Background: Atopic dermatitis (AD) is a cutaneous hypersensitivity associated with elevated levels of antigen-specific IgE, commonly to house dust mites (HDMs). It remains controversial as to whether sensitization and clinical disease are induced by cutaneous exposure to HDM.
Objectives: The objectives of this study were to determine whether repeated applications of Dermatophagoides farinae slurry to intact skin of Maltese-Beagle atopic (MAB) dogs would result in the development of clinical signs or lesions resembling spontaneous canine AD, to determine whether repeated slurry applications would induce elevations in mite-specific IgE and/or IgG, and to determine whether mite antigens could be demonstrated within the dermis of application sites.
Methods: Dogs received weekly slurry applications to the axilla and groin, and were patch tested at 120 days, or were patch tested at days 1, 60 and 120, but did not receive further slurry applications. Skin biopsies and serum samples were obtained on days 1, 60 and 120.
Results: Pruritic dermatitis was seen in all dogs by day 60. D. farinae-specific IgE was elevated by day 60. Histologic examination of early application sites revealed mild, mononuclear perivascular dermatitis. Later application sites were characterized by a dense inflammatory infiltrate and oedema in both the dermis and the epidermis. Immunofluorescent staining confirmed the presence of D. farinae antigens in the dermis.
Conclusions: This study demonstrated that epicutaneous application of HDM slurry to MAB dogs results in elevations of HDM-specific IgE, localized and generalized pruritic dermatitis resembling spontaneous canine AD, and histologic changes typical of IgE-driven inflammation. We feel that these results suggest that epicutaneous exposure to allergen may play an important role during both the sensitization and the perpetuation of AD, and provide support for the use of a canine model in the investigation of the pathogenesis of AD.