Role of epicutaneous exposure to Dermatophagoides farinae in the development of IgE-dependent and independent allergic dermatitis in the dog

by Pucheu-Haston, Cherie.

PUCHEU-HASTON, CHERIE. Role of epicutaneous exposure to Dermatophagoides farinae in the development of IgE-dependent and independent allergic dermatitis in the dog. (Under the direction of Dr. Bruce Hammerberg.) Atopic dermatitis (AD) is an inflammatory and pruritic allergic skin disease of humans and several species of domestic animals. It presents as a clinical syndrome with characteristic features, including a young age of onset, genetic predisposition, dermatitis of flexural skin and predisposition to secondary infections. Clinical disease is most frequently observed with IgE antibodies to environmental allergens, especially those associated with several species of housedust mite (HDM), including Dermatophagoides pteronyssinus and Dermatophagoides farinae. Although the immune response in established AD has been well studied, many questions remain regarding the development and perpetuation of clinical disease. For example, it remains unclear as to whether naturally occurring sensitization and the development of clinical disease can be induced by cutaneous exposure to HDM allergens. Most research on the role of epicutaneous allergen exposure during the sensitization phase of AD has been performed in mouse models. However, extrapolation of the results of murine studies to spontaneous human disease is limited by the existence of subtle but important differences in the cellular distribution and function of several receptors and mediators critical to the development and maintenance of cutaneous hypersensitivity. A complementary alternative model is the dog, a species in which spontaneous allergic diseases are common and artificial sensitization is both possible and commonly performed. Historically, research in this species has been limited due to the lack of caninespecific reagents, but recent advances in the development of monoclonal and polyclonal antibodies and primer sequences for use in the dog now allows research to be performed at a high level of sophistication. The current work describes the results of three experiments designed to further understanding of the role of epicutaneous allergen exposure in the development and perpetuation of AD. First, the gross, microscopic and inflammatory mediator responses of normal dog skin following IgE-mediated challenge were evaluated by intradermal injection of cross-linking anti-IgE antibodies. This study provided important baseline data and established optimized sample processing protocols for the following two studies. Second, the cutaneous and systemic response to cutaneous allergen exposure was evaluated by repeated epicutaneous application of a sonicated slurry of Dermatophagoides farinae house dust mites to the intact skin of allergy-predisposed Maltese-Beagle cross-bred dogs. This study demonstrated that both cutaneous and systemic inflammation similar to naturally-occuring AD can be induced in the dog by cutaneous exposure to a mix of mite allergens. Finally, the role of allergen proteolytic activity in facilitating epicutaneous sensitization was evaluated by repeated epicutaneous application of either proteolytically-active or –inactive Der f 1 house dust mite allergen. This study demonstrated demonstrate that cutaneous exposure to Der f 1 allergen through intact canine skin may be sufficient to induce sensitization, and suggest that this response may be facilitated by the proteolytic activity of the allergen. Role of epicutaneous exposure to Dermatophagoides farinae in the development of IgEdependent and independent allergic dermatitis in the dog By Cherie Pucheu-Haston A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Immunology Raleigh 2006 Approved by __________________________ Dr. Thierry Olivry ________________________ Dr. Gregg Dean ___________________________ Dr. Keith Linder ___________________________ Dr. Bruce Hammerberg Chair of Advisory Committee