DCs from GLA-SE but not SE-treated mice became active stimulators of the allogeneic mixed leukocyte reaction, inducing robust proliferation of both CD4+ and CD8+ T cells (Fig. 5C). To further evaluate the capacity of DCs to become immunogenic following antigen capture in vivo, mice were injected with anti-DEC-HIV gag and either GLA-SE or SE. After 4 h, splenic DCs were purified by cell sorting and injected into naïve mice i.v. In addition, to check that antigen presentation was performed by the transferred and not recipient DCs, MHCII−/− DCs were used as negative controls. Only WT DCs, after targeting with anti-DEC-gag and stimulated with GLA-SE in vivo, were capable
of inducing gag-specific T-cell immunity (Fig. 5D). These data indicate that GLA induces the full maturation of spleen and lymph node NVP-LDE225 DCs in vivo. The discovery of receptors
responsible for stimulating innate immunity, such as the TLR and RIG-like receptor pattern recognition receptors, makes it possible to test chemically defined agonists as new adjuvants to trigger the DC link between innate and adaptive immunity. To understand adjuvant action, these agonists need to be characterized in vivo at the level of antigen presenting DCs. Our experiments at this direct level indicate that a synthetic TLR4 agonist, GLA-SE, serves as an effective adjuvant and enhances MLN0128 mw the capacity of DCs in vivo to immunize against protein antigens. The adjuvant role of GLA-SE was dependent on TLR4. Similar results have been reported by Baldwin et al. where GLA induced production of IL-6 by click here monocyte-derived DCs in culture, and this was blocked with anti-TLR4 but not TLR2 antibodies 27. Our results extend prior research by showing a complete dependency of TLR4 stimulation for the induction of adaptive responses in vivo by GLA-SE. DCs are the major link between the innate and the adaptive immune system, and its appropriate activation and maturation by agonists for innate signaling receptors should allow for the induction of
an adaptive response 41, 42. However, much of the evidence involves studies of DCs stimulated in cell culture with adjuvants 43. In the current study, we demonstrated that GLA-SE injection together with a protein antigen allows the antigen-capturing DCs to quickly become immunogenic in vivo. Enhanced T-cell responses were detected when antigen was targeted to DCs. We did not detect qualitative difference in adaptive responses between untargeted or targeted protein. However, lower doses of antigen were required using anti-DEC-HIV gag p24 to achieve detectable responses. This finding highlights the importance of DCs for initiating adaptive T-cell immunity. After showing that DCs were essential for the generation of T-cell responses in lymph nodes to an s.c.