P4527c-Met as a novel T-cell marker in patients with acute myocarditis and dilated cardiomyopathy

Abstract

Background/Introduction: Acute myocarditis is the most common cause of presentations with apparent acute coronary syndrome but culprit-free angiography. Myocarditis is also a common cause of sudden cardiac death in young adults and is a frequent cause of dilated cardiomyopathy (DCM). Despite robust animal evidence for an autoimmune component, no specific immune markers for acute myocarditis have been described in humans. c-Met is the tyrosine kinase receptor for hepatocyte growth factor and its selective expression by heart-homing T-cells has recently been shown in mouse models of cardiac inflammation. Purpose: To investigate if c-Met-expressing T cells are increased in the peripheral blood samples from patients with acute myocarditis and dilated cardiomyopathy (DCM), and to characterise T-cell responses in acute myocarditis. Methods: Between June 2015 and January 2018, 39 patients with acute myocarditis, diagnosed on the basis of clinical and cardiac magnetic resonance (CMR) features, were prospectively enrolled within 10 days of presentation. Plasma and peripheral blood mononuclear cells (PBMCs) were isolated and cryopreserved for immune-phenotyping via flow cytometry. PBMCs from 10 patients with non-familial DCM and 10 healthy volunteers were used for comparison. T helper (Th) cell subtypes were studied after cell stimulation with phorbol 12-myristate-13-acetate (PMA) and ionomycin using flow cytometry markers for interferon-γ (Th1), interleukin (IL)-4 (Th2) and IL-17A (Th17). Results: Greater proportions of memory CD4+ and CD8+ T-cells were c-Met+ in patients with acute myocarditis compared to healthy controls (19.1% vs. 4.1%, p=0.003, 28.3% vs. 5.9%, p=0.003, Figure). DCM subjects also had higher proportions of c-Met+ memory CD4+ (30.3%) and CD8+ (16.9%) T-cells compared to healthy volunteers (p=0.003 and p=0.04). CD4+ c-Met+ T cells in acute myocarditis were more likely to express both of the other cardiotropic markers CCR4 and CXCR3 compared to healthy controls (57.1% vs 20.7% p=0.001). c-Met+ T cells were also more likely to express markers of early activation (CD4+ CD69+ (12.4% vs. 1.9%, p<0.0001), CD8+ CD69+ (18.3% vs. 1.4%, p<0.0001)) and exhaustion (CD8+ CD28- CCR7+ CD45RA+ TEMRA cells (14.9% vs 5.0% p=0.0008)) compared to c-Met- cells. CD4+ c-Met+ T cells were also more likely to produce IL-4 and IL-17 compared to CD4+ c-Met- cells. (Figure presented) Conclusion(s): The novel cardiotropic T-cell marker c-Met expression is increased in CD4 and CD8 memory T cells in patients with acute myocarditis. These cells exhibit distinct pro-inflammatory phenotypes. In the future, immunephenotyping in peripheral blood may help distinguish between inflammatory and other causes of acute myocardial injury.