Epitope analysis of antidesmoglein 1 autoantibodies from patients with pemphigus foliaceus across different activity stages

Background Pemphigus foliaceus (PF) and pemphigus vulgaris (PV) are closely related, but clinically distinct, autoimmune blistering diseases caused by autoantibodies against desmoglein (Dsg) 1 and Dsg3, respectively. Using ethylenediaminetetraacetic acid (EDTA)-treated Dsg3 enzyme-linked immunosorbent assay (ELISA) we have shown that the proportion of anti-Dsg3 antibodies against calcium-dependent epitopes decreased upon shifting to the inactive phase in patients with PV. Objectives To analyse the epitope profiles of anti-Dsg1 antibodies across the different activity stages of PF. Methods We evaluated five patients with PF who retained high serum levels of anti-Dsg1 antibodies in the inactive phase. Sera were obtained in both the active and inactive phases, and were analysed by EDTA-treated and exfoliative toxin-treated ELISAs. To map the epitopes of anti-Dsg1 antibodies, immunoprecipitation-immunoblotting was performed using a set of Dsg1/Dsg2 domain-swapped molecules. Results Anti-Dsg1 antibodies against the calcium-dependent epitopes of Dsg1 were the predominant antibodies in both the active and inactive phases. The proportion of anti-Dsg1 antibodies against the calcium-dependent epitopes did not change upon shifting to the inactive phase. The results of immunoprecipitation-immunoblotting showed that most of the anti-Dsg1 antibodies bound to the extracellular domains (EC) 1-2 of Dsg1. Conclusions In patients with PF, the calcium-dependent epitopes on EC1 and EC2 of Dsg1 contained definitively pathogenic and nonpathogenic epitopes. The disease activity might be differentially controlled by the antibodies between PF and PV depending on the presence or absence of the nonpathogenic epitope.