A quantitative assay for detection of SARS-CoV-2 neutralizing antibodies

Abstract

Objectives : Serological assays for SARS-CoV-2 have a critical role not only in diagnosis of COVID-19, but also in assessing the degree and duration of response of specific antibodies against the virus obtained through infection or vaccination. We present the results obtained with a competitive immunoenzymatic method (Chorus SARS-CoV-2 “Neutralizing” Ab) for quantitative determination of total neutralizing anti-S1 SARS-CoV-2 antibodies (IgG, IgM, and IgA) in human serum obtained on a disposable device with the Chorus TRIO instrument using a recombinant strong neutralizing antibody as tracer. Methods : A total of 694 sera were evaluated for SARS-CoV-2 neutralizing antibodies: 407 uninfected, 201 symptomatic subjects, 37 post-infection patients, and 49 vaccinated. Sixty-eight of the previous sera were used to compare the Chorus SARS-CoV-2 “Neutralizing” Ab results with those obtained with micro-neutralization of the Alpha and original variants. A set of 74 positive sera for other respiratory infections were analyzed to evaluate the possible cross reaction to SARS-CoV-2 virus. Results : Of the 694 samples, only 3 had discordant results between micro-neutralization and values measured by Chorus SARS-CoV-2 “Neutralizing” Ab: 1 false negative and 2 false positives. Values of sensitivity and specificity were very high: percent positive agreement (sensitivity) 99.6% (95% CI: 97.7 - 99.9) and percent negative agreement (specificity) 99.6% (95% CI: 98.0 -99.9). Concordance was high with a Gwet's Ac1 of 0.992. No significant differences were observed between the alpha and original variants. Conclusions : The Chorus SARS-CoV-2 “Neutralizing” Ab test was highly sensitive and specific, and varies from most other currently available tests since it analyzes only antibodies with viral-neutralizing capacity.

Two rapid SARS-CoV-2 disposable devices for semi-quantitative S-RBD antibody levels determination compared with CLIA and ELISA assays at different protective thresholds

“…Anti S-RBD IgG was measured by the validated chemiluminescent (CLIA) assay Maglumi 2000 plus (Snibe Diagnostics, Shenzhen, China, hereafter called the reference method) [7] . Anti S-RBD total Ab levels were measured in collected sera using an automated enzyme-linked immunosorbent competitive assay (ELISA) SARS-CoV-2 “Neutralizing” Ab Chorus (REF 81408) (DIESSE, Diagnostica Senese, Siena, Italy) (highly correlated with Nab titers [8] ) and results compared with that of the reference method. Chorus determines the total Ab capable of competing with a monoclonal antibody direct against an epitope of the wild type S-RBD portion of SARS-CoV-2.…”

Emerging clinically tested detection methods for COVID‐19

“…In this sense, Cerutti et al . [ 74 ] employed the Chorus SARS‐CoV‐2 ‘Neutralizing’ Ab assay to detect the neutralizing Abs from 694 patient samples. The system allowed the identification of individuals who have had COVID‐19 or who have been vaccinated, and also assessed the actual neutralizing capacity of the samples analyzed.…”

“…This assay detects only Abs with viral-neutralizing capacity. Among them, those able to recognize the spike protein RBD appear to have higher activity, followed by Abs that recognize the S1 domain, spike protein trimer and S2 subunit [74]. In this sense, Cerutti et al [74] employed the Chorus SARS-CoV-2 'Neutralizing' Ab assay to detect the neutralizing Abs from 694 patient samples.…”

Gold-silver alloy hollow nanoshells-based lateral flow immunoassay for colorimetric, photothermal, and SERS tri-mode detection of SARS-CoV-2 neutralizing antibody

“…In order to conduct live virus and pseudovirus neutralization testing, biosafety level 3 and 2 facilities must be equipped with biosafety level 3 [ 12 ]. Principle of testing neutralizing antibodies against SARS-CoV-2 based on the evaluation of their ability to inhibit binding between the SARS-CoV-2 S protein RBD and the angiotensin converting enzyme 2 (ACE2) protein, the enzyme-linked immunosorbent assay (ELISA) [ 13 , 14 ] and plasmon resonance assay (SPR) [ 15 , 16 ] have recently been developed for the purpose of neutralizing the SARS-CoV-2 virus. However, their reliance on large equipment and operators, as well as their time-consuming and labor-intensive operation, limit their widespread use.…”