Extended boiling of peanut progressively reduces IgE allergenicity while retaining T cell reactivity

Abstract

Background: Current peanut oral immunotherapy is hampered by frequent adverse events. It has been shown that boiling can reduce peanut allergenicity. Hypoallergenic peanut products have the potential to reduce treatment-related reactions during desensitization.

Objective: To show that extended boiling (for up to 12 h) can progressively reduce peanut allergenicity while retaining T cell reactivity.

Methods: Raw peanuts were boiled for half, 1, 2, 4 and 12 h in deionized water. After dehydration, boiled and raw peanuts were ground, defatted and soluble proteins extracted in PBS and cooking water (leachate) retained. SDS-PAGE, Western blot, inhibition ELISA, mass spectrometry and skin prick test were used to characterize changes to peanut allergens and human IgE reactivity. T cell responses to raw and boiled peanut extracts were determined by proliferation of CD4+/CD25+/CD134+ T cells in peanut-allergic and non-allergic individuals.

Results: Extended boiling progressively reduced peanut allergenicity through a combination of leaching of allergens into cooking water, fragmentation of allergens and denaturation of conformational epitopes. Two-hour boiling led to an eightfold reduction in IgE binding capacity of boiled peanuts as determined by inhibition ELISA, while 12-h boiling led to a 19-fold reduction. Mass spectrometry revealed an increasing number of unique allergen peptides with longer boiling times. Raw, 2- and 12-h boiled peanut extracts were equivalent in their ability to stimulate T cell activation and proliferation.

Conclusion and clinical relevance: Progressive reduction in peanut allergenicity with extended boiling does not affect T cell reactivity. Boiled peanuts may be a candidate for oral immunotherapy.

Keywords: T cell reactivity; extended boiling; hypoallergenic peanut; mass spectrometry; peanut allergy; peanut oral immunotherapy.