BARs supports mechanisms related to cross-reactivity of CM AAbs with the BAR, a potential AAb target in nonrecovery.