Mammalian-derived respiratory allergens - Implications for diagnosis and therapy of individuals allergic to furry animals

Furry animals cause respiratory allergies in a significant proportion of the population. A majority of all mammalian allergens are spread as airborne particles, and several have been detected in environments where furry animals are not normally kept. The repertoire of allergens from each source belongs to a restricted number of allergen families. Classification of allergen families is particularly important for the characterization of allergenicity and cross-reactivity of allergens. In fact, major mammalian allergens are taken from only three protein families, i.e. the secretoglobin, lipocalin and kallikrein families. In particular, the lipocalin superfamily harbours major allergens in all important mammalian allergen sources, and cross-reactivity between lipocalin allergens may explain cross-species sensitization between mammals. The identification of single allergen components is of importance to improve diagnosis and therapy of allergic patients using component-resolved diagnostics and allergen-specific immunotherapy (ASIT) respectively. Major disadvantages with crude allergen extracts for these applications emphasize the benefits of careful characterization of individual allergens. Furthermore, detailed knowledge of the characteristics of an allergen is crucial to formulate attenuated allergy vaccines, e.g. hypoallergens. The diverse repertoires of individual allergens from different mammalian species influence the diagnostic potential and clinical efficacy of ASIT to furry animals. As such, detailed knowledge of individual allergens is essential for adequate clinical evaluation. This review compiles current knowledge of the allergen families of mammalian species, and discusses how this information may be used for improved diagnosis and therapy of individuals allergic to mammals.