Date Published: January 23, 2017
Publisher: Public Library of Science
Author(s): Long Ma, Xiaomei Wang, Xiaoying Bi, Jiezuan Yang, Bin Shi, Xiaoyan He, Rui Ma, Qingqing Ma, Xinsheng Yao, Isabelle A Chemin.
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.
Immunization with recombinant hepatitis B virus (HBV) vaccine helps prevent the incidence of HBV infection and hepatitis B. Since 1990s, China has introduced the immunization program for HBV vaccination, which has rapidly reduced the carriage rate of hepatitis B surface antigen (HBsAg). This program has greatly prevented HBV infection and also reduced the number of new cases [1,2]. In China, the recombinant HBV vaccine commonly containing 5ug HBsAg. Following immunization in humans, the fragments captured and hydrolyzed by antigen presenting cells combine with major histocompatibility complex class II (MHC-II) molecules to form MHC-II antigen complexes, which are then secreted to the cell surface and interact with CD4+ T helper cell surface antigen to stimulate CD4+ T cells activation and transformation into Th2 cells. Th2 cells react with B lymphocytes that can recognize HBsAg, and the activated B lymphocytes then differentiate into plasma cells and secrete protective HBsAb. Additionally, B lymphocytes can not only act as antigen-presenting cells to directly recognize HBsAg, but also interact with activated Th2 cells to produce HBsAb .
Theoretically, B lymphocyte diversity in each individual is approximately 1011 types . However, due to bias in each accession of families, the estimated B lymphocyte BCR in the circulatory system of a healthy individual is found to be approximately 106 types [19,20], which is still a very large number. It is a challenge to completely identify the detailed characteristics of BCR repertoire. In the recent 5 years, HTS has been able to preliminarily assess the basic BCR repertoire characteristics of an individual in a specific time point to: (1) estimate the size and changes in the overall BCR repertoire of an individual, (2) show the uniqueness of BCR repertoire in different B lymphocyte subsets, (3) compare variations in the BCR repertoires between elderly and youth in response to the same vaccine, (4) show characteristics of humoral immune response towards different antigens (e.g., bacterial antigens, viral antigens, and autoimmune antigens) and to search for high affinity antibodies against different antigens, and (5) monitor the lymphoma, minimal residual disease, and immune reconstitution after hematopoietic stem cell transplantation via B lymphocyte cloning to further diagnose and monitor the diseases .