Eat Your Medicine
By Denise Mann
Jul 16, 2001 -- Picture this: You bring your child to the doctor for a back-to-school check-up and leave with a prescription for a granola bar that protects against measles, mumps, rubella, and tetanus.
Sound far-fetched? It's not, say a host of experts who are currently hard at work developing edible vaccines in the form of granola bars, bananas, potatoes, and even corn -- for conditions such as gastrointestinal illnesses, hepatitis B, and AIDS.
The best part? No shot required. But that's not the only potential benefit. They're cheaper to produce than injectable vaccines and don't require refrigeration or clean, sterile needles -- neither of which is often available in underdeveloped nations.
Welcome to the Wonderful World of Bioengineering
Milk-producing animals are also being looked at as potential drug-making factories. On farms across the world, goats, sheep, pigs, and other mammals are being genetically tweaked to produce human proteins in their milk. The protein is then extracted, purified, packaged, and prescribed as drugs.
Edible vaccines and drug-producing animals now join the ranks of cancer-fighting vegetables, herbicide-resistant soybeans, and corn that can kill the bugs that eat it. More than 76 million acres of the nation's farmland are already planted with genetically altered crops.
Some critics, however, fear that genetic tinkering could do more harm than good -- perhaps by introducing allergens into the food. For instance, if an allergy-causing substance -- say, the protein from a tree nut -- were introduced into a soybean, a person with a nut allergy who eats the altered soybean would then theoretically suffer the swelling of the tongue and throat, the diarrhea, hives, cramps, and other symptoms of that allergy.
"There's a lot of worry that genetically engineered proteins cause allergies, but they are pretty well-tested because everyone is aware that this could happen," says Ruth Kava, RD, PhD, director of nutrition at the American Council of Science and Health in New York City. "They test up, down, and sideways."
Genetically engineered produce recently received some public redemption. Government researchers found no evidence that genetically modified Starlink corn caused any allergic reactions in people who consumed it.
This altered corn spread through the human food supply accidentally and prompted a recall of taco shells and other products. It contains a bacterial gene that allows the corn to contain a protein that kills a common corn-eating pest. But the protein, Cry9C, has some characteristics of an allergen. Many people said they reacted to the food, but researchers now contend that the corn products were innocent of causing those reactions.
As it stands today, such foods don't require labeling, but labeling will most likely be required in the future, says Rebecca Goldberg, PhD, senior scientist at Environmental Defense in New York City.
To design edible vaccines, researchers introduce special genes into foods that, when eaten, will spur the production of human antibodies and, they hope, ward off specific diseases.
The first success in this area occurred in 1998 when researchers from the University of Maryland in Baltimore, the Boyce Thompson Institute for Plant Research in Ithaca, N.Y., and Tulane University in New Orleans showed that an edible vaccine can safely trigger significant immune responses in people. In the study, volunteers ate bite-sized pieces of raw potato that had been genetically engineered to produce part of the toxin secreted by the Escherichia coli bacterium, which causes diarrhea. More than 90% of those who ate the potatoes developed a fourfold increase in immunity.
John McClellan, director of marketing at ProdiGene in College Station, Texas, says his company is developing edible hepatitis B and AIDS vaccines. Exactly what shape these vaccines will take is not entirely clear, he says.
"The hepatitis B vaccine may be a prescription for corn in a tablet or in a granola bar, and it may involve eating one granola bar or taking a series of tablets," McClellan says. "The potential AIDS vaccine is harder to call. The testing is in such early stages that it is hard to say what regimen you would have to take it under."
That said, McClellan is very optimistic for eventual success. "Edible vaccines offer the ability to produce large volumes of proteins at very economical costs," he says.
On the forefront of edible vaccine research is William H.R. Langridge, PhD, professor of Biochemistry at the Center for Molecular Biology and Gene Therapy at Loma Linda University in Loma Linda, Calif.
"I think they will all pan out in some degree because it's possible to produce antibodies in plants, and mice and other animals do demonstrate an immune response when they eat them," says Langridge. "The future is very bright."
Along with colleague Jie YU, a PhD candidate, Langridge is developing an edible vaccine that is effective against three common diarrheal illnesses.
"We expect we will have a plant that can make all three antigens," he says. "We are starting a trial now and expect to have results within two or three months.
"The emphasis for a long time has been on injectable vaccines, but I think there are much simpler ways [to deliver vaccines] that are more effective," he adds. The perks of the edible model include, he says, "easy storability, palatability, easy ability to produce, and they don't need refrigeration or fermenting."
One of the problems involved in implementing vaccine programs in underdeveloped nations is that vaccines can't be stored properly and there is no access to sterile equipment.
"So having a vaccine in a food that people like to eat would probably go a long way to preventing disease and not passing it along thorough infected needles," ACSH's Kava says.
"It could be a great boon to undeveloped countries," she tells WebMD.
Thanks for the Mammaries
Taking a gene from one animal and putting it into another is known as transgenics -- and that's the very basic science behind a new trend in drug production.
Transgenic animals are bred to produce human proteins in their milk. For example, goats can be bred to produce an anti-clotting protein, called human antithrombin III, which is used in patients undergoing open-heart surgery. It's being studied in the U.S. and Europe.
And a Scottish company, PPL Therapeutics, is breeding sheep that may produce a protein that can help hemophiliacs who lack an important blood-clotting factor. Others are working at applying this technology to develop treatments for cystic fibrosis, stomach ailments, and cancer.
It's not simple or cheap, but these kinds of transgenic approaches are less expensive than obtaining the necessary proteins from humans. Again, however, the new method does raise some significant health questions: For instance, can infectious agents in animals -- such as mad cow disease -- cross species barriers and affect human health?
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