Single-cell profiling of human heart and blood in immune checkpoint inhibitor-associated myocarditis

2507

Background: Myocarditis due to immune checkpoint inhibitors (ICIs) is uncommon; however, myocarditis due to ICIs leads to severe morbidity and even death in 20-40% of cases. The molecular underpinnings of ICI-associated myocarditis are poorly understood, and there is an unmet clinical need to identify therapeutic targets and biomarkers that can aid in disease management. Methods: Heart tissue was obtained through endomyocardial biopsy or autopsy of patients receiving ICIs and was profiled with paired single-cell RNA sequencing (scRNA-seq) and T cell receptor sequencing (TCR) using the 10x Genomics Chromium system. A control dataset was constructed using scRNAseq data of heart tissue from patients receiving ICIs but without myocarditis and a published dataset from healthy patients not receiving ICIs. Peripheral blood mononuclear cells (PBMCs) were collected at the time of myocarditis diagnosis in a larger cohort of patients and analyzed with ICI-treated controls. The CITE-Seq protocol was used to measure paired scRNA-seq, TCR, and surface proteomics in PBMCs, using serial timepoints where available. Results: Heart tissue from 13 patients with myocarditis, including three fatal cases, and seven controls yielded 77,712 single cells. Blood profiling from 27 patients with ICI myocarditis and ICI-treated controls across 54 samples yielded over 230,000 cells. ICI myocarditis tissue demonstrated an increased T cell infiltrate (OR 8.94, FDR = 0.0021). Expression of multiple inflammatory pathways, most notably interferon responses, was up-regulated across multiple immune and non-immune cell types in the setting of myocarditis, providing important pathophysiological insights. T cell clones were also found to be shared between blood and heart, enabling the identification of putative pathogenic T cell subsets. Conclusions: Increased intramyocardial T cells and the activation of interferon response gene networks were seen in the setting of ICI myocarditis. These preliminary findings highlight potential pathological pathways in ICI myocarditis that could serve as biomarkers or therapeutic targets.

Investigating the tumor immune infiltrate for populations that predict immune-related adverse events (irAEs) in patients receiving PD-1 inhibitors

3116

Background: The mechanistic relationship between clinical benefit and immune-related adverse events (irAEs) in response to immune checkpoint inhibitors (ICIs) remains unclear, with several clinical studies reporting that irAEs are biomarkers of responses. Single-cell RNA sequencing (scRNAseq) analysis of tumors from patients with advanced melanoma before and after treatment with ICIs have identified immune cells that correlate with response to ICIs. We sought to evaluate if these populations were also associated with irAEs. Methods: A published scRNAseq data set generated with the Smart-Seq2 protocol (Sade-Feldman M, et al. Cell 2018.) was re-analyzed, stratified by two definitions of irAEs: (1) toxicity requiring systemic immunosuppression (prednisone > 10mg/day) or (2) systemic immunosuppression and/or endocrinopathy. Unbiased single-cell analysis was performed, followed by sub-clustering of T cell populations. The percentage of cells in each cluster was determined on a per sample basis. Results: 13,184 immune cells from 39 samples collected from 25 patients were re-analyzed. 27 samples were from patients who did not respond to ICIs, while 12 samples came from responding patients. 21 samples came from patients who required immunosuppression, 5 samples from patients with isolated thyroiditis, and 13 samples from patients who met neither irAE criteria. Unsupervised scRNAseq analyses focused on ICI efficacy re-capitulated published associations between response and populations that included B-cells (p < 0.01) and TCF7 expressing T-cells (p < 0.01). While these cell populations were not associated with either definition of toxicity, we observed a non-Treg CD4 expressing T cell population (0.8-10.5% cells/sample) that positively correlated with either definition of toxicity (p < 0.05) but not efficacy. Conclusions: In a patient cohort with advanced melanoma, tumor-infiltrating immune cell populations associated with response to ICI therapy were not associated with irAEs. This suggests that biomarkers of ICI response may not function as biomarkers of irAEs, and ongoing analysis will seek to validate this result. Understanding the differences between ICI response and irAEs may identify new therapeutic targets for maximizing efficacy while mitigating toxicity.

The effects of fitness-type exercise on iron status in adult women

To determine if compromised iron status results from fitness-type exercise, 24 women from a 35-min, 4-day/wk aerobic exercise class provided blood samples at wk 0, 6, and 13. Hb increased from wk 0 to wk 6 (p less than 0.001), and decreased from wk 6 to wk 13 (p less than 0.001). Hematocrit did not change from wk 0 to wk 6, but decreased from wk 6 to wk 13 (p less than 0.005). Ferritin concentrations were lower at wk 6 and 13 (p less than 0.01 and p less than 0.05) than initially. No changes in these measures were detected among 11 sedentary control subjects. Intakes of iron, ascorbic acid, protein, and energy were comparable between exercise and sedentary groups. Decreased resting and recovery step test heart rates indicated improved aerobic fitness in exercising subjects from wk 2 to wk 11. Thirteen weeks of aerobic exercise class did not induce iron deficiency anemia. Decreased plasma ferritin concentrations suggest a compromise in iron stores which appears to be stabilized after 6 wk.