Development of novel therapy against bullous diseases

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This study enhanced international collaboration between groups which lead the fields of investigative dermatology on autoimmune and inherited bullous diseases. In this study, a novel active disease model for pemphigus has been developed. Knockout mice do not acquire tolerance of the defective gene product. Using knockout mice lacking desmoglein 3 (Dsg3), the target antigen of pemphigus vulgaris (PV), we established a method to generate an active disease model for this autoantibody-mediated disease. Dsg3ィイD1-/-ィエD1 mice, but not Dsg3ィイD1+/-ィエD1 littermates, produced anti-Dsg3 IgG that was able to bind the native Dsg3 when immunized with recombinant mouse Dsg3. Splenocytes from the immunized Dsg3ィイD1-/-ィエD1 mice were then adoptively transferred into Rag-2ィイD1-/-ィエD1 immunodeficient mice expressing Dsg3. Anti-Dsg3 IgG was stably produced in the recipient mice for over 6 months without further boosting. This IgG bound to Dsg3 in vivo and disrupted the cell-cell adhesion of keratinocytes. Consequently, the recipient mice developed erosions in their oral mucous membranes with typical histologic findings of PV. As an innovative therapeutic approach, we have developed chimeric molecules for targeting of antigen-specific B cells in PV. The recombinant toxins fused with Dsg3 could eliminate Dsg3-specific hybridoma cells or anti-Dsg3 IgG producing B cells from immunized mice with a 60% reduction in cell number. For inherited skin diseases, we investigated the correlation between the type of mutations and the phenotype in dominant and recessive dystrophic epidermolysis bullosa. We also set up basic protocol for production of epidermal sheets for clinical application. Several recombinant adenoviruses were developed to introduce exogenous genes to epidermal cells.