Multiplex ACE2-RBD Binding Inhibition Assay: An Integrated Tool for Assessing Neutralizing Antibodies to SARS-CoV-2 Variants and Protection against Breakthrough Infections

SARS-CoV-2 remains a significant health threat due to its high infection and mutation rates. The emergence of new variants of concern poses challenges as they can lead to immune escape mutations, potentially reducing the efficacy of vaccines and antibody therapeutics. The receptor binding domain (RBD) of SARS-CoV-2 is particularly noteworthy as it is both the most rapidly evolving domain and the principal target of neutralizing antibodies. As an alternative to time-consuming and expensive neutralization assays, we have developed a bead-based multiplex surrogate virus neutralization test based on ACE2-RBD binding inhibition. We demonstrated how our high-throughput assay allows us to simultaneously assess anti-RBD neutralizing antibodies levels against multiple SARS-CoV-2 variants, providing data that is consistent with the gold-standard live virus neutralization assay. The utility of this assay was demonstrated by applying it to a large French population cohort to demonstrate that hybrid immunity (generated by a combination of vaccination and infection) is associated with protection against infection with the Omicron BA.1 and BA.2 lineages of SARS-COV-2.