Fig. 1

Infectivity of pseudotyped SARS-CoV-2 variants to mACE2-expressing cells. a Schematics of the Spike proteins of different SARS-CoV-2 variants which included D614 (Wuhan-Hu-1) virus, G614 (SYSU-IHV), B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.429 (Epsilon), B.1.525 (Eta), B.1.617.1 (Kappa), B.1.617.2 (Delta), and C.37 (Lambda). The mutation sites and types were indicated next to each backbone and written in red. b HEK293T-hACE2 and HEK293T-mACE2 cells were incubated with different pseudotyped SARS-CoV-2 viruses, followed by detecting the expression of luciferase at 48 h post infection. The fold changes of luciferase expression were normalized to viral titers followed by normalizing to the mock group and indicated as normalized infectivity (n = 3 for each group). The pseudotyped viruses were quantified and normalized with western blot with HIV-1 p24 protein antibody. c HEK293T cells were linearly transfected with different amounts (50, 100, and 200 ng in 24-well plates) of hACE2- or mACE2-expressing plasmids, followed by infecting with different pseudotyped SARS-CoV-2 viruses which included B.1.1.7, B.1.351, P.1, and B.1.617.1. The luciferase expression levels were quantified and indicated normalized infectivity. The expression levels of different amounts of hACE2- or mACE2-expressing plasmids transfected HEK293T cells were verified by western blot with antibodies against hACE2 and mACE2. GAPDH proteins were immunoblotted as the internal control (n = 3 for each group). d The pseudotyped B.1.1.7, B.1.351, P.1, and B.1.617.1 viruses (the initial copies of all the viruses were 2 × 10⁵ copies per μl) were twofold serially diluted and infected HEK293T-mACE2 cells. The normalized infectivity for each variant in each dilution was calculated as in c (n = 3 for each group). The pseudotyped viruses were quantified with western blot with HIV-1 p24 protein antibody. Data in b–d represented as mean ± SEM in triplicate. p Values were calculated by two-way ANOVA with Dunnett’s multiple comparisons test. ns = p ≥ 0.05, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001