Interrogating antiviral antibody responses with multiplexed, high-throughput serum assays

The COVID-19 pandemic underscored the need for rapid assessments of how our immune systems and medical interventions collaborate to generate antibodies against emerging viruses. Existing antibody-measuring techniques, however, are limited in their ability to probe antibodies' recognition of multiple, native-conformation antigens simultaneously. To increase the throughput and multiplexability of antibody profiling, we developed Antibody Reactivity Characterization by Antibody-Dependent Enhancement (ARCADE). This assay employs an antigen-agnostic Fc receptor-expressing cell line and a library of antigen-displaying, genetically barcoded lentiviruses that, when mixed with serum, infect cells and integrate their barcodes at rates reflecting the relative abundances and affinities of the antigen-specific antibodies present. Verified using sera from COVID-19-convalescent and -vaccinated donors, ARCADE delivers insights that align with and expand upon those offered by established immunoassays. ARCADE highlights, for example, how an mRNA-based vaccine elicits broader and stronger antibody responses than an adenovirus vector-based vaccine. With ARCADE, we can comprehensively assess how infection and vaccination impact antiviral antibody repertoires over time and across patient populations.