Circulating Autoantibodies Against Vasoactive Biomarkers Related to Orthostatic Intolerance in Long COVID Patients Compared to No-Long-COVID Populations: A Case-Control Study.

Endothelial dysfunction mediated by elevated levels of autoantibodies against vasoactive peptides occurring after COVID-19 infection is proposed as a possible pathomechanism for orthostatic intolerance in long COVID patients. This case-control study comprised 100 long COVID patients from our prospective POSTCOV registry and three control groups, each consisting of 20 individuals (Asymptomatic post-COVID group; Healthy group = pan-negative for antispike protein of SARS-CoV-2; Vaccinated healthy group = no history of COVID-19 and vaccinated). Autoantibodies towards muscarinic acetylcholine receptor M3, endothelin type A receptor (ETAR), beta-2 adrenergic receptor (Beta-2 AR), angiotensin II receptor 1 and angiotensin 1-7 (Ang1-7) concentrations were measured by enzyme-linked immunosorbent assay in long COVID patients and controls.