• Gerco den Hartog, Rutger M Schepp, Marjan Kuijer, Corine GeurtsvanKessel, Josine van Beek, Nynke Rots, KoopmansMarion P GMPGDepartment of Viroscience, Erasmus Medical Center, Rotterdam, the Netherlands., Fiona R M van der Klis, and Robert S van Binnendijk.
• Centre for Immunology of Infectious Diseases and Vaccines, National Institute for Public Health and the Environment, Bilthoven, the Netherlands.
• J. Infect. Dis. 2020 Oct 1; 222 (9): 1452-1461.

BackgroundThe COVID-19 pandemic necessitates better understanding of the kinetics of antibody production induced by infection with SARS-CoV-2. We aimed to develop a high-throughput multiplex assay to detect antibodies to SARS-CoV-2 to assess immunity to the virus in the general population.MethodsSpike protein subunits S1 and receptor binding domain, and nucleoprotein were coupled to microspheres. Sera collected before emergence of SARS-CoV-2 (n = 224) and of non-SARS-CoV-2 influenza-like illness (n = 184), and laboratory-confirmed cases of SARS-CoV-2 infection (n = 115) with various severities of COVID-19 were tested for SARS-CoV-2-specific IgG concentrations.ResultsOur assay discriminated SARS-CoV-2-induced antibodies and those induced by other viruses. The assay specificity was 95.1%-99.0% with sensitivity 83.6%-95.7%. By merging the test results for all 3 antigens a specificity of 100% was achieved with a sensitivity of at least 90%. Hospitalized COVID-19 patients developed higher IgG concentrations and the rate of IgG production increased faster compared to nonhospitalized cases.ConclusionsThe bead-based serological assay for quantitation of SARS-CoV-2-specific antibodies proved to be robust and can be conducted in many laboratories. We demonstrated that testing of antibodies against multiple antigens increases sensitivity and specificity compared to single-antigen-specific IgG determination.© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America.

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