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. 2021 Jun 10:12:695230.
doi: 10.3389/fimmu.2021.695230. eCollection 2021.

Detailed Multiplex Analysis of SARS-CoV-2 Specific Antibodies in COVID-19 Disease

Siggeir F Brynjolfsson  1   2 , Hildur Sigurgrimsdottir  1   2 , Elin D Einarsdottir  2 , Gudrun A Bjornsdottir  1   2 , Brynja Armannsdottir  3 , Gudrun E Baldvinsdottir  3 , Agnar Bjarnason  2   4 , Olafur Gudlaugsson  4 , Sveinn Gudmundsson  5 , Sigurveig T Sigurdardottir  1   2 , Arthur Love  2   3 , Karl G Kristinsson  2   3 , Bjorn R Ludviksson  1   2
Affiliations

Detailed Multiplex Analysis of SARS-CoV-2 Specific Antibodies in COVID-19 Disease

Siggeir F Brynjolfsson et al. Front Immunol. .

Erratum in

Abstract

A detailed understanding of the antibody response against SARS-CoV-2 is of high importance, especially with the emergence of novel vaccines. A multiplex-based assay, analyzing IgG, IgM, and IgA antibodies against the receptor binding domain (RBD), spike 1 (S1), and nucleocapsid proteins of the SARS-CoV-2 virus was set up. The multiplex-based analysis was calibrated against the Elecsys® Anti-SARS-CoV-2 assay on a Roche Cobas® instrument, using positive and negative samples. The calibration of the multiplex based assay yielded a sensitivity of 100% and a specificity of 97.7%. SARS-CoV-2 specific antibody levels were analyzed by multiplex in 251 samples from 221 patients. A significant increase in all antibody types (IgM, IgG, and IgA) against RBD was observed between the first and the third weeks of disease. Additionally, the S1 IgG antibody response increased significantly between weeks 1, 2, and 3 of disease. Class switching appeared to occur earlier for IgA than for IgG. Patients requiring hospital admission and intensive care had higher levels of SARS-CoV-2 specific IgA levels than outpatients. These findings describe the initial antibody response during the first weeks of disease and demonstrate the importance of analyzing different antibody isotypes against multiple antigens and include IgA when examining the immunological response to COVID-19.

Keywords: COVID-19; IgA; IgG; IgM; SARS-CoV-2; antibodies; multiplex.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
SARS-CoV-2 antibody levels as measured by a multiplex based assay and calibrated against the Elecsys® Anti-SARS-CoV-2 assay (Roche diagnostics). (A) 100 serum samples previously analyzed by Elecsys® assay (depicted on the x axis as negative and positive), were received from the Department of Clinical Microbiology, and SARS-CoV-2 IgG antibodies against the N protein were analyzed blindly by multiplex (left panel). Right top panel depicts the single sample that had a SARS-CoV-2 IgG >4 sample/pool ratio for the N protein. Bottom right panel depicts the samples that showed a >2 but <4 than 4 sample/pool ratio by multiplex. (B) Left panel depicts 36 serum samples received in 2019 by the Department of Immunology. SARS-CoV-2 IgG antibodies against the N protein were analyzed by multiplex. Right panel depicts the serum/pool ratio of the serum samples against RBD, S1 and N proteins. Samples above the cut-off level are color coded.
Figure 2
Figure 2
SARS-CoV-2 specific antibody levels against the RBD, S1, and N proteins in 221 COVID-19 patients. (A) Depicting the mean and standard deviation in sample/pool ratio of SARS-CoV-2 antibody levels for IgM, IgG, and IgA for weeks 1, 2, 3 and over 3 weeks. (B) Venn diagram showing the number of patients with a ratio >4 for IgM, IgG, and IgA against the RBD, S1 and N proteins. Patients below the cut-off value of 4 in ratio against all proteins are depicted as neg in the bottom right corner of each diagram. 35 out of the 251 samples were below 4 for all the proteins, for the three antibody isotypes. (C) The IgA sample/pool ratio in COVID-19 outpatients (n=168), inpatients (n=40), and ICU patients (n=13). *, **, *** and **** correspond to p=<0.05, p=<0.01, p<0.001 and p=0.0001, respectively.
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