Detection of neutralizing antibodies against multiple SARS-CoV-2 strains in dried blood spots using cell-free PCR

An easily implementable serological assay to accurately detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies is urgently needed to better track herd immunity, vaccine efficacy and vaccination rates. Herein, we report the Split-Oligonucleotide Neighboring Inhibition Assay (SONIA) which uses real-time qPCR to measure the ability of neutralizing antibodies to block binding between DNA-barcoded viral spike protein subunit 1 and the human angiotensin-converting enzyme 2 receptor protein. The SONIA neutralizing antibody assay using finger-prick dried blood spots displays 91-97% sensitivity and 100% specificity in comparison to the live-virus neutralization assays using matched serum specimens for multiple SARS-CoV-2 variants-of-concern. The multiplex version of this neutralizing antibody assay, using easily collectable finger-prick dried blood spots, can be a valuable tool to help reveal the impact of age, pre-existing health conditions, waning immunity, different vaccination schemes and the emergence of new variants-of-concern. Neutralizing antibodies are critical for conferring immunity against SARS-CoV-2. Here, Dahn et al. report a PCR assay termed SONIA (Split-Oligonucleotide Neighboring Inhibition Assay) for measuring neutralizing antibodies against multiple SARS-CoV-2 strains in fingerprick dried blood spot samples.

Automated summary

A PCR assay called SONIA is reported for measuring neutralizing antibodies against multiple SARS-CoV-2 strains in fingerprick dried blood spot samples. The assay shows high sensitivity and specificity, and can accurately detect neutralizing antibodies and help understand the impact of immunity, vaccine efficacy, and new variants.