Long COVID: New evidence for cause of fatigue syndrome

Dec. 16, 2022
Not excessive inflammatory reaction, but anti-inflammatory substances as triggers.

Researchers at the Joint Metabolome Facility of the University of Vienna and the Medical University of Vienna have now presented new evidence of triggers for fatigue following SARS-COV-2 infection. The team led by chemist Christopher Gerner showed that an exaggerated anti-inflammatory response is likely to be responsible for long COVID syndrome (LCS). The study has been published in "iScience".

Researchers at the Joint Metabolome Facility (University of Vienna and Medical University of Vienna) have now turned their attention to LCS using mass spectrometry-based post-genomic analysis techniques. The strength of these methods lies in the very comprehensive mapping of actual conditions, i.e. the traceability of disease processes taking place in a patient. Together with Klaus Schmetterer from the MedUni Vienna’s Department of Laboratory Medicine and Mariann Gyöngyösi, from MedUni Vienna´s Department of Medicine II and Head of the Long COVID Outpatient Clinic at AKH Vienna, patient cohorts were selected and analyzed to elucidate the molecular basis of LCS.

In the course of a viral infection, there is normally a very strong activation of the immune system. But in virtually all of the Long COVID patients studied, corresponding markers such as cytokines, acute phase proteins and eicosanoids, which indicate inflammation, were in fact hardly detectable.

Surprisingly, the differences were more pronounced in long COVID patients compared to asymptomatic patients recovering from COVID disease than to healthy controls.

Although auto-immunity was previously suspected as the main cause of Long COVID, there is no evidence of accompanying inflammatory processes in LCS patients.

Contrary to previous expectations, the researchers were able to find several anti-inflammatory proteins, lipids and metabolites in long COVID patients, which on the one hand could contribute to the most important LCS symptoms, and on the other hand point to the formation of alternatively polarized macrophages as the cause.

The blood plasma analyses of LCS patients allow a deep insight into the physiological processes of the patients. In the case of LCS patients, an active participation of so-called alternatively polarized macrophages became apparent. These cells are typically formed after all kinds of infections and are responsible for the coordination of regenerative processes. The molecular profile found in LCS patients, consisting of proteins, lipids and metabolites, is very characteristic for these cells.

University of Vienna release