Vinther, S. C.; Resag, A.; Le, K. T. T.; Zelle-Rieser, C. C.; Strandt, H.; Malle, M. G.; Christiansen, S. H.; Del Frari, B.; Stigger, T.; Schilling, B.; Wohlfarth, J.; Thiel, S.; Valero, J.; Stoitzner, P.; Kjems, J.

The skin is a diverse reservoir of immune cells with strong potential for immunotherapeutic delivery. Langerhans cells (LCs) in the epidermis are antigen-presenting cells, accessible for vaccination using carbohydrate-conjugated therapeutics targeting their endocytic lectin receptor, Langerin. As carbohydrate-lectin binding is highly dependent on valency, scaffolds that enable control over ligand spacing and stoichiometry are instrumental in enhancing receptor binding and selectivity. Here we utilized a self-assembled nucleic acid-based Holliday Junction scaffold, fully modified for nuclease protection and with a well-defined carbohydrate arrangement to optimize drug delivery to LCs. In vitro screening with Langerin-expressing cells revealed that mannosylated Holliday Junctions showed the strongest binding. This was confirmed in human epidermal cell suspensions, demonstrating specificity and valency-driven interactions. Topical administration of mannosylated scaffolds on skin explants enabled effective targeting of epidermal LCs. Finally, in an antigen-presentation assay, in vitro differentiated LCs loaded with mannosylated and peptide-conjugated scaffolds significantly enhanced T cell activation. Overall, our study presents a promising nucleic acid-based platform for precise LC targeting and drug delivery, with broad potential for skin-directed immunotherapies.