Anti‐CTLA‐4 m2a Antibody Exacerbates Cardiac Injury in Experimental Autoimmune Myocarditis Mice By Promoting Ccl5‐Neutrophil Infiltration

Abstract The risk for suffering immune checkpoint inhibitors (ICIs)‐associated myocarditis increases in patients with pre‐existing conditions and the mechanisms remain to be clarified. Spatial transcriptomics, single‐cell RNA sequencing, and flow cytometry are used to decipher how anti‐cytotoxic T lymphocyte antigen‐4 m2a antibody (anti‐CTLA‐4 m2a antibody) aggravated cardiac injury in experimental autoimmune myocarditis (EAM) mice. It is found that anti‐CTLA‐4 m2a antibody increases cardiac fibroblast‐derived C‐X‐C motif chemokine ligand 1 (Cxcl1), which promots neutrophil infiltration to the myocarditic zones (MZs) of EAM mice via enhanced Cxcl1‐Cxcr2 chemotaxis. It is identified that the C–C motif chemokine ligand 5 (Ccl5)‐neutrophil subpopulation is responsible for high activity of cytokine production, adaptive immune response, NF‐κB signaling, and cellular response to interferon‐gamma and that the Ccl5‐neutrophil subpopulation and its‐associated proinflammatory cytokines/chemokines promoted macrophage (Mφ) polarization to M1 Mφ. These altered infiltrating landscape and phenotypic switch of immune cells, and proinflammatory factors synergistically aggravated anti‐CTLA‐4 m2a antibody‐induced cardiac injury in EAM mice. Neutralizing neutrophils, Cxcl1, and applying Cxcr2 antagonist dramatically alleviates anti‐CTLA‐4 m2a antibody‐induced leukocyte infiltration, cardiac fibrosis, and dysfunction. It is suggested that Ccl5‐neutrophil subpopulation plays a critical role in aggravating anti‐CTLA‐4 m2a antibody‐induced cardiac injury in EAM mice. This data may provide a strategic rational for preventing/curing ICIs‐associated myocarditis.