Vaccine-mediated B cell responses to Staphylococcus aureus alpha-Hemolysin (Hla) and effect of different boosting intervals on functional antibodies (VAC7P.979)

Abstract

Abstract Primary exposure to an antigen generates, along with antibody-secreting cells (ASCs), a heterogeneous B-cell memory compartment that changes over time and that may respond in different ways when re-encountering the cognate antigen. The goal of this study is to characterize B-cell responses after priming and the effect of different boosting intervals on the differentiation and function of ASCs and memory B cells. We used an immunization strategy based on the Hla protein from S. aureus, adjuvanted with Alum, as it was previously reported to induce protective antibodies in several animal infection models. In this study we performed a time course analysis following one or two immunizations, two weeks apart. Mice immunized twice had increased magnitude and quality of the Hla-specific humoral responses compared to mice immunized once. Increasing the boosting interval from two weeks to 1 month or 4 months, Hla-specific humoral responses increased in term of total IgG, affinity, and Hla-neutralizing titers. Hla-specific ASCs and memory B cells persisted for 4 months after the last immunization. We recently set up a method to identify Hla-specific B cells by flow cytometry (FACS).In the future we intend to further characterize their phenotype and to extend these analyses to Hla-specific memory B cells induced by different adjuvant formulations. This work will provide new insights in the memory B-cell compartment that might benefit the design of new vaccination strategies.