Stem cells may be able to produce a protein that protects them against RNA viruses like SARS-CoV-2 and Zika. In the long term, this could open up new therapeutic avenues.
Stem cells have two key properties: they are self-renewing and they can differentiate. The first means that when a stem cell divides, two daughter cells identical to the mother cell are produced. Thanks to the second property, a stem cell can initiate a differentiation program that gradually transforms it. As a result, it becomes another cell. Totipotent and pluripotent stem cells can give rise to all cell types present in the body. However, those that are called multipotent are limited to only a few lineages.
According to a new study published in the journal Science, stem cells have another special feature: by expressing the antiviral Dicer (aviD) which can cut viral RNA, the cells can prevent RNA viruses-such as SARS-CoV-2 and Zika virus-from reproducing in the body. This form of protection, called RNA interference, was already known to scientists, but only in plant and invertebrate cells.
A protective mechanism used by plants and invertebrates
“It is fascinating to understand how stem cells protect themselves against RNA viruses,” explains Caetano Reis e Sousa, one of the authors. The fact that this protection is also used by plants and invertebrates suggests that it has existed for a long time in mammalian history. For some unknown reason, although all mammalian cells have the innate ability to trigger this process, it seems that only stem cells do so. More research is needed to understand this mechanism. However, scientists already believe that this discovery could allow the development of new antiviral treatments in the long term. “By learning more about this process and discovering the secrets of our immune system, we hope to open up new possibilities for drug development,” he says.
Cells are three times less likely to be infected by SARS-CoV-2 thanks to the aviD protein
The researchers first exposed human cells to SARS-CoV-2. Those with the antiviral protein Dicer were three times less likely to be infected with the virus than those without. They then conducted a second experiment with brain organoids – a three-dimensional multicellular structure – which they exposed to the Zika virus. They found that those with the aviD protein were less affected by the virus than those without it. “Why stem cells use this defense mechanism remains a mystery,” says Enzo Poirier, one of the authors of the study. There are still many unknowns about how these cells are protected against viruses. As a result, the scientists will continue their research to understand the mechanisms underlying the production, development, and role of the antiviral protein Dicer in mammalian stem cells.