Performance of the rapid high-throughput automated electrochemiluminescence immunoassay targeting total antibodies to the SARS-CoV-2 spike protein receptor binding domain in comparison to the neutralization assay

Katarina Resman Rus; Miša Korva; Nataša Knap; Tatjana Avšič Županc; Mario Poljak

doi:10.1016/j.jcv.2021.104820

Performance of the rapid high-throughput automated electrochemiluminescence immunoassay targeting total antibodies to the SARS-CoV-2 spike protein receptor binding domain in comparison to the neutralization assay

J Clin Virol. 2021 Jun:139:104820. doi: 10.1016/j.jcv.2021.104820. Epub 2021 Apr 10.

Authors

Katarina Resman Rus¹, Miša Korva¹, Nataša Knap¹, Tatjana Avšič Županc¹, Mario Poljak²

Affiliations

¹ Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia.
² Institute of Microbiology and Immunology, Faculty of Medicine, University of Ljubljana, Zaloška 4, 1000 Ljubljana, Slovenia. Electronic address: mario.poljak@mf.uni-lj.si.

Abstract

Background: Neutralization tests (NT) are the gold standard for detecting and quantifying anti-SARS-CoV-2 neutralizing antibodies (NAb), but their complexity restricts them to research settings or reference laboratories. Antibodies against S protein receptor binding domain (RBD) have been shown to confer a neutralizing activity against SARS-CoV-2. Assays quantitatively measuring anti-S1-RBD-SARS-CoV-2 antibodies could be of great value for NAb screening of potential donors for convalescent-phase plasma therapy, assessing natural or vaccine-induced immunity, stratifying individuals for vaccine receipt, and documenting vaccine response.

Methods: Elecsys Anti-SARS-CoV-2 S (Elecsys-S), a high-throughput automated electrochemiluminescence double-antigen sandwich immunoassay for quantitative measurement of pan-anti-S1-RBD-SARS-CoV-2 antibodies, was evaluated against NT on 357 patients with PCR-confirmed SARS-CoV-2 infection. NT was performed in a BSL-3 laboratory using a Slovenian SARS-CoV-2 isolate; the NT titer ≥1:20 was considered positive.

Results: Elecsys-S detected pan-anti-S1-RBD-SARS-CoV-2 antibodies in 352/357 (98.6 %) samples. NAb were identified by NT in 257/357 (72 %) samples. The Elecsys-S/NT agreement was moderate (Cohen's kappa 0.56). High NT titer antibodies (≥1:160) were detected in 106/357 (30 %) samples. Elecsys-S's pan-anti-S1-RBD-SARS-CoV-2 antibody concentrations correlated with individual NT titer categories (the lowest concentrations were identified in NT-negative samples and the highest in samples with NT titer 1:1,280), and the Elecsys-S cutoff value for reasonable prediction of NAb generated after natural infection was established (133 BAU/mL).

Conclusion: Although NT should remain the gold standard for assessing candidates for convalescent-phase plasma donors, selected commercial anti-SARS-CoV-2 assays with optimized cutoff, like Elecsys-S, could be used for rapid, automated, and large-scale screening of individuals with clinically relevant NAb levels as suitable donors.

Keywords: Antibody; Electrochemiluminescence; Immunoassay; Neutralization; SARS-CoV-2.

Publication types

Comparative Study
Research Support, Non-U.S. Gov't

MeSH terms

Antibodies, Viral / blood*
COVID-19 / diagnosis*
COVID-19 Serological Testing
High-Throughput Screening Assays
Humans
Immunoassay / methods*
Luminescent Measurements / methods*
Neutralization Tests*
Spike Glycoprotein, Coronavirus / chemistry
Spike Glycoprotein, Coronavirus / immunology*

Substances

Antibodies, Viral
Spike Glycoprotein, Coronavirus
spike protein, SARS-CoV-2