Clinical and laboratory investigation of allergy to genetically modified foods - Genetically Modified Foods Mini-Monograph

Environmental Health Perspectives, June 15, 2003 by Jonathan A. Bernstein, I. Leonard Bernstein, Luca Bucchini, Lynn R. Goldman, Robert G. Hamilton, Samuel Lehrer, Carol Rubin, Hugh A. Sampson

Technology has improved the food supply since the first cultivation of crops. Genetic engineering facilitates the transfer of genes among organisms. Generally, only minute amounts of a specific protein need to be expressed to obtain the desired trait. Food allergy affects only individuals with an abnormal immunologic response to food--6% of children and 1.5-2% of adults in the United States. Not all diseases caused by food allergy are mediated by IgE. A number of expert committees have advised the U.S. government and international organizations on risk assessment for allergenicity of food proteins. These committees have created decision trees largely based on assessment of IgE-mediated food allergenicity. Difficulties include the limited availability of allergen-specific IgE antisera from allergic persons as validated source material, the utility of specific IgE assays, limited characterization of food proteins, cross-reactivity between food and other allergens, and modifications of food proteins by processing. StarLink was a corn variety modified to produce a Bacillus thuringiensis (Bt) endotoxin, Cry9C. The Centers for Disease Control and Prevention investigated 51 reports of possible adverse reactions to corn that occurred after the announcement that StarLink, allowed for animal feed, was found in the human food supply. Allergic reactions were not confirmed, but tools for postmarket assessment were limited. Workers in agricultural and food preparation facilities have potential inhalation exposure to plant dusts and flours. In 1999, researchers found that migrant health workers can become sensitized to certain Bt spore extracts after exposure to Bt spraying. Thus, the potential for occupational and consumer risks needs to be assessed. Key words: allergens, Bacillus thuringiensis, crops, endotoxins, food hypersensitivity, genetic engineering, genetics, immunology, recombinant proteins, transgenic plants. Environ Health Perspect 111:1114-1121 (2003). doi:10.1289/ehp.5811 available via http://dx.doi.org/[Online 19 December 2002]

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Technology has been used for many years to improve our food supply since the first cultivation of crops such as wheat and barley in Mesopotamia in 6000 BC and the domestication of animals such as sheep and goats in southwestern Asia over 10,000 years ago. More recently, improvement of our food supply through genetic manipulation by breeding was accelerated in the development of hybrid crop varieties in the 1960s and 1970s (a period referred to as the green revolution), which more than doubled the crop production in developing countries. Breeding and selection have been used for many domesticated animal species that are food sources. A good example is chicken, one of the more expensive meats in the 1940s, and now one of the least expensive sources of meat. Cultivation, domestication, breeding, and selection of certain traits of plants and animals have created environmental impacts and major changes to human societies. Although use of technology in breeding plants and animals is not new, new methods of biotechnology incorporate genetic engineering, also referred to as molecular breeding. Genetic engineering facilitates the selection, identification, and transfer of genes encoding for a specific protein into the genome of another organism. This process can determine which proteins are introduced and where they are expressed; in most cases, only minute amounts of a protein need to be expressed to obtain the desired trait.

In assessing the public health aspects of genetically engineered foods, it is the proteins that are expressed that are of interest. Three possible modes of adverse health effects have been hypothesized: toxicity, impaired nutrition, and food allergy. Modifications of expression of protein in foods occur with all kinds of plant breeding, and these theoretical concerns are not unique to genetically engineered foods. However, because genetic engineering is a more powerful tool for making such changes, government authorities in the United States, Europe, Japan, Canada, and elsewhere have taken actions to regulate this class of foods.

In this article, we describe various clinical aspects of food allergy relevant to the assessment of novel proteins in genetically modified foods. Food allergy is among a spectrum of adverse reactions that can result when an individual ingests food or a food additive. Evaluation of novel proteins for potential allergenicity is based on a fundamental understanding of the clinical and biological aspects of these responses. Among food allergy researchers, a number of definitions of food allergy have been used. For the purpose of this article, allergy is defined as hypersensitivity and implies an immunologic reaction to food; other (nonimmunologic) adverse reactions to food will be referred to as "intolerance." This reflects the standard definitions of terms in the United States. It is important to note that the revised nomenclature for allergy proposed by the European Academy of Allergy and Clinical Immunology uses the terms "nonallergic food hypersensitivity" instead of "intolerance," and "food allergy" (IgE-mediated or not) instead of "hypersensitivity." Defined in this manner, food allergy affects only those individuals who have developed an abnormal immunologic response to food. To understand the public health impacts of food allergy, we must appreciate both the prevalence in the population and the clinical spectrum of food allergy.