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Dr. Alan McHughen, a Plant Biotechnology Extension Specialist at the
University of California, Riverside took the time to address some
misconceptions concerning transgenic agriculture and allergies, September
2005.

One of the greatest fears about biotechnology is that common foods might
inadvertently harbor new allergens, becoming an unexpected food hazard to
unknowing consumers. There is no evidence to support this fear, in spite of
years of consumption of a range of biotech foods by hundreds of millions of
people.

Biotechnology is instead being used to overcome the hazards of common food
allergies, in the process offering one of the greatest benefits of this
precise science. Instead of creating new allergenic threats, biotechnology
is eliminating allergens from common foods.

Q. How do food proteins cause allergy?

A. In humans and other mammals, the normal immunological response is to
protect against the presence of unusual, potentially harmful proteins. But
in the allergic person, the immune system overreacts to certain specific
proteins, the allergens. During an allergic reaction, the immunoglobulin
(IgE) defense responds to the presence of certain proteins (or to other
metabolites associated with proteins). The IgE antibodies bind to mast
cells, causing a release of histamine normally contained within the mast
cells. The released histamine, in turn, causes the inflammation we observe
as red wheals and rashes, and may constrict airways and dilate blood
vessels.

Depending on the severity of the reaction, the victim may suffer from mild
discomfort or irritation to, in extreme cases, potentially fatal
anaphylaxis. The major food allergenic proteins occur in just eight food
groups: wheat, soybeans, peanuts, tree nuts, milk, eggs, fish, and
shellfish. Together, these few foods are responsible for more than 90
percent of food allergies.

Q. What is genetic engineering doing to solve the allergenic protein
problem?

A. Genetic engineering of foods is now being used to alleviate the dangers
of allergens, through at least three different approaches:



One approach is simply to remove the offending protein from the food. This
strategy depends on identifying the specific allergenic protein, then
engineering the plant or animal not to produce that protein. This is not as
simple as it sounds, because foods contain as many as 10,000 different
proteins. Even the common Brazil nut?s allergenic protein was not identified
until recently (and that was with the help of biotechnological methods).

Also, the allergenic factor may be not one protein, but several. Peanuts,
another common allergenic food, contain at least three classes of allergenic
proteins; removing just one allergen will not necessarily help if the other
allergens remain.

Another complication: Sometimes the allergenic protein is a major component
of the food, so removing it will alter the characteristic nature of the
food. Or, the allergenic protein may play a crucial role in the growth or
development of the plant or animal producing it; removing the critical
protein may kill the plant or animal before it can be harvested. So, while
using biotechnology to remove a protein seems simple, it is not always
feasible.


A second strategy is to alter the protein so it still functions normally in
the crop or animal, but is not recognized by the allergic person?s body as
the trigger for an allergic response. We may be able to use genetic
engineering to change the structure of the protein at the IgE recognition
portion without affecting the normal function of the protein.

This approach is being undertaken in peanuts, where researchers are altering
the three major allergens to make them less recognizable by IgE antibodies.


A third method is to provide the body with a means to lessen the allergic
response. A feature common to many allergenic proteins is that they are very
stable and slow to digest in the stomach. Instead of being quickly destroyed
by digestion as most proteins are, allergenic proteins remain intact longer,
giving them time to prompt the allergenic response.

In this approach, researchers have identified a common mechanism that causes
digestive stability in the allergens, and have sought to overcome that
mechanism. Scientists have shown the potential for this approach by treating
milk, one of the common allergenic foods, with a common, non-allergenic
protein called Thioredoxin H, which breaks the chemical bonds in the
allergenic proteins. Milk so treated was 300 times less allergenic when fed
to sensitive dogs.


The researchers are now using genetic engineering to add additional
Thioredoxin H to wheat, soy, and other allergenic foods in the hope that the
additional enzyme (Thioredoxin is already present in small amounts) will
help break down the allergens.

All of these strategies are in early stages of research and are not ready
for market. However, preliminary results from all are encouraging and show
real potential for providing relief to millions of humans suffering allergic
reactions to common foods. Clearly, here is a use of genetic engineering
with real and important benefit to consumers.

References and further reading

Buchanan, B., Frick, O.L., Lemaux, P.G., and McHughen, A., ?Mitigation of
food allergies via crop biotechnology,? Symposium on Advances in Clinical
Nutrition, American College of Nutrition, San Antonio, Texas, October 5,
2002.

Burks W., Lehrer, S.B., and Bannon, G.A., ?New approaches for treatment of
peanut allergy,? Clinical Reviews in Allergy & Immunology 27 (3): 191?196,
December 2004.

Konan K.N., Viquez, O.M., and Dodo, H.W., ?Silencing the three major
allergens for the production of hypoallergenic peanut,? Journal of Allergy
and Clinical Immunology 111 (4): L6, April 2003.

[www.ars.usda.gov] ? Researchers
Develop First Hypoallergenic Soybeans, originally published in Agricultural
Research, September 2002.

[www.agribiotech.info]

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