Selecting COVID ‐19 convalescent plasma for neutralizing antibody potency using a high‐capacity SARS‐CoV ‐2 antibody assay

  1. Erin Goodhue Meyer
  2. Graham Simmons
  3. Eduard Grebe
  4. Michael Gannett
  5. Sergej Franz
  6. Orsolya Darst
  7. Clara Di Germanio
  8. Mars Stone
  9. Paul Contestable
  10. Alicia Prichard
  11. Rita Reik
  12. Ralph Vassallo
  13. Pampee Young
  14. Michael P. Busch
  15. Phillip Williamson
  16. Larry J. Dumont

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Abstract

Background

Efficacy of COVID‐19 convalescent plasma (CCP) is hypothesized to be associated with the concentration of neutralizing antibodies (nAb) to SARS‐CoV‐2. High capacity serologic assays detecting binding antibodies (bAb) have been developed; nAb assays are not adaptable to high‐throughput testing. We sought to determine the effectiveness of using surrogate bAb signal‐to‐cutoff ratios (S/Co) in predicting nAb titers using a pseudovirus reporter viral particle neutralization (RVPN) assay.

Methods

CCP donor serum collected by three US blood collectors was tested with a bAb assay (Ortho Clinical Diagnostics VITROS Anti‐SARS‐CoV‐2 Total, CoV2T) and a nAb RVPN assay. Prediction effectiveness of various CoV2T S/Co criteria was evaluated for RVPN nAb NT 50 titers using receiver operating characteristics.

Results

Seven hundred and fifty‐three CCPs were tested with median CoV2T S/Co and NT 50 of 71.2 of 527.5. Proportions of donors with NT 50 over target nAb titers were 86% ≥1:80, 76% ≥1:160, and 62% ≥1:320. Increasing CoV2T S/Co criterion reduced the sensitivity to predict NT 50 titers, while specificity to identify those below increased. As target NT50 titers increase, the CoV2T assay becomes less accurate as a predictor with a decline in positive predictive value and rise in negative predictive value.

Conclusion

Selection of a clinically effective nAb titer will impact availability of CCP. Product release with CoV2T assay S/Co criterion must balance the risk of releasing products below target nAb titers with the cost of false negatives. A two‐step testing scheme may be optimal, with nAb testing on CoV2T samples with S/Cos below criterion.

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  1. ScreenIT

    SciScore for 10.1101/2020.08.31.20184895: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    RandomizationPreparation of Samples: Either refrigerated serum from the routine donation testing tubes, or frozen serums from randomly selected CCP donations were sent to the CTS in St. Petersburg, Florida.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    15 The VITROS CoV2T test is an antigen sandwich immunoassay designed to qualitatively detect antibody to the S1 subunit of the SARS-CoV-2 spike glycoprotein, including IgA, IgM and IgG.
    SARS-CoV-2 spike glycoprotein, including IgA, IgM
    suggested: None
    The amount of HRP conjugate bound is indicative of the amount of anti-SARS-CoV-2 antibody present.
    anti-SARS-CoV-2
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    16 Briefly, HEK293T cells were transfected with human ACE2 and TMPRSS2 by TransIT-2020.
    HEK293T
    suggested: None
    Software and Algorithms
    SentencesResources
    Fifty percent neutralization titers (NT50) were estimated by calculating percent of no serum control and plotting non-linear regression curves constructed in GraphPad Prism version 8.4 (GraphPad Software, San Diego, CA).
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)
    A non-parametric Spearman rank correlation coefficient was performed between CoV2T and RVPN (SAS 9.4, SAS Institute, Cary, NC).
    SAS Institute
    suggested: (Statistical Analysis System, RRID:SCR_008567)

    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:
    As applied to CCP on the large-scale experience in the US, it is not possible to provide timely screening of CCP products due to technological limitations. Therefore, it is imperative to apply high throughput bAb assays as indicators of nAb levels. We have demonstrated that the CoV2T test system, while not a perfect predictor of nAb titers, is capable of identifying donors with no Ab response. The test system also presents a S/CO readout with a large dynamic range. This output range can be exploited to provide reasonable PPV as a screening tool. For example, a S/CO criterion of 30 applied to a previously qualified CCP donor population is expected to result in 90% of CCP with NT50 ≥1:160. We further illustrated that reflex testing of CCPP in the intermediate zone of S/CO 1-30 could provide additional units at or above the desired NT50. Such an approach will permit high throughput screening for timely provision of CCP. The selection of targeted nAb titers for clinical use will significantly affect the yield and availability of CCP transfusion. Due to inherent limitations of large volume testing for neutralization titers, we present a potential reflex testing algorithm using initial high-throughput CoV2T testing. The S/CO thresholds selected for routine product release will need to balance the risk of releasing products without the minimum target nAb titer. Organizations may consider this testing scheme or develop others to effectively select for CCP. Another approach that could...

    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.
    • Thank you for including a protocol registration statement.

    About SciScore

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  2. Version published to 10.1111/trf.16321
  3. Version published to 10.1101/2020.08.31.20184895 on medRxiv