MPLA incorporation into DC-targeting glycoliposomes favours anti-tumour T cell responses

Abstract Dendritic cells (DC) are attractive targets for cancer immunotherapy as they initiate strong and long-lived tumour-specific T cell responses. DC can be effectively targeted in vivo with tumour antigens by using nanocarriers such as liposomes. Cross-presentation of tumour antigens is enhanced with strong adjuvants such as TLR ligands. However, often these adjuvants have off-target effects, and would benefit from a DC-specific targeting strategy, similar to the tumour antigen. The goal of this study was to develop a strategy for specifically targeting DC with tumour antigen and adjuvant by using glycoliposomes. We have generated liposomes containing the glycan Lewis(Le)^X which is highly specific for the C-type lectin receptor DC-SIGN expressed by DC. Le^X-modified liposomes were taken up by human monocyte-derived DC in a DC-SIGN-specific manner. As adjuvants we incorporated the TLR ligands Pam₃CySK₄, Poly I:C, MPLA and R848 into liposomes and compared their adjuvant capacity on DC. Incorporation of the TLR4 ligand MPLA into glycoliposomes induced DC maturation and production of pro-inflammatory cytokines, in a DC-SIGN-specific manner, and DC activation was comparable to administration of soluble MPLA. Incorporation of MPLA into glycoliposomes significantly enhanced antigen cross-presentation of the melanoma tumour antigen gp100_280-288 peptide to CD8⁺ T cells compared to non-glycosylated MPLA liposomes. Importantly, antigen cross-presentation of the gp100_280-288 peptide was significantly higher using MPLA glycoliposomes compared to the co-administration of soluble MPLA with glycoliposomes. Taken together, our data demonstrates that specific targeting of a gp100 tumour antigen and the adjuvant MPLA to DC-SIGN-expressing DC enhances the uptake of peptide-containing liposomes, the activation of DC, and induces tumour antigen-specific CD8⁺ T cell responses. These data demonstrate that adjuvant-containing glycoliposome-based vaccines targeting DC-SIGN⁺ DC represent a powerful new approach for CD8⁺ T cell activation.