A characteristic fingerprint of proteins can be found in the blood of people with long-term complaints after Covid-19 (long covid or post-covid) that cannot be seen in people who have recovered from Covid-19. The proteins are related to a disturbed immune response, changes in blood clotting and tissue damage. The markers found could help develop a diagnostic test and treatments.
For the extensive study, which was conducted on Thursday Science popped up, a group of international researchers repeatedly screened the blood of 113 patients who had had Covid-19 – both mild and severe. The researchers measured the concentrations of almost 6,600 proteins in the blood of all participants in the acute phase of the disease, after six months and, where possible, also after a year. As a check, they also analyzed the blood of 39 healthy people.
After six months, forty patients still reported several long-term complaints, such as fatigue, shortness of breath, chest pain or gastrointestinal complaints. The rest had recovered or only had changes in smell or taste.
There were striking changes in the blood of people with long Covid that indicate a disruption of the so-called complement system. This part of the immune system is activated by pathogens themselves, or by antibodies bound to pathogens or cells.
Inner lining of blood vessels
The researchers also saw proteins that indicate changes in blood clotting and damage or inflammation of the lining of blood vessels. This indicates a persistent interaction between clotting and inflammation, they write.
The changes found have similarities with previous insights into long covid. These indicate dysregulation of the immune system, persistent activation of immune cells and the production of autoantibodies, which unintentionally target the body's own tissues. “The complement system and antibodies are strongly intertwined, and platelets and blood vessel walls also seem to be activated by microclots, which are full of antibodies,” says Jeroen den Dunnen, immunologist at the Amsterdam UMC. He is investigating, among other things, the role of autoantibodies in long Covid.
He believes that a shortcoming of the study is that no distinction was made between people who got long Covid after hospitalization and people who got it after a mild infection. “These are really two different groups. In the first group, older men with underlying conditions are overrepresented, and the immune system response is much more extreme in severe acute Covid-19. In the second group, younger and previously healthy women are overrepresented. Worldwide, we are now mainly looking at the second group when studying long Covid.” Of the forty long Covid patients in this study, the majority had been admitted to hospital. “That clouds the picture,” says Den Dunnen. “The question remains whether a good universal marker will be rolled out here for long Covid.”
Also read
Searching for the explanation for long covid
#blood #people #long #Covid #characteristic #fingerprint #proteins
