Fig. 2: The infectivity of SARS-CoV-2 Variants in primate cell lines and Furin/TMPRSS2/CTSL expressed 293T-ACE2 cells.

a–d SARS-CoV-2-susceptible cells as indicated were used to compare the infectivities among 10 SARS-CoV-2 variants. Pseudostyped virus was quantified via RT-PCR and all strains were diluted to the same copy number. Cells were harvested 24 h after pseudostyped virus infection and analyzed for luminescence activities (RLUs). Relative infectivities compared with the D614G reference strain are displayed as the RLU ratio to D614G. e–h furin, TMPRSS2, and cathepsin L (CTSL)-stably overexpressing 293T-hACE2 cells were used compared to mock 293T-hACE2 cells. All cells were infected with the same copy number of pseudotyped SARS-CoV-2 variants. Chemiluminescence signals were detected 24 h later. Data shown indicate relative changes in infectivity due to the enzyme overexpression. Relative RLUs were compared with or without the indicated enzyme first, and then compared with the D614G reference strain. e RLU of cells infected with D614G virus. f–h Ratios by which enzyme overexpression induced enhanced infection, compared with D614G. The results were obtained from four independent experiments and the values shown indicate means ± SEMs. Dashed/dotted lines indicate the threshold of fourfold/twofold difference. Asterisks indicate statistical significance.