Dystrophic epidermolysis bullosa (DEB) is an incurable, inherited mechano-bullous disease of the skin characterized by skin fragility, blister formation, and chronic wounds. DEB is caused by defects in the human gene encoding type VII collagen, the major component of anchoring fibrils that anchor the epidermis to the dermis. Anchoring fibrils are attenuated, diminutive, or absent in DEB. Our long-term objectives are to develop therapeutic strategies for DEB. During the last funding cycle, we made significant progress towards developing ex vivo gene therapy for DEB. In addition, we exceeded our original Aims on several fronts to develop cell-based therapy, protein-based therapy, and in vivo gene therapy strategies for DEB. Our studies demonstrated the feasibility of using protein therapy by injecting recombinant type VII collagen intradermally into mice and mice transplanted with a human DEB skin equivalent. Other studies with these models demonstrated in vivo gene therapy via intradermal injection of recombinant lentivirus vectors expressing human type VII collagen and in vivo cell therapy via intradermal injection of gene-corrected fibroblasts. These studies were conducted in hairless, immunodeficient mice and immunodeficient mice transplanted with a human DEB skin xenograft. These immunodeficient animals preclude assessment of potential immune responses to neo-antigens. Immune responses are likely to complicate gene therapy trials, especially when a patient has a null mutation such as RDEB. In addition, prior to using any of these approaches in DEB patients, we need studies in a preclinical animal model to determine the safety, efficacy, and potential immune responses with these approaches. Fortunately, there are several DEB animal models available, including a spontaneously occurring mutation in dogs and a murine knockout model created by targeted disruption of the type VII collagen gene.
Our aims for the next funding period are: 1) To verify the feasibility of protein-based therapy for DEB using DEB mouse and dog models, 2) To determine the safety and efficacy of lentiviral vectorbased in vivo gene therapy in DEB animal models, 3) To validate the fibroblast-based approach for correction of RDEB defects in these animal models, 4) To characterize immune responses to a neo-antigen and develop strategies to blunt these responses in the DEB mouse model, and 5) To evaluate the feasibility of intravenous injection of genecorrected fibroblasts that home to skin for DEB treatment. We believe the proposed experiments will give us sufficient information to consider clinical protocols for humans, the long-term goal of this work.
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