Impairment of health after overcoming the acute phase of COVID-19 is being observed more and more frequently. Here different symptoms of neurological and/or cardiological origin have been reported. With symptoms, which are very similar to the ones reported but are not caused by SARS-CoV-2, the occurrence of functionally active autoantibodies (
f
AABs) targeting G-protein coupled receptors (GPCR-
f
AABs) has been discussed to be involved.
We, therefore investigated, whether GPCR-
f
AABs are detectable in 31 patients suffering from different Long-COVID-19 symptoms after recovery from the acute phase of the disease.
The spectrum of symptoms was mostly of neurological origin (29/31 patients), including post-COVID-19 fatigue, alopecia, attention deficit, tremor and others. Combined neurological and cardiovascular disorders were reported in 17 of the 31 patients. Two recovered COVID-19 patients were free of follow-up symptoms. All 31 former COVID-19 patients had between 2 and 7 different GPCR-
f
AABs that acted as receptor agonists. Some of those GPCR-
f
AABs activate their target receptors which cause a positive chronotropic effect in neonatal rat cardiomyocytes, the read-out in the test system for their detection (bioassay for GPCR-
f
AAB detection). Other GPCR-
f
AABs, in opposite, cause a negative chronotropic effect on those cells. The positive chronotropic GPCR-
f
AABs identified in the blood of Long-COVID patients targeted the β
2
-adrenoceptor (β
2
-
f
AAB), the α
1
-adrenoceptor (α
1
-
f
AAB), the angiotensin II AT1-receptor (AT1-
f
AAB), and the nociceptin—like opioid receptor (NOC-
f
AAB). The negative chronotropic GPCR-
f
AABs identified targeted the muscarinic M
2
-receptor (M
2
-
f
AAB), the MAS-receptor (MAS-
f
AAB), and the ETA-receptor (ETA-
f
AAB). It was analysed which of the extracellular receptor loops was targeted by the autoantibodies.