Vero CCL-81 and Calu-3 Cell Lines as Alternative Hosts for Isolation and Propagation of SARS-CoV-2 Isolated in Malaysia

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as the etiologic agent for the pneumonia outbreak that started in early December 2019 in Wuhan City, Hubei Province, China. To date, coronavirus disease (COVID-19) has caused almost 6 million deaths worldwide. The ability to propagate the virus into a customizable volume will enable better research on COVID-19 therapy, vaccine development, and many others. In the search for the most efficient replication host, we inoculated three (3) local SARS-CoV-2 isolates of different lineages (Clade L/Lineage B Wuhan, Clade GR/Lineage B.1.1.354, and Clade O/Lineage B.6.2) into various clinically important mammalian cell lines. The replication profile of these isolates was evaluated based on the formation of cytopathic effects (CPE), viral load (Ct value and plaque-forming unit (pfu)), as well as observation by electron microscopy (EM). Next-generation sequencing (NGS) was performed to examine the genomic stability of the propagated SARS-CoV-2 in these cell lines. Our study found that Vero E6 and Vero CCL-81 cell lines posed similar capacities in propagating the local isolates, with Vero CCL-81 demonstrating exceptional potency in conserving the genomic stability of the Lineage B Wuhan isolate. In addition, our study demonstrated the utility of Calu-3 cells as a replication host for SARS-CoV-2 without causing substantial cellular senescence. In conclusion, this study provides crucial information on the growth profile of Malaysian SARS-CoV-2 in various mammalian cell lines and thus will be a great source of reference for better isolation and propagation of the SARS-CoV-2 virus isolated in Malaysia.