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Authors: Natacha S. Ogando, Tim J. Dalebout, Jessika C. Zevenhoven-Dobbe, Ronald W. Limpens, Yvonne van der Meer, Leon Caly, Julian Druce, Jutte J. C. de Vries, Marjolein Kikkert, Montserrat Bárcena, Igor Sidorov, Eric J. Snijder

Link to paper: https://www.biorxiv.org/content/10.1101/2020.04.20.049924v1

Journal/ Pre-Print: bioRxiv

Key Words: SARS-CoV-2, COVID-19, replication kinetics, drugs

Research Highlights 

1. In Vero E6 cells, SARS-CoV-2 generates higher levels of viral RNA but less progeny virus in comparison to SARS-CoV.

2. Remdesivir, Alisporivir and chloroquine prevent the cytopathic effects of SARS-CoV and SARS-CoV-2.

3. Pre-treatment of cells with pegylated IFNα prevents the cytopathic effects of SARS-CoV-2 but not SARS-CoV.

Summary 

This study details the basic replication features of SARS-CoV and SARS-CoV-2 in Vero E6 cells. Low passage SARS-CoV-2 isolates gain mutations surrounding the ‘furin like’ S1/S2 cleavage site upon propagation in cell culture. SARS-CoV-2 infection has an increase in the rate of production of viral RNA in compared to SARS-CoV but produces lower titres of infectious virus. The authors show that available SARS-CoV antibodies for light microscopy effectively detect SARS-CoV-2 proteins. A comparison of cellular morphology by cryo-electron microscopy showed minor differences between SARS-CoV and SARS-CoV-2 infection. Finally, the study shows in vitro that Remdesivir, Alisporivir and chloroquine are effective against SARS-CoV-2 in vitro.

Impact for SARS-CoV2/COVID19 research efforts

Understand the virology and/or cell biology of SARS-CoV2/COVID19

· Contains information useful for people trying to study SARS-CoV-2 in vitro (e.g. poor replication in HuH7 cells, set up suitable system for drugs screening).

Study Type

In vitro study

Strengths and limitations of the paper

Novelty: Interesting observations that SARS-CoV2 gains mutations surrounding the ‘furin like’ S1/S2 cleavage site in culture.

Standing in the field: Results are largely in agreement with similar publications.

Appropriate statistics: No statistics are used hence it is not possible to know if results are significant.

Viral model used: BetaCoV/Australia/VICO1/2020

Translatability: Drugs shown to inhibit replication of SARS-CoV2 are clinically relevant.

Main limitations: The data set is not coherent showing a number of unrelated phenotypes. The authors use a single cell line to support conclusions; although these are individually interesting. The paper’s complete lack of statistics makes it impossible to know if phenotypes seen are significant (for example, if RNA levels are actually increased in SARS-CoV2 infected cells compared to those infected with SARS-CoV).