Comparison of intradermal injection and epicutaneous laser microporation for anti-tumor vaccine delivery in a human skin explant model

Human skin is a prime vaccination site containing multiple antigen presenting cells (APC), including Langerhans cells (LC) and dendritic cells (DC). APC deliver antigens to lymph nodes for induction of adaptive immunity through stimulating antigen specific T- and B-cells. Since intradermal (ID) injections require specific training, easy applicable delivery systems like laser microporation are emerging. In mice, combination of laser treatment and allergen injection showed enhanced T-cell responses and skewing of B-cell responses without adjuvants. However, it remains to be elucidated whether laser microporation can alter human skin DC phenotype and function without adjuvants. In an ex-vivo human skin explant model, we compared ID injection and laser microporation as anti-tumor vaccination strategy. A melanoma specific synthetic long peptide and multivalent dendrimer with gp100 antigen were used as vaccine formulation to measure DC phenotype, emigration and ability to stimulate gp100 specific CD8+ T-cells. We show that skin DC phenotype and emigration capacity was similar after laser microporation and ID injection. However, laser microporation reduced vaccine uptake by DCs, resulting in decreased induction of gp100 specific CD8+ T-cell activation. To conclude, in our human skin model ID injection remains the most potent strategy to deliver antigens to skin APC for T-cell induction.