Abstract
Peanut allergic individuals can be both co-sensitized and co-allergic to peanut and tree nuts. At the moment, standard diagnostic approaches do not always allow differentiation between clinically relevant sensitization and nonsignificant cross-reactions, and the responsibility of each allergen remains unclear. The objective of this study was therefore to determine a peanut sensitization profile in a cohort of Canadian peanut allergic children and assess the immunoglobulin E (IgE) molecular cross-reactivity between peanut, almond, hazelnut and pistachio. The specific IgE (sIgE) levels of each patient serum were determined by ImmunoCAP, indirect ELISA and immunoblot to examine their sIgE-binding levels and profiles to peanut proteins. Reciprocal inhibition ELISA and immunoblotting were used to study sIgE cross-reactions between peanut and the selected tree nuts using an adjusted and representative serum pool of the nine allergic patients. The results showed that the prepared peanut and tree nut protein extracts allowed for the detection of the majority of peanut and selected tree nut known allergens. The reciprocal inhibition ELISA experiments showed limited sIgE cross-reactivities between peanut and the studied tree nuts, with peanut being most likely the sensitizing allergen and tree nuts the cross-reactive ones. In the case of hazelnut and pistachio, a coexisting primary sensitization to hazelnut and pistachio was also demonstrated in the serum pool. Reciprocal inhibition immunoblotting further revealed that storage proteins (2S albumin, 7S vicilin and 11S legumin) could possibly account for the observed IgE-cross-reactions between peanut and the studied tree nuts in this cohort of allergic individuals. It also demonstrated the importance of conformational epitopes in the exhibited cross-reactions.
Highlights
Peanut and tree nuts are among the most potent food allergens
A complete inhibition (100%) of immunoglobulin E (IgE)-binding was obtained when the pooled sera was preincubated with the peanut extract. These results indicate the presence in the sera of a majority of specific IgE (sIgE) that recognize peanut proteins and which do not bind to the studied tree nut proteins, suggesting a moderate level of cross-reactivity between peanut and tree nuts
The pattern of sensitization to peanut allergens of a cohort of Canadian peanut-allergic children showed a typical North American sensitization profile, with intense reactivity to major peanut storage proteins corresponding to Ara h 2, Ara h 6, Ara h 1 and/or Ara h3
Summary
Peanut and tree nuts are among the most potent food allergens. Allergic reactions to tree nuts and peanut are associated with a higher degree of severity and are identified as leading causes of fatal induced anaphylaxis in North America [1,2]. A more recent survey conducted between 2015 and 2016 estimates the prevalence of peanut allergies in children in the United States to be 2.5% [5], while Weinberger and Sicherer [2] reported an estimated tree nut prevalence varying between ~0.05% and 7.3%. For those who are allergic to peanut or tree nuts, a stringent avoidance of the causal allergen and prompt treatment of reactions remains the cornerstone of treatment. The reaction is caused by proteins that are highly conserved from an evolutionary point of view and that, given their widespread presence, have been termed panallergens, such as the prolamin, PR-10, profilins and lipid transfer protein families [7]
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