Genetically engineered tomatoes dangle from a vine in a greenhouse at California State University, Sacramento. Sacramento Bee/Anne Chadwick Williams

CSUS lab seeks vaccines you can eat

By Edie Lau -- Bee Science Writer
Published 2:15 a.m. PDT Sunday, July 28, 2002

The tomato study started simply as a student's search for a master's thesis project.

Four years later, a biology laboratory at California State University, Sacramento, is attempting to grow antibodies in tomatoes, an early step toward making genetically engineered "edible vaccines" and medicines.

If successful -- and researchers believe it's only a matter of time, perhaps months -- the project will thrust the laboratory into a new and swiftly evolving sector of the controversial biotechnology industry.

The unprecedented mating of pharmaceutical production with agriculture already is eliciting concern from environmentalists. It's also spurring government to craft new rules to prevent drug-producing crops from mixing with food or dispersing their drug-making DNA in the environment.

The fact that a lab at CSUS -- where teaching is emphasized over research -- has jumped into the field of making "transgenic" organisms illustrates the spreading know-how about altering the genes of living things.

Transforming plants is "actually easier to do than a lot of the other molecular biology stuff we do," said Nicholas Ewing, the associate professor of biology leading the study.

His project is focused on making ripening tomatoes produce within their flesh compounds for laboratory or medical use. The idea is to manipulate a plant's genes so it generates proteins that mimic some part of the microbes and viruses that cause diseases, anything from AIDS to smallpox to cholera. The proteins, once eaten, would stimulate the body to develop immunity against the actual pathogen.

But there are questions about the safety of transgenic plants: Can they keep their engineered genes to themselves, or might the genes "escape" into wild plants or other crops? What might happen to wild animals or microorganisms that eat plants engineered to produce drugs?

And probably the most critical question from the perspective of regulators is: How do you ensure that drug-making crops don't mix with domestic animal feed or human food?

Such questions largely are left to regulators to answer, sometimes prodded by environmentalists.

A committee of the U.S. Food and Drug Administration and U.S. Department of Agriculture recently drafted a guide for industry on the production of drugs derived from bioengineered plants. The guide is expected to be released for public review this summer.

"Our expectations are of the highest stringency to keep this material from the food supply," said Keith Webber, the FDA scientist who chaired the committee.

Beyond developing proteins as vaccines, plants may be engineered to produce other drugs. The Vacaville company Large Scale Biology, for example, is testing a drug for non-Hodgkin's lymphoma extracted from an altered relative of tobacco.

Plants also may be transformed to produce antibodies, the workhorse proteins of human and other animal immune systems that are used widely as laboratory tools. Ewing's lab now is collaborating with Antibodies Inc., a company in Yolo County, to make in tomatoes an antibody that the company normally produces in cell cultures.

Richard Krogsrud, chief executive officer of Antibodies Inc., said a plant system, once developed, might be more efficient and less expensive than using cell cultures.

Ewing also is collaborating with Jean VanderGheynst, a biological engineer at the University of California, Davis, who will help develop a means of extracting the proteins once the tomatoes are ready for harvest.

VanderGheynst became involved as a result of the interest of a graduate student.

She said the student had considered doing a doctoral thesis on the safety of transgenic plants in the environment but was discouraged after consulting a variety of scientists in the field.

"The viewpoint that he got from people he spoke with was that it was fairly safe and not really worth pursuing as a research project," VanderGheynst said. "And (that such a project) would be one that would likely not be funded."

But VanderGheynst acknowledged that the safety question is unresolved. "I don't think there's enough information to say one way or another," she said.

The risk of engineered crops showing up where they're not supposed to is more than theoretical. In 2000, a transgenic corn called StarLink intended only for animal feed and not human consumption turned up in taco shells, tortilla chips and other groceries.

StarLink was engineered to produce its own pesticide, and the U.S. Environmental Protection Agency had concerns that some people might be allergic to the insecticidal protein. While no reports of illness resulted, the contamination forced costly product recalls and deepened public suspicions about the safety of genetically modifying crops.

Webber said pharmaceutical crops would be controlled in a markedly different way. "StarLink corn was a commodity corn grown on millions of acres for animal consumption," he said. "Also, StarLink corn was deregulated by the USDA. The USDA will not ever deregulate pharmaceutical plants, which means that anyone growing a plant for pharmaceutical purposes will always need to have a permit ... and those permits come with required conditions for containment."

Conditions include keeping buffer zones around the plants to prevent the spread of pollen to other crops and weeds, and harvesting into sealable containers for transport, Webber said.

One consequence of the need to segregate drug-making plants is that the products will have to be processed more like conventional pharmaceuticals.

"You're not going to find things that look like fruit leathers (such as Fruit Roll-Ups) or food for general consumption," Webber said.

That picture of edible vaccines differs notably from the concept that was first developed about 15 years ago. Back then -- and sometimes still today -- edible vaccines were characterized as fresh fruits and vegetables that would serve as cheap and easy vehicles for immunizing poor people, particularly in developing countries, where the refrigeration needed to preserve conventional vaccines and sterile needles can be hard to come by.

Advocates also talked about sparing babies everywhere painful shots by immunizing them with bites of tasty bananas.

"That's a lot of gee-whiz stuff. The reality is, that's not going to happen," said Louise Henderson, chief of biotechnology and diagnostics at the USDA's Center for Veterinary Biologics, which reviews new animal vaccines and diagnostic test kits.

Besides the need to keep the crops separate from food and feed, technical hurdles exist. For example, fruits and vegetables do not grow to uniform sizes, nor has a plant been engineered yet that produces the desired protein in uniform amounts.

"It's very important when you deliver any biologic or drug that you deliver (a specific) dosage," Henderson said.

Processing the plants -- turning them into powders or purees, for example -- also helps eliminate another risk: dispersing seeds via the digestive tract. Tomato seeds in particular have been known to survive the trip through the body and sewage treatment plant to sprout in sludge.

Accidental release of engineered genes into the environment is a chief concern of Belinda Martineau, a plant biotechnology consultant and author in Davis.

Martineau is a scientist who was involved in the making of the first bioengineered food, the Flavr Savr tomato sold by Calgene in 1994. In a book, "First Fruit," published last year, Martineau emphasizes the need for diligent, case-by-case safety assessments.

One major problem, Martineau said, is that scientists focused on transforming plants often lack understanding of potential environmental effects.

"These gene jockeys, they can't look beyond their little gene," she said. "They make all these comments about how safe it is in the environment, but they are not ecologists. They're not that up on the food web, really."

She believes the weakness is in oversight of the system. "There should be a certain amount of basic research that goes on, (but) ... we need a better system for saying what goes forward and what doesn't," Martineau said.

The public's wariness about genetically modified crops has caused some of the most gung-ho scientists to lower their sights. Charles Arntzen, a pioneer in edible vaccine research, wishes now that he hadn't used that term.

"I would now use the words 'plant-derived vaccine,' " said Arntzen, a plant molecular biologist at the Arizona Biomedical Institute in Tempe. "At one time I didn't fully appreciate the absolute requirement for dosage, for keeping good records of who was being immunized. I just had a focus on how to get something to the developing world. The more I work with vaccine specialists, the more I realize that ... this is a medicine and should be treated as such."

Arntzen said he is working chiefly with tomatoes these days because they can be grown entirely in greenhouses, then processed into a freeze-dried juice.

"We are concerned about public perception about plants with pharmaceuticals, and we are going to do all our production in containment greenhouses," he said. "We don't want anyone suggesting that pollen will escape to the outside; we don't want anyone to think these tomatoes will appear in a pizza someplace."

Because of his interest in tomatoes, Arntzen has talked with Ewing at CSUS about using the university's patented system for inducing the plants to produce medicinal proteins upon ripening.

VanderGheynst, the UC Davis collaborator, said the system may enable the plants to be grown safely outside. "Wouldn't it be interesting if we could harvest the tomatoes before they're ripe and control the ripening off-site so you wouldn't even have the antibody in the field?" she said.

Even still, the question of moving the CSUS experiment outdoors is a big one. Krogsrud at Antibodies Inc. said the company has space on its 40-acre property, but he's not convinced using it for transgenic tomatoes is a good idea.

"It's a great commitment, and has a lot of regulatory aspects to it," he said.

VanderGheynst said some of the "scale-up" work -- growing plants in larger quantities -- might be done at UC Davis, but probably not on outdoor campus plots because of security concerns. Protesters two years ago uprooted corn and beets they thought were genetically modified.

Ewing, who is still attempting to get the greenhouse-grown tomatoes to produce the desired antibody, said that because of public suspicions of genetically modified plants, he sometimes thinks, "Forget it."

Then he remembers the potential benefits. "This is really interesting, and there's some good. You can make pharmaceuticals really cheaply," he said, so he keeps at it.