Skin Immunity towards neo-self antigens

The potential of replacing defective genes in the skin by ex vivo gene therapy has been suggested for many years, and this may be a feasible therapeutic strategy for genetic skin disorders such as epidermolysis bullosa, xeroderma pigmentosum or ichthyoses. However, the immune response to neoantigens poses a major obstacle towards the application of gene substitution therapy in the skin. It has been shown that neoantigens expressed in keratinocytes elicit specific immune responses towards skin grafts. In these models however the impact of inflammation induced by the skin grafting procedure was impossible to separate from the specific immune response elicited by the neoantigen. The project proposed here is designed to test the hypothesis that the expression of a neo-self antigen in the skin will result in the induction of tolerance under steady state (non-inflammatory) conditions and that a pathologic autoimmune response will develop under inflammatory conditions. We propose to utilize a new mouse model that will allow us to address the issue of immune responses against skin neoantigens in a noninvasive, non- inflammatory manner. A membrane bound form of the model-antigen chicken ovalbumin will be expressed in the skin in an inducible manner. We will define (1) the local stimuli that trigger autoimmune reactions, (2) the importance of persistent antigen expression and the risk of antigen spreading (3) determine the effect of transgene expression levels on the immune reaction in ex vivo gene therapy. The proposed research will provide an insight into the immune response to neo-self antigens. Our model offers the possibility to analyze single stimulating factors that may have an impact on the resulting immune reaction in a system with reduced complexity. Knowledge about these stimuli will be important in the development of gene therapy approaches because manipulating or avoiding them will reduce the risk of immune responses towards the neo-self antigen. This will be a significant step towards successful skin gene therapy especially in patients that have not developed self-tolerance towards the newly introduced antigen due to null-mutations in the respective gene.