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Covid-19 and the brain: coronavirus tunnels – Science et Avenir

Normally, the coronavirus uses the Spike protein on its surface to attach to the ACE2 receptor on the surface of certain human cells. Once attached, the virus fuses its shell with the cell membrane and thus introduces its material into the cell. But some cells have very few, if any, ACE2 receptors, so they need to be protected from the coronavirus. This is the case, for example, with neurons. But the significant neurological impact that Covid-19 can have on patients shows that neurons are not as well protected.

Research has shown that much of this neurological damage is indirect: it is not caused directly by infection of neurons, but by infection of the epithelial cells that line the blood vessels that supply the brain. But the coronavirus has been shown to be good at infecting neurons despite the lack of ACE2 receptors. A new study by the Pasteur Institute in Paris, published July 20, 2022 in the journal Science Advances, reveals the way the virus enters neurons: nanotunnels.

coronavirus tunnels

The researchers cultured human neuronal cells along with epithelial cells previously infected with the coronavirus. They observed that infection increased the amount of these nanotubes produced by infected epithelial cells; that these nanotunnels connect these cells to each other as well as to neurons; and that the virus can travel within these tunnels (but also outside), moving from one cell to another. Thus, the coronavirus will use this strategy to move from infected epithelial cells to neurons, bypassing the absence of the ACE2 receptor in these cells.

Hidden path, but already used by other viruses

These tunnels are formed by actin nanotubes and usually allow cells to exchange material with each other. Some other viruses have already learned to use them to move from one cell to another, such as the influenza virus or HIV. And it seems that the coronavirus has also managed to find this short cut. “Nanotubes are like tunnels with roads on their surface, they allow the virus to infect cells that normally would not allow the virus to enter, and also facilitate the spread of the virus between other cells,” Chiara Zurzolo, author of the study, summed up in the press. release.

Road to long Covid?

But in addition to accelerating the spread of the virus, this alternative route of infection could also allow the virus to hide better from our defenses: “These tunnels could facilitate the immune exit of the coronavirus,” confirms Chiara Zurzolo, adding that this mechanism could allow the virus to remain incognito in the body for longer time. Thus, these nanotubes may be one of the keys to the persistence of the virus seen in some long-term Covid-19s, and in particular to the long-term neurological and cognitive symptoms often seen in these patients.

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