Plasma cell immunoglobulin heavy chain repertoire dynamics before and after tetanus booster vaccination

Antibody sequence repertoire analysis of plasma cells (PC) isolated before and 1 week after a vaccine provides time-specific snapshots of the antibody response. Comparison of the immunoglobulin (Ig) sequences pre- and post-vaccination allows analysis of maturation over time and identification of antigen specific Ig. Here we compare the Ig heavy chain (Ig-H) repertoire of circulating PCs isolated from 10⁹ peripheral blood mononuclear cells (PBMC) collected by apheresis 1 week after a tetanus toxoid vaccine booster with the Ig-H repertoire of PCs collected 2 and 11 weeks prior to the booster. A total of 21,060 unique Ig nucleotide sequences encoding 14,307 unique heavy chain complementarity determining region 3 (CDR-H3) amino acid sequences, also called clonotypes, were identified. Only 466 clonotypes (3.3%) were present at all 3 time points. In contrast, 90% of the 30 highest frequency CDR-H3 regions at +1w were also identified at another time point and 50% were present at all time points, suggesting the rapid expansion of a memory B cell population. The tetanus toxoid specificity of the CDR-H3 region with the 7th highest frequency at +1w was confirmed using immunoprecipitation and mass spectroscopy, and two public tetanus toxoid-specific CDR-H3 regions were also overrepresented at +1w. In summary, we have used the tetanus vaccine model system to demonstrate that bulk PC Ig repertoire analysis can identify PC populations that expand and mature following antigen exposure. The application of this approach before and after clinical infections should advance our understanding of clinical protection and facilitate vaccine design.