SARS-CoV-2 pseudovirus neutralization assay
The neutralizing activity of serum samples to pseudotyped SARS-CoV-2 variants was detected by chemiluminescence method (8). Firstly, serum samples were performed by 3-fold serial dilutions ranging from1:10 to 1:7290. SARS-CoV-2 pseudovirus (650TCID50/ well) were mixed with diluted serum in 96-well plates and incubated at 37°C, 5%CO2 for 1 h. Subsequently, the Vero cells (2x104/ well) were added and cultured for 24 h. The expression level of luciferase was detected by the chemiluminescence signals, and the relative luminescence unit (RLU) values was determined. The 50% neutralization dilution (ND50) level was calculated using the Reed-Muench method.