Cardiac Autoantibodies Promote a Fibrotic Transcriptome and Reduced Ventricular Recovery in Human Myocarditis

Jennifer Myers ¹ Clayton Sandel ¹ Kathy Alvarez ¹ Lori Garman ¹ Graham Wiley ² Courtney Montgomery ² Patrick Gaffney ² Stavros Stavrakis ¹ DeLisa Fairweather ³ Katelyn Bruno ⁴ Daniel Zhao ¹ Leslie Cooper ³ Madeleine W Cunningham ^1*

• ¹ University of Oklahoma Health Sciences Center, Oklahoma City, United States
• ² Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States
• ³ Mayo Clinic Florida, Jacksonville, Florida, United States
• ⁴ University of Florida, Gainesville, Florida, United States

Myocarditis leads to dilated cardiomyopathy (DCM) with one-third failing to recover normal ejection fraction (EF 50%). Our previous studies have supported a Th17 autoimmune pathogenesis where IL17A and IL-6 are elevated in myocarditis patients who do not recover normal EF. In the non-recovered group, autoantibody mechanisms of pathogenesis in myocardial injury and systolic dysfunction are not fully understood. Furthermore, in our myocarditis cohort, cardiac myosin (CM) autoantibodies (AAbs) were elevated and cross-reactive with the β-adrenergic receptor (βAR). Here we studied cross-reactive CM/βAR serum AAbs and human myocarditis-derived monoclonal antibodies (mAbs) to define their potential pathogenic mechanisms and to identify unique human CM epitopes associated with non-recovery in a longitudinal (n=41) cohort. Elevated CM IgG AAbs in the nonrecovered phenotype correlated with reduced EF and poor outcomes. Human CM epitopes unique to the nonrecovered phenotype shared strong amino acid sequence homology with extracellular loops of βARs and supported molecular mimicry and cross-reactivity between CM and βR. Myocarditis-derived IgG and human mAb 2C.4 activated protein kinase A (PKA) in an IgG, CM, and βAR-dependent manner in H9c2 heart myoblast cell line, and transcriptomic analysis revealed mAb 2C.4 induced fibrosis pathways which were highly similar pathways seen with isoproterenol, a beta receptor agonist. Our data translate into new mechanistic insights from our small longitudinal group of myocarditis/DCM patients and into potential therapeutic targets and biomarkers for future studies.