Sprinkled like confetti throughout this image are dozens of green, yellow, and red-ringed axons—nerve cell fibers that transmit electrical signals throughout the nervous system. The axons are bundled in a human cranial nerve, shown here in a cross-section view (see illustration below for context). Nerves like this exit the brainstem and project to areas of the tongue, mouth, and throat, where taste signals are detected and relayed back to the brain.
Credit: Lynn Vitale-Cross, Ildiko Szalayova, and Aiden Scoggins
A research team led by NIDCR senior investigator Eva Mezey, MD, Ph.D., found that the outer surfaces of the axons in these nerves are studded with protein “entry factors” used by the SARS-CoV-2 virus to invade cells. The presence of entry factors like TMPRSS2 proteins (yellow) and ACE2 receptors (red) points to the possibility that the virus could infect taste-sensing nerves and offers a potential explanation for the taste loss that affects about 39 percent of those who have COVID-19….