Scientists at Johns Hopkins Medicine, experimenting with a small number of human cell samples, report that the “hook” of cells used by SARS-CoV-2, the virus that causes COVID-19, to latch onto and infect cells is up to 700 times more prevalent in the olfactory supporting cells lining the inside of the upper part of the nose than in the lining cells of the rest of the nose and windpipe that leads to the lungs. These supporting cells are necessary for the function and development of odor-sensing cells.
The findings, from a preliminary study of cells lining both the nose and trachea, could advance the search for the best target for topical or local anti-viral drugs to treat COVID-19, and offers further clues into why people with the virus sometimes lose their sense of smell.
“Loss of the sense of smell is associated with COVID-19, generally in the absence of other nasal symptoms, and our research may advance the search for a definitive reason for how and why that happens, and where we might best direct some treatments,” says Andrew Lane, M.D., professor of otolaryngology-head and neck surgery, and director of the Division of Rhinology and Skull Base Surgery at the Johns Hopkins University School of Medicine.
Scientists have known that SARS-CoV-2 latches on to a biological hook on the surface of many types of human cells, called an angiotensin-converting enzyme 2 receptor (ACE2). The receptor reels in essential molecules.
They found high levels of ACE2 among certain types of nasal cells where odor-sensing neurons are found. These cells had a 200-fold to 700-fold increase in ACE 2 proteins compared with other samples from the nose and trachea.
Because the cells with high levels of ACE2 are associated with odor sensing, the researchers suggest that infection of these cells may be the reason some people with COVID-19 experience loss of smell.
The cells lining the nose may prove to be a key entry point for SARS-CoV-2, and Lane says there may be ways to target those particular cells with topical anti-viral drugs or other therapies directly to that area.