Abstract 4142506: Comparative Proteomic Analysis of Myocarditis: COVID-19 mRNA Vaccination vs. Pre-Pandemic Viral Etiologies

Introduction: Myocarditis has been reported after mRNA-based COVID-19 vaccination, but the immune mechanisms remain unclear. This study aimed to identify the proteome-based immunopathogenesis of post-vaccination myocarditis compared to viral myocarditis in the pre-COVID-19 era. Methods: Proteomic analysis of right ventricle (RV) biopsy specimens was performed in myocarditis patients (pre-pandemic viral myocarditis: n=3, post-vaccination myocarditis: n=3) and controls (normal endomyocardial biopsy specimens of heart transplant recipients, n=4) using mass spectrometry. Differentially expressed proteins were analyzed with CIBERSORTx, Gene Ontology (GO) analysis, and Ingenuity Pathway Analysis (IPA). To examine the relationship between the SARS-CoV-2 spike protein and post-vaccination myocarditis, immunohistochemistry (IHC), mass spectrometry analysis of spike protein, and activation-induced marker (AIM) assay in T cells from RV samples were conducted. Results: In the proteomic analysis, 6,861 proteins were identified. Post-vaccination myocarditis showed increased extracellular matrix formation and cardiac fibrosis. Both pre-pandemic and post-vaccination myocarditis had elevated pro-inflammatory cytokine activities. However, post-vaccination myocarditis exhibited higher expression of interferon-alpha (IFNα) and pattern recognition receptor activation, including TLR3 and TLR7. Pre-pandemic myocarditis showed higher activation of the complement system, neutrophils, and NK cells, whereas post-vaccination myocarditis showed increased Th2 cell activation and classical macrophage activation. Spike protein and related T-cell activation were not detected. Conclusion: The immune activation in myocarditis after COVID-19 mRNA vaccination may be triggered by the mRNA in the vaccine via an IFNα-driven immune response, leading to autoimmune-like features. Further studies are necessary to validate whether these proteins correlate with clinical characteristics.