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

Abstract

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.

Pemphigus

“…Surprisingly, anti-desmoglein 3-secreting B cells that use V H 1-46 have relatively few somatic mutations and require few to none of these mutations to bind to desmoglein 3, in contrast to B cells using other V H genes, which are highly mutated and require somatic mutations to maintain desmoglein 3 autoreactivity 60,83 . These data indicate that naive V H 1-46 B cells might be prone to desmoglein 3 autoreactivity.…”

“…In pemphigus vulgaris and paraneoplastic pemphigus, V H 1-46 antibody heavy chain gene usage by desmoglein 3-reactive B cells is commonly observed 83,84 . Surprisingly, anti-desmoglein 3-secreting B cells that use V H 1-46 have relatively few somatic mutations and require few to none of these mutations to bind to desmoglein 3, in contrast to B cells using other V H genes, which are highly mutated and require somatic mutations to maintain desmoglein 3 autoreactivity 60,83 .…”

“…These data indicate that naive V H 1-46 B cells might be prone to desmoglein 3 autoreactivity. Interestingly, AK23, a pathogenic mouse monoclonal anti-desmoglein 3 antibody cloned from pemphigus vulgaris model mice, was transcribed from a gene that was highly homologous to the human V H 1-46 gene and had few somatic mutations 83 , suggesting similar selection mechanisms in response to desmoglein 3 in humans and mice.…”

“…V H 1-46 usage has been described in B cells responding to the rotavirus capsid protein VP6 (REFS 83,87). However, crossreactivity of V H 1-46 B cells to both desmoglein 3 and VP6 in patients with pemphigus vulgaris is rare owing to the different nature of the somatic mutations that favour reactivity against desmoglein 3 versus VP6.…”

Restricted, canonical, stereotyped and convergent immunoglobulin responses

“…Other stereotyped autoantibody responses include antidesmoglein antibodies in pemphigus patients which tend to be from B cells with highly similar variable region gene rearrangements encoded by VH1-46 and with highly similar CDR3s [46,47]. B-cell clonal expansions found in the salivary glands of patients with Sjö gren's syndrome tend to use one of three VH genes, including the pervasive VH1-69 gene in a third of the isolates [48].…”