Tunneling nanotubes provide a novel route for SARS-CoV-2 spreading between permissive cells and to non-permissive neuronal cells.
SARS-CoV-2 entry into host cells is mediated by the binding of its spike glycoprotein to the angiotensin-converting enzyme 2 (ACE2) receptor, highly expressed in several organs, but very low in the brain. The mechanism through which SARS-CoV-2 infects neurons is not understood. Tunneling nanotubes (TNTs), actin-based intercellular conduits that connect distant cells, allow the transfer of cargos, including viruses. Here, we explored the neuroinvasive potential of SARS-CoV-2 and whether TNTs are involved in its spreading between cells in vitro. We report that neuronal cells, not permissive to SARS-CoV-2 through an exocytosis/endocytosis dependent pathway, can be infected when co-cultured with permissive infected epithelial cells. SARS-CoV-2 induces TNTs formation between permissive cells and exploits this route to spread to uninfected permissive cells in co-culture. Correlative Cryo-electron tomography reveals that SARS-CoV-2 is associated with the plasma membrane of TNTs formed between permissive cells and virus-like vesicular structures are inside TNTs established both between permissive cells and between permissive and non-permissive cells. Our data highlight a potential novel mechanism of SARS-CoV-2 spreading which could serve as route to invade non-permissive cells and potentiate infection in permissive cells.