Direct capture of neutralized RBD enables rapid point-of-care assessment of SARS-CoV-2 neutralizing antibody titer. Connelly et al.
Summary: Neutralizing antibody (NAb) titer is a key biomarker of protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but point-of-care methods for assessing NAb titer are not widely available. Here, we present a lateral flow assay that captures receptor binding domain (RBD) that has been neutralized from binding angiotensin converting enzyme 2 (ACE2). Quantification of neutralized RBD in this assay correlates with NAb titer from vaccinated and convalescent patients. This methodology demonstrated superior performance in assessing NAb titer compared to either measurement of total anti-spike immunoglobulin G titer or quantification of the absolute reduction in binding between ACE2 and RBD. Our testing platform has the potential for mass deployment to aid in determining at population scale the degree of protective immunity individuals may have following SARS-CoV-2 vaccination or infection, and can enable simple at-home assessment of NAb titer. Supplemental data files that show (Table S1): Human plasma SARS-CoV-2 antibody measurement averages. Human plasma sample source information, total anti-spike IgG, pseudoviral neutralization ID50 titer, and LFA signals. (Table S2): Antibody measurement technical replicate data and smartphone image capture comparison. Technical replicates for select samples showing precision and reproducibility of total anti-spike IgG, pseudoviral neutralization ID50 titer, and LFA signals. Also shown are comparisons of signal intensities quantified from images taken with two different smartphone brands. (Table S3): Sensitivity and specificity for identifying NAb titers. Sensitivity and specificity values used in ROC-AUC analysis for comparing LFA N/I ratio diagnostic performance to anti-spike total IgG ELISA and LFA loss of I signal. This data is from the paper titled Direct capture of neutralized RBD enables rapid point-of-care assessment of SARS-CoV-2 neutralizing antibody titer.