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Type-1 hypersensitivity reactions to Malassezia pachydermatis extracts in atopic dogs
D O Morris1, N B Olivier, E J Rosser
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing 48824-1314, USA.
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.