| Adjuvants function in vaccine preparations to enhance the effector immune response to poorly immunogenic antigens. Immune stimulation is accomplished through the activation of antigen presenting cells (APCs) leading to increased antigen presentation and enhanced co-stimulatory capacity towards T cell activation. Co-stimulatory molecules, such as CD86, function in cooperation with T cell receptor engagement to fully activate T cells, which are then able to co-stimulate antigen specific B cells for antibody production. Neisseria meningitidis porin, PorB, acts as an immune adjuvant and has previously been shown to upregulate MHC class II and CD86 on dendritic cells and B cells in a Toll-like receptor 2 (TLR2) dependent manner. The link between CD86 upregulation and the adjuvant effect of PorB is demonstrated in mice immunized with PorB and capsular polysaccharide from Neisseria: when CD86 blocking antibodies are co-administered the mice produced significantly less polysaccharide specific antibody. TLR mediated APC stimulation activates signaling cascades, including mitogen activated protein kinases (MAPKs). We sought to characterize these signaling molecules in PorB induced CD86 upregulation. PorB activated murine bone marrow derived macrophages resulting in increased CD86 surface expression and phosphorylation of the MAPKs Erk, p38 and JNK. Moreover, TLR2 expression was required for these effects. Inhibition of JNK, but not Erk or p38, prevented PorB induced CD86 upregulation. In contrast, activation of CD86 surface expression by lipooligosaccharide (LOS) from N. meningitidis, a TLR4 ligand, required p38 but not Erk or JNK. Our studies suggest that two pathways can lead to CD86 upregulation in murine macrophages: thus using TLR2 and TLR4 agonists together as adjuvants may result in a more effective vaccine. |
