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Identification of Pathogenic Immune Cell Subsets in Checkpoint Inhibitor-induced Myocarditis

ABSTRACT: Immune checkpoint inhibitors (ICIs) are monoclonal antibodies used widely to activate the immune system against tumor cells. Despite their therapeutic benefits, ICIs are known to cause immune-related adverse events (irAE) such as myocarditis, a rare but serious side effect with up to 50% mortality. To identify pathogenic immune subset(s) responsible for ICI myocarditis and other irAE, we performed single cell mass cytometry (CyTOF) on peripheral blood mononuclear cells from 40 patients and controls with irAE including four patients with ICI myocarditis. We also profiled 15 patients/controls using single cell RNA sequencing (scRNA-seq) with feature barcoding for surface marker expression confirmation. In both CyTOF/scRNAseq analyses, we found expansions of cytotoxic CD8+ T effector cells re-expressing CD45RA (Temra CD8+ cells) in ICI myocarditis patients compared to controls. Using T cell receptor sequencing, we demonstrated a significant clonal expansion of CD8+ Temra cells in myocarditis patients. Transcriptomic profiling of these Temra CD8+ clones confirmed their highly activated and cytotoxic phenotype with expression of granzyme/perforin. Longitudinal data revealed the progression of these Temra CD8+ cells into an exhausted phenotype two months after diagnosis of myocarditis and after treatment with glucocorticoids. Differential expression of several proinflammatory chemokines (CCL4/CCL4L2/CCL5) was uncovered in the clonally expanded Temra CD8+ cells and ligand-receptor analysis implicated their regulation of other inflammatory cells such as monocytes and NK cells. These data suggest that the therapeutic modulation of these chemokines may serve as an attractive strategy for reducing life-threatening irAE in ICI-treated cancer patients.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE180045 | GEO | 2022/06/29

REPOSITORIES: GEO

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Project description:Immune checkpoint inhibitors (ICIs), antibodies targeting PD-1/PD-L1 or CTLA4 have revolutionized cancer management but are associated with devastating immune-related adverse events (irAEs) including myocarditis. The main risk factor for ICI myocarditis is the use of combination PD-1 and CTLA4 inhibition. ICI-myocarditis is often fulminant and is pathophysiologically characterized by myocardial infiltration of T lymphocytes and macrophages. While much has been learned regarding the role of T-cells in ICI-myocarditis, little is understood regarding the identity, transcriptional diversity, and functions of infiltrating macrophages. We employed an established murine ICI myocarditis model (Ctla4+/-Pdcd1-/- mice) to explore the cardiac immune landscape using single-cell RNA-sequencing, immunostaining, and molecular imaging. We observed marked increases in CCR2+ monocyte-derived macrophages and CD8+ T-cells in this model. The macrophage compartment was heterogeneous and displayed marked enrichment in an inflammatory CCR2+ subpopulation expressing Cxcl9, Cxcl10, Gbp2b, and Fcgr4 that originated from CCR2+ monocytes. Importantly, a similar macrophage population expressing CXCL9, CXCL10, and CD16α (human homologue of mouse FcgR4) were found selectively in patients with ICI myocarditis compared to other forms of heart failure and myocarditis. In silico prediction of cell-cell communication suggested interactions between T-cells and Cxcl9+Cxcl10+ macrophages via IFN-γ and CXCR3 signaling pathways. Depleting CD8+T-cells and blockade of IFN-γ signaling blunted the emergence of Cxcl9+Cxcl10+ macrophages in the heart and attenuated myocarditis suggesting that this interaction was necessary for disease pathogenesis. Collectively, these data demonstrate that ICI-myocarditis is associated with the emergence of a specific population of inflammatory macrophages and suggest the possibility that IFN-γ blockade may serve as an effective treatment for this devastating condition.

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Identification of Pathogenic Immune Cell Subsets in Checkpoint Inhibitor-induced Myocarditis

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