Combined TLR and CD40 triggering induces potent CD8+ T cell expansion with variable dependence on type I IFN.

Toll-like receptors are important in the activation of innate immunity, and CD40 is a molecule critical for many T and B cell responses. Whereas agonists for either pathway have been used as vaccine adjuvants, we show that a combination of Toll-like receptor (TLR)7 and CD40 agonists synergize to stimulate CD8+ T cell responses 10-20-fold greater than the use of either agonist alone. Antigen-specific CD8+ T cells elicited from combination CD40/TLR7 treatment demonstrated both lytic activities and interferon (IFN)gamma production and an enhanced secondary response to antigenic challenge. Agonists for TLRs 2/6, 3, 4, and 9 also synergized with CD40 stimulation, demonstrating that synergy with the CD40 pathway is a property of TLR-derived stimuli in general. The CD8+ T cell expansion induced by CD40/TLR7 triggering was independent of CD4+ T cells, IFNgamma, and IL-12 but dependent on B7-mediated costimulation and surprisingly on type I IFN. These studies provide the rational basis for the use of TLR and CD40 agonists together as essential adjuvants to optimize vaccines designed to elicit protective or therapeutic immunity.

The immune response modifier and Toll-like receptor 7 agonist S-27609 selectively induces IL-12 and TNF-alpha production in CD11c+CD11b+CD8- dendritic cells.

IL-12 and TNF-alpha production by dendritic cells (DCs) is a critical step in the initiation of local inflammation and adaptive immune responses. We show in this study that a small molecule immune response modifier that is a Toll-like receptor 7 (TLR7) agonist induces IL-12 and TNF-alpha production from murine CD11c(+)CD11b(+)CD8(-) DCs, a subset not previously known for this activity. Stimulation of these DCs through TLR7 in vivo induces significant cytokine production even 12 h after initial stimulation, as well as migration of the DC into T cell zones of the lymphoid tissue. In contrast, stimulation through TLR4 and TLR9 induced IL-12 production predominantly from CD8(+) DCs, consistent with previously published data. All TLR stimuli induced the increase in surface expression of the activation markers B7-1, B7-2, and class II in both CD8(+) and CD8(-) DCs, demonstrating that CD8(+) DCs do respond to TLR7-mediated stimuli. To date this is the only known stimuli to induce preferential cytokine production from CD8(-) DCs. Given the efficacy of TLR7 agonists as antiviral agents, the data collectively indicate that stimulation of CD8(-) DCs through TLR7 most likely plays a role in the generation of antiviral immune responses.