Basophil Activation and Peanut-Specific IgE Are Not Predictors of Threshold Dose during a Double-Blind Placebo-Controlled Food Challenge (DBPCFC)

Rationale: Immunologic markers associated with allergen dose threshold are being pursued with limited success using classic markers such as IgE and skin prick testing.  We hypothesized that basophil activation in response to peanut antigen and peanut-specific IgE may correlate with the amount of peanut allergen that could be ingested prior to a subject developing an allergic response during a DBPCFC.

Methods: A retrospective chart review was performed using 54 subjects, 1-11 years old.  Whole blood from each subject was collected prior to the subjects undergoing a graded DBPCFC (50mg, 100mg, 200mg, 500mg, and 1150mg peanut or oat flour). Serum was analyzed for peanut-specific IgE. Whole blood was divided and stimulated in the presence of IL-3 with several dilutions of peanut antigen (1000, 100, 10, and 1 ng/mL) and media alone, after which flow cytometric analysis of the activation marker CD63 was assessed.   Pearson and Spearman correlations, and logistic regression were used to investigate prediction of DBPCFC response.   

Results: The immune markers were poorly correlated with amount of peanut consumed during DBPCFC. The largest correlation observed [with 95% confidence interval] was for basophils stimulated with 100 ng/mL of peanut antigen: Spearman r = -0.23 [-0.47, 0.05], N=51. For peanut-IgE, Spearman r = 0.04 [-0.27, 0.34], N=42.

Conclusions: Peanut-specific IgE and basophil activation were not predictive of the amount of peanut ingested during a DBPCFC in this cohort.  Further studies are needed, ideally incorporating additional markers such as component-resolved analyses.