Correlative multi-scale cryo-imaging unveils SARS-CoV-2 assembly and egress

Mendonça, Luiza; Howe, Andrew; Gilchrist, James B.; Sheng, Yuewen; Sun, Dapeng; Knight, Michael L.; Zanetti-Domingues, Laura C.; Bateman, Benji; Krebs, Anna-Sophia; Chen, Long; Radecke, Julika; Li, Vivian D.; Ni, Tao; Kounatidis, Ilias; Koronfel, Mohamed A.; Szynkiewicz, Marta; Harkiolaki, Maria; Martin-Fernandez, Marisa L.; James, William; Zhang, Peijun

Since the outbreak of the SARS-CoV-2 pandemic, there have been intense structural studies on purified viral components and inactivated viruses. However, structural and ultrastructural evidence on how the SARS-CoV-2 infection progresses in the native cellular context is scarce, and there is a lack of comprehensive knowledge on the SARS-CoV-2 replicative cycle. To correlate cytopathic events induced by SARS-CoV-2 with virus replication processes in frozen-hydrated cells, we established a unique multi-modal, multi-scale cryo-correlative platform to image SARS-CoV-2 infection in Vero cells. This platform combines serial cryoFIB/SEM volume imaging and soft X-ray cryo-tomography with cell lamellae-based cryo-electron tomography (cryoET) and subtomogram averaging. Here we report critical SARS-CoV-2 structural events – e.g. viral RNA transport portals, virus assembly intermediates, virus egress pathway, and native virus spike structures, in the context of whole-cell volumes revealing drastic cytppathic changes. This integrated approach allows a holistic view of SARS-CoV-2 infection, from the whole cell to individual molecules.