Pneumonia is the leading infectious cause of death in children worldwide, accounting for nearly a million infant deaths yearly. Likewise, community-acquired pneumonia is a leading cause of severe illness and death among the elderly, with Streptococcus pneumoniae (pneumococcus) being the principal etiologic bacterial agent. Pneumococcal infections in both children and adults are preventable by vaccination; however current vaccines do not offer the level of protection needed due to multiple limitations and insight on protective cellular immunity is currently incomplete.
Memory B cells (Bmem) are central in immunization, as re-exposure to antigens leads to rapid generation of high-affinity antibody responses. The magnitude of Bmem after vaccination is associated with long-lasting humoral immunity and increased booster response. Studies with the experimental human pneumococcal carriage (EHPC) model, in which healthy adult volunteers are intranasally inoculated with S. pneumoniae, show that naturally-acquired serotype-specific IgG+ Bmem correlate with protection in healthy UK adults. However, whether specific subsets vaccine-induced B cells responses are associated to protection remains unknown. Therefore, characterization of the cellular responses to pneumococcal immunization by integrating multiple analytical approaches may provide critical insight into protective immunity.
The objectives of IDSpnBmem were to phenotypically characterize pneumococcal antigen-specific B cells and elucidate understanding of protective immunity via linking phenotypic and transcriptomic characterization with functionality of the humoral response. This was performed using two methods (spectral flow cytometry and 10X single-cell sequencing) from participant of different age groups (children, adults and elderly) exposed to various immunization methods (polysaccharide conjugate vaccination, polysaccharide non-conjugate vaccination, natural exposure and experimental human challenge) and compare across antigen specificities.
