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Background: Better understanding of the relationship between antibody response to peanut and clinical sensitivity might lead to more accurate prognostication., Objective: We sought to investigate peanut-specific IgE and IgG4 epitope diversity in relation to challenge-defined clinical sensitivity to peanut in a group of peanut-sensitized children., Methods: Clinical sensitivity was determined by means of double-blind, placebo-controlled peanut challenges in 24 sensitized children. Six atopic control subjects were included. Specific IgE and IgG4 binding to 419 overlapping 15-amino-acid peptides representing the sequence of recombinant Ara h 1, Ara h 2, and Ara h3 was analyzed by means of microarray immunoassay., Results: Peanut-sensitized patient sera bound significantly more IgE and IgG4 epitopes than control sera. This patient group reacted to the same Ara h 1, Ara h 2, and Ara h 3 epitopes as reported previously. There was a positive correlation between IgE epitope diversity (ie, number of epitopes recognized) and clinical sensitivity (r = 0.6), such that patients with the greatest epitope diversity were significantly more sensitive than those with the lowest diversity (P = .021). No specific epitopes were associated with severe reactions to peanut. IgG4 binding was observed to largely similar epitopes but was less pronounced than IgE binding and did not relate to the clinical sensitivity to peanut. IgE and IgG4 epitope-recognition patterns were largely stable over a 20-month period., Conclusion: Clinical sensitivity, as determined by means of double-blind, placebo-controlled peanut challenge, is positively related to a more polyclonal IgE response, which remains stable over time.

Background: Hazelnut allergy in birch pollen-exposed areas is usually due to cross-reactivity (Cor a 1 and 2) and is usually mild in nature (oral allergy). In areas without birches, severe reactions are more prevalent and linked to sensitization to the lipid transfer protein (LTP) Cor a 8., Objective: We sought to investigate whether sensitization to LTP plays a role in more severe (objective) hazelnut-induced symptoms in children from a birch-endemic area., Methods: Sensitization to Cor a 8, Cor a 2, Cor a 1, and Bet v 1 was determined by means of RASTs and immunoblotting in hazelnut-sensitized children with (n = 8) and without (n = 18) objective reactions during double-blind, placebo-controlled food challenges. Additionally, samples from 191 hazelnut-sensitized nonchallenged children were analyzed., Results: Children with objective reactions during double-blind, placebo-controlled food challenge had higher IgE titers to hazelnut (P < .001) and recognized more allergens on immunoblotting (P = .001) than those without such reactions. All children with objective symptoms were sensitized to Cor a 8 (0.51-23.3 IU/mL) compared with only 1 child without objective reactions (0.90 IU/mL). In a multivariate analysis only IgE against Cor a 8 remained as an independent risk factor (undefined odds ratio; P < .0001). In the group of nonchallenged children (n = 191), the prevalence of LTP sensitization was greater than 30%. Unexpectedly, sensitization to Cor a 1 was observed in children not sensitized to Bet v 1., Conclusion: Sensitization to hazelnut LTP is a risk factor for objective symptoms in children from a birch-endemic area.

Background: Current labeling practices for allergenic foods like peanut can be inadequate. For future regulatory and industry guidelines, information on no-observed-adverse-effect levels (NOAELs) and eliciting doses (EDs) for allergenic foods is necessary., Objective: To determine NOAEL and ED in a representative group of peanut-sensitized children, relate these data to history and sensitization, and evaluate the outcome of dietary management., Methods: From an overall eligible group of 96 peanut-sensitized children, a representative group of 27 was evaluated by questionnaires, skin prick test, determination of specific IgE, and double-blind placebo-controlled food challenge (DBPCFC) with peanut according to the international consensus protocol, with 9 doses ranging from 10 microg to 3 g peanut flour. Dietary management was evaluated over a 12-month period., Results: Twenty-two children (81%) had a positive DBPCFC. The NOAEL in this group was 1 mg peanut flour, corresponding to 2 mg whole peanut. The ED for subjective symptoms (10 mg to 3 g) was significantly lower than for objective symptoms (100 mg to 3 g; P = .002). Severe reactions occurred only at high doses. EDs were not correlated to previous reactions by history, skin prick test, or specific IgE levels. All patients with a positive DBPCFC were advised to follow a strict diet. During the follow-up period, 10 patients had a less strict diet likely containing traces of peanut. In 3 cases, a mild reaction occurred with food products labeled "may contain peanut.", Conclusion: The NOAEL in a representative group of children with peanut allergy was 2 mg. Dietary compliance in half of this group was inadequate.