The global marketing of GM food has been dealt a blow following reports of allergic reactions to StarLink corn, which was detected in corn food products last fall. (See "Outcry Over Cry9C," ISB News Report, March 2001, http://www.isb.vt.edu/news/2001/news01.mar.html#mar0105.) Further public distrust of transgenic crops is likely to be fueled by these allegations, in spite of a recent Centers for Disease Control (CDC) report countering the claims that StarLink was responsible for the allergic reactions.(1)

This "StarLink event" is helping to create a climate in which biotechnology companies increasingly feel compelled to convince the public that food from transgenic plants is essentially identical to that from traditional crops, and poses no greater risks. Public concern over food allergies in general is also making it difficult to allay the fears about the safety of GM foods. Public awareness of food allergies becomes evident during a trip to the grocery store. A label on a box of instant cake mix warns of an allergy risk because the ingredients contain wheat and freeze-dried egg. A can of beans provides a similar precaution because it was prepared with peanut oil.

Investigations of any and all potential food allergy risks associated with GM food are vital for consumer protection. The US EPA and FDA regulatory agencies are responding to public fears about GM foods by providing increasingly close scrutiny of GM-derived commodities. Few traditionally grown foods and consumer products receive this intensity of inquisition.

Cry9C is a protein in StarLink corn that is being scrutinized as the potential allergen. This insecticidal protein, produced naturally by Bacillus thuringiensis subspecies tolworthi, is a variant of a number of Bt toxins, including the commercially used Cry1A. Bt toxins work by binding to specific receptors on insect midgut cells, causing lysis and ultimate decay of the insect's digestive tract. Bt proteins are host specific and do not bind to vertebrate cells. According to the CDC, the Cry9C protein shares several molecular properties with proteins that are known food allergens, which is given as a reason the EPA did not license StarLink corn for human consumption.

A large number of proteins, as well as other organic compounds, including complex carbohydrates, terpene-derived compounds, and simple aromatic molecules, are known to induce allergic reactions. Eggs, milk, peanuts, soybeans, and wheat lead the list of foods causing allergies in infants and young children. Adults are more likely to show allergies to crustaceans, eggs, fish, mollusks, peanuts, tree nuts, and wheat. Researchers working with the augmentation of these and related compounds in GMO foods must take into consideration safety concerns and market resistance to any resulting products intended for human consumption.

The incidence of food allergies in the human population is low, approximately 1% for adults and 5% for infants. It is estimated that about 7.5% of the population has reported some type of food allergy or sensitivity. These data are not conclusive, however, and percentages may be exaggerated by conditions mimicking food allergies such as food insensitivities, mild food poisoning, chemical hypersensitivities, reactions to food additives, and allergic reactions to molds or pollens.(2)

In their investigation, the CDC established that 28 of the people who filed adverse event reports (AERs) with the CDC after eating corn products containing the Cry9C protein had experienced a true allergic reaction, unrelated to any other medical condition. The human allergic response produces IgE antibodies to the offending antigen, which can be detected in blood serum; consequently, the CDC initially developed an ELISA test for Cry9C-specific IgE antibodies. Coded serum samples were analyzed from three groups of people: the 28 individuals who reported experiencing an allergic reaction to StarLink; people reported to be highly sensitive to a large variety of allergens; and historically banked serum samples collected before Cry9C entered the food supply. Their study could not confirm a link between Cry9C and the production of detectable amounts of Cry9C-specific IgE. However, the CDC report provided a carefully worded conclusion, stating, "Although our results do not provide any evidence that the allergic reactions experienced by the people who filed AERs were associated with hypersensitivity to Cry9C protein, we cannot completely rule out this possibility, in part because food allergies may occur without detectable serum IgE to the allergens."

In summary, the CDC did not exhaustively resolve the issue of allergenicity to Cry9C. The CDC's guarded conclusions still leave the EPA with the responsibility to decide how to regulate GMOs containing the Cry9C protein and related compounds, and the wary public to decide, once again, whether to feel reassured or apprehensive about eating GM food.

Sources

1. Centers for Disease Control. 2001. Investigation of human health effects associated with potential exposure to genetically modified corn. A report to the US Food and Drug Administration from the Centers for Disease Control and Prevention. http://www.cdc.gov/nceh/ehhe/Cry9CReport/executivesummary.htm

2. US Food and Drug Administration. 1994. FDA Consumer: Food Allergies—Rare But Risky. (Updated, 1997.) http://www.cfsan.fda.gov/~dms/wh-alrg1.html

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