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SARS-CoV-2 egress from Vero cells: a morphological approach

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Abstract

Despite being extensively studied because of the current coronavirus disease 2019 (COVID-19) pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) interactions with mammalian cells are still poorly understood. Furthermore, little is known about this coronavirus cycle within the host cells, particularly the steps that lead to viral egress. This study aimed to shed light on the morphological features of SARS-CoV-2 egress by utilizing transmission and high-resolution scanning electron microscopy, along with serial electron tomography, to describe the route of nascent virions towards the extracellular medium. Electron microscopy revealed that the clusters of viruses in the paracellular space did not seem to result from collective virus release. Instead, virus accumulation was observed on incurved areas of the cell surface, with egress primarily occurring through individual vesicles. Additionally, our findings showed that the emission of long membrane projections, which could facilitate virus surfing in Vero cells infected with SARS-CoV-2, was also observed in non-infected cultures, suggesting that these are constitutive events in this cell lineage.

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Data availability

The data that support the findings of this study are available from the corresponding author on reasonable request.

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Acknowledgements

We thank Adelia Mara Belém Lima and Lorian Cobra Straker for support in the electron microscope at CENABIO facilities; Willian Ferreira da Silva and Bráulio Soares Archanjo for support in the Orion Microscope at INMETRO facilities. We also thank Edison Luiz Durigon (USP), Ester Sabino (IMT-SP), Fernando Spike (FEEVALE-SC) and João Renato Rebello Pinho (HIAE).

Funding

Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro–FAPERJ, grant No. E-26/010.000978/2019; Financiadora de Estudos e Projetos–FINEP; Conselho Nacional de Desenvolvimento Científico e Tecnológico–CNPq.

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Authors and Affiliations

  1. Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho 373, Prédio CCS, Bloco C, Subsolo, Cidade Universitária, Rio de Janeiro, RJ, CEP:21941902, Brazil

    Lucio Ayres Caldas, Fabiana Avila Carneiro, Ingrid Augusto, Kildare Miranda & Wanderley de Souza

  2. Núcleo Multidisciplinar de Pesquisas em Biologia - NUMPEX-BIO, Campus Duque de Caxias Geraldo Cidade, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Duque de Caxias, RJ, Brazil

    Lucio Ayres Caldas & Fabiana Avila Carneiro

  3. Laboratório de Genética e Imunologia das Infecções Virais, Departamento de Virologia, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

    Isadora Alonso Corrêa & Luciana Jesus da Costa

  4. Laboratório de Virologia Molecular, Departamento de Genética, Instituto de Biologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

    Isadora Alonso Corrêa, Luciana Jesus da Costa & Amilcar Tanuri

  5. Instituto Nacional de Ciência e Tecnologia de Biologia Estrutural e Bioimagem (INBEB) and Centro Nacional de Biologia Estutural e Bioimagem (CENABIO), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil

    Kildare Miranda & Wanderley de Souza

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  1. Lucio Ayres Caldas
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  2. Fabiana Avila Carneiro
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  3. Ingrid Augusto
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  8. Wanderley de Souza
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Contributions

I.A.C. and L.J.C. conducted the Isolate preparations, virus growth, and infections; L.A.C. and F.A.C. performed the sample preparations and microscopy analysis;  I.A. and K.M. performed the FIB and tomographic image alignment and reconstruction;  L.A.C., F.A.C., L.J.C., K.M. and W.S. performed the analysis of the results;   W.S. and A.T. contributed to the initial conception and design of this work;  L.A.C. and F.A.C. wrote the first draft of the manuscript. All the authors were involved in reviewing and editing the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Lucio Ayres Caldas.

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Supplementary information

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Supplementary file1 Tomogram showing viruses held in plasma membrane invagination. Two slices of 200 nm were used (MP4 9411 KB)

Supplementary file2 Infected Vero cells processed by FIB. Purple, plasma membrane; yellow, virus; light blue, viral factory; blue cyan, LVCV; dark blue, nucleus; brown, mitochondria (MP4 71874 KB)

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Caldas, L.A., Carneiro, F.A., Augusto, I. et al. SARS-CoV-2 egress from Vero cells: a morphological approach. Histochem Cell Biol 161, 59–67 (2024). https://doi.org/10.1007/s00418-023-02239-9

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