SARS-CoV-2 Serum Neutralization Assay: A Traditional Tool for a Brand-New Virus.

Giulia Matusali,Daniele Lapa,Giuseppe Ippolito,Silvia Meschi,Maria Capobianchi,Roberta Gagliardini,Andrea Antinori,Emanuele Nicastri,Francesca Colavita,Licia Bordi,Angela Corpolongo,Concetta Castilletti,Pierluca Piselli

doi:10.3390/v13040655

Giulia Matusali, Daniele Lapa + Show 11 more

Open Access

https://doi.org/10.3390/v13040655

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Abstract

SARS-CoV-2 serum neutralization assay represents the gold standard for assessing antibody-mediated protection in naturally infected and vaccinated individuals. In the present study, 662 serum samples collected from February 2020 to January 2021 from acute and convalescent COVID-19 patients were tested to determine neutralizing antibody (NAb) titers using a microneutralization test (MNT) for live SARS-CoV-2. Moreover, anti-SARS-CoV-2 IgG, IgA, and IgM directed against different viral antigens were measured by high-throughput automated platforms. We observed higher levels of NAbs in elderly (>60 years old) individuals and in patients presenting acute respiratory distress syndrome. SARS-CoV-2 NAbs develop as soon as five days from symptom onset and, despite a decline after the second month, persist for over 11 months, showing variable dynamics. Through correlation and receiver operating characteristic (ROC) curve analysis, we set up a testing algorithm, suitable for the laboratory workload, by establishing an optimal cutoff value of anti-SARS-CoV-2 IgG for convalescent plasma donors to exclude from MNT samples foreseen to have low/negative NAb titers and ineligible for plasma donation. Overall, MNT, although cumbersome and not suitable for routine testing of large sample sizes, remains the reference tool for the assessment of antibody-mediated immunity after SARS-CoV-2 infection. Smart testing algorithms may optimize the laboratory workflow to monitor antibody-mediated protection in COVID-19 patients, plasma donors, and vaccinated individuals.

Highlights

When the novel coronavirus, first identified in December 2019 in Wuhan, China, was recognized as the etiologic agent of a severe acute respiratory syndrome, molecular assays were the first tool developed and commercialized for the diagnostic response to the outbreak
Through correlation and receiver operating characteristic (ROC) curve analysis, we set up a testing algorithm, suitable for the laboratory workload, by establishing an optimal cutoff value of anti-SARS-CoV-2 IgG for convalescent plasma donors to exclude from microneutralization test (MNT) samples foreseen to have low/negative neutralizing antibody (NAb) titers and ineligible for plasma donation
763 serum samples from 662 symptomatic COVID-19 patients were analyzed to explore the correlation of neutralizing antibody response with personal and clinical characteristics of the patients, as well as the duration of neutralizing antibody response

Summary

Introduction

First identified in December 2019 in Wuhan, China, was recognized as the etiologic agent of a severe acute respiratory syndrome (later named SARS-CoV-2), molecular assays were the first tool developed and commercialized for the diagnostic response to the outbreak. These assays measure acute infection, detecting viral RNA in respiratory samples, and are essential for individuals who require healthcare by tracing the infection in the population and reducing viral transmission. For SARS-CoV-2 seroprevalence and antibody kinetics studies, high-throughput platforms (i.e., enzyme-linked immunosorbent assay (ELISA) and chemiluminescent immunoassay (CLIA)) able to detect IgG, as well as IgA and IgM, have been widely used, allowing for faster turnaround times and easy expansion of testing capacity

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