SARS-CoV-2 Neutralization Assay

Five-fold serially diluted plasma from COVID-19 convalescent individuals and healthy donors or four-fold serially diluted monoclonal antibodies were incubated with the SARS-CoV-2 or SARS-CoV pseudotyped virus for 1 hour at 37°C degrees. The mixture was subsequently incubated with 293T_ACE2 cells for 48 hours after which cells were washed twice with PBS and lysed with Luciferase Cell Culture Lysis 5x reagent (Promega). Nanoluc Luciferase activity in lysates was measured using the Nano-Glo Luciferase Assay System (Promega) with Modulus II Microplate Reader User interface (TURNER BioSystems). Relative luminescence units obtained were normalized to those derived from cells infected with SARS-CoV-2 or SARS-CoV pseudotyped virus in the absence of plasma or monoclonal antibodies. The half-maximal inhibitory concentration for plasma (NT₅₀) or monoclonal antibodies (IC₅₀) was determined using 4-parameter nonlinear regression (GraphPad Prism).