ScRNA-seq and flow cytometry based analysis reveals that chronic heart failure associates with enhanced activation and clonal expansion of T cells with predictive autoreactive capacity
Authors: Abplanalp W , Merten M , Cremer S , Rasper T , Holz K , Schuhmacher B , Macinckovic I , Tombor L S , John D , Hoffmann J , Zeiher A M , Dimmeler S 
Published: November 2023

Abstract

Background
Chronic heart failure (HF) is marked by adverse remodelling and chronic inflammation causing impaired function of the heart and poor prognosis. While much is known about the immune response immediately after MI, little is known of the role of the immune system in chronic HF. Our aim is to elucidate the response of T cells to HF.

Methods and Results
In a pilot study assessing healthy controls (HC) and HF patients (n=16), scRNA-seq showed an enhanced T cell activation profile in HF patients combined with an increased capacity for adhesion and antigen-presentation on monocytes. A confirmation cohort of n=180 HC and HF patients using flow cytometry of peripheral blood confirmed an increase of T cell memory/effector cells (HF=65%, HC=53% activated T cells), representing activated and stimulated T cells, and a reduction in the non-active naïve T cell compartment in HF patients. Correspondingly, APCs showed a higher immune stimulatory profile (e.g. HLA-DR, ICAM-1, TREM-1).
Immune secretome analysis further supports the chronic inflammatory phase by significantly increased serum levels of sICAM-1, IL6 and TNFRI. Given that T cells showed strong activation profiles in HF patients, we investigated whether T cells are preferentially clonally expanded in the same patients. Bulk TCR sequencing revealed that TCR diversity was significantly reduced (p=0.03) along with clonal expansion of T cells in HF patients. To assess what these clonally expanding T cells might be targeting, we utilized epitope prediction tools to identify 22 unique human-derived epitopes found only in HF patients. ScRNA-seq of CD45+ sorted cardiac-derived and circulating cells of the same HF patient (N=1) versus healthy controls (n=4) showed clonal expansion of TCRs in the cardiac tissue and blood in HF and epitope prediction confirmed epitopes found in bulk TCR sequencing.
We then assessed the T cell response in a time course post-myocardial infarction in mice with scRNA-seq. We found an accumulation of specifically pro-inflammatory (Th17 T cells in the heart at days 14, 28 and 48 post-MI. Dimensional reduction analysis of T cells from all time points showed that T cells appearing at days 28 and 48 post-MI were more pro-inflammatory than at the earlier time points.
To assess the impact of immune dysregulation in HF on cardiac cells, we cultured the secretome of HF or HC immune cells with endothelial cells. We found that HF secretomes decreased viability of endothelial cells and increased monocyte adhesion to stimulated endothelial cells (p=0.005). Additionally, the immune regulatory molecule PDL-1 was downregulated in HF secretome treated endothelial cells (p=0.014).

Conclusion
This study suggests that chronic HF may drive persistent T cell activation and clonal expansion, with potential cardiac-relevant autoimmune implications causing or promoting adverse remodelling. These data also provide additional insights for therapeutic cardio-immunological interventions.