Breakthrough identifies which cells Covid-19 is likely attacking

A global research effort has identified cells that may be targeted by Covid-19 as they are more prone to infection.

As efforts continue to better understand Covid-19 and how we can treat it, a team including researchers from MIT may have made a breakthrough. In a study published to Cell, the team said it had identified specific types of cells that the coronavirus appears to be targeting.

Using existing data on the RNA found in different types of cells, the researchers were able to search for cells that express the two proteins that help the coronavirus enter human cells. This led to the discovery of a subset of cells in the lung, nasal passages and the intestine that express RNA for both of these proteins considerably more than other cells.

‘Paints a more precise picture’

The research was developed from an early discovery that the viral ‘spike’ protein binds to a receptor on human cells known as angiotensin-converting enzyme 2 (ACE2). Another human protein, an enzyme called TMPRSS2, helps to activate the coronavirus spike protein, to allow for cell entry.

Using data collated from the Human Cell Atlas project, which catalogues gene activity for every cell type in the body, the team showed that the proteins that the coronavirus uses to infect cells were found in the nasal passage cells responsible for creating mucus.

In the lungs, the RNA proteins were found in the cells that line the air sacs of the lungs that keep them open. While in the intestine, the cells responsible for the absorption of nutrients expressed the RNA proteins.

“This may not be the full story, but it definitely paints a much more precise picture than where the field stood before,” said Jose Ordovas-Montanes, a senior author of the study.

“Now we can say with some level of confidence that these receptors are expressed on these specific cells in these tissues.”

Surprising phenomenon

A surprising phenomenon found during the research showed that the ACE2 gene appeared to be correlated with activation of genes that are known to be turned on by interferon, a protein that the body produces in response to viral infection.

Previous studies showed ACE2 plays a role in helping lung cells to tolerate damage, but this is the first time it has been connected with the interferon response. This suggests the coronavirus may have evolved to hijack the host cells’ natural defences.

Alex K Shalek, another senior author of the study, said of this finding: “It’s hard to make any broad conclusions about the role of interferon against this virus. The only way we’ll begin to understand that is through carefully controlled clinical trials.

“What we are trying to do is put information out there, because there are so many rapid clinical responses that people are making. We’re trying to make them aware of things that might be relevant.”