Targeted Delivery of Tumor Necrosis Factor–Related Apoptosis-Inducing Ligand to Keratinocytes with a Pemphigus mAb

We determined the feasibility of using an anti-desmoglein (Dsg) mAb, Px44, to deliver a biologically active protein to keratinocytes. Recombinantly produced Px44-green fluorescent protein (GFP) injected into mice and skin organ culture delivered GFP to the cell surface of keratinocytes. We replaced GFP with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to produce Px44-TRAIL. We chose TRAIL as a biological model because it inhibits activated lymphocytes and causes apoptosis of hyperproliferative keratinocytes, features of various skin diseases. Px44-TRAIL formed a trimer, the biologically active form of TRAIL. Standard assays of TRAIL activity showed that Px44-TRAIL caused apoptosis of Jurkat cells and inhibited IFN-γ production by activated CD4+ T cells. Enzyme-linked immunoassay with Px44-TRAIL showed delivery of TRAIL to Dsg. Immunofluorescence with Px44-TRAIL incubated on skin sections and cultured keratinocytes or injected into mouse skin, human organ culture, or human xenografts detected TRAIL on keratinocytes. Px44-TRAIL caused apoptosis of the hyperproliferative, but not differentiating, cultured keratinocytes through binding to Dsg3. Foldon, a small trimerization domain, cloned into Px44-TRAIL maintained its stability and biological activity at 37° C for at least 48 hours. These data suggest that such targeted therapy is feasible and may be useful for hyperproliferative and inflamed skin diseases.