The LPS derivative, monophosphoryl lipid A (MPLA), was created through chemical modifications to the lipid A portion of LPS from the Salmonella minnesota R595 strain 20. MPLA adsorbed to alum, named Adjuvant System 04 (AS04) and owned by GlaxoSmithKine, is currently used in both Fendrix for hepatitis B and Cervarix for human papilloma virus 3, 21 vaccines. These vaccines are well tolerated and safe for human use, and generate high titers of antibodies conferring seroprotection to infection 20, 22, 23. In addition, when added to DCs in vitro, MPLA increases cell surface expression of costimulatory molecules as well as migration

to lymph nodes and production of inflammatory cytokines 24, 25. MPLA promotes a Th1-cell immune response in an ovalbumin-specific TCR transgenic system 6, 25. However, in contrast to Mata-Haro et al. 6, we have previously found that MPLA and LPS are relatively weak learn more adjuvants for inducing CD4+ T-cell responses from the polyclonal repertoire of intact mice, while still able to induce strong antibody responses 4, 26. Glucopyranosyl lipid A (GLA) is a new synthetic lipid A agonist that combines six acyl chains with a single phosphorylation site. GLA has been formulated as a proprietary stable

oil-in-water emulsion (GLA-SE) as well as in an aqueous form 27. GLA has already exhibited a good safety profile when tested in combination with the Fluzone vaccine against influenza in monkeys and a recently completed phase I trial 28. In mice,

GLA-SE in combination MG-132 with Fluzone enhanced vaccine-specific antibody responses and hemagglutination-inhibition titers, compared with emulsion alone and GLA as an aqueous formulation with Fluzone. Furthermore, Fluzone plus GLA-SE induced a Th1 type cell-mediated response with IFN-γ and IL-2 production, whereas Fluzone plus the emulsion alone induced a predominant Type 2 response 27, 28. However, the effects of GLA-SE on DCs in vivo have not been examined. To understand how the new chemically defined GLA-SE adjuvant works, we have many studied T-cell and antibody responses to the HIV gag p24 protein delivered within a monoclonal antibody to the DC endocytic receptor (DEC)-205, an uptake receptor, on DCs versus non-targeted gag p24. Protein vaccines are inefficiently captured by antigen presenting cells 29 but targeting vaccine proteins to DEC-205 enhances antigen presentation greater than 100-fold 26, 30, 31. Here we will show that GLA-SE serves as an adjuvant for the induction of antibody and T-cell responses to a HIV gag p24 protein in mice, including Th1 type CD4+ T cells in the intestinal mucosa. We find that DCs are required for adjuvant action, and that the GLA-SE adjuvant quickly renders the DCs functionally mature or immunogenic in vivo. To test the efficacy of GLA-SE as an adjuvant, we immunized mice with anti-DEC-HIV gag p24 or non-targeted gag-p24 protein along with GLA-SE twice i.p. over 4 weeks.