Mapping of B cell epitopes on desmoglein 3 in pemphigus vulgaris patients by the use of overlapping peptides

Background: Pemphigus vulgaris (PV) is a severe autoimmune blistering disease associated with autoantibodies to desmoglein 3 (Dsg 3), a transmembrane glycoprotein of the cadherin family. Previous studies mainly focused on the mapping of conformational epitopes of Dsg 3 using recombinant fragments of Dsg 3 and competition ELISA. Objective: Here, we performed a mapping of linear B cell epitopes on Dsg 3 in PV patients by the use of overlapping synthetic peptides. Methods: A set of 254 overlapping synthetic peptides of 14 amino acids length covering the entire Dsg 3 extracellular domain was generated. Sera of patients with active PV (n= 10) and healthy volunteers (n= 10) were tested for IgG reactivity with the 254 peptides by ELISA. Testing each peptide separately, 7 major antigenic sites were identified. In order to validate these reactivities, 7 corresponding peptides of 13-33 amino acids in length were generated and employed by ELISA. Additional sera of active PV patients (n= 17) and healthy volunteers (n= 20) were tested and the most reactive peptide was used to specifically purify anti-Dsg 3 antibodies from PV sera (n= 3). Results: The major autoantibody reactivity in PV sera was mapped to amino acids 333-356 within the EC3 domain. Purifying patients IgG using the identified peptide, however, failed to induce acantholysis in keratinocyte dissociation assay. Conclusion: We conclude that linear epitopes do not play a major pathogenic role in human PV.