2 cell types are entry points for virus
The respiratory tract is filled with numerous cells, among which are goblet cells and ciliated cells.Updated: Apr 26, 2020 04:20 IST
Scientists have identified two types of cells in the nose that are likely to be point of infection for the Sars-CoV-2 virus, which causes Covid-19, in the body.
The respiratory tract is filled with numerous cells, among which are goblet cells and ciliated cells. While goblet cells secrete mucous to trap pathogens and foreign matter, ciliated cells have hair like structures that transport such trapped matter out of the body.
According to a study published in Nature Medicine, these cells also have high levels of the proteins ACE2, which acts as a receptor for the virus’s spike protein to attach itself to, and TMPRSS2 which helps the virus to enter the cell, and thereafter replicate and causes infection. The conclusions of the study stress the importance of wearing masks to both prevent infection and also reduce transmission of the disease, experts said.
In usual circumstances, ACE2 is recognized as a potential therapeutic strategy in hypertension and cardiovascular disease, diabetes, lung injury, and fibrotic disorders. TMPRSS2 is understood to be involved in a variety of biological processes, whose malfunction often leads to human diseases and disorders.
The researchers analysed multiple Human Cell Atlas (HCA), which provides reference maps of all the cells in the body. These included cells from the lung, nasal cavity, eye, gut, heart, kidney and liver. They looked for cells that expressed the of two key entry proteins and found them in the nose, eyes and intestine.
This suggests infection via the eye and tear ducts, and a potential for faecal-oral transmission, the study said.
“Earlier studies had also pointed out that the ACE2 receptor is expressed more in the epithelial cells of the nose but this study shows that the protease which helps with the binding of the spike protein of the virus are co-expressed in the nose and hence these cells are more likely to get infected. This study shows that the upper respiratory tract gets affected first by the infection. This is why its transmissibility increases manifold, making SARS-CoV-2 more infectious than SARS,” said Dr. Shobha Broor, former head of the AIIMS department of virology who has read the study.
Dr Martijn Nawijn, from the University Medical Center Groningen in the Netherlands and co-author of the study, said in a statement published in ScienceDaily, a website for latest research: “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.”