The loss of smell or anosmia is one of the symptoms of COVID-19 that attracted the most attention at the beginning of the pandemic, since it was even the case that many people who had been infected with the coronavirus, but were unaware of it because they were Asymptomatic, they realized they might have contracted the disease because they suddenly lost their ability to smell.
However, the sense of smell does not always recover after overcoming the infection, and this alteration is also suffered by many patients with persistent COVID. A new study has now found that the reason some people fail to regain their sense of smell after COVID-19 is related to an ongoing immune attack on olfactory nerve cells and a reduction in the number of those cells, they show. the results of the work published in Science Translational Medicine.
The research has been carried out by a team of scientists led by Duke Health, and although it has focused on finding out why millions of people have lost their sense of smell or have suffered olfactory alterations due to COVID, and have not fully recovered this sense, it has also clarified the possible causes that would explain other prolonged symptoms of COVID, such as general fatigue, breathing difficulties or mental confusion, which could be caused by similar biological mechanisms.
“We are hopeful that modulating abnormal immune response or repair processes within the nose could help restore, at least partially, the sense of smell.”
“One of the first symptoms that has generally been associated with COVID-19 infection is loss of smell,” says Dr. Bradley Goldstein, an associate professor in Duke’s Department of Head and Neck Surgery and Communication Sciences. and the Department of Neurobiology and main author of the work.
“Fortunately, many people who have an impaired sense of smell during the acute phase of the viral infection will regain their sense of smell in the next one to two weeks, but some will not,” Goldstein said. “We need to better understand why this subset of people will have a persistent loss of smell for months to years after being infected with SARS-CoV2.”
An inflammatory process that affects olfactory cells
The researchers analyzed olfactory epithelial samples from 24 biopsies, including nine from patients suffering from long-term loss of smell after COVID-19. The analysis showed widespread infiltration of T cells involved in an inflammatory response in the olfactory epithelium, the tissue in the nose where nerve cells for smell are found. This unique inflammation process was maintained despite no detectable levels of SARS-CoV-2 being seen. In addition, the number of olfactory sensory neurons was reduced, possibly because of tissue damage sustained by ongoing inflammation.
“The findings are surprising,” Goldstein said. “It’s almost like some kind of autoimmune process in the nose.” The researcher has highlighted that knowing which are the damaged areas and the type of cells involved is essential to start developing treatments, and that it is encouraging to observe that the neurons seemed to maintain a certain capacity for repair, even after the long-term immune attack.
“We are hopeful that modulating the abnormal immune response or repair processes within the nose of these patients could help restore, at least partially, the sense of smell,” Goldstein said, adding that they are currently working on on it in his lab, and that the study findings may inform further research into other persistent COVID symptoms that might be experiencing similar inflammatory processes.
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