Blood clots continue to wreak havoc for patients with severe COVID-19 infection, and a new study explains what may spark them in up to half of patients.
The culprit: an autoimmune antibody that’s circulating in the blood, attacking the cells and triggering clots in arteries, veins, and microscopic vessels. Blood clots can cause life-threatening events like strokes. And, in COVID-19, microscopic clots may restrict blood flow in the lungs, impairing oxygen exchange.
Image/Stephanie King/ Michigan Medicine
Outside of novel coronavirus infection, these clot-causing antibodies are typically seen in patients who have the autoimmune disease antiphospholipid syndrome. The connection between autoantibodies and COVID-19 was unexpected, says co-corresponding author Yogen Kanthi, M.D., an assistant professor at the Michigan Medicine Frankel Cardiovascular Center and a Lasker Investigator at the National Institutes of Health’s National Heart, Lung, and Blood Institute.
“In patients with COVID-19, we continue to see a relentless, self-amplifying cycle of inflammation and clotting in the body,” Kanthi says. “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.”
‘Some of the worst clotting we’ve ever seen’
Co-corresponding author Jason Knight, M.D., Ph.D., a rheumatologist at Michigan Medicine, has been studying antiphospholipid syndrome antibodies in the general population for years.
“Half of the patients hospitalized with COVID-19 were positive for at least one of the autoantibodies, which was quite a surprise,” says Knight, also an associate professor of internal medicine and a leading expert on diseases caused by autoantibodies.
In the new Science Translational Medicine publication, they found about half of the patients who were very sick with COVID-19 were exhibiting a combination of high levels of both the dangerous antibodies and super-activated neutrophils, which are destructive, exploding white blood cells. In April, the team was the first to report that patients hospitalized for severe COVID-19 had higher levels of neutrophil extracellular traps in their blood.
To learn more, they studied the explosive neutrophils and the COVID-19 antibodies together in mouse models 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 says. “We’ve discovered a new mechanism by which patients with COVID-19 may develop blood clots.”
Read more at Michigan Health Lab
