Isolation of pathogenic monoclonal anti-desmoglein 1 human antibodies by phage display of pemphigus foliaceus autoantibodies

Pemphigus foliaceus ( PF) is a blistering disease caused by autoantibodies to desmoglein 1 ( Dsg1) that cause loss of epidermal cell adhesion. To better understand PF pathophysiology, we used phage display to isolate anti-Dsg1 mAbs as single- chain variable fragments ( scFvs) from a PF patient. Initial panning of the library isolated only non- pathogenic scFvs. We then used these scFvs to block non- pathogenic epitopes and were able to isolate two unique scFvs, each of which caused typical PF blisters in mice or human epidermis models, showing that a single mAb can disrupt Dsg1 function to cause disease. Both pathogenic scFvs bound conformational epitopes in the N terminus of Dsg1. Other PF sera showed a major antibody response against the same or nearby epitopes defined by these pathogenic scFvs. Finally, we showed restriction of the heavy- chain gene usage of all anti- Dsg1 clones to only five genes, which determined their immunological properties despite promiscuous light- chain gene usage. These mAbs will be useful for studying Dsg1 function and mechanisms of blister formation in PF and for developing targeted therapies and tools to monitor disease activity.