CD73-A2a adenosine receptor axis promotes innate B cell antibody responses to pneumococcal polysaccharide vaccination.

Many individuals at risk of streptococcal infection respond poorly to the pneumococcal polysaccharide vaccine Pneumovax 23. Identification of actionable pathways able to enhance Pneumovax responsiveness is highly relevant. We investigated the contribution of the extracellular adenosine pathway regulated by the ecto-nucleotidase CD73 in Pneumovax-induced antibody responses. Using gene-targeted mice, we demonstrated that CD73-or A2a adenosine receptor deficiency significantly delayed isotype switching. Nevertheless, CD73- or A2aR- deficient adult mice ultimately produced antigen-specific IgG3 and controlled Streptococcus pneumoniae infection as efficiently as wild type (WT) mice. Compared to adults, young WT mice failed to control S. pneumoniae infection after vaccination and this was associated with lower levels of CD73 on innate B cells. We hypothesized that pharmacological activation of A2a receptor may improve Pneumovax 23 immunization in young WT mice. Remarkably, administration of the A2a adenosine receptor agonist CGS 21680 significantly increased IgG3 responses and significantly enhanced survival after S. pneumoniae challenge. Our study thus suggests that pharmacological activation of the A2a adenosine receptor could improve the efficacy of Pneumovax 23 vaccination in individuals at risk of streptococcal infection.