It is known that being infected with Covid-19 can affect your sense of smell, but in some cases, the sense of smell does not return to its normal function properly.
A new study suggests that infection with SARS-CoV-2 causes the immune system to constantly attack neurons in the nose, and then there is a decrease in the number of these neurons, as a result of which people cannot smell as well as they usually do.
In addition to answering a question that has baffled experts, the study could also help us understand what “long Covid” is and why some people can’t fully recover from Covid-19.
“Fortunately, many people with an altered sense of smell during the acute phase of a viral infection recover within the next week or two, but some cannot. We need to understand better,” says neuroscientist Bradley Goldstein of Duke University in North America. Carolina: Why does this subgroup of people continue to lose their sense of smell consistently for months and even years after being infected with SARS-CoV-2?
The team studied samples of nasal tissue – the olfactory epithelium – taken from 24 people, including nine who suffered long-term loss of smell after contracting Covid-19. This tissue carries the nerve cells responsible for detecting odors.
After a detailed analysis, the researchers noted the widespread use of T cells, a type of white blood cell that helps the body fight infection. These T cells triggered an inflammatory response inside the nose.
However, like many other biological responses, T cells do more harm than good: they damage olfactory epithelial tissue. At the same time, the inflammatory process was still evident even in tissues where SARS-CoV-2 was not detected.
“The results are amazing,” says Goldstein. “It’s like some kind of autoimmune process in the nose.”
And while the number of olfactory sensory neurons was lower in study participants who lost their sense of smell, the researchers reported that some neurons appear to be able to recover even after being bombarded with T cells – an encouraging sign.
The researchers suggest that similar inflammatory biological mechanisms may underlie other long-term coronavirus symptoms, including excessive fatigue, shortness of breath and “brain fog” that makes it difficult to concentrate.
The team then wants to take a closer look at the specific areas of tissue that have been damaged and the types of cells involved. This, in turn, will pave the way for the development of possible treatments for those suffering from long-term anosmia.
“We hope that changing the abnormal immune response or repairing the nose in these patients will help to at least partially restore the sense of smell,” says Goldstein.
The study was published in the journal Science Translational Medicine.
Source: Science Alert