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      Evaluation of a novel multiplexed assay for determining IgG levels and functional activity to SARS-CoV-2

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          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Highlights

          • Simultaneous measurement of IgG to several SARS-CoV-2 antigens.
          • Sensitive and specific assay for Trimeric spike, RBD and Nucleocapsid antigen.
          • IgG values correlates well with pseudoneutralization measured on the same platform.
          • No pseudoneutralisation from cross reactive seasonal coronoavirus antibodies.

          Abstract

          Background

          The emergence of SARS-CoV-2 has led to the development of serological assays that could aid in an understanding of the burden of COVID-19 disease. Many available tests lack rigorous evaluation and therefore results may be misleading.

          Objectives

          The aim of this study was to assess the performance of a novel multiplexed immunoassay for the simultaneous detection of antibodies against SARS-CoV-2 trimeric spike (S), spike receptor binding domain (RBD), spike N terminal domain and nucleocapsid antigen and a novel pseudo-neutralisation assay.

          Methods

          A multiplexed solid-phase chemiluminescence assay (Meso Scale Discovery) was evaluated for the simultaneous detection of IgG binding to four SARS-CoV-2 antigens and the quantification of antibody-induced ACE-2 binding inhibition (pseudo-neutralisation assay). Sensitivity was evaluated with a total of 196 COVID-19 serum samples (169 confirmed PCR positive and 27 anti-nucleocapsid IgG positive) from individuals with mild symptomatic or asymptomatic disease. Specificity was evaluated with 194 control serum samples collected from adults prior to December 2019.

          Results

          The specificity and sensitivity of the binding IgG assay was highest for S protein with a specificity of 97.4 % and sensitivity of 96.2 % for samples taken 14 days and 97.9 % for samples taken 21 days following the onset of symptoms. IgG concentration to S and RBD correlated strongly with percentage inhibition measured by the pseudo-neutralisation assay.

          Conclusion

          Excellent sensitivity for IgG detection was obtained over 14 days since onset of symptoms for three SARS-CoV-2 antigens (S, RBD and N) in this multiplexed assay which can also measure antibody functionality.

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          Most cited references 4

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          Diagnostic tests 4: likelihood ratios.

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            Comparison of four new commercial serologic assays for determination of SARS-CoV-2 IgG

            Highlights • 4 new SARS-CoV-2 IgG assays can identify individuals with past SARS-CoV-2 infection • Combination of two different assays may increase sensitivity and specificity
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              Is Open Access

              Relationship between Anti-Spike Protein Antibody Titers and SARS-CoV-2 In Vitro Virus Neutralization in Convalescent Plasma

              Newly emerged pathogens such as SARS-CoV-2 highlight the urgent need for assays that detect levels of neutralizing antibodies that may be protective. We studied the relationship between anti-spike ectodomain (ECD) and anti-receptor binding domain (RBD) IgG titers, and SARS-CoV-2 virus neutralization (VN) titers generated by two different in vitro assays using convalescent plasma samples obtained from 68 COVID-19 patients, including 13 who donated plasma multiple times. Only 23% (16/68) of donors had been hospitalized. We also studied 16 samples from subjects found to have anti-spike protein IgG during surveillance screening of asymptomatic individuals. We report a strong positive correlation between both plasma anti-RBD and anti-ECD IgG titers, and in vitro VN titer. Anti-RBD plasma IgG correlated slightly better than anti-ECD IgG titer with VN titer. The probability of a VN titer ≥160 was 80% or greater with anti-RBD or anti-ECD titers of ≥1:1350. Thirty-seven percent (25/68) of convalescent plasma donors lacked VN titers ≥160, the FDA-recommended level for convalescent plasma used for COVID-19 treatment. Dyspnea, hospitalization, and disease severity were significantly associated with higher VN titer. Frequent donation of convalescent plasma did not significantly decrease either VN or IgG titers. Analysis of 2,814 asymptomatic adults found 27 individuals with anti-RBD or anti-ECD IgG titers of ≥1:1350, and evidence of VN ≥1:160. Taken together, we conclude that anti-RBD or anti-ECD IgG titers can serve as a surrogate for VN titers to identify suitable plasma donors. Plasma anti-RBD or anti-ECD titer of ≥1:1350 may provide critical information about protection against COVID-19 disease.
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                Author and article information

                Contributors
                Journal
                J Clin Virol
                J. Clin. Virol
                Journal of Clinical Virology
                The Author(s). Published by Elsevier B.V.
                1386-6532
                1873-5967
                2 August 2020
                2 August 2020
                Affiliations
                [a ]Great Ormond Street Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1 EH, UK
                [b ]Great Ormond Street Children’s Hospital NHS Foundation Trust, Great Ormond Street, London, WC1N 3JH, UK
                Author notes
                [* ]Corresponding author at: Great Ormond Street Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1 EH, UK. d.goldblatt@ 123456ucl.ac.uk
                Article
                S1386-6532(20)30314-0 104572
                10.1016/j.jcv.2020.104572
                7396134
                © 2020 The Author(s). Published by Elsevier B.V.

                Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

                Categories
                Article

                Microbiology & Virology

                sars-cov-2, covid19, immunology, immunoassays

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