[Detection of Autoantibodies Against the 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-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, 12patients with coronary heart disease with no ventricular arrhythmias, and 19 healthy volunteers (control group). The level of autoantibodies against the 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 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 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 1-adrenergic receptor autoantibodies. The results in DCM patients generally correspond to the expected. Decreased level of autoantibodies in patients with "idiopathic" 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.

[Synthetic conformational antigen, simulating the extracellular part of M2-muscarinic receptor and its reactivity with sera from patients with idiopathic arrhythmias].

Linear peptides corresponding to fragment 83-98 of the first loop and fragments 168-192 and 171-182 of the second extracellular loops of M2-muscarinic receptor (marker of early cardiac disorders and arrhythmias) were synthesized by Fmoc-SPPS method. A new conformational antigen was synthesized by method of selective ligation of linear peptides by disulfide bond with native localization. Peptides were studied in reaction with sera from patients with idiopathic arrhythmias. A new conformational antigen was recognized by sera from patients with idiopathic arrhythmias with high reactivity.