Potent induction of antibody-secreting B-cells by human dermal-derived CD14+ dendritic cells triggered by dual toll-like receptor ligation

Clinical adjuvant combinations stimulate potent B-cell responses in vitro by activating dermal dendritic cells

CD14⁺ dermal DCs (CD14⁺ DDCs) have a natural capacity to activate naïve B-cells. Targeting CD14⁺ DDCs is therefore a rational approach for vaccination strategies aimed at improving humoral responses towards poorly immunogenic antigens, for example, HIV-1 envelope glycoproteins (Env). Here, we show that two clinically relevant TLR ligand combinations, Hiltonol plus Resiquimod and Glucopyranosyl lipid A plus Resiquimod, potently activate CD14⁺ DDCs, as shown by enhanced expression of multiple cytokines (IL-6, IL-10, IL-12p40 and TNF-α). Furthermore, the responses of CD14⁺ DDCs to these TLR ligands were not compromised by the presence of HIV-1 gp120, which can drive immunosuppressive effects in vitro and in vivo. The above TLR ligand pairs were better than the individual agents at boosting the inherent capacity of CD14⁺ DDCs to induce naïve B-cells to proliferate and differentiate into CD27⁺ CD38⁺ B-cells that secrete high levels of immunoglobulins. CD14⁺ DDCs stimulated by these TLR ligand combinations also promoted the differentiation of Th1 (IFN-γ-secreting), but not Th17, CD4⁺ T-cells. These observations may help to identify adjuvant strategies aimed at inducing better antibody responses to vaccine antigens, including, but not limited to HIV-1 Env.