Langerin-mediated internalization of a modified peptide routes antigens to early endosomes and enhances cross-presentation by human Langerhans cells

The potential of the skin immune system to generate immune responses is well established, and the skin is actively exploited as a vaccination site. Human skin contains several antigen-presenting cell subsets with specialized functions. In particular, the capacity to cross-present exogenous antigens to CD8+ T cells is of interest for the design of effective immunotherapies against viruses or cancer. Here, we show that primary human Langerhans cells (LCs) were able to cross-present a synthetic long peptide (SLP) to CD8+T cells. In addition, modification of this SLP using antibodies against the receptor langerin, but not dectin-1, further enhanced the cross-presenting capacity of LCs through routing of internalized antigens to less proteolytic early endosome antigen 1+early endosomes. The potency of LCs to enhance CD8+T-cell responses could be further increased through activation of LCs with the toll-like receptor 3 ligand polyinosinic:polycytidylic acid (pI:C). Altogether, the data provide evidence that human LCs are able to cross-present antigens after langerin-mediated internalization. Furthermore, the potential for antigen modification to target LCs specifically provides a rationale for generating effective anti-tumor or anti-viral cytotoxic T lymphocyte responses

Lipo-Based Vaccines as an Approach to Target Dendritic Cells for Induction of T- and iNKT Cell Responses

In this study we developed a liposome-based vaccine containing palmitoylated synthetic long peptides (SLP) and alpha galactosylceramide (αGC) to specifically target dendritic cells (DC) for activation of both innate (invariant natural killer T-cells [iNKT]) and adaptive (CD8+ T-cells) players of the immune system. Combination of model tumor specific antigens (gp100/MART-1) formulated as a SLP and αGC in one liposome results in strong activation of CD8+ and iNKT, as measured by IFNγ secretion. Moreover, addition of lipo-Lewis Y (LeY) to the liposomes for C-type lectin targeting increased not only uptake by monocyte-derived dendritic cells (moDC), dermal dendritic cells and Langerhans cells but also enhanced gp100-specific CD8+ T- and iNKT cell activation by human skin-emigrated antigen presenting cells in an ex vivo explant model. Loading of moDC with liposomes containing LeY also showed priming of MART-126−35L specific CD8+ T-cells. In conclusion, chemically linking a lipid tail to a glycan-based targeting moiety and SLP combined with αGC in one liposome allows for easy generation of vaccine formulations that target multiple skin DC subsets and induce tumor antigen specific CD8+ T- and iNKT cells. These liposomes present a new vaccination strategy against tumors