The effects of storage conditions on the stability of house dust mite extracts

Purpose: Allergen extracts from the house dust mite (HDM, Dermatophagoides pteronyssinus) are widely utilized for diagnosis and treatment of allergic diseases. It is known that allergen extracts degrade and lose potency when stored over time. Methods: This study aimed to determine the optimal conditions for stability of allergen extracts. This study was undertaken to investigate the optimal storage conditions for HDM extracts, the effects of adding 0.03% human serum albumin (HSA) and 50% glycerol were evaluated at -20°C, 4°C, and room temperature (RT). Changes in protein and group 1 major allergen (Der p 1) concentration, as well as allergenicity were measured over a 1 year period using the Bradford assay, twosite ELISA, and ELISA inhibition. Results: Protein concentrations decreased by 86%, 51%, and 6% at RT, 4°C, and -20°C, respectively, when stored in distilled water. Overall allergenicity remained high (89.9%) when the extracts was reconstituted in 50% glycerol solution, and was 93.1% when reconstituted in 50% glycerol and 0.03% HSA at RT. Allergenicity was decreased to 36.6% and 33.3%, however, reconstitution in DW or 0.03% HSA solution at RT, respectively. Allergenicity was remained high as 92.0%-97.0% when stored at 4°C regardless of the buffer conditions. Conclusions: Storage temperature is the most important factor in preserving allergenicity of HDM extracts, which is ideal at 4°C. The addition of 50% glycerol to the storage buffer was also found to play an important role in increasing the shelf-life of HDM extracts at RT.