Convergent Features and Cross-reactivity Patterns in Human Memory B-cell Repertoires Against Seasonal and Avian Influenza Strains 9182

Abstract Description Memory B-cell (MBC) repertoires are key to understanding adaptive immunity against influenza, particularly the interplay between vaccine-elicited responses and cross-reactivity to zoonotic strains. We analyzed repertoires from peripheral blood of 53 recent flu vaccinees and 20 unvaccinated healthy donors using a DNA-tagged multi-antigen panel approach combined with droplet-based sequencing to reconstruct heavy- and light-chain antibody (Ab) sequences with their binding specificity and breadth, from 13,138 cells. MBCs were sorted against 18 influenza hemagglutinins (HAs), spanning recent human H1 and H3 strains and avian and bat H4–H18. Recent vaccinees showed higher proportions of strain-specific Abs, particularly for H1, while unvaccinated donors displayed broader within-group cross-reactivity across group 1 or 2 HAs. H1- and H3-binding Abs exhibited distinct V-gene enrichments, specific CDR3 motifs, and constrained CDR3 lengths, recurring across donors. Additionally, we observed within-donor convergence, where clones derived from different germline V gene alleles were selected toward similar binding profiles. Abs binding to non-human HAs predominantly originated from expanded clones that showed cross-reactivity with human HAs. These findings reveal conserved and convergent features of HA-specific MBC repertoires, providing insight for vaccine development and evaluation of cross-reactivity to potential avian influenza threats. Funding Sources NIAID/NIH Contract:75N93021C00015 Topic Categories Vaccines and Immunotherapy (VAC)