Insights into the Replication Kinetics Profiles of Malaysian SARS-CoV-2 Variant Alpha, Beta, Delta, and Omicron in Vero E6 cell line

Comprehending the replication kinetics of SARS-CoV-2 variants helps explain why certain var-iants spread more easily and are more contagious, and pose significant health menaces to the global populations. The replication kinetics of Malaysian isolates of the Alpha, Beta, Delta, and Omicron variants were studied in the Vero E6 cell line. Their replication kinetics were deter-mined using the plaque assay, quantitative real-time PCR (qRT-PCR), and viral growth curve. The Beta variant exhibited the highest replication rate at 24 hours post-infection (h.p.i), as evi-denced by the highest viral titers and lowest viral RNA multiplication threshold. The plaque phenotypes also varied among the variants, in which the Beta and Omicron variants formed the largest and smallest plaques, respectively. All studied variants showed strong cytopathic effects after 48 h.p.i. The whole-genome sequencing highlighted cell-culture adaptation, where the Beta, Delta and Omicron variants acquired mutations at the multibasic cleavage site after three cycles of passaging. The findings suggest a strong link between the replication rates and their respec-tive transmissibility and pathogenicity. This is essential in predicting the impacts of the upcom-ing variants on the local and global populations and is useful in designing preventive measures to curb the virus outbreaks.