Optimal conditions for the storage of German cockroach extract

Allergen extracts are commonly utilized for diagnosis and immunotherapy; however, the stability of protease‑rich extracts is important for a precise diagnosis and treatment efficacy. The present study determines the optimal conditions for the storage of German cockroach allergen extract. Cockroach extracts were reconstituted in four buffers: normal saline (NS), 50% glycerol in NS, 0.3% phenol in NS, or 0.3% phenol and 50% glycerol in NS. The extracts in different buffers were stored either at room temperature (18‑26˚C, RT) or refrigerated (2‑8˚C). Subsequently, the protein concentration and allergen content (Bla g 1 and Bla g 2) in the extracts were examined for the course of one year. Extract potency was estimated by inhibition ELISA. At least 90.5% protein, 94.4% Bla g 1, 65.2% Bla g 2, and 91.4% potency remained after one year when 50% glycerol NS was added to the extract with refrigeration. However, less than 13.7% protein, 17.1% Bla g 1, 0% Bla g 2 and 32.5% potency were maintained after one year when 50% glycerol NS was not added to the extract and was maintained at RT. The addition of 0.3% phenol NS did not show significant effects on extract stability. The addition of 50% glycerol NS and refrigerated storage temperature were found to be important factors for increasing the shelf life of protease‑rich cockroach extract.