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Friday 6 November 2020
One of the puzzling complications of Covid 19 disease is that the patient’s blood clots. Why this happens so far has remained unclear. Now US scientists are finding an approach and already have an idea of which drugs might work.
In the case of Sars-CoV-2 infections, in addition to diseases of the lungs and other organs, blood coagulation disorders are also repeatedly observed in the patient. In some Covid 19 sufferers, the blood really seems to pool. This leads to stroke or pulmonary embolism. When examining deceased patients, doctors often found thrombosis and blood clots in the arteries, veins and even capillaries. “In patients with Covid-19 we see a relentless and self-reinforcing vicious cycle of inflammation and aggregation of blood throughout the body,” explains Yogendra Kanthi of the University of Michigan.
He is co-author of a US study that investigated the cause of this increased clotting and was published in the journal “Science”. Because so far the cause has remained unclear. “Most patients have normal levels of blood clotting factors, fibrinogen and platelets, which suggests Covid-19 causes a unique prothrombotic condition,” explain Kanthi and colleagues. Theoretically, this could be a direct effect of the virus, but inflammation of the blood vessels or disturbances in the biochemical regulation of blood clotting also appeared as possible causes, as well as the body’s immune reaction to coronary infection.
For their study, the scientists analyzed the blood of 172 patients with Covid-19 treated in hospital with a severe course. They specifically looked for eight antibodies typical of the so-called antiphospholipid syndrome. This autoimmune disease can also lead to fatal blood clots.
More antibodies, more serious diseases
“A good half of the patients with Covid-19 were positive for at least one of these autoantibodies,” reports Jason Knight, one of the authors of the study. A quarter of the patients had two or more of these antibodies. There were clear links to the course of Covid 19 disease: the more autoantibodies the patient had in their blood, the more severe the course of the disease.
“This suggests that these autoantibodies could be the culprits of this vicious circle of blood clotting and inflammation that makes many Covid patients sick,” says Kanthi. Apparently, infection with Sars-CoV-2 directly or indirectly promotes the production of these misdirected antibodies and thus derails blood clotting. Affected patients often also had white blood cells that were hyperactivated by antibodies. These immune cells then produce extracellular fibers which normally help fight bacteria and thus form a kind of network. In this case, however, they further increase blood clotting. When the scientists checked their results with mice, they used antibodies from seriously ill Covid-19 patients to produce “astonishing levels of thrombosis” in them as well.
The study findings could also lead to better treatment of this derailed blood clotting. In addition to the heparin anticoagulant, already administered in many cases of Covid-19, the antiphospholipid syndrome is also treated with the active ingredient dipyridamole. “It’s an old drug that’s safe, cheap, and widely available,” says Kanthi.
Initial tests now suggest that this agent could also help with Covid-19. Therefore, the research team has already started a clinical trial with the drug. They also recommend checking the effectiveness of blood washing, which specifically filters certain components of the blood.
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