Long-hauler COVID-19 survivors report lasting symptoms weeks to months after recovery. These lingering issues may be due to a prolonged immune response according to a study published in eLife. In the study, researchers noted that serious complications due to blood clotting were associated with the lingering immune response in the blood vessels after recovery.
"During the initial stages of infection, SARS-CoV-2, the virus that causes COVID-19, may attack the lining of the blood vessels which can trigger inflammation and an immune response. This can result in blood vessel damage in the short term," explains first author Florence Chioh, a researcher at Lee Kong Chian School of Medicine (LKCMedicine) in Singapore. She continued, "For our study, we wanted to investigate what happens in the blood vessels of COVID-19 survivors over the longer term."
Chioh, and colleagues, started by collecting blood samples from COVID-19 survivors within a month of their discharge from the hospital. They discovered COVID-19 survivors have twice as many damaged blood vessel cells, known as circulating endothelial cells, in their blood. Even more of these damaged blood vessel cells were found in survivors who had conditions such as hypertension or diabetes that can also damage the blood vessels.
The team also found that survivors had high amounts of T cells and inflammatory proteins called cytokines that are produced by immune cells, even though the virus was absent.
"We show that an overactive immune system is the likely cause of blood vessel damage seen in some COVID-19 survivors," Chioh says. "This may cause 'leakiness' in the blood vessels that increases the risk of blood clots."
Image credit: CDC