Entry points for COVID-19 Virus mapped: May help contain the spread of the disease, say experts

Researchers have 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. Read on to know more.

The COVID-19 virus has spread to almost the entire world in a very short span of time. The main mode of transmission of this virus is via droplets that an infected person releases when he sneezes or coughs. You may inhale this directly or touch a contaminated surface and then touch your face. Then the virus regains entry through your mouth nose and eyes. Now researchers have discovered that goblet and ciliated cells in the nose have high levels of the entry proteins that the COVID-19 coronavirus uses to get into our cells. They are hopeful that the identification of these cells may help explain the high transmission rate of the virus.

Experts identify viral-entry proteins to explain high transmission rate

The journal Nature Medicine published the findings of this study, which also shows that cells in the eye and some other organs also contain the viral-entry proteins. The study 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. Though experts have known that this new strain of coronavirus that causes COVID-19 disease 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.

About the study

To discover which cells could be involved in COVID-19 transmission, researchers looked at many Human Cell Atlas (HCA) consortium datasets of single-cell RNA sequencing, from more than 20 different tissues of non-infected people. They looked at cells from the lung, nasal cavity, eye, gut, heart, kidney and liver. They were looking for individual cells which expressed both of two key entry proteins that are used by the COVID-19 virus to infect our cells. They saw 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. They found 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. The two key entry proteins ACE2 and TMPRSS2 were also present in cells in the cornea of the eye and in the lining of the intestine. This suggests another possible route of infection via the eye and tear ducts, say researchers. They also discovered receptors in the intestines and vital organs such as the heart.

Route to heart mapped too

According to researchers, this study provides crucial insights not only into how the virus gains access to the body, but also how the virus could target organs outside of the airways and lead to systemic disease. They say that heart tissue damage and consequent heart failure are observed in up to 20 per cent of COVID-19 patients. Therefore, it was very important to investigate how the virus could enter heart cells, by mapping the location of the COVID-19 receptor in the heart, and the proteases that enable the virus to gain entry to cells.