Quantification of antibody avidities and accurate detection of SARS-CoV-2 antibodies in serum and saliva on plasmonic substrates.
Accurate assays for the detection of antibodies to SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) are essential for the control of the COVID-19 (coronavirus disease 2019) pandemic. Here, we report antibody and antibody-avidity assays, relying on near-infrared-fluorescence amplification by nanostructured plasmonic gold substrates, for the simultaneous detection of antibodies to the S1 subunit of the spike protein and to the receptor binding domain of SARS-CoV-2 in human serum and saliva, and for quantifying immunoglobulin avidities against coronavirus antigens from SARS-CoV-2, SARS-CoV-1 and the common-cold viruses OC43, HKU1, NL63 and 229E. The antibody assay detected immunoglobulin M in 87% (52 of 60) COVID-19-positive serum samples collected 6 or more days after symptom onset (and the immunoglobulins M and G in all 33 samples collected at least 15 days after symptom onset), and correctly classified 456 out of the 457 COVID-19-negative serum samples tested (424 of them collected before the pandemic, including 73 that were positive for other viruses). We used the antibody-avidity assay to study antibody-maturation patterns, anamnestic responses, and cross-immunity to the common-cold coronaviruses.
Liu, T; Hsiung, J; Zhao, S; Kost, J; Sreedhar, D; Hanson, CV; Olson, K; Keare, D; Chang, ST; Bliden, KP; Gurbel, PA; Tantry, US; Roche, J; Press, C; Boggs, J; Rodriguez-Soto, JP; Montoya, JG; Tang, M; Dai, H
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