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A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG

Knowledge of the antibody-mediated immune response to SARS-CoV-2 is crucial to understand virus immunogenicity, establish seroprevalence, and determine whether subjects or recovered patients are at risk for infection/reinfection and would therefore benefit from vaccination. Here, we describe a novel...

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Autores principales: Zarletti, Gianpaolo, Tiberi, Massimo, De Molfetta, Veronica, Bossù, Maurizio, Toppi, Elisa, Bossù, Paola, Scapigliati, Giuseppe
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695166/
https://www.ncbi.nlm.nih.gov/pubmed/33171590
http://dx.doi.org/10.3390/v12111274
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author Zarletti, Gianpaolo
Tiberi, Massimo
De Molfetta, Veronica
Bossù, Maurizio
Toppi, Elisa
Bossù, Paola
Scapigliati, Giuseppe
author_facet Zarletti, Gianpaolo
Tiberi, Massimo
De Molfetta, Veronica
Bossù, Maurizio
Toppi, Elisa
Bossù, Paola
Scapigliati, Giuseppe
author_sort Zarletti, Gianpaolo
collection PubMed
description Knowledge of the antibody-mediated immune response to SARS-CoV-2 is crucial to understand virus immunogenicity, establish seroprevalence, and determine whether subjects or recovered patients are at risk for infection/reinfection and would therefore benefit from vaccination. Here, we describe a novel and simple cell-ELISA specifically designed to measure viral spike S1-specific IgG produced in vitro by B cells in peripheral blood mononuclear cell (PBMC) cultures from a cohort of 45 asymptomatic (n = 24) and symptomatic (n = 21) individuals, with age ranging from 8 to 99 years. All subjects underwent ELISA serological screening twice, at the same time as the cell-ELISA (T2) as well as 35–60 days earlier (T1). Cryopreserved PBMCs of healthy donors obtained years before the COVID-19 pandemic were also included in the analysis. The preliminary results presented here show that out of 45 tested subjects, 16 individuals (35.5%) were positive to the cell-ELISA, 11 (24.5%) were concomitantly positive in the serological screening (T1 and/or T2), and only one person was exclusively positive in ELISA (T1) and negative in cell-ELISA, though values were close to the cutoff. Of note, five individuals (11.2%) tested negative in ELISA but positive in cell-ELISA and thus, they appear to have circulating B cells that produce antibodies against SARS-CoV-2, likely at levels that are undetectable in the serum, which challenges the negative results of the serological screening. The relative level of in vitro secreted IgG was measurable in positive subjects, ranging from 7 to 50 ng/well. Accordingly, all anti-SARS-CoV-2 antibody-positive subjects previously reported moderate to severe symptoms attributable to COVID-19, even though the RT-PCR data were rarely available to confirm viral infection. Overall, the described cell-ELISA might be an effective method for detecting subjects who encountered the virus in the past, and thus helpful to improve serological ELISA tests in the case of undetectable/equivocal circulating IgG levels, and a suitable and improved tool to better evaluate SARS-CoV-2-specific humoral immunity in the COVID-19 pandemic.
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spelling pubmed-76951662020-11-28 A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG Zarletti, Gianpaolo Tiberi, Massimo De Molfetta, Veronica Bossù, Maurizio Toppi, Elisa Bossù, Paola Scapigliati, Giuseppe Viruses Brief Report Knowledge of the antibody-mediated immune response to SARS-CoV-2 is crucial to understand virus immunogenicity, establish seroprevalence, and determine whether subjects or recovered patients are at risk for infection/reinfection and would therefore benefit from vaccination. Here, we describe a novel and simple cell-ELISA specifically designed to measure viral spike S1-specific IgG produced in vitro by B cells in peripheral blood mononuclear cell (PBMC) cultures from a cohort of 45 asymptomatic (n = 24) and symptomatic (n = 21) individuals, with age ranging from 8 to 99 years. All subjects underwent ELISA serological screening twice, at the same time as the cell-ELISA (T2) as well as 35–60 days earlier (T1). Cryopreserved PBMCs of healthy donors obtained years before the COVID-19 pandemic were also included in the analysis. The preliminary results presented here show that out of 45 tested subjects, 16 individuals (35.5%) were positive to the cell-ELISA, 11 (24.5%) were concomitantly positive in the serological screening (T1 and/or T2), and only one person was exclusively positive in ELISA (T1) and negative in cell-ELISA, though values were close to the cutoff. Of note, five individuals (11.2%) tested negative in ELISA but positive in cell-ELISA and thus, they appear to have circulating B cells that produce antibodies against SARS-CoV-2, likely at levels that are undetectable in the serum, which challenges the negative results of the serological screening. The relative level of in vitro secreted IgG was measurable in positive subjects, ranging from 7 to 50 ng/well. Accordingly, all anti-SARS-CoV-2 antibody-positive subjects previously reported moderate to severe symptoms attributable to COVID-19, even though the RT-PCR data were rarely available to confirm viral infection. Overall, the described cell-ELISA might be an effective method for detecting subjects who encountered the virus in the past, and thus helpful to improve serological ELISA tests in the case of undetectable/equivocal circulating IgG levels, and a suitable and improved tool to better evaluate SARS-CoV-2-specific humoral immunity in the COVID-19 pandemic. MDPI 2020-11-08 /pmc/articles/PMC7695166/ /pubmed/33171590 http://dx.doi.org/10.3390/v12111274 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Brief Report
Zarletti, Gianpaolo
Tiberi, Massimo
De Molfetta, Veronica
Bossù, Maurizio
Toppi, Elisa
Bossù, Paola
Scapigliati, Giuseppe
A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title_full A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title_fullStr A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title_full_unstemmed A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title_short A Cell-Based ELISA to Improve the Serological Analysis of Anti-SARS-CoV-2 IgG
title_sort cell-based elisa to improve the serological analysis of anti-sars-cov-2 igg
topic Brief Report
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695166/
https://www.ncbi.nlm.nih.gov/pubmed/33171590
http://dx.doi.org/10.3390/v12111274
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