A cautionary perspective regarding the isolation and serial propagation of SARS-CoV-2 in Vero cells

Simon Funnell, Babak Afrough, John James Baczenas, Neil Berry, Kevin Bewley, Rebecca Bradford, Clint Florence, Yann Le Duff, Mark Lewis, Ryan V. Moriarty, Shelby L.O. Connor, Karen L. Osman, Steven Pullan, Sujatha Rashid, Kevin Richards, Kimberly J. Stemple, Ivana Knezevic*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)
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An array of SARS-CoV-2 virus variants have been isolated, propagated and used in in vitro assays, in vivo animal studies and human clinical trials. Observations of working stocks of SARS-CoV-2 suggest that sequential propagation in Vero cells leads to critical changes in the region of the furin cleavage site, which significantly reduce the value of the working stock for critical research studies. Serially propagating SARS-CoV-2 in Vero E6 cells leads to rapid increases in genetic variants while propagation in other cell lines (e.g. Vero/hSLAM) appears to mitigate this risk thereby improving the overall genetic stability of working stocks. From these observations, investigators are urged to monitor genetic variants carefully when propagating SARS-CoV-2 in Vero cells.

Original languageEnglish
Article number83
Number of pages5
Journalnpj Vaccines
Issue number1
Early online date17 Jun 2021
Publication statusPublished - 17 Jun 2021

Bibliographical note

Funding Information: The authors would like to thank the combined resources and staff of the CFAR Repository, NGS and bioinformatics and animal model groups at NIBSC. This project has been funded in whole or in part with Federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN272201600013C, managed by ATCC. PHE would like to acknowledge the support of many colleagues in the National Infection Service and funding in part from both CEPI and the UK Department of Health. All animal experimentation work conducted in the UK was completed under the authority and in accordance with the UK Home Office Animal (Scientific) Procedures Act. The University of Wisconsin-Madison would like to thank Dr. Robert Seder for permitting reference to in vivo experimental data conducted at the NIAID VRC in this publication.
S.L.O. and J.J.B. manage a fee-for-service pathogen sequencing unit that is a part of Research Services at the Wisconsin National Primate Research Center. All other authors declare no competing interests.

Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

Publisher Copyright: © 2021, The Author(s).

Citation: Funnell, S.G.P., Afrough, B., Baczenas, J.J. et al. A cautionary perspective regarding the isolation and serial propagation of SARS-CoV-2 in Vero cells. npj Vaccines 6, 83 (2021).

DOI: https://doi.org/10.1038/s41541-021-00346-z


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