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Dimeric IgA is a specific biomarker of recent SARS-CoV-2 infection

Drummer HE, Van H, Klock E, Zheng S, Wei Z, Boo I, Center RJ, Li F, Bhat P, Ffrench R, Lau JS, McMahon J, Laeyendecker O, Fernandez RE, Manabe YC, Klein SL, Quinn TC, Anderson DA.

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  • Published 28 Jun 2021

  • DOI 10.1101/2021.06.28.21259671

Abstract

Current tests for SARS-CoV-2 antibodies (IgG, IgM, IgA) cannot differentiate recent and past infections. We describe a point of care, lateral flow assay for SARS-CoV-2 dIgA based on the highly selective binding of dIgA to a chimeric form of secretory component (CSC), that distinguishes dIgA from monomeric IgA. Detection of specific dIgA uses a complex of biotinylated SARS-CoV-2 receptor binding domain and streptavidin-colloidal gold. SARS-CoV-2-specific dIgA was measured both in 112 cross-sectional samples and a longitudinal panel of 362 plasma samples from 45 patients with PCR-confirmed SARS-CoV-2 infection, and 193 discrete pre-COVID-19 or PCR-negative patient samples. The assay demonstrated 100% sensitivity from 11 days post-symptom onset, and a specificity of 98.2%. With an estimated half-life of 6.3 days, dIgA provides a unique biomarker for the detection of recent SARS-CoV-2 infections with potential to enhance diagnosis and management of COVID-19 at point-of-care.