Innate immune response after adenoviral gene delivery into skin is mediated by AIM2, NALP3, DAI and mda5

Methods for human skin gene therapy requires efficient and stable introduction of genes into skin cells. Transient cutaneous gene therapy is an attractive approach in the treatment of skin diseases. The 'Achilles heel' of adenoviral gene therapy is its immunogenicity and many aspects of adenovirus induced cutaneous immune reaction still remain unanswered, particularly the role of keratinocytes. Therefore, human keratinocytes were transfected with adenoviral DNA and cytokine expression was analyzed. Moreover, adenoviral transduction of full-skin was performed ex vivo and in vivo. We observed cytokine induction after cytoplasmatic internalization of adenoviral DNA into epidermal cells. Inhibition of AIM2, NALP3, DAI or mda5 downregulated the cytokine response. Transduction of immunocompetent mice led to a detectable transgene expression for 12 days. Re-application of the vector led to a decrease in intensity and duration of transgene expression limited to 4 days and an increased cytokine expression. In contrast, immunodeficient mice showed a reduced expression of cytokines after DNA internalization. AIM2, NALP3, DAI and mda5 are essential in the induction of an innate immune response towards adenoviral DNA. This immune reaction leads to a decrease in transduction efficiency of the vector after re-application and modulation of these receptor systems stabilizes transgene expression.