Allergen-Free Shrimp?
Seafood Marks a Place in Food Safety Research

A buffet of shrimp cocktail, lobster on the half shell, and king crab sounds like a seafood dream come true, but for people with shellfish-food allergies, it can be a nightmare instead.

Now, new genetic studies show promise for putting allergen-free shrimp on our dinner plates someday, scientists said today at the 2003 American Association for the Advancement of Science (AAAS) Annual Meeting.

"It's definitely possible that we'll have foods that are less of a risk for allergy," said Samuel B. Lehrer of Tulane University in New Orleans, Louisiana, where shrimp is a key element of the local cuisine. "There's a lot of work we need to do to be sure to know what to ask."

Lehrer and others are conducting studies on shrimp to better understand the genetic basis for the proteins in foods that cause allergic responses in some people. An expert in food allergens and allergen detection, Lehrer also addressed issues of allergenicity in new products being developed through genetic engineering, and gave an "understanding of the framework that's involved and changing, and a sense of what's being ensured so we don't have exposure to new allergens."

Research in shrimp allergenicity owes its recent strides to ongoing research in plant foods, such as soy and peanuts.

Food allergies are immune responses to proteins from foods that somehow did not get broken down by cooking or digestion. Instead, they entered the bloodstream and interact with antibodies on cells lining the gut, and in the nose, throat, skin, and lungs, for example. These cells then release chemical mediators including histamines, which create unpleasant and sometimes life-threatening allergic responses.

Lehrer has identified the major shrimp allergen and the epitopes—the allergenic portion of the molecule—that bind with an antibody called immunoglobulin E (IgE). The reaction that results from the allergen or epitope causes classical allergic reactions of itchiness around the eyes, throat, skin, and mouth.

Improved detection methods for unknown food allergens can also contribute toward better safety for new food products that are altered through genetic engineering, according to Lehrer, who is in the process of developing an immunological test, with mice, to check foods for allergenicity.

Work on altering animal-based allergens is generally much less further along than that for plant-based food allergens, for which breeding programs and food processing have been used to address allergenicity. Now, working directly at the gene level may put allergen-free peanuts, soybeans, or shrimp on our dinner plates someday, according to Lehrer. "There's concern that new epitopes can be made," Lehrer says of the techniques used to transfer genes in and out of a food plant or animal.

While testing for known allergens has been established, testing proteins that may be expressed in genetically modified foods, which have no previous human exposure, is needed. This scenario raises an interest in developing models for testing allergenicity, says Lehrer, who is developing a mouse-based model to test exactly this. "If there's a way to validate the mouse responses are similar to the human response, this would be a useful way to screen novel proteins.... We saw very good responses to peanut allergens and shrimp allergens and they seem to be similar to human responses. Now, we want to look at responses on an epitope level." Lehrer is also looking at less commonly allergenic materials, like rice, beef and corn.

The biotechnology used to alter food products can also be used to improve food safety by preventing the production of allergy-causing agents, according to Lehrer, who describes his work with shrimp as an example. Lehrer has located the gene sequence that encodes the shrimp allergen and regions of the sequences for the different molecules that interact with the antibody IgE. By altering the epitopes in shrimp allergens that bind to IgE—by just one amino acid—the binding action could be stopped. "This can possibly be used therapeutically or even in reducing the allergenicity of a particular food," Lehrer says.

15 February 2003

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