Allergen stabilities and compatibilities in mixtures of high-protease fungal and insect extracts

Background: Current practice guidelines state that protease-rich fungal and insect extracts can be combined when preparing immunotherapy vaccines, but data supporting the stability of allergens in these mixtures have not been reported. Objective: To determine the stabilities and compatibilities of Alternaria alternata and German cockroach allergens in mixtures with other high-protease fungal and insect (cockroach, imported fire ant) extracts at final extract concentrations consistent with injection dose targets for maintenance immunotherapy. Methods: Mixtures containing Alternaria, German cockroach, and other fungal and insect extracts frequently included in immunotherapy vaccines were analyzed by a combination of quantitative analyses (enzyme-linked immunosorbent assays for multiallergen immunoglobulin E [IgE]-binding potency, major Alternaria allergen Alt a 1, and major German cockroach allergens Bla g 1 and Bla g 2) and qualitative methods (immunoblotting). Mixtures and analogous single-extract controls containing 10 to 50% glycerin were evaluated after storage for up to 12 months at 2 degrees C to 8 degrees C. Results: Mixtures of extracts within the same phylogenetic groups (fungal-fungal, insect-insect) retained favorable Alternaria and German cockroach allergen levels and activities under most conditions examined. For several cross-taxonomic (fungal-insect) extract combinations at 10 to 25% glycerin concentrations, different immunochemical test methods measuring single (major) or multiple allergens yielded threefold to 10-fold variations in allergen recoveries. Conclusion: Allergen compatibilities can be compromised in some fungal-insect extract mixtures, contrary to current immunotherapy practice parameter recommendations. Separation of these products into different treatment vials may be required to produce stable mixtures for subcutaneous immunotherapy. Data from assay methodologies with distinct binding specificities provide a critical assessment of allergen activities in high-protease extract mixtures. (C) 2012 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.