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One of the more surprising symptoms of COVID-19 is blood clots that many patients, including young people, experience due to infection. Blood clots can in some cases lead to dangerous obstruction in the lungs, causing stroke and even death, even in people with no history of circulatory disease.
In an article published in Science Earlier this week, researchers provided a glimpse of what could lead to blood clots from COVID-19 infection. The team found that a specific set of antibodies called autoantibodies – counterfeit versions of cells that protect the body from pathogens, but instead attack. its own cells (in this case the body’s own blood vessel cells) —that may be partly responsible for the disease-related risk of blood clots. Of the 172 patients hospitalized with COVID-19, they found that half produced these autoantibodies. In addition, when the scientists injected autoantibodies into the mice, the animals developed blood clots.
In April, the same group of scientists reported that the inflammation associated with COVID-19 could lead to blood clots in the small vessels in the lungs, and these clots are mostly surrounded by an immune cell called neutrophils. In patients with COVID-19, these neutrophils can explode inside small blood vessels, creating sticky molecular traps that attract other clotting factors to circulate in the blood. “Theoretically, we think the This is intended to trap things like bacteria or viruses. “But if [neutrophils] over-stimulated, they can also grow and block blood vessels and lead to blood clotting. In previous research, Kanthi and his colleagues found that COVID-19 patients who had many of these “traps” in their blood systems were more likely to have severe illness or respiratory failure.
“The inflammation leads to blood clotting and blood clotting leads to more inflammation,” he said. “It becomes an endlessly self-amplifying cycle of inflammation and coagulation, leading to sicker patients.”
Their latest Science , the researchers found that the autoantibodies promote this cycle of inflammation and blood clotting. The autoantibodies found in COVID-19 patients are the same as the antibodies doctors find in patients with an autoimmune disease called antiphospholipid syndrome, in which the antibodies form a blood clot by way of attracting clotting factors that ultimately block blood flow. Understanding how these antibodies contribute to blood clotting risk in patients with that syndrome has led experts such as Jason Knight, who studied antiphospholipids, to predict similar clotting conditions in COVID patients. -19. “By May, blood clotting is everything everyone says about a COVID-19 patient,” said Knight, associate professor of rheumatism at the University of Michigan and one of the study authors. “When we started an autopsy, we found clotting microvascular in the lungs.”
Such coagulation in small vessels – sometimes too small to be obtained by CT scan – is one of the hallmarks of a COVID-19-associated blockage of blood flow. Not only does the patient develop so-called blood clots in larger vessels including veins and arteries, which can lead to deep vein thrombosis and stroke, but the infection sometimes causes blood clots. in the small vessels in the lungs – which can cause breathing problems —And autoantibodies may be the reason for that, as they can bind to vascular cells everywhere.
In fact, COVID-19 could be considered “the extreme version of certain diseases, one of which is the antiphospholipid syndrome,” Kanthi said. That means studying these patients may help to better understand COVID-19 and how coronavirus contributes to blood clotting. To begin with, Knight studied a drug, dipyridamole, approved to treat stroke and prevent blood clots in people with mechanical heart valves, to see if it could reduce the risk of blood clots in patient COVID-19 or not. The drug is relatively inexpensive and directly reduces neutrophil activation, which in turn can reduce the formation of active neutrophil traps in the vessels. Self-antibody testing is already available to doctors, Knight said, so eventually, COVID-19 patients can be tested for their antibody levels and then tested for receive more aggressive blood-thinning medications or other medications such as dipyridamole, if it proves to be effective, to protect them from blood clotting.
The team is currently enrolling COVID-19 patients to study anticoagulants and may have an answer by the end of the year, Knight said. These findings could open up new understanding of how the virus affects blood clotting in the body; “The fact that the body’s own autoantibodies can trigger such extensive clotting is new,” Kanthi said. “We know antibodies like this can exist [from our knowledge of antiphospholipid syndrome] but no one has ever considered whether they could cause blood clots ”.
It is not yet clear when during infection these autoantibodies begin to form and what makes people more likely to create them. A person’s genetics, history of previous viral and bacterial infections, as well as a reversible immune response suggested by COVID-19 may all contribute to that risk. But the fact that half of the patients are able to produce these clot-boosting antibodies means that a better understanding of what these risk factors are and being able to identify harborers they, which can prevent them from getting a more serious and potentially fatal COVID-19 infection.