Quantitation and thermal stability of the mite allergen DPT 12 in whole mite extracts

Twelve whole mite extracts (WME) from seven sources were examined for their content of the allergen Dpt 12, protein content, and the inhibitory capacity in RAST by use of paper discs coupled with either WME or Dpt 12. Linear regression analysis demonstrated that the concentration of Dpt 12 determined either by single radial immunodiffusion or by RAST inhibition did not correlate with either the RAST-inhibition titer with use of discs coupled with WME or with protein content, suggesting that Dpt 12 content does not reflect the overall potency of WMEs. However, statistically significant correlations were obtained between Dpt 12 content and whole mite-RAST inhibition titers if extracts from the same manufacturer were examined or if data obtained from extracts containing large Dpt 12 to protein concentrations (greater than 25%) were excluded from the analysis. In contrast, statistically significant correlations between protein concentration and WME-RAST inhibition titers (p = 0.00037) and between Dpt 12 content and Dpt 12 RAST-inhibition titers (p = 0.00001) were found. Thermal stability studies demonstrated that Dpt 12 per se and WMEs were stable at 4 degrees C for up to 3 mo. Storage at 23 degrees C for 3 mo, however, resulted in partial loss of both Dpt 12 and whole-mite activity. Substantial losses occurred at 36 degrees C for both 1-month and 3-month incubation periods. Esterase, esterase lipase, and alkaline phosphatase were found in three WMEs studied. Dpt 12 was biochemically unrelated to these enzymes.