NEW ORLEANS—Genetically modified food has become so prevalent that most everyone in the United States has consumed some—knowingly or not. The concept behind altering the genetic code of food crops, however, remains controversial because of concern that it may generate harmful or nutritionally inferior products.

Not to worry, say advocates. They assert that genetically modified foods such as corn, potatoes, and soy beans are more healthful, less expensive, and better for the environment. The modifications in these crops address deficiencies in nutrients or improve insect resistance so that pesticide use can be decreased. Genetically modified food can often be produced in larger quantities on less land than can non-modified food.

Opponents point out, however, that allergic reactions are a major risk of consuming genetically modified food. And the exogenous proteins used to make the modifications could be the trigger.

How great is this risk? And how can physicians determine if an allergic reaction was caused by a genetically modified food? Several experts addressed these questions during a symposium at the 57th Annual Meeting of the American Academy of Allergy, Asthma, and Immunology held in New Orleans.[1]

THE RISK IS LOW—FOR NOW

Genetically modified food has an extraordinarily low risk of allergenicity, maintained Stephen L. Taylor, PhD, because current modification techniques call for the insertion of only trace amounts of a few novel proteins.[1] Because most foods are not innately allergenic despite having millions of proteins, adding a few more is unlikely to make them so, said Dr. Taylor, head of the Department of Food Sciences and Technology at the University of Nebraska in Lincoln.

Most of the novel proteins now in use are enzymes unstable to digestion, commented Dr. Taylor, who is also Director of the Food Processing Center at the University of Nebraska. “The chances of them surviving to become allergens in the gastrointestinal [GI] tract are probably quite small,” he stressed.

Genetically modified food also undergoes thorough assessment for allergenicity before coming to market. These assessments have become increasingly rigorous and are monitored by many governments, including those in the United States, Canada, Japan, and Europe, Dr. Taylor related.

The source of the protein used is key, said Dr. Taylor, and the risk of allergenicity is greatest when modifications are made with genetic material from known allergens—peanuts, for example. Genes from known allergens are currently not used in any of the available genetically modified foods. Further, they are uncommon in those that are being developed. This risk may increase in a few years, he cautioned, because future generations of these foods are likely to contain large amounts of many novel proteins.

SPOTTING AN ALLERGIC REACTION

Food allergy is an immunoglobulin E (IgE)–mediated immune response that starts with an initial allergenic food exposure and results in sensitization.[2] Symptoms may occur with subsequent exposures. About 2% of adults and 5% of children have food allergies. Further, 70% to 75% of adverse reactions are caused by milk, eggs, or peanuts.

Allergic reactions to a food are usually limited to the skin, respiratory tract, or GI tract. Symptoms include urticaria, angioedema, pharyngeal edema, wheezing, coughing, vomiting, diarrhea, and abdominal pain. “We might want to ask about [these types of symptoms] if someone is complaining about [an allergic reaction to] a genetically modified organism or food,” said Wesley Burks, MD, Chief of Pediatric Allergy and Immunology at the University of Arkansas for Medical Sciences and Arkansas Children’s Hospital in Little Rock.

Physicians should also ask about the type and amount of food ingested, and whether the patient has eaten it before. The chance of food allergy decreases if the food is unlikely to contain an allergen, the patient reports the same type and degree of symptoms with consumption of different quantities, or there has been no previous exposure. Timing is vital: Symptoms almost always occur within two hours of consuming an allergenic food and often within seconds to minutes.

A skin prick, radioallergosorbent, or immunoblot test should reveal evidence of specific IgE. Though these tests are not now readily available for office use, Dr. Burks predicted that they will be eventually.

Underlying asthma should be suspected if symptoms do not improve when foods thought to be allergenic are removed from the diet. In the absence of anaphylaxis, subsequent challenge with these foods may help patients understand that food allergy is not causing their symptoms, Dr. Burks said.

MAKING FOODS NONALLERGIC

Management of food allergy consists of minimizing symptoms with medication, patient education about which foods to avoid, and therapies that modulate the immune response to allergenic foods.[3] However, genetic engineers are starting to explore another possibility—making allergenic foods hypoallergenic.

Gary Bannon, PhD, and his research team have focused their efforts on peanuts because the exposure risk to this food is high and it can trigger particularly severe allergic reactions in peanut-sensitive individuals. The researchers have successfully altered the three major peanut allergens—Ara h 1, 2, and 3—to prevent the IgE binding necessary for an allergic response.

Their method consists of substituting alanine for amino acids in the allergens’ IgE–binding epitopes. “We have been fairly successful in reducing IgE binding to all three allergens,” reported Dr. Bannon, Vice Chairman and Professor in the Department of Biochemistry and Molecular Biology at the University of Arkansas, Little Rock. The immunoglobulin reaction to genetically modified peanut allergen was assessed in mice, which were sensitized to wild-type Ara h 2 and then desensitized with modified Ara h 2.[4] IgE and IgG2a levels rose when the mice received the wild-type allergen and fell when they were given the mutant allergen.

In addition, genetically modified Ara h 2 was associated with lower anaphylaxis and histamine-release scores. And, it still showed the ability to interact with T cells, a characteristic that may be necessary for effective immunotherapy, Dr. Bannon said. This mouse model is clinically relevant, he suggested, because the IgE–binding epitopes on Ara h 2 are the same in peanut-sensitive mice and humans. “More important,” he added, “the same immunodominant epitopes are recognized in mouse versus man.”

—Timothy Begany