Evaluation of a New Spike (S)-Protein-Based Commercial Immunoassay for the Detection of Anti-SARS-CoV-2 IgG.

Kirsten Alexandra Eberhardt,Philipp Schommers,Eva Heger,Max Augustin,Felix Dewald,Lutz Gieselmann,Maike Wirtz,Franziska Kleipass,Clara Lehmann,Wibke Johannis,Florian Klein,Manuel Koch,Henning Gruell,Karl August Brensing,Kanika Vanshylla,Roman-Ulrich Müller,Veronica Di Cristanziano

doi:10.3390/microorganisms9040733

Abstract

Background: The investigation of the antibody response to SARS-CoV-2 represents a key aspect in facing the COVID-19 pandemic. In the present study, we compared the new Immundiagnostik IDK® anti-SARS-CoV-2 S1 IgG assay with four widely-used commercial serological assays for the detection of antibodies targeting S (spike) and NC (nucleocapsid) proteins. Methods: Serum samples were taken from an unbiased group of convalescent patients and from a negative control group. Sample were simultaneously analyzed by the new Immundiagnostik IDK® anti-SARS-CoV-2 S1 IgG assay, by the DiaSorin LIAISON® SARS-CoV-2 S1/S2 IgG assay, and by the Euroimmun anti-SARS-CoV-2 S1 IgG ELISA. Antibodies binding NC were detected by the Abbott SARS-CoV-2 IgG assay and by the pan-immunoglobulin immunoassay Roche Elecsys® anti-SARS-CoV-2. Moreover, we investigated samples of a group of COVID-19 convalescent subjects that were primarily tested S1 IgG non-reactive. Samples were also tested by live virus and pseudovirus neutralization tests. Results: Overall, the IDK® anti-SARS-CoV-2 S1 IgG assay showed the highest sensitivity among the evaluated spike (S) protein-based assays. Additionally, the Immundiagnostik assay correlated well with serum-neutralizing activity. Conclusions: The novel IDK® anti-SARS-CoV-2 S1 IgG assay showed high sensitivity and specificity, representing a valid option for use in the routine diagnostic.

Highlights

The investigation of the humoral response to SARS-CoV-2 represents a key aspect in facing the COVID-19 pandemic
We investigated two subgroups of this cohort: group A included all convalescent patients with previous SARS-CoV-2 infection who attended the clinic between August and September 2020, regardless of their IgG ratio values
Group B included a group of individuals who attended the clinic between April and July 2020 and were tested IgG negative or borderline in our routine screening using the Euroimmun S1 IgG enzyme-linked immunosorbent assays (ELISA) despite prior SARS-CoV-2 infection

Summary

Introduction

The investigation of the humoral response to SARS-CoV-2 represents a key aspect in facing the COVID-19 pandemic. Virus neutralization (VN) assays, based on live virus or pseudovirus, are considered the gold standard to conclude on the presence and quantity of specific neutralizing antibodies. They are time intensive and require biosafety level 2 or 3 facilities [6]. Various methods for antibody detection are available, including chemiluminescence immunoassays (CLIA), chemiluminescent microparticle immunoassays (CMIA), electrochemiluminescence immunoassays (ECLIA), and enzyme-linked immunosorbent assays (ELISA) They can be divided into assays recognizing specific anti-SARS-CoV-2 antibodies against different antigens, including the spike (S) protein or components thereof (e.g., S1/S2 domains or the receptor-binding domain [RBD]) and the nucleocapsid (NC) protein [8]. We compared the new Immundiagnostik IDK®anti-SARS-CoV-2 S1 IgG assay with four widely-used commercial serological assays for the detection of antibodies targeting S (spike) and NC (nucleocapsid) proteins

Methods

Results

Conclusion