Accurate and sensitive detection of antibody to SARS-CoV-2 remains an essential component of the pandemic response. Measuring antibody that predicts neutralising activity and the vaccine response is an absolute requirement for laboratory-based confirmatory and reference activity. The viral receptor binding domain (RBD) constitutes the prime target antigen for neutralising antibody. A double antigen binding assay (DABA), providing the most sensitive format has been exploited in a novel hybrid manner employing a solid-phase S1 preferentially presenting RBD, coupled with a labelled RBD conjugate, used in a two-step sequential assay for detection and measurement of antibody to RBD (anti-RBD). This class and species neutral assay showed a specificity of 100 % on 825 pre COVID-19 samples and a potential sensitivity of 99.6 % on 276 recovery samples, predicting quantitatively the presence of neutralising antibody determined by pseudo-type neutralization and by plaque reduction. Anti-RBD is also measurable in ferrets immunised with ChadOx1 nCoV-19 vaccine and in humans immunised with both AstraZeneca and Pfizer vaccines. This assay detects anti-RBD at presentation with illness, demonstrates its elevation with disease severity, its sequel to asymptomatic infection and its persistence after the loss of antibody to the nucleoprotein (anti-NP). It also provides serological confirmation of prior infection and offers a secure measure for seroprevalence and studies of vaccine immunisation in human and animal populations. The hybrid DABA also displays the attributes necessary for the detection and quantification of anti-RBD to be used in clinical practice. An absence of detectable anti-RBD by this assay predicates the need for passive immune prophylaxis in at-risk patients.
© 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Rosadas, C., Khan, M., Parker, E., Marchesin, F., Katsanovskaja, K., Sureda-Vives, M., Fernandez, N., Randell, P., Harvey, R., Lilley, A., Harris, B., Zuhair, M., Fertleman, M., Ijaz, S., Dicks, S., Short, C., Quinlan, R., Taylor, G., Hu, K., McKay, P., Rosa, A., Roustan, C., Zuckerman, M., El Bouzidi, K., Cooke, G., Flower, B., Moshe, M., Elliott, P., Spencer, A., Lambe, T., Gilbert, S., Kingston, H., Baillie, J., Openshaw, P., Semple, M., Cherepanov, P., McClure, M., Tedder, R. & ISARIC4C Investigators 2022, 'Detection and quantification of antibody to SARS CoV 2 receptor binding domain provides enhanced sensitivity, specificity and utility', Journal of Virological Methods, 302, article no: 114475. http://dx.doi.org/10.1016/j.jviromet.2022.114475