Tunneling nanotube-mediated intercellular spread of SARS-CoV-2 variants in epithelial cells reveals a host-targeted antiviral vulnerability.

We demonstrate that SARS-CoV-2 exploits tunneling nanotubes (TNTs) as actin-based conduits for intercellular transmission in epithelial cells. TNT formation was markedly enhanced in the Delta variant compared with the ancestral Wuhan-Hu-1 and Omicron strains, consistent with their relative transmissibility. The Delta variant also promoted extensive filopodia and branched TNT networks, facilitating efficient cell-to-cell dissemination. Confocal and ultrastructural analyses revealed active transfer of mitochondria and lysosomes through these nanotubes, indicating that SARS-CoV-2 co-opts host organelle trafficking to support replication and persistence. Pharmacological inhibition of Cdc42-dependent actin remodeling or CaMKII signaling disrupted TNT formation. Collectively, these findings identify TNTs as a crucial pathway for variant-dependent SARS-CoV-2 dissemination in epithelial cells and reveal host cytoskeletal dynamics as a tractable antiviral target for limiting viral spread.