Epicutaneous administration of the pattern recognition receptor agonist polyinosinic‐polycytidylic acid activates the MDA5/MAVS pathway in Langerhans cells

Abstract

Together with keratinocytes (KCs) and the dense network of Langerhans cells (LCs), the epidermis is an ideal portal for vaccine delivery. Pattern recognition receptor agonists, in particular polyinosinic–polycytidylic acid [p(I:C)], are promising adjuvant candidates for therapeutic vaccination to generate protective T-cell immunity. Here we established an ex vivo skin explant model to study the expression and activation of double-stranded RNA (dsRNA)-sensing pattern recognition receptors in LCs and KCs in human skin. Whereas KCs expressed all known dsRNA sensing receptors at a constitutive and inducible level, LCs exclusively expressed melanoma differentiation–associated protein 5 (MDA5) in untreated skin and freshly isolated cells. Comparative assessments of downstream signaling pathways induced by p(I:C) revealed distinct mitochondrial antiviral-signaling protein, IFN-regulatory factor 3, and NF-κB activation in LCs and KCs. Consequently, p(I:C) treatment of LCs significantly induced IFN-α and IFN-β mRNA expression, while in KCs an up-regulation of IFN-β and TNF-α mRNA was detectable. Stimulation of LCs with specific ligands revealed that not the TLR3- but only the MDA5-specific ligand induced IFN-α2, IFN-β, and TNF-α cytokines, but no IL-6 and -8. In KCs, both ligands induced production of high IL-6 and IL-8 levels, and low IFN-α2 and IFN-β levels, indicating that different dsRNA-sensing receptors and/or downstream signaling pathways are activated in both cell types. Our data suggest that MDA5 may be an attractive adjuvant target for epicutaneous delivery of therapeutic vaccines with the goal to target LCs.—Tajpara, P., Schuster, C., Schön, E., Kienzl, P., Vierhapper, M., Mildner, M., Elbe-Bürger, A. Epicutaneous administration of the pattern recognition receptor agonist polyinosinic–polycytidylic acid activates the MDA5/MAVS pathway in Langerhans cells.

Notch-Mediated Generation of Monocyte-Derived Langerhans Cells: Phenotype and Function

“…Similarly, moLCs were responsive to TLR or RIG-I-like receptor ligands according to their gene expression profile and upregulated HLA-DR, CD83, and CCR7 after stimulation with lipopolysaccharide or PolyI:C but not with CpG. Because TLR3 mRNA was undetectable in the RNA-seq analysis, we confirmed the mRNA expression of the RIG-Ilike receptors RIG-I and MDA-5 in moLCs as alternative receptors for PolyI:C. Accordingly, it was reported recently that MDA-5 is the main sensor for PolyI:C in skin LCs (Tajpara et al, 2018). This is of potential clinical importance because PolyI:C is already being used as an adjuvant in DC-based cancer vaccines (Dhodapkar et al, 2014).…”

A Preclinical Model for Studying Herpes Simplex Virus Infection

“…Dermatome-cut (0.5-mm) skin was incubated in 1.2 U/ml Dispase II in phosphate buffered saline (Roche Diagnostics, Indianapolis, IN), overnight at 4 C. The next day, epidermis was separated mechanically and digested with 2.5 mg/ml of bovine trypsin and 0.05 U/ml DNase I (both from Sigma-Aldrich) for 30 minutes at 37 C. Keratinocytes were cultured in a serum-free keratinocyte growth medium (KGM2; Lonza, Basel, Switzerland), as reported previously (Mildner et al, 2006). Two methods were applied for the separation of epidermal Langerhans cells, essentially as described (Tajpara et al, 2018).…”

Octenidine-based hydrogel shows anti-inflammatory and protease-inhibitory capacities in wounded human skin

“…Because there are increasing restrictions in Europe for using animals for testing compound properties and in line with the 3Rs (reduction, refinement, and replacement of animal models), ex vivo models represent an ideal preclinical platform. Therefore, we have employed a recently established ex vivo human wound model 17 , 20 and a proteomic as well as ELISA-based approach to determine the protein profile of OCT-treated wounded skin, aiming to further unravel the largely unknown mechanism by which OCT might contribute to tissue regeneration and improved wound healing.…”