Anti-desmoglein2 autoantibodies are present in patients with cardiac sarcoidosis and correlate with cardiac inflammation

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): The Zurich ACM Program is supported by generous grants from the Georg and Bertha Schwyzer-Winniker Foundation, the Baugarten Foundation, Swiss National Science Foundation, Swiss Heart Foundation and Wild Foundation. This work is also supported by a Canadian Institutes of Health Research grant (FRN: 162402) and the Labatt Heart Centre and Waugh Family Innovation Funds, Caitlin Elizabeth Morris Memorial Fund, Alex Corrance Memorial Foundation and Meredith Cartwright.

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) has several phenocopies such as cardiac sarcoidosis (CS), idiopathic outflow tract ventricular tachycardia (OT-VT) and myocarditis. Differentiation between these entities can be challenging. Recently, we have identified diagnostic anti-desmoglein-2 autoantibodies (anti-DSG2 Abs) in patients with ARVC.

PURPOSE We sought to examine whether anti-DSG2 Abs are also present in clinical phenocopies of ARVC.

METHODS Anti-DSG2 Abs in sera of 25, 19 and 22 patients with sarcoidosis, OT-VT and myocarditis, respectively, were assessed by western blots and ELISA. Clinical and imaging parameters, as well as conventional biomarkers were correlated to detected anti-DSG2 Ab intensity levels.

RESULTS Anti-DSG2 Abs, at various intensities, were identified in 6/25 (24%) patients with sarcoidosis, all presenting with CS, but were absent in patients with OT-VT and myocarditis. Cardiac 18F- fluorodeoxyglucose positron emission tomography (18F-FDG PET) was positive in all sarcoidosis patients with positive anti-DSG2 Abs, corresponding to a median PET maximum standardized uptake value (SUVmax) of 5.65 [IQR: 5.15 – 10.9]. In sarcoidosis patients without anti-DSG2 Abs, the SUVmax values were significantly lower with a median of 0 [IQR: 0 – 4] (p = 0.011). The Pearson correlation coefficient (R) was 0.188 (p = 0.039) indicating a positive correlation between cardiac 18F-FDG uptake and anti-DSG2 Abs. No significant correlation was detected for any of the other clinical parameters and biomarkers.

CONCLUSIONS In addition to being present in ARVC, anti-DSG2 Abs are also found in CS, a common phenocopy of ARVC; conversely, anti-DSG2 Abs are absent in idiopathic OT-VT and myocarditis. Anti-DSG2 Ab levels positively correlate with myocardial disease activity in CS as indicated by cardiac 18F-FDG PET scanning. Abstract Figure. Central illustration

ARVC specific autoantibody identifies cardiac sarcoidosis and correlates with inflammation activity

Introduction

Cardiac sarcoidosis (CS) is an inflammatory granulomatous disease of unknown origin. CS and arrhythmogenic right ventricular cardiomyopathy (ARVC) are overlapping syndromes. With both, patients are at increased risk of ventricular arrhythmias and sudden cardiac death. However, the diagnosis of CS is challenging, especially in patients with no extracardiac involvement, but correct diagnosis has large therapeutic impact. Recently, a novel diagnostic autoantibody (anti-DSG2 Ab) was identified in ARVC. We sought to identify this antibody in CS patients and correlate its levels with inflammation activity using cardiac positron-emission-tomography (18-FDG-PET).

Methods

Recombinant human desmoglein-2 (DSG2) proteins on western blots were exposed to sera as well as purified IgG of 14 patients with sarcoidosis (all confirmed by histology) and 6 controls (1 ARVC patient (positive control) and 5 healthy control subjects (negative control)). Clinical patient characteristics were correlated to detected antibody intensity levels.

Results

The sarcoidosis cohort comprised 43% (6/14) male patients and the average age was 50±12 years. Anti-DSG2 Abs were identified in 43% (6/14) and were detected faintly (below cut off level) in 21% (3/14) of all sarcoidosis patients. Antibody was also present in the ARVC patient (1/1) and was absent in all control subjects (5/5). Myocardial inflammation was present in 18-FDG PET imaging in all CS patients with positive anti-DSG2 Abs, corresponding to an average SUV (standardized uptake value) of 8.1±4.2. In patients with faint or no antibody, the SUV values were significantly lower with 1.2±2.1 and 3.2±4.0, respectively (P=0.044, one-way ANOVA). The Pearson correlation coefficient (R) was 0.6 (P=0.037) for SUV vs. higher antibody levels assessed by pixel count of the western blot bands for purified IgG.

Conclusions

Anti-DSG2 Abs are not only a specific biomarker for ARVC, but are also found in CS, suggesting a similar pathophysiological mechanism in these overlapping syndromes, both involving cardiac inflammation and myocyte cell death. Moreover, antibody levels correlate with disease activity on cardiac PET imaging. Larger cohorts are necessary to confirm these findings.

Funding Acknowledgement

Type of funding source: None