Longitudinal cloning and genetic characterization of human pemphigus autoantibodies in active disease, remission, and relapse

Pemphigus vulgaris (PV) and pemphigus foliaceus (PF) represent prototypes of tissue-specific, blistering autoimmune diseases of the skin and mucous membranes and are characterized by autoantibodies (auto-AB) against the keratinocyte adhesion proteins desmoglein 3 (Dsg 3) and desmoglein 1 (Dsg 1). Despite the availability of the monoclonal anti-CD20 antibody rituximab, current therapeutic approaches are nonspecific: Rituximab eliminates not only pathogenic but almost all circulating B cells, and the development of targeted therapies (e.g., anti-idiotypic antibodies) while preserving the function of the patient's immune system is desirable. The innovative technique of phage display (PhDp) allows for the genetic characterization of human anti-Dsg 3/1 antibodies from PV/PF patients, which can be cloned as scFvs and classified according to pathogenicity. Based on previous findings, this project hypothesizes that only a characteristic oligoclonal set of anti-Dsg B cell clones is present throughout the entire course of pemphigus (with initial manifestation, remission, and relapse), and that the resulting autoantibodies undergo affinity maturation over time through somatic hypermutation.
We also hypothesize that rituximab induces complete remission in some patients without the development of new B cell clones. These hypotheses will be tested by a) using the PhDp to longitudinally clone anti-Dsg antibodies in PV/PF patients, b) applying the PhDp to detect any anti-Dsg B cell clones in patients remitted with rituximab, and c) determining the clonal relatedness, somatic hypermutation, and binding to common Dsg epitopes of the cloned autoantibodies in relapsed patients. The results of this longitudinal study will contribute to a better understanding of the pathophysiology and the development of more specific therapies for pemphigus. They will also allow for a better understanding and explanation of fundamental autoimmune B cell processes in humans.