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.
Bibliographical noteFunding 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.
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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).