Coronavirus – how the nose is a route of infection

Scientists have found that two types of cells found in the nose are a mechanism that the SARS-CoV-2 virus uses as a means to enter the body and trigger an infection. Significantly, nasal swabs have yielded higher viral loads than throat swabs.

The research, from the Netherlands, shows that once inside the human body, human enzymes termed proteases (specifically, in relation to the novel coronavirus, this is a protease called TMPRSS2 or ‘transmembrane protease, serine 2’) are capable to cleaving the coronavirus in half.

With this process, one viral fragment functions to bind to a receptor termed ACE2, and this is a path to get into cells.  The coronavirus deploys its spike glycoprotein (the ‘corona’ shape), to bind its receptor, and mediate membrane fusion and virus entry.

Proteases

Proteases are enzymes that catalyze the breakdown of proteins into smaller polypeptides or single amino acids. This happens by cleaving peptide bonds found within proteins through triggering  a reaction called hydrolysis.

This is an area of focus because ACE2 and TMPRSS2 have been detected in both nasal and bronchial epithelium by immunohistochemistry.

Key risks around the nose

A science team from University Medical Center Groningen, looking at different points of viral entry and the relative risks around this, indicate that with the nose, cells called goblet and ciliated cells contain particularly high levels of the protease TMPRSS2 as well as ACE2 proteins.

https://www.youtube.com/watch?v=tOZGeHMplrc&feature=emb_title

This important finding could provide the answer as to why the virus can be transmitted so readily.

Data source

To arrive at the conclusion about the vulnerability around the nose, the research team drew upon datasets located within the Human Cell Atlas (HCA) to identify the cells that express ACE2 and TMPRSS2.

This inquiry also signalled that cells in the lining of the intestine and the cornea of the eye also provide easy pathways for the virus to cause an infection.

Research significance

Talking to the science website Laboratory Roots, the lead researcher Dr. Martijn Nawijn states: “This is the first time these particular cells in the nose have been associated with COVID-19…our findings are consistent with the rapid infection rates of the virus seen so far.”

He adds: “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.”

Such knowledge can provides the basis for developing potential treatments to reduce the spread of the virus.

Research paper

The research has been published in the journal Nature Medicine. The research paper is titled “SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes.”

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)