Researchers from ACS Pharmacology & Translational Science have reported that loss of sense of smell or taste, which is considered one of the early symptoms of SARS-CoV-2, might not be one of the symptoms of the virus.
Research has shown that SARS-CoV-2 enters human cells through angiotensin-converting enzyme 2 (ACE2), a receptor on the surface of some cells, including those of the human tongue.
For this, they studied mice as a model organism. Although the mouse version of ACE2 isn’t susceptible to SARS-CoV-2, studying where it was expressed in mice could help clarify what happens when people become infected and lose the sense of taste.
By analysing data from the oral cells of adult mice, the researchers found that ACE2 was enriched in cells that give the tongue its rough surface, but couldn’t be found in most taste bud cells.
This means the virus probably does not cause taste loss through direct infection of these cells, the researchers said. Instead, the taste buds might be damaged by inflammation caused by the infection.
The team also showed that other viruses that affect taste, including the flu virus, might affect different tongue cell types.
Previous studies in humans that were not focused on oral cells suggest ACE2 could be expressed at an early foetal stage and then again at a later stage.
Hence, the team noted that foetuses could have distinct susceptibilities to SARS-CoV-2 infection at different stages.
It maintained that more study is needed to determine the timing and location of human ACE2 expression.