Polio (IPV) booster immunization, Ex vivo stimulation of day 21 PBMCs

In eight adults, two to five decades after their childhood immunization. IPV immunization elicited highly skewed plasma IgG recall repertoires, dominated by a small subset of total antibody lineages that were detectable prior to boosting. These IgG lineages spiked logarithmically in abundance and potently cross-neutralized multiple PV serotypes in vitro. Notably, these dominant plasma IgG lineages were clonally linked to class-switched MBCs that circulated in blood 21 days post-boost and bore heavily mutated VH and VL variable region genes. Importantly, IPV-primed ex vivo B-cell cultures yielded clonal expansions that mirrored the dominant post-boost plasma IgG lineages in vivo, providing an in vitro mechanistic correlate of recall immunity. Together these findings demonstrate a decades-long interconnectivity between persistent MBC clones and the serological IgG repertoire. They further highlight the central role of immunological imprinting, whereby cross-reactive MBC clones, originally primed in childhood, can be reactivated to dominate the circulating IgG recall response more than 50 years after initial exposure.