Protein Allergy and Genetically Engineered Crops

Abstract

The first genetically engineered (GE) food crop (tomato) was introduced in 1995, followed by the successful development and commercial release of maize, soybeans, cotton, canola, potatoes, papaya, alfalfa, squash, and sugar beets with specific new genetic traits. Genetic engineering is a process to introduce specific genetic changes to improve common crop varieties in specific ways not achievable by conventional breeding. In many cases, this has been accomplished by the insertion of DNA sequences from unrelated sources into the genome of food crops specifically to endow them with biological activities that they otherwise would not possess. The most well-established GE crops express novel proteins that provide the plants with selective insecticidal activity or tolerance to certain herbicides. While there has been ongoing public debate about potential adverse impacts due to consumption of foods produced from these GE crops on human or animal health, the safety of each new event has been evaluated and communicated to regulatory authorities and all necessary regulatory approvals secured prior to their commercial release. A rigorous safety assessment process exists for GE crops. It includes an evaluation of the introduced protein, as well as the crop containing such protein with the goal of demonstrating the GE crop is ‘as-safe-as’ non-GE crops in the food supply. One of the major questions for GE crops involves the assessment of the expressed novel protein or crop for allergenic potential. Currently, no single factor is recognized as a predictor for protein allergenicity. Therefore, a weight-of-the-evidence approach, which considers a variety of factors and approaches for an overall assessment of allergenic potential, is conducted. This assessment is based on what is known about allergens, including the history of exposure and safety of the gene(s) source; protein structure (e.g., amino acid sequence identity to known allergens); stability to pepsin digestion in vitro; an estimate of exposure of the novel protein(s) to the gastrointestinal tract where absorption occurs [e.g., protein abundance in the crop, processing effects (i.e., heat stability)]; glycosylation status; and when appropriate, specific IgE binding studies with sera from relevant clinically allergic subjects. In addition, the amino acid sequences of introduced proteins are evaluated for their potential to induce non-IgE-mediated celiac disease. Since GE crops were first commercialized almost 30 years ago, there is no evidence that the introduced novel protein(s) in any approved GE crop has caused food allergy.