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SARS-CoV-2 Infects Brain Via Tunnelling Nanotubes
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) appears to gain access to the brain and cause neurological manifestations by hijacking tunneling nanotubes, according to study findings published online ahead of print in Science Advances.
“Our data highlight a previously unknown mechanism of SARS-CoV-2 spreading, likely used as a route to invade nonpermissive cells and potentiate infection in permissive cells,” wrote researchers from Institut Pasteur in Paris, France.
The angiotensin-converting enzyme 2 (ACE2 receptor) serves as a gateway for SARS-CoV-2 to enter cells in the lungs and olfactory epithelium, but it is not expressed by neurons, leading scientists to wonder how the virus is able to enter neuronal cells and infect the brain.
Using state-of-the-art electron microscopy approaches, researchers found that nanotubes, tiny bridges that link infected cells with neurons, are formed to penetrate neurons despite the fact that they lack the ACE2 receptor. The transient dynamic structures are a result of membrane fusion in distant cells and enable the exchange of cellular material without the need for membrane receptors. Researchers at Institut Pasteur have previously shown that nanotubes play a role in degenerative diseases such as Alzheimer disease and Parkinson disease by facilitating the transport of proteins responsible for those diseases.
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The research team identified multiple SARS-CoV-2 viral particles located both inside as well as on the surface of nanotubes.
“Nanotubes can be seen as tunnels with a road on top,” said researcher Chiara Zurzolo, MD, PhD, head of the Institut Pasteur’s Membrane Traffic and Pathogenesis Unit, “which enable the infection of nonpermissive cells like neurons but also facilitate the spread of infection between permissive cells.”
Because nanotubes between neurons are invisible to the immune system, the environment “may represent a mechanism for immune evasion and viral persistence that could be favorable to the virus,” Dr Zurzolo said.
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