Comparison of commercial peanut skin test extracts.

Abstract

Skin prick testing is a major tool for diagnosing food allergy. Food allergen extracts have not been standardized; this may lead to great variability in the predictive accuracy of skin prick tests. Six commercial peanut skin test extracts were compared in vitro with RAST inhibition assays, ELISA, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting with sera from peanut-allergic adults and in vivo by skin prick testing. ELISA showed that the content of peanut allergens Ara h I and Ara h II in the extracts ranged from 0.0015 to 0.0236 and 0.0001 to 0.0164 mg Eq/ml, respectively. RAST inhibition studies showed that the extracts produced curves of similar slope, suggesting conservation of allergenic epitopes. SDS-PAGE revealed differences in protein profiles because roasted extracts generally possessed the same number and proportion of major protein bands but raw extracts varied more in both respects. SDS-PAGE and immunoblotting showed that two of the extracts contained major IgE-binding protein bands that did not appear in the others. One roasted extract gave little protein banding and consequently little IgE binding. Skin testing results showed no differences in the ability of the extracts to provoke a positive skin test response in peanut-sensitive subjects.