Cloning and establishment of canine desmocollin-1 as a major autoantigen in canine pemphigus foliaceus

Pemphigus foliaceus (PF) is the most common antibody-mediated autoimmune skin disease of dogs. Desmoglein-1 (DSG1), the major human PF antigen, represents only a minor autoantigen in canine PF (cPF). A recent immunomapping study proposed desmocollin-1 (DSC1) as a relevant candidate autoantigen for cPF. To investigate this hypothesis, 85 cPF sera were screened for the presence of anti-DSC1 IgG using indirect immunofluorescence (IIF) on live canine DSC1-transfected 293T cells. Seventy-five sera contained detectable antikeratinocyte IgG on IIF using footpad substrate (IIFpos cPF), while 10 did not (IIFneg cPF). Sera from 35 healthy dogs, eight from exfoliative superficial pyoderma (ESP)-affected dogs and 21 dogs with non-PF autoimmune blistering skin diseases served as controls. All sera were tested concurrently by IIF on canine DSG1-transfected as well as nontransfected cells. None of the healthy dog or ESP sera labelled any of the transfected or nontransfected cells. Fifty-seven of 75 IIFpos cPF (86%) and 7/10 of IIFneg cPF sera (70%) contained detectable anti-DSC1 IgG. None of these sera recognized nontransfected cells. Five cPF sera (6%) recognized DSG1 in addition to DSC1. Finally, 5/21 (24%) sera from dogs with non-PF autoimmune blistering diseases contained low anti-DSC1 IgG titers. In 7/10 dogs (70%), from whom serial serum samples were collected during treatment, anti-DSC1 IgG titers decreased in parallel with the reduction in disease clinical severity. Altogether, these findings suggest that DSC1 is a major autoantigen in cPF.