The Role of MyD88 in the Adjuvant Activity of Neisseria meningitidis PorB (53.5)

Abstract

Abstract Adjuvants enhance the response to poorly immunogenic antigens in vaccines. Our laboratory has shown by ELISA that Neisseria meningitidis outer membrane protein PorB acts as an adjuvant by eliciting a greater serum concentration of antigen-specific IgG when compared to immunization with antigen alone, with Ovalbumin as the antigen. PorB is a TLR2 ligand and signals through the adaptor protein MyD88. We compared the adjuvant effect of PorB to other adjuvants (Alum, MPL & CpG) in WT & MyD88 KO mice. PorB adjuvant activity was ablated in MyD88 KO mice and consistent with previous investigations: MPL & CpG adjuvant activity was also MyD88-dependent while Alum acted independently of MyD88. In addition, we previously observed PorB had residual adjuvant activity in TLR2 KO mice. One hypothesis was that PorB could stimulate the Nalp3 inflammasome and induce IL-1β production without a second signal e.g. ATP. Therefore, bone marrow-derived macrophages were stimulated with PorB ± ATP. The IL-1β production was analyzed by ELISA and compared to IL-1β production from stimulation with other TLR ligands. We found that PorB required ATP in order to sufficiently produce IL-1β, disproving our hypothesis. Overall, our results show an importance for MyD88 in both the adjuvant pathway of PorB & other TLR ligand-based adjuvants. One future direction for this work is MyD88 deletion in an antigen-presenting cell-specific manner to examine the role of each cell type in the adjuvant activity of PorB.