SARS Coronavirus-2 Microneutralisation and Commercial Serological Assays Correlated Closely for Some but Not All Enzyme Immunoassays

  1. Gregory J. Walker
  2. Zin Naing
  3. Alberto Ospina Stella
  4. Malinna Yeang
  5. Joanna Caguicla
  6. Vidiya Ramachandran
  7. Sonia R. Isaacs
  8. David Agapiou
  9. Rowena A. Bull
  10. Sacha Stelzer-Braid
  11. James Daly
  12. Iain B. Gosbell
  13. Veronica C. Hoad
  14. David O. Irving
  15. Joanne M. Pink
  16. Stuart Turville
  17. Anthony D. Kelleher
  18. William D. Rawlinson

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Abstract

Serological testing for SARS-CoV-2-specific antibodies provides important research and diagnostic information relating to COVID-19 prevalence, incidence and host immune response. A greater understanding of the relationship between functionally neutralising antibodies detected using microneutralisation assays and binding antibodies detected using scalable enzyme immunoassays (EIA) is needed in order to address protective immunity post-infection or vaccination, and assess EIA suitability as a surrogate test for screening of convalescent plasma donors. We assessed whether neutralising antibody titres correlated with signal cut-off ratios in five commercially available EIAs, and one in-house assay based on expressed spike protein targets. Sera from recovered patients or convalescent plasma donors who reported laboratory-confirmed SARS-CoV-2 infection (n = 200), and negative control sera collected prior to the COVID-19 pandemic (n = 100), were assessed in parallel. Performance was assessed by calculating EIA sensitivity and specificity with reference to microneutralisation. Neutralising antibodies were detected in 166 (83%) samples. Compared with this, the most sensitive EIAs were the Cobas Elecsys Anti-SARS-CoV-2 (98%) and Vitros Immunodiagnostic Anti-SARS-CoV-2 (100%), which detect total antibody targeting the N and S1 antigens, respectively. The assay with the best quantitative relationship with microneutralisation was the Euroimmun IgG. These results suggest the marker used (total Ab vs. IgG vs. IgA) and the target antigen are important determinants of assay performance. The strong correlation between microneutralisation and some commercially available assays demonstrates their potential for clinical and research use in assessing protection following infection or vaccination, and use as a surrogate test to assess donor suitability for convalescent plasma donation.

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  1. Version published to 10.3390/v13020247
  2. ScreenIT

    SciScore for 10.1101/2020.12.07.20245696: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: Ethics approval to compare and validate antibody SARS-CoV-2 assays as part of a larger project to collect, manufacture and supply convalescent plasma to patients enrolled in clinical trials and for COVID-19 Immunoglobulin was approved by the Lifeblood Ethics Committee (approval number Hoad 30042020).
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableThe donors ranged in age from 20 to 78 years old (mean =45·3 years) with 54.6% being males.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Euroimmun Anti-SARS-CoV-2 ELISA: The Anti-SARS-CoV-2 (Euroimmun, Germany) is an enzyme linked immunosorbent assay (ELISA) based platform that utilizes recombinant S1 protein to bind anti-SARS-CoV-2 antibodies in serum or plasma.
    Anti-SARS-CoV-2
    suggested: None
    A secondary antibody (antihuman-IgG conjugated with the enzyme alkaline phosphatase, Virion/Serion) was then added to wells for 30 minutes to detect and bind the immune complex.
    antihuman-IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    A suspension of Vero E6 cells containing 2×104 cells was added to each well, and plates were incubated at 37°C (5% CO2) for three days.
    Vero E6
    suggested: None
    Software and Algorithms
    SentencesResources
    Abbott Architect SARS-CoV-2 IgG: The Architect SARS-CoV-2 IgG (Abbott Diagnostics, Australia) is a chemiluminecent microparticle immunoassay (CMIA) for the detection of IgG antibodies to the nucleocapsid (N) protein of SARS-CoV-2 in serum and plasma.
    Abbott Architect
    suggested: (Abbott ARCHITECT i1000sr System, RRID:SCR_019328)
    Abbott
    suggested: (Abbott, RRID:SCR_010477)
    Figures including optical density ratios and ROC curves were generated in GraphPad Prism 9.
    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:
    A limitation of this work is that the timing of serum collection was not standardised, and that samples obtained were not tested equally across all assays due to limitations in sample volume and dead volume requirements of the automated EIAs. Nonetheless, the relatively large number of samples run remains a strength of this study, and allows for a head-to-head comparison of commercially available SARS-CoV-2 serological tests seen in few other studies. We and others have shown that commercially available serological assays for SARS-CoV-2 have varying performance that is dependent on both the platform and marker used. The assay chosen by end-users should be tailored to specific applications - for example, assays measuring antibodies to the nucelocapsid antigen might be best suited to disease surveillence as spike-protein based vaccines become available. During the COVID-19 pandemic, serological assays will be crucial in answering questions of immune protection against reinfection. If convalescent plasma or COVID-19 immunoglobulin is found to be a potentially effective therapeutic intervention, high throughput serological assays that closely correlate with neutralisation antibody levels are vital for scalability. As further testing platforms become available, validation studies such as this are needed to identify assays that inform on antibody titre and functionality.

    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

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  3. Version published to 10.1101/2020.12.07.20245696v1 on medRxiv