Genetically Engineered Foods are not Potentially More Allergenic than their Counterparts
Prof. C Kameswara Rao
Foundation for Biotechnology Awareness and Education,
Bangalore, India krao@vsnl.com, www.fbae.org, www.fbaeblog.org

Risk of allergy from genetically engineered (GE) foods has been made a major biosafety issue, based on two, but now defunct cases.  

A gene for the Brazil nut protein was introduced into soybean to increase the content of methionine, an essential amino acid.   The serum from people allergic to Brazil nuts cross-reacted with extracts of transgenic soybean and not with extracts of its isogenic.      Though no one actually developed allergy by eating the transgenic soybean, since the transgenic is likely to affect people who are allergenic to Brazil nuts, Pioneer Hi-Bred International, the developer of the product, did not proceed with it, an example of self-regulation.  

The Bt Cry9 protein in the Aventis Starlink Bt corn is more stable in simulated digestion than other Bt proteins, and so it was thought that it might be allergenic.  The United States Department of Agriculture (USDA) cleared it for use as both food and feed, but the US Environment Protection Agency (EPA) took a precautionary measure and approved this corn only for animal feed, as animals do not generally suffer from food allergies.   When subsequent studies have shown that Bt Cry9 protein is not allergenic, the EPA too cleared it as food.   Bt Cry9 protein was never demonstrated to be allergenic.  The US Centers for Disease Control (CDC) tested 17 alleged samples of blood from people claimed to have developed allergenic reactions to Starlink and found that none of the blood samples showed cross-reactivity to Cry9 Bt protein.  The Cry9 gene is not deployed in any commercial product now.   Since transgenic products approved as only feed may get into the food products, as has happened with Starlink Bt Cry9 corn that appeared in Taco Bell taco shells, no transgenic is now approved exclusively for use as feed.    This shows that the regulatory regime is in fact functioning effectively.

Ignoring the scientific background and the fact that the two transgenes are not deployed in any product, these cases are repeated ad nauseam to make the world believe that all GE foods are allergenic.  

The term allergy is used very carelessly and most people do not seem to have an idea of what it actually implies.   True allergy involves the immune system.   Often food allergy is not differentiated from other types of adverse non-immunological reactions to food.  Since the public fear allergy, it was is being exploited to whip up fear against GE foods.  

Allergy (or hypersensitivity) is neither new nor universal and it is not an infection that may spread.   Every one of us suffers from one or the other kind of allergy for a certain time in our lives.   Most allergies disappear as mysteriously as they appear.  

Walnuts, pecans, Brazil nuts, cashews, peanuts, soybeans, some varieties of rice and wheat, cucumbers, mushrooms, fish, shellfish, eggs, milk, etc., as also certain drugs like penicillin, cause true allergy in certain individuals.  

Mammalian systems produce different classes of immunoglobulin (Ig) antibodies to most proteins, in an effort to ward off infections (visit www.fabe.org, for a detailed article on Immunology and Immunotechnology).   The IgM antibodies form first, but both the quantity and importance of the later formed IgG antibodies is far greater.   IgA antibodies are involved in the defense of the oral cavity.   The function of IgD antibodies is not well understood.   For some unknown reasons, our immune system also produces another class of antibodies, the IgE, in response to a few proteins, leading to allergenic reactions, manifesting as skin rashes, intestinal inflammation and cramps or respiratory disorders.  

Some non-protein compounds, such as penicillin, may cause severe allergies, and these are called haptens.   But haptens must bind to an endogenous carrier protein to cause allergy.

Repeated exposure to an allergen results in higher and higher titres of IgG antibodies, which neutralize the allergen before it had a chance to elicit IgE antibodies.      This is how we overcome allergies naturally or allergies are clinically treated.   Nevertheless, the best way to avoid allergy is to avoid contact with the allergen, basing on each individual’s experience.  

Tests for allergy are based on models of known allergenic proteins.   Certain short stretches of amino acids (the components of proteins), and not the whole protein, trigger the production of IgE antibodies.   Data have been gathered on more than 200 food proteins with such allergenic sites, but there is no consensus on the allergenic sequences of amino acids in them.   

If a gene product in an isogenic were an allergen, it would be so in the transgenic as well.   Proteins that are normally not allergenic will not suddenly become allergens in a transgenic plant.   The risk of allergy needs to be considered when a GE food or drug contains new protein(s), coded by the introduced genes, but not present in the isogenic variety.   For example, the Bt protein in the Bt potato tuber is new.   Now this protein is known to be safe for human consumption.   Similarly, the iron carrier protein ferritin, whose gene from bean or soybean is being introduced into rice to enhance its iron content, is not allergenic.  

A protein that is degraded before reaching the intestine is very unlikely to cause an allergy.     This has been a basis to investigate a protein further for its allergenic potential.

It is near impossible to test for all the antigens and haptens in a product for the potential of allergy.   Even so, scientists have not been complacent—every new protein in a transgenic food or feed is examined for allergenicity.   In fact, among all the foods we consume, the GE foods are the most thoroughly tested for allergenicity and toxicity.  

While there are no reliable data on food allergies in the developing countries, in the US 5 to 8 per cent of the children and 1 to 2 per cent of the adults are prone to true allergy to some foods.   These people avoid the foods they are allergic to.  

Food and drug based allergies cause several deaths every year. In highly sensitive individuals even 1/44,000 of a peanut kernel may cause anaphylaxis.   Nevertheless, there never was even a simmer of protest against marketing any of the non-GE foods established as severely allergenic.

Concern for public safety is very essential, but spreading fear on political compulsions, exploiting ignorance, is undesirable.   What we need is a rational attitude with concern for the larger benefits for the larger sections of the society and not irrational blanket bans.