The epitope stability of Group 1 and Group 2 allergens in mite extracts (1)
Organization to be standardized. In 1988, reference mite extracts prepared from the whole bodies of D. pteronyssinus and D. farinae were selected by the Center for Biologics Evaluation and Research (CBER), US Food and Drug Administration to be used as reference standards. Mite extracts prepared from the whole bodies of mites were known to contain a variety of proteolytic enzymes which might cause degradation of proteins during storage.
Similar results were obtained for Der f 1, Der f 2, and Der p 1 when two different sets of antibodies were used by different laboratories in the sandwich ELISA.
The allergen contents in these extracts decreased at a relatively fast pace in the presence of 50% glycerol. Der f 1 was stable for 3 years and Der f 2 was stable for 1 year when stored at 4°C. Both Der f 1 and Der f 2 were relatively stable at room temperature for 9 months but started to break down after 12 months. Der p 1 and Der p 2 were not stable at any of the storage conditions, although they degraded more slowly at 4 °C as compared with higher temperatures. None of the Group 1 and 2 allergens retained their integrity at 50 °C.
After 30 months of storage, degradation of major allergens occurred even at -20 °C.
A degradation pattern similar to that of the sandwich ELISA results. After 9 months at 50 °C, neither Group 1 nor 2 allergens were detectable by immunoblot.
Relative potency decreased with increasing storage temperatures, but the decrease in potency was about the same for samples stored at 4 °C and those stored at 26 °C.
All mite extracts sold in the US market contained 50% glycerol and were stored at 2 to 8 °C prior to shipping.