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Safety assessment of biotechnology food products with respect to allergenicity
The safety evaluation of genetically modified food crops includes testing for stability in pepsin digestion and in some cases, testing for protein-specific human IgE if allergy is suspected. The studies described in this dissertation included tests of potential improvements in both the pepsin stability assay and the specificity of IgE binding. Inclusion of routine pepsin activity determination as quality control checks and 100% and 10% of undigested test protein in the SDS-PAGE stained gels improved objective estimation of end point of digestion. The in vitro IgE tests were improved by using inhibition assays with and without protease-digested glycoproteins [purified navy bean alpha-amylase inhibitor (αAI) and phytohemagglutinin (PHA)] to distinguish IgE binding between protein and carbohydrate determinants as these have different biological relevance. ^ Application of the recommended changes in the allergenicity evaluation was tested by evaluating αAI from transgenic and non-transgenic legumes. The αAI confers protection against predation by beetles. Bioinformatics comparison of αAI to allergens listed in http://AllergenOnline.org/ using the 80mer FASTA search identified a 42% amino acid sequence identity match between αAI and peanut agglutinin (PNA), a minor allergen. IgE tests with sera from 34 legume-allergic subjects (33 allergic to peanut) showed relatively weak IgE binding by 35% of subjects to PNA and 11% to αAI, although IgE inhibition tests revealed a lack of common IgE binding epitopes between PNA and αAI. Three of 13 PNA-positive sera had biologically relevant IgE to PNA but not to αAI based on induced β-hexosaminidase release from sensitized humanized rat basophilic leukemia cells. This evidence indicates a lack of cross-reactivity between αAI and PNA. Further, all IgE binding to αAI was to the cross-reactive carbohydrate determinants which failed to induce basophil activation. The stability of αAI to pepsin digestion and exhibited positive IgE binding are considered as risk factors in the allergenic safety assessment. However, the actual risks of allergy due to legume αAI are clearly low based on extensive consumption of the primary source, common beans which rarely cause allergy. ^
Agriculture, Food Science and Technology
Ofori-Anti, Afua Okobea, "Safety assessment of biotechnology food products with respect to allergenicity" (2010). ETD collection for University of Nebraska - Lincoln. AAI3412901.