Location: Healthy Processed Foods ResearchTitle: Identification, characterization, and initial epitope mapping of pine nut allergen Pin k 2
|FAN, YUTING - Jiangnan University|
|JIANG, YI - Shenzhen University|
|LYU, SHU-CHEN - Stanford University|
|NADEAU, KARI - Stanford University|
Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2016
Publication Date: 10/26/2016
Citation: Zhang, Y., Du, W., Fan, Y., Jiang, Y., Lyu, S., Nadeau, K.C., McHugh, T.H. 2016. Identification, characterization, and initial epitope mapping of pine nut allergen Pin k 2. Food Research International. 90:268-274. doi.org/10.1016/j.foodres.2016.10.043.
Interpretive Summary: Most food allergens have been defined by the observation that serum immunoglobulin E (IgE) molecules from allergy patient sera recognize a protein band from a food extract (or a protein expressed from an expression library) followed by the identification of the specific IgE binding protein by sequencing with mass-spectrometry, or other methods. Knowing that the 7S vicilin from a number of nuts (including peanuts, hazelnuts, cashews, pistachios, walnuts, and stone pine nuts) are allergens, we focused on a strategy to determine if Korean pine vicilin is a food allergen by testing whether it binds directly to IgE antibodies in sera from patients who are known to be allergic to pine nuts. This manuscript reports the expression and purification of recombinant Korean pine vicilin, the identification of this protein as a food allergen, and the deduction of information on linear IgE epitopes. These results may spped up the discovery of additional food allergens in tree nuts and accelerate the progress of understanding the allergenicity of food proteins.
Technical Abstract: The aims of this study were to predict, identify and characterize pine nut allergens. Korean pine (Pinus koraiensis) vicilin was predicted to be a pine nut allergen. Recombinant Korean pine vicilin was expressed in E. coli and purified. Natural Korean pine vicilin isolated from pine nuts (which displayed multiple bands in SDS-gels due to posttranslational digestion) and its full length recombinant counterpart were used to test whether it is a food allergen. The recognition of the protein (and its fragments) by patient serum IgE was analyzed by Western blot. The study included fourteen patients diagnosed with clinical pine nut allergy. Twenty nine percent of the patient sera recognized both the natural and recombinant pine nut vicilin, indicating that Korean pine vicilin is a bona fide food allergen. The serum recognition patterns of the naturally occurring protein fragments suggested that some of linear IgE epitopes may be mapped to the fragment boundaries. The chemical and thermal stability of the recombinant protein was investigated. It underwent a thermal transition with a Tm=76.6 °C. The transition was accompanied by an increase in the amplitude of the circular dichroism signal at 220 nm. Urea induced unfolding of the recombinant protein had a Cm of 4.6 M.