Development of chimeric molecules for recognition and targeting of antigen-specific B cells in pemphigus vulgaris

Pemphigus vulgaris (PV) is an autoimmune blistering disease characterized b y circulating pathogenic IgG antibodies against desmoglein 3 (Dsg3), The pu rpose of this study was to develop chimeric molecules for specific recognit ion and elimination of autoimmune B cells in PV, Mouse hybridoma cell lines producing anti-Dsg3 antibody (5H10, 12A2) were developed as an in vitro mo del system for targeting B cells, Dsg3-GFP, a baculoprotein containing the entire extracellular domain of Dsg3 fused with green fluorescence protein, recognized and targeted the hybridoma cells through their surface immunoglo bulin receptors in an antigen-specific way The epitopes of these monoclonal antibodies were mapped on the amino terminal EC1 and part of EC2, a region considered functionally important in cadherins, Chimeric toxin molecules c ontaining the mapped region (Dsg3 Delta N1) and modified Pseudomonas exotox in were produced in bacteria (Dsg3 Delta N1-PE40-KDEL, PE37-Dsg Delta N1-KD EL) and tested in vitro on hybridoma cell lines. The chimeric toxins, but n ot Dsg3 Delta N1 alone, showed dose-dependent toxic activity with a reducti on in hybridoma cell number to 40-60% of toxin-negative control cultures, c ompared with little or no effect on anti-Dsg3-negative hybridoma cells. Fur thermore, these toxins showed toxic effects on anti-Dsg3 IgG-producing B ce lls from Dsg3 Delta N1-immunized mice, with a 60% reduction in cell number compared with Dsg3 Delta N1 alone. Thus, specific recognition and targeting of antigen-specific B cells in PV was demonstrated: this strategy may hold promise as a future therapeutic option for PV and other autoimmune disease s.