Development of an enzyme-linked immunosorbent assay for detection of circulating IgG autoantibodies against canine desmoglein 3 in dogs with pemphigus

Pemphigus, a group of autoimmune blistering dermatoses recognized in humans and dogs, is divided into three subgroups: pemphigus vulgaris (PV), pemphigus foliaceus (PF) and paraneoplastic pemphigus (PNP). Previously, we have demonstrated that circulating anti-desmoglein 3 (Dsg3) IgG in dogs with PV and PNP disrupts Dsg3-mediated keratinocyte cell-cell adhesion. The aim of this study was to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of circulating IgG against canine Dsg3 in dogs with pemphigus. A secreted form of recombinant protein representing the entire extracellular domain of canine Dsg3 (cDsg3) was produced by baculovirus expression and used as the coated antigen in the ELISA. The titre of anti-cDsg3 ELISA was significantly higher in canine PV (n = 14) than that in healthy dogs (n = 44) (P < 0.05). Of the canine PV and PNP sera, 11/14 (79%) canine PV sera and the canine PNP serum were positive in the anti-cDsg3 ELISA. On the other hand, 14/37 (38%) sera from canine PF and 9/18 (50%) sera from canine autoimmune subepidermal bullous dermatoses were positive in the ELISA. Circulating IgG against cDsg3 was not recognized in dogs with superficial pyoderma (n = 5), atopic dermatitis (n = 8), or in healthy dogs (n = 44). Moreover, IgG immunoreactivity against cDsg3 in all 21 sera was completely absorbed by preincubation with cDsg3. These findings altogether suggest that the anti-cDsg3 ELISA can be used as a rapid screening test for the detection of circulating anti-Dsg3 IgG autoantibodies in canine pemphigus.