%0 Journal Article %A Barbara Storti %A Paola Quaranta %A Cristina Di Primio %A Nicola Clementi %A Pietro Giorgio Spezia %A Vittoria Carnicelli %A Giulia Lottini %A Emanuele Paolini %A Giulia Freer %A Michele Lai %A Mario Costa %A Fabio Beltram %A Alberto Diaspro %A Mauro Pistello %A Riccardo Zucchi %A Paolo Bianchini %A Giovanni Signore %A Ranieri Bizzarri %T A spatial multi-scale fluorescence microscopy toolbox discloses entry checkpoints of SARS-CoV-2 variants in VeroE6 cells %D 2021 %R 10.1101/2021.03.31.437907 %J bioRxiv %P 2021.03.31.437907 %X We developed a multi-scale microscopy imaging toolbox to address some major issues related to SARS-CoV-2 interactions with host cells. Our approach harnesses both conventional and super-resolution fluorescence microscopy (Airyscan, STORM, and STED) and easily matches the spatial scale of single virus-cell checkpoints. We deployed this toolbox to characterize subtle issues related to the entry phase of SARS-CoV-2 variants in VeroE6 cells. Our results suggest that the variant of concern B.1.1.7, currently on the rise in several countries by a clear transmission advantage, in these cells outcompetes its ancestor B.1 in terms of a much faster kinetics of entry. Given the molecular scenario (entry by the only late pathway and similar fraction of pre-cleaved S protein for B.1.1.7 and B.1), the faster entry of B.1.1.7 could be directly related to the N501Y mutation in the S protein, which is known to strengthen the binding of Spike RBD with ACE2. Remarkably, we also observed directly the significant role of clathrin as mediator of late entry endocytosis, as already suggested for other CoVs and from pseudovirus-based infection models. Overall, we believe that our fluroescence microscopy-based approach represents a valuable tool for evaluating the entry kinetic of SARS-CoV-2 and its variants.Competing Interest StatementThe authors have declared no competing interest. %U https://www.biorxiv.org/content/biorxiv/early/2021/03/31/2021.03.31.437907.full.pdf