As knowledge of the mucosal immune system was emerging, so were the genetic engineering tools that enable researchers to insert vaccine molecules into plants. The next logical step was to investigate whether food plants carrying vaccines could immunize the digestive tract. “The tools and knowledge converged that naturally led us down this path,” according to William Langridge, a molecular biologist at California’s Loma Linda School of Medicine.
Langridge converted the plebeian potato into a cholera vaccine by adding genes for cholera toxin. In mice that ate the raw potatoes, the toxin bound cells in the gut and triggered the production of antibodies against cholera. To make the potatoes more appealing, Langridge boiled small cubes of his special spuds until soft-surprisingly, at least half the vaccine remained active. Flash cooking methods, like deep fat frying, may preserve more vaccine, he suspects. (Imagine getting your vaccination from a bag of chips or a plate of fries.) Langridge’s experiments have sparked interest from biotechnology companies, but it’s too early in negotiations to identify them, he says.
Potatoes are a dietary staple in Peru, Bolivia and India-countries where cholera causes dehydrating diarrhea and death-so the potato is a “good target plant,” Langridge says. He calculated that eating one boiled potato weekly for a month should protect against cholera. Booster spuds may be needed if protection falls. “Food plants move us closer to achieving a low-cost, convenient, effective and safe strategy for prevention of infectious enteric (intestinal) diseases,” says Langridge. When grown locally in developing countries, edible vaccines could circumvent problems of transportation and refrigeration that hamper effective vaccination programs.
While researchers from Cornell University’s Boyce Thompson Institute for Plant Research (BTI) have also experimented with potato-based vaccines, they now are turning their attention to plants more commonly eaten raw. “Potatoes were the proof-of-concept crop,” says Cornell researcher Hugh Mason, “but bananas and tomatoes look more promising for human consumption.”
In June, BTI announced a research and license agreement with Axis Genetics, a biopharmaceutical firm in Cambridge, England. Axis will back BTI’s edible vaccine research for three years, in return for exclusive use of BTI technology.