Quantitative Measurement of IgG to Severe Acute Respiratory Syndrome Coronavirus-2 Proteins Using ImmunoCAP

  1. Behnam Keshavarz
  2. Joesph R. Wiencek
  3. Lisa J. Workman
  4. Matthew D. Straesser
  5. Lyndsey M. Muehling
  6. Glenda Canderan
  7. Fabrizio Drago
  8. Catherine A. Bonham
  9. Jeffrey M. Sturek
  10. Chintan Ramani
  11. Coleen A. McNamara
  12. Judith A. Woodfolk
  13. Alexandra Kadl
  14. Thomas A.E. Platts-Mills
  15. Jeffrey M. Wilson

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Abstract

<b><i>Background:</i></b> Detailed understanding of the immune response to severe acute respiratory syndrome coronavirus (SARS-CoV)-2, the cause of coronavirus disease 2019 (CO­VID-19) has been hampered by a lack of quantitative antibody assays. <b><i>Objective:</i></b> The objective was to develop a quantitative assay for IgG to SARS-CoV-2 proteins that could be implemented in clinical and research laboratories. <b><i>Methods:</i></b> 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. Plasma and serum samples from patients hospitalized with COVID-19 (<i>n</i> = 60) and samples from donors banked before the emergence of COVID-19 (<i>n</i> = 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. <b><i>Results:</i></b> At a cutoff of 2.5 μg/mL, the assay demonstrated sensitivity and specificity exceeding 95% for IgG to 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. <b><i>Conclusions:</i></b> 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 mutated COVID-19 proteins, has good performance characteristics, and has a readout in standardized units.

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  1. Version published to 10.1159/000514203
  2. ScreenIT

    SciScore for 10.1101/2020.11.09.20228411: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIRB: Paired serum and plasma samples were available from 36 patients with COVID-19 seen in outpatient post-hospitalization follow-up clinic as part of a University of Virginia (UVA) Institutional Review Board (IRB) approved investigation.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The recombinant monoclonal anti-SARS-CoV-2 spike glycoprotein S1 antibody (CR3022) was purchased from Abcam (Cambridge, MA)
    The recombinant monoclonal anti-SARS-CoV-2 spike glycoprotein S1 antibody
    suggested: None
    anti-SARS-CoV-2 spike glycoprotein S1
    suggested: (Abcam Cat# ab273074, RRID:AB_2847846)
    CR3022
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Reagents: Recombinant SARS-CoV-2 S1 receptor-binding domain subunit (RBD) and recombinant SARS-CoV-2 nucleocapsid protein which had been expressed in HEK293 cells were purchased from RayBiotech (Peachtree Corners,
    HEK293
    suggested: CLS Cat# 300192/p777_HEK293, RRID:CVCL_0045)
    Software and Algorithms
    SentencesResources
    All analyses were performed using GraphPad Prism V8.4 (San Diego, CA).
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Acknowledging these limitations, the assay we have described has several strengths compared to many of the serological approaches currently being used in COVID-19 research and patient care. The ImmunoCAP-based assay we have described can readily be adapted to study IgG to SARS-CoV-2 and also a host of other antigens by using the streptavidin-biotin technique. The assay has good performance characteristics, has a quantitative read-out in standardized units and could be used by laboratories across the globe that routinely use the ImmunoCAP.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  3. Version published to 10.1101/2020.11.09.20228411v1 on medRxiv