Bullous Pemphigoid (BP) is an autoimmune blistering skin disease. This condition is characterized by potentially life-threatening humoral immune reactions to an epidermal cell surface protein, BP180 (also known as collagen XVII). Global immunosuppressive treatments are generally used to control such antibody-mediated disorders;however, serious side effects underscore the critical need for specific targeted therapy. The goal of this R21 application is to explore and develop a therapy that would deplete autoreactive B-cells in an antigen-specific manner. Our hypothesis for this exploratory/developmental research grant (R21) application is that a BP180-specific antigen-toxin is capable of greatly reducing the production of anti-BP180 antibodies by binding to, and selectively killing, BP180-specific B-cells. The cytotoxic moiety of this fusion protein is human angiogenin, a plasma RNase that is non-toxic until it is delivered into the cytoplasm of the target cell. The first aim will focus on generating and characterizing the angiogenin-antigen fusion and control proteins necessary to test our hypothesis. Biochemical and immunological analyses will be carried out to ensure that the enzymatic activity of angiogenin and the antigenic properties of the BP180 moiety have not been altered. The second aim is directed toward testing the efficacy of the antigen-toxin in vitro and in vivo. Our in vitro approaches involve monitoring cell death in BP180-specific B-cell hybridomas (both human and murine), as well as on BP patients'peripheral blood cells. Non-specific immune cells will be used as negative control. In vivo testing of the efficacy and safety of this antigen-toxin will be carried out using a murine model that reproduces the anti-BP180 immune response in BP. The effects of the treatments will be quantified by following anti-BP180 antibody titers and monitoring BP180-specific B-cell populations in the mice. The fate of other cells of the innate and adaptive immune systems will be followed. This study represents the first test of an angiogenin-antigen in an in vivo system. RELEVANCE of this research to public health: If our hypothesis is confirmed, the findings from this project could well lead to the development of specific therapies for patients with BP and other B-cell driven autoimmune disorders. The expected outcome is a significant reduction in the morbidity and mortality associated with these clinical conditions. We envision that antigen-specific immuno-modulation could also be employed to improve the outcomes of certain types of gene replacement therapy, in which a humoral immune response to the transgene product is a serious pitfall.