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Food Allergy Laboratory, INRA, SPI-CEA Saclay, F-91191 Gif sur Yvette
The incidence of food allergy is increasing and the severity of the symptoms commonly observed is worsening. The number of incriminated food allergens is also increasing. There is therefore a need to assess and identify the allergenicity of (new) foods and to consider ways of creating or, on the opposite, of suppressing immunoreactive structure through new technologies for the production and the processing of foods.
Allergenic foods are numerous and each food contains many allergens. They are generally glycoproteins and each of the protein constituents of a food may thus be allergenic. Observations of structure, function and physico-chemical properties of food allergens suggest that they may share common characteristics. Most (plant) allergens belong to protein families involved in biological functions such as defence, storage, transfer of ligands or enzymatic activity. Some have a compact 3 dimensional structure, stabilized by disulfide bonds which protects an active site. In terms of physico-chemical properties, allergens are often stable molecules, i.e. that are quite resistant to denaturation and proteolytic degradation by (gut) proteases and also by heat treatments. On the opposite labile proteins are sometimes considered to be very likely non allergenic.
Each allergen generally comprises numerous immunoreactive molecular structures (epitopes) that appear to be widely spread all along the molecule. Besides conformational epitopes, linear epitopes, i.e. peptide fragments as short as 12-14 amino acid residues, may account for a large part of the allergenicity of the whole protein and even be involved in specific clinical manifestations of food allergy. As far as food allergens are concerned those IgE binding epitopes may be located in hydrophobic regions of the protein where they are buried within its tertiary structure. They are then unmasked and become available for antibody recognition when the protein is degraded during digestion in the gut. Moreover immunological cross-reactions between allergens from various origins also suggest that homologous amino acid sequences, i.e. similar linear epitopes, could be partly responsible for their allergenicity and could represent structures where the frequence and intensity of IgE binding is the highest.
A better understanding of the molecular mechanisms of allergen-IgE interactions would allow to predict the allergenicity of a (novel) foodstuff. Identification of allergenic constituents and characterization of major IgE binding epitopes would then make possible to modify those structures in order to decrease the allergenic potential of this (novel) food.
Those aspects will be further discussed in the paper from different examples of food allergens.
ENZYMATIC MODIFICATION AS A TOOL FOR ALTERATION OF ALLERGENIC ACTIVITY OF FOOD PROTEINS
Central Food Research Institute, H-1022 Budapest, Herman O. 15, Hungary
One of the major challenges of food science and molecular allergy is to predict the allergenic activity of food proteins, particularly in novel foods.
Multidimensional electrophoretic techniques and immunoblotting were used for identification of the changes in the pattern of the structure and biological activity of food proteins in point of view of food safety.
Enzymatic modifications can use as a tool for alteration of the epitope-structures and reduce the allergenic activity of proteins.
Detection in more detail of the immunogenicity and cross-reactivity of plant proteins can gain a better understanding of the fundamental origins of protein allergenicity and can help in the identification and characterization the hazards and
EFFECTS OF PROTEOLYTIC HYDROLYSIS ON GLIADIN IMMUNOGENICITY
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