As a team of scientists led by Duke Health reports, some reasons people who do not recover their sense of smell after Covid-19 is due to an ongoing immune attack on olfactory neurons and a decrease in their number.
The findings, published online December 21 in Science Translational Medicine, provide important insight into a burning problem that has plagued millions of people who have not fully recovered their sense of smell. feeling after Covid-19.
While focusing on the smell of loss, this finding also sheds light on the possibility underlying cause of other persistent Covid-19 symptoms – including generalized fatigue, shortness of breath and brain fog – can be triggered by similar biological mechanisms.
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“One of the first symptoms commonly associated with a Covid-19 infection is a loss of smell,” said senior author Bradley Goldstein, MD, Ph.D., associate professor in the Department of Head and Neck Surgery and Science Duke communication said. of Neuroscience.
“Fortunately, many people with an altered sense of smell during an acute viral infection recover their sense of smell within the next one to two weeks, but some do not,” Goldstein said. “We need to better understand why this group of people will continue to experience loss of smell months to years after infection with SARS-CoV2.”
For the study, Goldstein and colleagues at Duke, Harvard and the University of California-San Diego analyzed olfactory epithelium samples collected from 24 biopsies, including nine patients with long-term loss of smell. after Covid-19.
This biopsy-based approach — using sophisticated single-cell analyzes in collaboration with Sandeep Datta, MD, Ph.D., at Harvard University — demonstrates widespread penetration of T cells are involved in the inflammatory response in the olfactory epithelium and tissues. in the nose where the olfactory neurons are located. This unique inflammatory process persisted despite the absence of detectable levels of SARS-CoV-2.
In addition, the number of olfactory sensory neurons was reduced, possibly due to damage to delicate tissues due to ongoing inflammation.
“These findings are astounding,” Goldstein said. “It’s almost like a sort of autoimmune-like process in the nose.”
Goldstein says understanding which sites are damaged and what cell types are involved is an important step in starting to design treatments. He said researchers are encouraged that neurons appear to maintain some repair capacity even after long-term immune attack.
“We hope that modulating the abnormal immune response or repair process in the noses of these patients could help restore at least part of the sense of smell,” Goldstein said, noting that this work is currently not working. is being carried out in his laboratory.
He said the findings from this study could also inform additional research into other lingering Covid-19 symptoms that may be undergoing a similar inflammatory process.
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