Spark multifunction microplate reader

Vero-E6_ACE2 cells were seeded in 96-well plates (NEST Biotechnology, Wuxi, China) to a density of 2 × 10⁴ cells/well. Serum samples were two-fold diluted starting from 1:8. SARS-CoV-2 pseudoviruses (5 × 10⁴ relative luminescence units, RLU) were mixed with an equal volume of diluted sera and incubated for 1 h at 37 °C. Then, the mixture of a patient's serum and SARS-CoV-2 pseudoviruses was added to a well of a 96-well plate for 72 h. Luciferase activity was tested using Bio-Lite Luciferase Assay Kit (Vazyme Biotech co., Ltd, Nanjing, China) and Tecan Spark multifunction microplate reader (Tecan, Austria). The neutralizing antibody titer was defined as the maximum dilution of serum at 50% neutralization (ND₅₀). The positive threshold of this assay was 1:8.

ASP300S automatic tissue dehydrator, HistoCore Arcadia H Leica ASP Leica embedding machine, NANOCUT automatic semi-thin paraffin slicer, all from Leica, Germany; Dyy-6c electrophoresis apparatus, Beijing Liuyi Instrument Factory; Tgl-16 refrigerated centrifuge, Hunan Xiangyi Laboratory Instrument Development Co., LTD. (Changsha, China); Spark Multi-function microplate reader, Tecan, Switzerland; 5810R table top high speed refrigerated centrifuge, Eppendorf, Germany were all used in the experiment.