Abstract
Background: Antibodies against SARS-CoV-2 can be detected by various testing platforms, but a detailed understanding of assay performance is critical.Methods: We developed and validated a simple enzyme-linked immunosorbent assay (ELISA) to detect IgG binding to the receptor-binding domain (RBD) of SARS-CoV-2, which was then applied for surveillance. ELISA results were compared to a set of complimentary serologic assays using a large panel of clinical research samples.Results: The RBD ELISA exhibited robust performance in ROC curve analysis (AUC> 0.99; Se = 89%, Sp = 99.3%). Antibodies were detected in 23/353 (6.5%) healthcare workers, 6/9 RT-PCR-confirmed mild COVID-19 cases, and 0/30 non-COVID-19 cases from an ambulatory site. RBD ELISA showed a positive correlation with neutralizing activity (p = <0.0001, R2 = 0.26).Conclusions: We applied a validated SARS-CoV-2-specific IgG ELISA in multiple contexts and performed orthogonal testing on samples. This study demonstrates the utility of a simple serologic assay for detecting prior SARS-CoV-2 infection, particularly as a tool for efficiently testing large numbers of samples as in population surveillance. Our work also highlights that precise understanding of SARS-CoV-2 infection and immunity at the individual level, particularly with wide availability of vaccination, may be improved by orthogonal testing and/or more complex assays such as multiplex bead assays.
Highlights
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first emerged in Wuhan, China in December 2019 and rapidly spread to cause an unprecedented pandemic [1]
All data and specimens included in this study were obtained and utilized under protocols approved by the appropriate institutional review boards (IRB), and informed consent was obtained
To establish a simple serologic assay for SARS-CoV-2-specific IgG detection, an ELISA using an receptor-binding domain (RBD) antigen was validated by testing a large set of human sera with known infection status (Table 1)
Summary
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) first emerged in Wuhan, China in December 2019 and rapidly spread to cause an unprecedented pandemic [1]. Validated sensitive and specific serologic assays are critical tools for evaluating exposure and immunity to emerging infectious diseases. Measures of SARS-CoV-2-specific antibodies are becoming increasingly important to measure the breadth and durability of vaccine responses, especially with the emergence of novel variant strains. CoV infection elicits human antibody (Ab) responses to additional structural and non-structural proteins, with the nucleocapsid (N) being used in serologic assays in addition to S-derived antigens [2]. Antibodies against SARS-CoV-2 can be detected by various testing platforms, but a detailed understanding of assay performance is critical
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