COVID-19: Key nose cells identified as likely entry points of virus

London: Scientists have identified two specific cell types in the nose as likely initial infection points for the novel coronavirus that causes COVID-19. The researchers, including those from the Wellcome Sanger Institute in the UK and University Medical Centre Groningen in the Netherlands, discovered that goblet and ciliated cells in the nose have high levels of the entry proteins that the COVID-19 virus uses to get into our cells.

The identification of these cells could help explain the high transmission rate of COVID-19, they said. The finding, published in the journal Nature Medicine, shows that cells in the eye and some other organs also contain the viral-entry proteins.

The study also predicts how a key entry protein is regulated with other immune system genes and reveals potential targets for the development of treatments to reduce transmission. While it is known that the virus that causes COVID-19 disease, known as SARS-CoV-2, uses a similar mechanism to infect our cells as a related coronavirus that caused the 2003 SARS epidemic, the exact cell types involved in the nose had not previously been pinpointed, the researchers said.

To discover which cells could be involved in COVID-19 transmission, they analysed datasets of single cell RNA sequencing, from more than 20 different tissues of non-infected people. These included cells from the lung, nasal cavity, eye, gut, heart, kidney and liver.

The researchers looked for which individual cells expressed both of two key entry proteins that are used by the COVID-19 virus to infect our cells. “We found that the receptor protein – ACE2 – and the TMPRSS2 protease that can activate SARS-CoV-2 entry are expressed in cells in different organs, including the cells on the inner lining of the nose,” said Waradon Sungnak from Wellcome Sanger Institute.

“We then revealed that mucus-producing goblet cells and ciliated cells in the nose had the highest levels of both these COVID-19 virus proteins, of all cells in the airways. This makes these cells the most likely initial infection route for the virus,” Sungnak said. This is the first time these particular cells in the nose have been associated with COVID-19,” said Martijn Nawijn, from the University Medical Center Groningen.

“While there are many factors that contribute to virus transmissibility, our findings are consistent with the rapid infection rates of the virus seen so far. The location of these cells on the surface of the inside of the nose make them highly accessible to the virus, and also may assist with transmission to other people,” Nawijn said.