Stabilized trimeric s protein

An immunoassay detecting SARS-CoV-2 N and S antigens was developed using the Meso Scale Discovery (MSD) platform (Meso Scale Diagnostics, Rockville, MD, USA), which uses electrochemiluminescence for detection. A monoclonal antibody pair for N antigen detection, MM08 and MM05, was sourced from Sino Biological (Beijing, People’s Republic of China). A monoclonal antibody pair for S antigen detection, L2355 and L2215, from sourced from Leinco Technologies (Fenton, MO, USA). The capture antibodies were labeled with biotin using the EZ-Link Sulfo-NHS-LC-LC biotinylation kit (ThermoFisher Scientific, Waltham, MA, USA), and the detector antibodies were labeled with SULFO-TAG(GOLD SULFO-TAG NHS-Ester, Meso Scale Diagnostics). Any unbound biotin or SULFO-TAG was removed using desalting columns (Zeba 40k MWCO, ThermoFisher Scientific). The concentrations of antibodies were measured at 280 nm via a spectrophotometer (NanoDrop 2000C, ThermoFisher Scientific), and concentration of detector antibody following labeling and desalting was assumed to be 90% recovery of the starting concentration. Standards were prepared from recombinant HEK293-expressed full-length SARS-CoV-2 N protein and stabilized trimeric S protein (Acro Biosystems).

An immunoassay detecting SARS-CoV-2 N and S antigens was developed using the Meso Scale Discovery (MSD) platform (Meso Scale Diagnostics, Rockville, MD, USA), which uses electrochemiluminescence for detection. A monoclonal antibody pair for N antigen detection, MM08 and MM05, was sourced from Sino Biological (Beijing, People’s Republic of China). A monoclonal antibody pair for S antigen detection, L2355 and L2215, from sourced from Leinco Technologies (Fenton, MO, USA). The capture antibodies were labeled with biotin using the EZ-Link Sulfo-NHS-LC-LC biotinylation kit (ThermoFisher Scientific, Waltham, MA, USA), and the detector antibodies were labeled with SULFO-TAG(GOLD SULFO-TAG NHS-Ester, Meso Scale Diagnostics). Any unbound biotin or SULFO-TAG was removed using desalting columns (Zeba 40k MWCO, ThermoFisher Scientific). The concentrations of antibodies were measured at 280 nm via a spectrophotometer (NanoDrop 2000C, ThermoFisher Scientific), and concentration of detector antibody following labeling and desalting was assumed to be 90% recovery of the starting concentration. Standards were prepared from recombinant HEK293-expressed full-length SARS-CoV-2 N protein and stabilized trimeric S protein (Acro Biosystems).