Conjugation of peptide to small gold nanoparticles for intradermally administered antigen specific immunotherapy

Background. Antigen specific immunotherapy, in which autoantigen molecules or peptide epitopes thereof are delivered into patients to promote immune tolerance, is an attractive approach to the treatment of antigen specific autoimmune diseases as it provides a potential means of slowing disease progression without systemic immunosuppression. Skin dendritic cells, particularly epidermal Langerhans cells, are believed to be pivotal determinants of skin immunity and tolerance and as such they represent an attractive target for antigen specific immunotherapy. They can be targeted in a minimally invasive manner by microneedle delivery systems. Gold nanoparticles (GNPs) are an attractive drug delivery platform for immunotherapy because they have potential anti-inflammatory properties and could facilitate delivery of an autoantigen. Methods. This study aimed to manufacture autoantigen loaded small GNPs for localised delivery into human skin using the regulatory approved hollow microneedles (MicronJet600) to target localised dendritic cells. A library of GNP-peptide complexes with a small (< 5nm) diameter and a negative surface charged (-40 to -60mV) were manufactured at a range of peptide doses. Results. Complexes remained physically stable upon extrusion through the hollow microneedle device and were able to rapidly and extensively diffuse throughout the dermis and epidermis following microneedle-mediated delivery in to excised human skin. Intracellular uptake of the GNP-peptide complexes in both dermal and epidermal cells was extensive, with Langerhans cells proving to be the most efficient cells at internalising the complex (94% of the local population within the treated region of skin). Experiments in human cell culture demonstrated that uptake of GNP-peptide complexes by dendritic cells reduced their subsequent capacity to activate naïve T cells. This is indicative of the GNP-peptide complex functionality as a tolerogenic treatment for autommune diseases and encourages development of the drug delivery platform, which is now being evaluated in clinical trials.