Evaluation of serological anti-SARS-CoV-2 chemiluminescent immunoassays correlated to live virus neutralization test, for the detection of anti-RBD antibodies as a relevant alternative in COVID-19 large-scale neutralizing activity monitoring

• Published in: Clinical immunology (Orlando, Fla.) Vol. 234; p. 108918
• Main Authors: Cristiano, Antonio, Pieri, Massimo, Sarubbi, Serena, Pelagalli, Martina, Calugi, Graziella, Tomassetti, Flaminia, Bernardini, Sergio, Nuccetelli, Marzia
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2022
• Subjects: Adult; Aged; Aged, 80 and over; Animals; Anti-SARS-CoV-2 antibodies; Antibodies, Neutralizing - immunology; Antibodies, Viral - immunology; Cell Line; Chlorocebus aethiops; COVID-19; COVID-19 - immunology; COVID-19 Serological Testing - methods; Female; Humans; Immunoassay - methods; Live virus neutralization test; Male; Middle Aged; Neutralization Tests - methods; Protein Binding - immunology; SARS-CoV-2; SARS-CoV-2 - immunology; Serological immunoassays; Spike Glycoprotein, Coronavirus - immunology; Vero Cells; Young Adult; COVID-19; Live virus neutralization test; SARS-CoV-2; Anti-SARS-CoV-2 antibodies; Serological immunoassays
• ISSN: 1521-6616; 1521-7035; 1521-7035
• DOI: 10.1016/j.clim.2021.108918

The Spike-Receptor Binding Domain (S-RBD) is considered the most antigenic protein in SARS-CoV-2 and probably the key player in SARS-CoV-2 immune response. Quantitative immunoassays may help establish an anti-RBD Abs threshold as an indication of protective immunity. Since different immunoassays are commercial, the standard reference method for the neutralizing activity is the live Virus Neutralization Test (VNT). In this study, anti-RBD IgG levels were detected with two chemiluminescent immunoassays in paucisymptomatic, symptomatic and vaccinated subjects, and their neutralizing activity was correlated to VNT titer, using SARS-CoV-2 original and British variant strains. Both immunoassays confirmed higher anti-RBD Abs levels in vaccinated subjects. Furthermore, despite different anti-RBD Abs median concentrations between the immunoassays, a strong positive correlation with VNT was observed. In conclusion, although the SARS-CoV-2 immune response heterogeneity, the use of immunoassays can help in large-scale monitoring of COVID-19 samples, becoming a valid alternative to VNT test for diagnostic routine laboratories. •The Spike-Receptor Binding Domain is one of the most antigenic protein in COVID-19•Anti-RBD Abs levels as an indication of protective SARS-CoV-2 immunity•Quantitative Anti-RBD immunoassays correlated to live virus neutralization analysis•Higher anti-RBD detected in vaccinated subjects than recovered COVID-19 patients•Anti-RBD immunoassays as a large-scale alternative to VNT in routine laboratories