20 May 2002 17:00 EST

by Mary Beth Nierengarten, BioMedNet News

Minneapolis - Agriculture and medicine, long historical twins, are slowly returning to each other after centuries of being separated by evolutionary changes in science and technology, today heard biotechnologists at a meeting on nutrition and health in Minnesota.

Spurred by the need to improve disease prevention and treatment, as well as reduce costs that are making health care prohibitively high, experts in plant breeding, agricultural research, medicine, and other disciplines are returning to food as a source for bolstering health.

Plant-produced antibiotics, allergen-free food, and edible vaccines were among the topics discussed at the 14th Annual Conference on Foods for Health, sponsored by the National Agricultural Biotechnology Council, in Minneapolis.

Basic research in all of these areas shows the feasibility and practicality of modifying a well-understood crop, such as corn, to generate therapeutic agents.

Antibiotics produced by the endosperm in corn is scheduled to enter a clinical trial next year to test its efficacy for herpes simplex virus (HSV), according to Mich Hein, president of Epicyte Pharmaceutical.

If successful, this plant-produced antibiotic could be produced in large quantities at a low cost. This is important, says Hein, given the fact that more than 50 million people chronically suffer from HSV, and another 1.5 million people newly acquire it annually in the US.

Researchers at ProdiGene are also using corn to generate proteins and edible vaccines. "A major technical challenge," said John Howard, the company's chief scientific officer, "is whether we can make functional proteins in plants."

ProdiGene has successfully achieved this by developing production of avidin (a protein from chicken eggs) from transgenic maize. The company says that its avidin can be stored for years without lost activity, has not shown any threat of passing on salmonella contamination, and is partially protected from degradation after digestion by bio-encapsulation in corn.

ProdiGene is also working on developing edible vaccines for hepatitis B, transmissible gastroenteritis virus (TGEV), E. coli labrile toxin (Lt-B), and AIDS.

By modifying a major protein structure of TGEV's molecular properties, researchers found that TGEV-S (the newly formed corn-based antibody) induced memory that was boosted by a subclinical viral challenge, and offered total protection when given orally to pigs. Currently, ProdiGene is trying to commercialize and license this product as a vaccine candidate.

Researchers at the company are also finding promising results for a vaccine for Lt-B (travelers's diarrhea) by extracting ETEC, the active ingredient in Lt-B, and putting it into corn that is then fed to mice. Evidence so far shows that Lt-B germ is protective against Lt.

Another area that holds much promise at the research stage is the development of allergen-free foods.

Samuel Lehrer, research professor of medicine at Tulane University, discussed both failures and successes in this newly emerging field. Highlighting the concern of introducing allergens into genetically-modified foods, Lehrer noted the attempt to generate transgenic soybeans expressing the brazil nut protein, methionine, despite concerns about the allergenicity of brazil nuts. Evidence confirmed the presence of the Brazil nut allergen in the transgenic soybeans and the product was cancelled.

Some success in this area has been achieved in research on the major allergen in shrimp. Examining the coiled-coil structure of tropomyosin, which is present in all living creatures, "we wanted to investigate one of the chains and find the molecule that causes the allergen," said Lehrer.

The research shows that the development of hypoallergenic shrimp requires, first, determining amino acid substitutes that inactivate all allergenic epitopes, and then developing and expressing a modified gene for tropomyosin. Development further requires testing recombinant protein allergenicity, and suppressing native and expressing mutated tropomyosin in shrimp.

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