Shared VH1-46 gene usage by pemphigus vulgaris autoantibodies indicates common humoral immune responses among patients

Pemphigus vulgaris (PV) is a potentially fatal blistering disease caused by autoantibodies against desmoglein 3 (Dsg3). Here, we clone anti-Dsg3 antibodies from four PV patients and identify pathogenic VH1-46 autoantibodies from all four patients. Unexpectedly, VH1-46 autoantibodies had relatively few replacement mutations. We reverted antibody somatic mutations to their germline sequences to determine the requirement of mutations for autoreactivity. Three of five VH1-46 germline-reverted antibodies maintain Dsg3 binding, compared to zero of five non-VH1-46 germline-reverted antibodies. Site-directed mutagenesis of VH1-46 antibodies demonstrate that acidic amino acid residues introduced by somatic mutation or heavy chain VDJ recombination are necessary and sufficient for Dsg3 binding. Our data suggest that VH1-46 autoantibody gene usage is commonly found in PV because VH1-46 antibodies require few to no mutations to acquire Dsg3 autoreactivity, which may favor their early selection. Common VH gene usage indicates common humoral immune responses, even among unrelated patients.