Signatures of the neutralizing dengue virus-reactive memory B cell repertoire identified by multiplexed envelope dimer probes

Sequential dengue virus (DENV) infection is thought to induce long-lived protection against dengue. However, little is known about the specificity, phenotype, and repertoire of the enduring B cell response due to limitations in high-throughput methods. We used stabilized DENV envelope (E) dimers as probes for in-depth memory B cell repertoire characterization using two complementary sequencing strategies. Using Rapid Assembly, Transfection, and Production of Immunoglobulins (RATP-Ig), we isolated 227 DENV2 E dimer-specific memory B cells from an immune donor, of which 87% bound at least two serotypes, 68% bound the fusion loop (FL-sensitive), and 42% were neutralizing. Among the most neutralizing, cross-binding antibodies, the FL-sensitive antibodies had weaker but broad neutralization, including to other flaviviruses, whereas FL-‘agnostic’ antibodies mapped to E domain II and III and were potently neutralizing, but only against one or two serotypes. Competitive binding of the DENV1-4 E dimers distinguished the more potently neutralizing FL-agnostic antibodies and broad and potent anti (α)- envelope dimer epitope (EDE) antibodies from the low-quality FL-sensitive antibodies. Further, analysis of the heavy chain complementarity determining region 3 (CDRH3) showed FL-sensitive and α-EDE antibodies were more negatively charged, but α-EDE antibodies were distinguished by longer and more aromatic CDRH3s. We then demonstrated how oligonucleotide-tagged DENV1-4 dimers and proteogenomic single-cell B cell receptor sequencing (LIBRA-seq) could identify memory B cells predicted to have potent neutralization based on DENV-binding and CDRH3 physiochemical properties. This study provides insight into the secondary DENV-specific B cell repertoire and approaches for identifying protective antibodies as part of large-screening efforts.