Quantitative measurement of IgG to SARS-CoV-2 proteins using ImmunoCAP.
Publication/Presentation Date
11-12-2020
Abstract
BACKGROUND: Detailed understanding of the immune response to SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), has been hampered by a lack of quantitative antibody assays.
OBJECTIVE: To develop a quantitative assay for IgG to SARS-CoV-2 proteins that could readily be implemented in clinical and research laboratories.
METHODS: The biotin-streptavidin technique was used to conjugate SARS-CoV-2 spike receptor-binding-domain (RBD) or nucleocapsid protein to the solid-phase of the ImmunoCAP resin. Plasma and serum samples from patients with COVID-19 (n=51) and samples from donors banked prior to the emergence of COVID-19 (n=109) were used in the assay. SARS-CoV-2 IgG levels were followed longitudinally in a subset of samples and were related to total IgG and IgG to reference antigens using an ImmunoCAP 250 platform.
RESULTS: Performance characteristics demonstrated 100% sensitivity and 99% specificity at a cut-off level of 2.5 µg/mL for both SARS-CoV-2 proteins. Among 36 patients evaluated in a post-hospital follow-up clinic, median levels of IgG to spike-RBD and nucleocapsid were 34.7 µg/mL (IQR 18-52) and 24.5 µg/mL (IQR 9-59), respectively. Among 17 patients with longitudinal samples there was a wide variation in the magnitude of IgG responses, but generally the response to spike-RBD and to nucleocapsid occurred in parallel, with peak levels approaching 100 µg/mL, or 1% of total IgG.
CONCLUSIONS: We have described a quantitative assay to measure IgG to SARS-CoV-2 that could be used in clinical and research laboratories and implemented at scale. The assay can easily be adapted to measure IgG to novel antigens, has good performance characteristics and a read-out in standardized units.
Published In/Presented At
Earasi, K., Welch, C., Zelickson, A., Westover, C., Ramani, C., Sumner, C., & Davis, E. M. (2020). Proteus empyema as a rare complication from an infected renal cyst, a case report. BMC pulmonary medicine, 20(1), 314. https://doi.org/10.1186/s12890-020-01346-w
Disciplines
Medicine and Health Sciences
PubMedID
33200147
Department(s)
Department of Medicine
Document Type
Article