Wheezing after receiving on the treadmill. Swallow air while doing housework. Shortness of breath is one of many scary and uncomfortable symptoms that can persist in Covid patients for months after their initial infection. But while these symptoms were a mystery at the start of the pandemic, scientists are slowly unraveling their causes—getting us closer to finding a treatment.
In an article recently published in the journal European Respiratory Journal, researchers at the University of Manchester in the United Kingdom have identified a possible culprit—immune cells called monocytes. These soft, bluish-gray cells float through the bloodstream, looking for signs of trouble. When they encounter an invading pathogen, such as a bacteria or virus, they create other important immune cells and alert the immune system to activate additional defenses. Monocytes are particularly important during lung injury. At the first sign of trouble, they travel to the lungs, producing specialized macrophages – immune cells that eat pathogens – that become the first line of immune defense against invading germs.
It appears that Covid infections can actually mess up the way these immune cells work — that is, they may react abnormally to subsequent events”. In Covid patients who experienced persistent shortness of breath after infection, the researchers found abnormal mononuclear cells. Compared with healthy individuals, these patients have monocytes with different levels of proteins attached to them, which are important for directing cells toward the lungs. The scientists say these results link abnormal mononuclear cells to persistent Covid and lung damage — paving the way for potential therapies to correct abnormalities or alleviate symptoms.
Pearmain and team have good reason to be suspicious of these cells. Other researchers have found that SARS-CoV-2 affects monocytes. According to Judy Lieberman, a biologist at Harvard Medical School, in severe cases of Covid, infected monocytes often die by releasing a lot of alarm molecules into the body, trigger a large amount of additional inflammation. “It’s like a transition loop,” she said. “Once this happens, it is extremely difficult to control.” These results point to a potential role for dysfunctional monocytes in long-term Covid, as inflammation is known to contribute to some of the lingering symptoms.
Pearmain and the team decided to investigate. To find out exactly what these cells were doing during Covid and Covid’s extended period, the scientists turned to blood samples. Starting in the summer of 2020, in several UK hospitals, Pearmain and team drew blood from 71 patients during their hospital stay with Covid. Over the next few months, they also collected blood from 142 separate patients previously hospitalized with Covid, collecting samples during follow-up visits.
The patients who were monitored had had Covid about six months earlier, and by this point after the infection, Pearmain said, you would expect any immune dysfunction caused by the virus to be fine, Pearmain said. determined. However, this is not what the team is seeing. “It’s clear that a lot of people are still really struggling with the shortness of breath, fatigue and so many other lingering symptoms of Covid,” he said. Specifically, 48% of patients monitored reported shortness of breath, 44% fatigue. The team found a long Covid pool to study — so it’s time to take a closer look at their immune cells.