. Viral supernatant was collected at 48 h post-transfection and frozen at −80 °C until use. The serially diluted monoclonal antibodies or sera were incubated with 200 TCID50 of pseudovirus at 37 °C for 1 h. The antibody-virus mixtures were subsequently added to pre-seeded HEK 293T-ACE2 cells. 48 h later, infected cells were lysed to measure luciferase activity using a commercial kit .
. The tested antibodies were serially diluted, mixed with 50 μL of SARS-CoV-2 in 96-well plates, and incubated for 1 hour at 37 °C. Mixtures were then transferred to 96-well plates pre-seeded with 1 × 10/well Vero-E6 cells and incubated at 37 °C for 24 h. The culture medium was then removed, and the plates were air-dried in a biosafety cabinet for 20 min. Cells were then fixed with a 4% paraformaldehyde solution for 30 min and air-dried in the BSC again.