The impact of vaccination on the memory B cell subset repertoire
Creators: name: Muir, Luke
Publisher: name: Imperial College London
Year: 2018

description: Human memory B cells play a vital role in the long-term protection of the host from pathogenic rechallenge. Successful vaccines readily induce long-lived B cell memory that is maintained for decades. Recent observations have shown that vaccination or infection do not produce a homogenous population of memory cells but a constellation of subsets depending on the kinetic time point, location, and type of vaccination or infection. Studies of these subsets in murine models have recently highlighted the importance of the IgM+ memory B cell subset in mediating long term protection by providing rapid and flexible secondary responses. However, the presence and role of memory B cell subsets in humans is still poorly understood. This thesis is based on the premise that previous analysis of memory B cell repertoire responses in unsorted B cells from the blood, with a focus on IgG+ responses, provides an incomplete view of B cell memory development. This thesis will investigate how vaccination with the protective tetanus toxin containing Boostrix-IPV vaccine impacts the antigen specific memory B cell response across different subsets. Subsequently, the memory B cell subset response to a homologous prime-boost HIV-1 envelope vaccine schedule will be investigated. Understanding differential responses of these memory B cell subsets to vaccination may prove critical in the creation of novel, effective vaccines to HIV-1. In order to study memory B cells, expansion and differentiation culture protocols are often employed for clonal proliferation and activation of quiescent memory B cells. Despite publication of numerous protocols for bulk memory B cell culture there is no literature on optimised conditions for the study of memory B cell subsets. By using a novel design of experiments approach the optimal memory B cell expansion and differentiation conditions for human memory B cell subsets are defined and the resultant cell populations characterised by IgH sequencing and flow cytometry. The optimised conditions were subsequently utilised to induce expansion and differentiation of memory B cell subsets pre-and post-vaccination and the antigen specific memory B cells assessed via ELISpot assays. Interestingly the long-lived tetanus toxin specific response appears to preferentially reside in the CD27+ IgM+ IgD+ and IgM+ IgD- populations whilst booster vaccination induces a mixed population of both CD27+ IgM+ IgD- and IgG+ memory B cells. Similarly, vaccination with HIV-1 envelope protein induces a mixed population of both CD27+ IgM+ IgD- and IgG+ memory B cells. Overall the optimised memory B cell culture conditions work equally for all memory B cell isotypes, inducing multiple rounds of memory B cell proliferation and differentiation, and do not alter the Ig genotype of the stimulated cells. Therefore, these novel expansion conditions offer a robust platform for investigating the response of memory B cell subsets to vaccination and/or infection. Analysis of vaccine responses show that HIV-1 envelope vaccination induces a similar memory B cell subset profile to the protective Boostrix-IPV vaccine and similar to results seen in murine models IgM+ memory B cell subsets may be important in mediating long term immunity.