| Summary: | Immunization with recombinant HBV vaccine induces specific immune responses in human causing B lymphocytes to produce protective HBsAb, and to form memory B lymphocytes, thereby facilitating HBV immunity in the body. However, B lymphocytes heterogeneity and characteristics are not fully elucidated. In this study, we conducted high-throughput sequencing of BCR heavy chain CDR3 repertoires in 3 healthy volunteers before and after the third immunization with recombinant HBV vaccine. We used Roche 454 Genome Sequencer FLX system to perform a comparative analysis of IgM and IgG H chain CDR3 repertoires. First, we found that the diversity of IgG H chain CDR3 repertoires was 1/6 of IgM on average. Moreover, after the third immunization with HBV vaccine, the diversity of IgG H chain CDR3 repertoires was 1/26 of IgM on average. Second, we detected relatively high levels of HBsAbs in all the healthy volunteers after immunization with HBV vaccine. The volunteers shared a small number of CDR3 sequences before and after immunization, and among each other. However, we did not find completely identical BCR H chain CDR3 amino acid sequences in these volunteers. Lastly, after immunization with recombinant HBV vaccine, the volunteers showed high frequency of IgG H chain CDR3 amino acid sequences mostly resulting from rearrangements of IGHV, IGHD and IGHJ, suggesting that the mechanism of high frequency CDR3 generation might be associated with the maturation of IgG affinity (somatic hypermutation) during the recombinant HBV vaccine-induced B lymphocyte responses. This study identified the characteristics and changes of BCR CDR3 repertoires before and after immunization with HBV vaccine, and evaluated the performance of the sequencing technology for this application. Our findings provide a basis for further research in B lymphocyte generated HBsAb heterogeneity and monitoring the maintenance of memory B lymphocytes.
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