Peanut extract

End point titration SPTs were performed on school-aged PA children using serial 10-fold dilutions of peanut extract (Greer Laboratories, Lenoir NC) with the GREER pick system. The starting concentration was the standard peanut extract (1:20 wt/vol) with serial 10-fold dilutions (1:200, 1:2000, 1:20,000, and 1:200,000 wt/vol). Peanut SPT was not performed on 3 PA subjects since they were unable to discontinue their antihistamines due to eczema.

The baseline OFC consisted of a cumulative dose of one gram of peanut protein using oat flour as placebo. Subsequent challenges utilized a cumulative dose of 10 grams. OFCs were double-blind through the blinded phase of the protocol and then performed as open challenges. OFCs were considered positive with clear objective signs (e.g. diffuse urticaria, wheezing) or convincing subjective symptoms (e.g. severe, persistent abdominal pain).
Skin prick testing (SPT) was performed at baseline and just prior to each OFC using peanut extract (Greer Laboratories, Lenoir, NC), serial ten-fold dilutions (1:20, 1:200, 1:2,000, 1:20,000, and 1:200,000 wt/vol) of peanut extract, and a panel of 9 other food and environmental allergens (soy, cashew, hazelnut, walnut, cat, dust mite, oak, ragweed, and timothy), using the Greer Pick device.
Laboratory studies included peanut-specific IgE and IgG₄ levels which were measured prior to each OFC (ImmunoCAP). In addition, extensive mechanistic studies, described in detail in the accompanying manuscript¹⁸ were performed prior to each OFC, including spontaneous and stimulated basophil activity, allergen-induced cytokine expression in expression in dendritic cell (DC)-T cell co-cultures by multiplexing technology, and peanut-induced expression of MHC II and costimulatory molecules on DCs by flow cytometry.

BALB/c wild-type mice were injected with 100 μg of peanut extract (Greer Laboratories, Lenoir, NC) adsorbed to 1 mg of alum on days 0 and 14. On days 21, 23, and 25, mice were challenged with 50 μg of peanut extract in 50 μL of PBS intranasally, followed by oral gavage with 2 mg of ground peanut in 200 μL on days 27 and 29. Mice were sacrificed on day 30 and esophagi excised and analyzed.