New studies suggest that the presence of ongoing inflammation that damages and destroys cells in the nose could be the explanation for why other people fail to regain their sense of smell after COVID-19.
The study, a collaboration between researchers at Duke, Harvard and the University of California, San Diego, adds insight into a challenge that has affected millions of others who have not fully regained their sense of smell after COVID-19. The findings were published online Dec. 21, 2022, in the journal Science Translational Medicine.
A symptom long linked to COVID-19 infection is loss of smell, says lead researcher Bradley Goldstein, MD, PhD, associate professor of head and neck surgery and communication sciences and neurobiology at Duke University School of Medicine in Durham, North Carolina.
“Most other people who have an impaired sense of smell in the acute phase of viral infection will regain their sense of smell within a week or two, but some don’t,” says Dr. Goldstein.
According to an article published in July 2022 in The BMJ, approximately 15 million COVID-19 survivors worldwide suffer a loss of smell that continues even after recovering from the virus.
“One of the main motivations of our study is that we don’t have very fast or effective remedies for that kind of odor loss; there’s a genuine unmet need to expand those kinds of remedies,” Goldstein says.
Using a biopsy-based technique (taking a small pattern of tissue) of the nose’s olfactory domain, the researchers had to read a lot about cells from other people who have a long loss of smell from COVID compared to other people who have a general sense of smell, Goldstein says.
The researchers analyzed the olfactory epithelium (the layer of tissue in the nose where smell nerve cells are located) from 24 biopsies, adding up those of nine patients with long-term odor loss due to COVID-19.
Scientists have discovered enough evidence of mobile T (a type of mobile white blood cell that is a vital component of the immune system) as well as inflammation. “We didn’t expect to see this kind of inflammation; it almost feels like some kind of autoimmune procedure in the nose,” Goldstein says.
People who had long-term odor loss due to COVID-19 had no evidence of exclusive inflammation.
In addition, the researchers discovered fewer olfactory sensory neurons in other people who had lost their sense of smell, suggesting that the immune reaction had destroyed those important sensory cells in the nose.
“These findings provide key insights into what might cause long-term odor loss in other people with COVID for a long time,” says Akiko Iaki, PhD, director of the Center for Infection and Immunity at Yale School of Medicine in New Haven. Although Dr. Iaki is not involved in this research, she is co-principal investigator of several studies on prolonged COVID.
Learning which sites in the nose are damaged and what types of cells are affected is a very important first step in starting to design remedies to correct smell, Goldstein says. Long-term immune response, a sign the researchers found encouraging.
According to the study authors, remedies that decrease this immune reaction or improve repair processes in patients’ noses can help at least partially correct the sense of smell. One treatment option may use creams or sprays to block immune cells that produce inflammation in the nasal lining, they wrote.
Researchers want to conduct more studies on more people, Goldstein says. “There are a lot of unanswered questions about what those cells do. We want to find out if there are specific drug targets that we can use to try to fix the problem. “,” he says.
Prolonged COVID can affect many other organs or systems in the frame in other ways, and odor loss is just one of many symptoms, Goldstein says. available and relatively easy to biopsy,” he says.
This location could be useful for researchers reading other long-term symptoms of COVID, such as fatigue, shortness of breath, and mental confusion, symptoms that are studied in the same way as loss of smell.
“Our observations of T cells and inflammation in the nose may potentially be applicable to understanding what happens in other parts of the framework that could be triggered through biological mechanisms,” Goldstein says.
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