New Delhi: Severe Covid-19 patients often develop blood clots that can cause fatal strokes and restrict blood flow in the lungs. A study has now revealed that it is the production of certain antibodies triggered by SARS-CoV-2 that causes the clots.
According to the study published in Science Translational Medicine journal this week, an autoimmune antibody circulating in the blood attacks the cells and triggers clots in arteries, veins, and microscopic vessels.
Usually, such antibodies are found in patients who have the autoimmune disease called antiphospholipid syndrome — a disorder in which the immune system mistakenly attacks normal proteins in the blood.
According to Yogen Kanthi, assistant professor at the University of Michigan and one of the authors of the study, the connection between autoantibodies and Covid was unexpected.
“In patients with COVID-19, we continue to see a relentless, self-amplifying cycle of inflammation and clotting in the body,” Kanthi said in a statement. “Now we’re learning that autoantibodies could be a culprit in this loop of clotting and inflammation that makes people who were already struggling even sicker.”
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What the research says
The researchers, who studied 172 patients hospitalised with Covid-19, found that half of the patients who were very sick were exhibiting a combination of high levels of both the dangerous antibodies and ‘super-activated’ neutrophils, which are destructive, exploding white blood cells.
The team studied these neutrophils and antibodies together in mice to see if this could be the dangerous combination behind the clots.
“Antibodies from patients with active COVID-19 infection created a striking amount of clotting in animals — some of the worst clotting we’ve ever seen,” Kanthi said.
The team will now work on finding out whether severely ill patients would have better outcomes if the antibodies are blocked or removed.
Treatments like plasmapheresis, which involves draining blood through an IV and replacing it with fresh plasma that does not contain antibodies associated with blood clots, are commonly used in severe autoimmune diseases.
“We know people with the highest levels of autoantibodies did worse in terms of respiratory function, and the antibodies caused inflammation even in healthy cells,” Yu Zuo, an assistant professor at University of Michigan, said in the statement.
“We don’t yet know what is triggering the body to produce these antibodies, so the next step would be additional research to identify the triggers and the targets of the antibodies,” said co-corresponding author Jason Knight.
The team has also started conducting a randomised clinical trial to test a well-known anti-clotting agent, dipyridamole, in patients with Covid to determine whether it can reduce excessive blood clots.
“Dipyridamole is an old drug that is safe, inexpensive, and scalable,” Kanthi said.
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