Fig. 3.

Potent neutralization of SARS-CoV-2 pseudovirus (A) and live virus (B) by mouse serum, correlation analysis for pseudo-neutralization and competitive ELISA (C). (A) Pseudoviruses were pre-incubated with serially diluted serum and then used to infect 293T-ACE2 cells. 24 hrs later, luciferase activities in cell lysates were recorded. 50% neutralizing antibody titers (NT₅₀) was obtained by non-linear fitting of plots of neutralization against serum dilution folds in Graphpad Prism 7. (B) Neutralization of live virus by a microneutralization assay. Virus-induced cytopathic effects (CPE) were observed under the microscopy. The neutralization capacity (NT₁₀₀) was expressed as the lowest dilution folds capable of completely preventing virus induced CPE in 100% of the wells. Experiments were performed in duplicate and the error bars denote ± SD, n = 2. Statistical significance was defined as *: P < 0.05. (C) Correlation analysis between pseudo-neutralization antibody titers (NT₅₀) and competitive ELISA (EC₅₀) for sera of day 13 and day 27. Correlation and linear regression analyses were performed in GraphPad Prism using Pearson’s correlation coefficients. Statistical significance was calculated using the two-tailed test. The dashed lines indicate the standard deviations of the linear regression plots.