New coronavirus targets cells in the nose, lungs, and gut

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A new study suggests that SARS-CoV-2, the virus that causes Covid-19, is most likely to target specific cells present in the nasal passages, lungs, and small intestine.
Researchers may have identified the cells that SARS-CoV-2 most likely targets in the body.
A new study by researchers from the Massachusetts Institute of Technology (MIT) and Harvard University, both in Cambridge, MA — alongside colleagues from other institutions — may have pinpointed the cells that SARS-CoV-2 primarily targets in the human body.
The study — the findings of which will soon appear in the journal Cell — built on existing investigations showing that SARS-CoV-2 uses two proteins that act as receptors to invade host cells and replicate. These proteins are angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2).
The researchers wanted to find out which cells in the human body express these proteins, and they focused on sets of cells in the nasal passages, lungs, and small intestine. This was because people with COVID-19 most often experience respiratory and digestive symptoms.
The researchers used existing information to inform their study and help them pick the tissues that they then analyzed and experimented with. Looking at cells from the nasal passages, lungs, and small intestine, the investigators were able to pinpoint the types of cell that SARS-CoV-2 most likely “latches onto.”
The researchers found that in the nasal passages, “goblet secretory cells” — which produce mucus — express RNA that allows them to produce both ACE2 and TMPRSS2. In lung tissue, they settled on type II pneumocytes, which are the cells that line the alveoli (air sacs) and allow them to stay open. Finally, in the small intestine, the team closed in on absorptive enterocytes, which are the cells that ensure the absorption of key nutrients.
During the course of their study, the researchers also found that the gene that encodes ACE2 may be associated with the activation of genes that also respond to interferon. This is a protein that helps trigger the immune response. Following further experiments, the team found that interferon was able to activate the ACE2 gene in airway epithelial cells.
This unexpected finding led the researchers to believe that coronaviruses may have “learned” to turn on proteins that are meant to help cells maintain their integrity against those very cells. “This isn’t the only example of that,” notes Ordovas-Montanes.