Effect of roasting on the allergenicity of major peanut allergens Ara h 1 and Ara h 2/6: the necessity of degranulation assays.

BACKGROUND

Peanuts are often consumed after roasting, a process that alters the three-dimensional structure of allergens and leads to Maillard modification. Such changes are likely to affect their allergenicity.

OBJECTIVE

We aimed to establish the effect of thermal treatment mimicking the roasting process on the allergenicity of Ara h 1 and a mix of 2S albumins from peanut (Ara h 2/6).

METHODS

Ara h 1 and Ara h 2/6 were purified from raw peanuts and heated in a dry form for 20 min at 145°C in the presence (R+g) or absence (R-g) of glucose, and soluble proteins were then extracted. Sera obtained from 12 well-characterized peanut-allergic patients were used to assess the IgE binding and degranulation capacities of the allergens.

RESULTS

Extensive heating at low moisture resulted in the hydrolysis of both Ara h 1 and Ara h 2/6. However, in contrast to Ara h 2/6, soluble R+g Ara h 1 formed large aggregates. Although the IgE-binding capacity of R+g and R-g Ara h 1 was decreased 9000- and 3.6-fold, respectively, compared with native Ara h 1, their capacity to elicit mediator release was increased. Conversely, both the IgE-binding capacity and the degranulation capacity of R-g Ara h 2/6 were 600-700-fold lower compared with the native form, although the presence of glucose during heating significantly moderated these losses.

CONCLUSIONS AND CLINICAL RELEVANCE

Extensive heating reduced the degranulation capacity of Ara h 2/6 but significantly increased the degranulation capacity of Ara h 1. This observation can have important ramifications for component-resolved approaches for diagnosis and demonstrates the importance of investigating the degranulation capacity in addition to IgE reactivity when assessing the effects of food processing on the allergenicity of proteins.