Epidermolysis bullosa acquisita (EBA) is an autoimmune blistering disease characterized by autoantibodies to type VII (anchoring fibril) collagen. Therefore, it is a prototypic autoimmune disease defined by a well-known autoantigen and autoantibody. In this study, we injected hairless immune competent mice with purified immunoglobulin G (IgG) fraction of serum from rabbits immunized with the non-collagenous amino-terminal domain (NC1) of human type VII collagen, the domain known to contain immunodominant epitopes. As a control, identical mice were injected with the IgG fraction of serum from non-immunized rabbits. Mice injected with immune IgG developed subepidermal skin blisters and erosions, IgG deposits at the epidermal-dermal junction of their skin, and circulating anti-NC1 antibodies in their serum-all features reminiscent of patients with EBA. Similar concentrations of control IgG purified from normal rabbits did not induce disease in the mice. These findings strongly suggest that autoantibodies that recognize human type VII collagen in EBA are pathogenic. This murine model, with features similar to the clinical, histological, and immunological features of EBA, will be useful for the fine dissection of immunopathogenic mechanisms in EBA and for the development of new therapeutic interventions.
Epidermolysis bullosa acquisita (EBA) is an autoimmune sub-epidermal blistering disease characterized by autoantibodies to type VII (anchoring fibril) collagen. To date, however, direct evidence for a pathogenic role of human EBA autoantibodies has not been demonstrated. In this study, we affinity-purified anti-type VII collagen antibodies from EBA patients' sera and then injected them into adult hairless immunocompetent mice. Mice injected with EBA autoantibodies developed skin fragility, blisters, erosions, and nail loss on their paws - all features of EBA patients. By clinical, histological, immunological, and ultrastructural parameters, the induced lesions were reminiscent of human EBA. Histology showed bullous lesions with an epidermal-dermal separation. IgG and C3 deposits were observed at the epidermal-dermal junction. All mice had serum antibodies that labeled the dermal side of salt-split human skin like EBA sera. Direct immunogold electron microscopy specifically localized deposits of human IgG to anchoring fibrils. (Fab')(2) fragments generated from EBA autoantibodies did not induce disease. We conclude that EBA human patient autoantibodies cause sub-epidermal blisters and induce EBA skin lesions in mice. These passive transfer studies demonstrate that human EBA autoantibodies are pathogenic. This novel EBA mouse model can be used to further investigate EBA autoimmunity and to develop possible therapies.
Dystrophic epidermolysis bullosa (DEB) is a family of inherited mechanobullous disorders caused by mutations in the gene, COL7A1, that codes for type VII, (anchoring fibril), collagen, which is critical for epidermal-dermal adherence. Most gene therapy approaches have been ex vivo, involving cell culture and culture graft transplantation, which is logistically difficult. To develop a more simplified approach, we engineered a self-inactivating lentiviral vector expressing human type VII collagen and injected this vector intradermally into hairless, immunodeficient mice and into a human DEB composite skin equivalent grafted onto immunodeficient mice. In both situations, the vector transduced dermal cells, which in turn synthesized and exported type VII collagen into the extracellular space. Remarkably, the type VII collagen selectively adhered to and incorporated into the basement membrane zone (BMZ) between the dermis and the epidermis, where it formed anchoring fibril structures. In the case of the DEB skin equivalent, the newly expressed type VII collagen reversed the DEB phenotype characterized by poor epidermal-dermal adherence and anchoring fibril defects. A single lentiviral vector injection provided stable type VII collagen at the BMZ for at least 3 months. These data demonstrate efficient and long-term type VII collagen gene transfer in vivo using direct intradermal injection of an engineered lentiviral vector.
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