Using proteomics, the large-scale study of proteins, researchers from the University of Zurich and University Hospital Zurich have identified a pattern in blood proteins in patients with long COVID and the effect of these proteins on a part of the immune system called the complement system.
Part of the innate immune system, the complement system comprises distinct proteins in the plasma and on cell surfaces that react with one another to enhance – complement – the ability of antibodies and phagocytic cells to clear microbes and damaged cells, promote inflammation, and attack pathogens.
To identify biomarkers of long COVID, serum was collected from healthy controls and COVID-19 patients during acute infection with the virus and at six-month follow-up, and two high-throughput proteomics approaches were used to measure 6,596 different serum proteins. The researchers observed differences in serum protein levels between patients with severe COVID-19 and those with mild acute COVID-19, and differences between long COVID patients and those without long COVID, during both the acute phase of the infection and at six-month follow-up.
In patients with long COVID, the complement system no longer returns to its basal state, but remains activated and, thus, also damages healthy cells.Onur Boyman, corresponding author of the study.
The study’s findings have generated guarded excitement in the medical community.
These are interesting research findings which suggest that people with Long Covid have persisting abnormalities in some blood proteins that are linked to a part of the immune system orchestra called complement.
However, it is premature to conclude that an accurate diagnostic biomarker has now been found for Long Covid.
Before doing so the findings need to be replicated by other research groups to ensure they are valid.
Specification to Long Covid also needs to be established by making sure that these abnormalities are not present in other long term conditions that involve infection and/or inflammation.
Dr Charles Shepherd,
Trustee and Hon. Medical Adviser to the ME Association.
Nature: Long-COVID signatures identified in huge analysis of blood proteins
NewsGP: Study links blood protein changes to long COVID
Neuroscience News: Blood Proteins Reveal Clues in Long Covid Puzzle
Swiss Info: Zurich researchers find protein clue in long Covid puzzle
News Medical: Study finds patients with long COVID exhibit complement dysregulation with signs of thromboinflammation
Financial Times: Blood protein changes offer clue to solving long Covid riddle (paywalled)
Medpage Today: Blood Protein Changes May Unravel Long COVID Mysteries (paywalled)