Detection of Autoantibodies Against the beta(1)-Adrenergic Receptor in the Sera of Patients via the Competitive cell-Based Enzyme Linked Immunosorbent Assay

Objective. This study aimed to assess the level of anti-beta(1)-adrenergic receptor autoantibodies in patients with ventricular arrhythmias with no signs of organic heart disease and with presence of cardiovascular pathology in comparison with a group of healthy volunteers. Material and methods. The study included 44 patients with ventricular arrhythmias with no signs of organic heart disease ("idiopathic"), 34 patients with diagnosed dilated cardiomyopathy (DCM) of inflammatory origin, 35 patients with coronary heart disease and ventricular arrhythmias, 12 patients with coronary heart disease with no ventricular arrhythmias, and 19 healthy volunteers (control group). The level of autoantibodies against the beta(1)-adrenergic receptor was determined by the developed competitive cell-based enzyme-linked immunosorbent assay (ELISA) and by the standard ELISA using peptides corresponding to the second extracellular loop of the beta(1)-adrenergic receptor. Results. Elevated level of autoantibodies detected by a competitive cell-based ELISA was observed in 62% of patients with DCM compared to 21% of healthy volunteers (p = 0.0006). In patients with "idiopathic" ventricular arrhythmias, the level of beta(1)-adrenergic receptor autoantibodies was lower than in healthy subjects (p=0.003). Coronary heart disease patients with or without ventricular arrhythmias exhibited no differences from the control group. The number of significantly positive signals in peptide-based ELISA did not exceed 10% in any of the groups. No correlation between the data from competitive cell-based ELISA and peptide-based ELISA was found. Conclusions. This study demonstrated that competitive cell-based ELISA technique can be applied for detection of beta(1)-adrenergic receptor autoantibodies. The results in DCM patients generally correspond to the expected. Decreased level of autoantibodies in patients with oidiopathic ventricular arrhythmias indicates that this disease is related to changes in the immune system. Such relation is not observed in the case of coronary heart disease patients.