Abstract 7474: T-cell responses across heart, blood, and tumor in patients with immune checkpoint inhibitor-related myocarditis (irMyocarditis)

Abstract Introduction: Immune checkpoint inhibitor (ICI)-related myocarditis (irMyocarditis) is a potentially lethal complication of ICI use that is characterized by the presence of clonally expanded T cells in the heart. The antigens recognized by these expanded intracardiac T-cell clones and their relationships to T-cell clones in the blood and tumors of irMyocarditis patients are poorly understood. Methods: Paired single-cell RNA sequencing (scRNA-seq) and T-cell receptor (TCR) sequencing was performed on heart tissue (n = 13) and peripheral blood from patients with irMyocarditis (n = 25) and ICI-treated controls (n = 28) using the 10X Chromium (10X Genomics) system. TCR-β chain sequencing was performed (Adaptive Biotechnologies) on four autopsy cases of patients with available scRNA-seq data and irMyocarditis heart, tumor, and histologically normal tissue. An established high-throughput protocol was used to screen expanded intracardiac TCRs against candidate antigens (Oliveira G, et al. Nature 2021). Briefly, full-length TCRs were cloned, transduced into donor T cells, and screened against autologous or major histocompatibility complex (MHC) Class I-matched antigen presenting cell lines pulsed with peptide pools that covered the full length of the ⍺-myosin, troponin-I, and troponin-T proteins alongside pools of common viral antigens and appropriate controls. Results: scRNA-seq data showed that TCRs shared between heart and blood are predominantly found in circulating CD8 T cell subsets as compared to circulating CD4 T cell subsets. The gene expression patterns of these shared T-cell clones in circulation appear distinct in fatal and non-fatal irMyocarditis patients, with shared T-cell clones in fatal cases expressing cycling markers (MKI67, STMN1) and the chemokine receptor CXCR3. TCR-β chain sequences most enriched in irMyocarditis tissue relative to control tissues were distinct from those enriched in tumor tissues, and their full-length TCR sequences could be recovered from scRNA-seq data. In total, 52 cardiac-expanded TCRs across eight donors were screened against candidate antigens. None of the screened TCRs recognized the putative cardiac autoantigens. Conclusions: T-cell clones expanded in irMyocarditis are shared in circulation, where the gene expression of these clones may help to distinguish fatal from non-fatal irMyocarditis. TCRs enriched in irMyocarditis appear to be largely distinct from those enriched in tumor and likely recognize currently unknown cardiac autoantigens. Citation Format: Steven Blum, Daniel A. Zlotoff, Neal P. Smith, Isabela J. Kernin, Swetha Ramesh, Giacomo Oliveira, Leyre Zubiri, Joshua Caplin, Nandini Samanta, Sidney Martin, Mike Wang, Alice Tirard, Pritha Sen, Yuhui Song, Katherine Xu, Jaimie L. Barth, Kamil Slowikowski, Mazen Nasrallah, Jessica Tantivit, Kasidet Manakongtreecheep, Benjamin Y. Arnold, John McGuire, Alexander B. Afeyan, Christopher J. Pinto, Daniel McLoughlin, Monica Jackson, PuiYee Chan, Aleigha Lawless, William A. Michaud, Tatyana Sharova, Linda T. Nieman, Justin F. Gainor, Dejan Juric, Mari Mino-Kenudsen, Ryan J. Sullivn, Genevieve M. Boland, James R. Stone, Catherine J. Wu, Molly F. Thomas, Tomas G. Neilan, Kerry L. Reynolds, Alexandra-Chloé Villani. T-cell responses across heart, blood, and tumor in patients with immune checkpoint inhibitor-related myocarditis (irMyocarditis) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7474.