Type-1 hypersensitivity reactions to Malassezia pachydermatis extracts in atopic dogs

Abstract

SUMMARY Objective To investigate the potential allergenic role of the yeast Malassezia pachydermatis in dogs with clinical diagnosis of atopic dermatitis. Animals 5 clinically normal nonatopic dogs, 10 atopic dogs with cytologic evidence of Malassezia dermatitis, and 12 atopic dogs without cytologic evidence of Malassezia dermatitis. Procedure A crude yeast extract was produced by disrupting the cell wall of M pachydermatis . The crude extract and 8 of its fractions, which were generated by fractionation in a high-performance liquid chromatography column, were injected along with 46 commercial allergens for intradermal allergy testing of normal and atopic sample populations. Significant difference between atopic populations was evaluated, using a threshold concentration of crude yeast extract that failed to induce wheal-and-flare responses in normal nonatopic dogs. Results Atopic dogs with cytologic evidence of Malassezia dermatitis had significantly greater wheal-and-flare reactions to intradermal injection of crude extract of M pachydermatis than did atopic dogs without cytologic evidence of Malassezia dermatitis. Conclusions It is concluded that M pachydermatis is capable of promoting type-1 hypersensitivity reactions in dogs with an atopic dermatitis phenotype. Clinical Relevance Currently, Malassezia dermatitis is principally managed by use of antifungal chemotherapy. Because the yeast appears to be a contributing allergen in dogs with atopic dermatitis, hyposensitization with M pachydermatis extracts may offer a future alternative to extended or repeated episodic administration of antifungals for extended control of recurrent infections. ( Am J Vet Res 1998;59:836–841)