Micro-organism infects mini-organ: the effect of the coronavirus on our intestines

-June 12, 2020. Several months into the corona crisis you probably have some idea of what the symptoms of infection with the coronavirus (SARS-CoV-2) are. The most recognizable are common cold-like symptoms, fever, and coughing. But did you know that a lot of patients also experience intestinal issues such as diarrhea, cramps and feeling nauseous? 

That is kind of odd for a virus that is primarily known for being airway-related. A group of Dutch scientists of the Utrecht Hubrecht Institute, the Rotterdam Erasmus MC and Maastricht University dove into the matter. An extra advantage: by using modern methods no human test subjects were needed.

Receptor plays major role

To infect a cell viruses bind to a receptor on the membrane of a cell. This receptor is usually a protein on the membrane that has a role in normal cell functioning, but is now hijacked by the virus to infect the cell. Which receptor a virus uses depends on the type of virus. In case of the current coronavirus this receptor is called ACE-2, an enzyme on the membrane that plays a role in maintaining a stable blood-pressure and fluid balance. This receptor can be found in multiple sites of the body, such as the lungs, arteries, heart, kidneys and also the intestines. But the fact that this receptor is present on cells in these sites doesn’t necessarily mean that all of these sites are automatically infected by the virus. However, it does mean that it is theoretically possible. A good reason to investigate this for one of these sites: the intestines. But how do you study if the virus can multiply in intestinal cells without using human subjects? The group of Dutch scientists used an elegant solution.

Researchers infect mini-intestines

For their research the Dutch scientists decided to use intestinal organoids, cultured spheres of human intestinal cells that behave like mini-intestines. These intestinal organoids were infected with the coronavirus in a controlled environment, after which they were observed under an electron microscope. The result was that virus particles could be observed both within and outside of the intestinal cells, which points to replication of the virus in the cells. To elucidate how the cells respond to the virus, the researchers determined which genes were active in the cells during the infection. This provides a picture of what the cells are doing when the virus goes around infecting cells. That is good to know, because with this knowledge we might find new entries for pharmaceuticals.

Continued research?

Now that it has become clear that the virus can replicate within the mini-intestines the question rises if this is also what happens in patients. Is the virus wreaking havoc in their intestines? And if so, does this contribute to the spreading of the virus? These questions will definitely be looked into with increased interest now that this piece of research has seen the light. The group of Dutch scientists will continue their alliance with new research, this time comparing coronavirus infection in intestinal organoids with infection in lung organoids. Stay tuned.