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

Simon G P Funnell; Babak Afrough; John James Baczenas; Neil Berry; Kevin R 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 S Richards; Kimberly J Stemple; Ivana Knezevic

doi:10.1038/s41541-021-00346-z

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

NPJ Vaccines. 2021 Jun 17;6(1):83. doi: 10.1038/s41541-021-00346-z.

Authors

Simon G P Funnell^{1

2

3}, Babak Afrough¹, John James Baczenas⁴, Neil Berry⁵, Kevin R Bewley¹, Rebecca Bradford⁶, Clint Florence⁷, Yann Le Duff⁵, Mark Lewis⁷, Ryan V Moriarty⁴, Shelby L O Connor⁴, Karen L Osman¹, Steven Pullan¹, Sujatha Rashid⁶, Kevin S Richards^{1

8}, Kimberly J Stemple⁷, Ivana Knezevic⁹

Affiliations

¹ PHE Porton Down, National Infection Service, Public Health England, Salisbury, Wiltshire, UK.
² Quadram Institute Bioscience, Norwich Research Park, Norfolk, UK.
³ World Health Organization, Geneva, Switzerland.
⁴ Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, WI, USA.
⁵ Division of Infectious Disease Diagnostics, National Institute for Biological Standards and Control, London, UK.
⁶ Biodefense and Emerging Infections Resources, NIH, Bethesda, MD, USA.
⁷ Office of Biodefense, Research Resources and Translational Research, Division of Microbiology and Infectious Diseases, NIAID, NIH, Bethesda, MD, USA.
⁸ Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, UK.
⁹ World Health Organization, Geneva, Switzerland. knezevici@who.int.

Abstract

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.

Abstract

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