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INT – ALLERGY TESTING
When food causes allergies
23 November, 2005. Source: Checkbiotech, Annette Ryser
Researchers at the University of Nebraska and the Netherlands reviewed the process for evaluating the potential risk of allergies in genetically modified food crops.
Genetically modified (GM) crops may contain new proteins from other plants or from bacteria, fungi and animals. While biotechnologists praise GM crops for their excellent properties in agriculture, consumers would like to know what there are going to eat.
One of the many questions regarding genetically engineered crops is the one of allergenicity: Can the new introduced protein cause allergies in human consumers, when they eat GM crops? Is it a so called allergen? If, for instance, an allergenic protein from peanut were transferred into rice, then those individuals who experience allergic reactions to peanuts could unexpectedly react when consuming the modified rice. While the number of individuals who experience severe food allergic reactions is relatively small, it is important to protect the most susceptible people.
Minimizing the risk of food allergies
There is still no test that can predict with 100 percent certainty whether a new
protein might cause allergic reactions in a specific individual, or whether introducing a new food to a child might cause allergies. However, Dr. Richard E. Goodman from the University of Nebraska and colleagues provide a comprehensive review in International Archives of Allergy and Immunology on how GM crops can be evaluated to assess their potential allergenic properties before being grown commercially. Dr. Goodman noted,”Food produced from GM crops must be as safe as the unmodified varieties.”
Dr. Goodman recommends four general methods to identify proteins that would present a high risk of causing food allergies with some individuals. This process has been used to assess the potential allergenicity of all commercially available GM crops in the US since 1996, with minor revision as knowledge of food allergens and allergies have improved, as outlined in the Codex Alimentarius Commission of the United Nations FAO in 2003.
Four different tests
1. All proteins consist of a sequence of molecules called amino acids. The amino acid sequences of all known food allergens are listed in searchable databases. If a new protein is going to be introduced into a food crop, its amino acid sequence should first be compared with sequences from all known allergens. If there is high similarity of the new protein with a protein from the allergen database, further testing is necessary to either prove, or disprove the potential allergenicity.
2. The new protein must also be tested for resistance to digestion by the stomach enzyme, pepsin, in an acidic solution (pH1.2). This is an ideal digestion assay that provides a good correlation for food allergens. It is not meant to absolutely mimic digestion in all people. The more stable the new protein is under these conditions, the more likely it is to cause food allergies.
3. The specific allergic reactions experienced by most people happen because their immune system produced IgE antibodies that bind to specific proteins. Therefore, when a new protein is taken from a source that is a major allergen, or when the sequence of the new protein is nearly identical to a known allergen, blood samples (sera) from individuals with allergies to the source or to the matched allergen are tested. The test is to determine whether the IgE binds tightly to the new protein. If it does, there would be an increased risk of allergy, if not, the risk is minimal.
4. In addition, the amount of the new protein in a GM crop must be analysed. Many food allergens cause an allergic response when found in large amounts. However, not all abundant proteins are allergenic. Abundance and resistance to digestion by pepsin should be considered together.
Successful assessment of Brazil nut protein in soy
It can happen that during the pre-market testing a protein is recognized as an
allergen. Should this occur, Dr. Goodman’s message is clear –the product must not be commercially released - unless clearly proven to pose minimal risk, or unless the product can be clearly segregated and labeled for the allergic consumer. There is one well documented case where a company introduced a gene from Brazil nuts into soybeans to improve the nutritional quality. Antibodies from some Brazil nut allergic individuals were tested and found to bind to the protein. Therefore product development was cancelled. The assessment worked, as that GM product was never consumed as food.
Dr. Goodman admonished, if this strategy is followed, the application of the allergenicity assessment can greatly reduce the risk of introducing allergenic proteins to food crops. The assessment should certainly always be improved, going hand in hand with the increasing knowledge of the experimental methods within the field of allergen testing. However, new tests must be rigorously validated and demonstrated to be predictive.
“The process of specifically modifying single genes of food crops opens the door to a wide variety of benefits,” said Dr. Goodman. So, considering the great power of biotechnology, it is essential to keep it as safe as possible.
Dr. Goodman currently directs the AllergenOnline database at the University of Nebraska.
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