Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Primary and Secondary Prevention of Peanut and Tree Nut Allergy

Location: Food Processing and Sensory Quality Research

Title: Computationally predicted IgE epitopes of walnut allergens contribute to cross-reactivity with peanuts

Authors
item Maleki, Soheila
item Teuber, Suzanne -
item Cheng, Hsiaopo
item Chen, Deliang -
item Comstock, Sarah -
item Ruan, Sanbao
item Schein, Catherine -

Submitted to: Allergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 24, 2011
Publication Date: October 2, 2011
Citation: Maleki, S.J., Teuber, S.S., Cheng, H., Chen, D., Comstock, S.S., Ruan, S., Schein, C. 2011. Computationally predicted IgE epitopes of walnut allergens contribute to cross-reactivity with peanuts. Allergy. 66(12):1522-1529.

Interpretive Summary: Cross reactivity between peanuts and tree nuts implies that similar immunoglobulin E (IgE) binding sites are present in their proteins. To determine whether walnut amino acid sequences, similar to known peanut IgE binding sequences, react with IgE from sera of patients with allergy to walnut and/or peanut, and if these can be predicted with our computer model found on structural data base for allergic proteins (SDAP). Patient sera was characterized by immune methods to test for IgE-binding to proteins from walnut and peanut allergens. The IgE binding tests and immunoassays show that peanut and predicted walnut epitope sequences compete with a purified peanut allergen, Ara h 2, for binding to IgE in serum from a cross-reactive patient (patients that react to both peanut and walnut). Sequences from a major walnut allergen, Jug r 2, which was predicted to be similar to one of the peanut allergens Ara h 2, a 2s-albumin, bound IgE in sera from five patients who reacted to either walnut, peanut, or both. A predicted walnut epitope competed for IgE binding to Ara h 2 in serum, as well as, the known IgE epitope from Ara h 2.

Technical Abstract: Cross reactivity between peanuts and tree nuts implies that similar IgE epitopes are present in their proteins. To determine whether walnut sequences similar to known peanut IgE binding sequences, according to the property distance (PD) scale implemented in the Structural Database of Allergenic Proteins (SDAP), react with IgE from sera of patients with allergy to walnut and/or peanut. Patient sera was characterized by Western blotting for IgE-binding to nut protein extracts, and to peptides from walnut and peanut allergens, similar to known peanut epitopes as defined by low PD values, synthesized on membranes. Competitive ELISA was used to show that peanut and predicted walnut epitope sequences compete with purified Ara h 2 for binding to IgE in serum from a cross-reactive patient. Sequences from the vicilin walnut allergen, Jug r 2, which had low PD values to epitopes of the peanut allergen Ara h 2, a 2s-albumin, bound IgE in sera from five patients who reacted to either walnut, peanut, or both. A walnut epitope recognized by six patients mapped to a surface-exposed region on a model of the N-terminal pro-region of Jug r 2. A predicted walnut epitope competed for IgE binding to Ara h 2 in serum, as well as, the known IgE epitope from Ara h 2.

Last Modified: 9/20/2014