Immunity for Breakfast

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Science  08 May 1998:
Vol. 280, Issue 5365, pp. 831
DOI: 10.1126/science.280.5365.831a

Scientists have been keen to harness edible plants as cheap, low-tech vehicles for delivering vaccines against common ailments in developing countries. Now a team has reported the results of the first edible vaccine trial in people, which suggest that raw potatoes can deliver immunity against a major food-poisoning bacterium.

Charles Arntzen and his colleagues at the Boyce Thompson Institute for Plant Research at Cornell University in Ithaca, New York, targeted one of the most common causes of diarrhea, a strain of Escherichia coli that kills 2 million children a year in developing countries. They inserted a gene for part of an E. coli toxin into the potato genome. Next, they fed chunks of raw potato to 11 volunteers once a week for 3 weeks and compared their immune reactions to those of three people fed unaltered potatoes. (Cooked spuds won't work because heat destroys the toxin.) In the May issue of Nature Medicine, the researchers report that all but one of the vaccinated subjects produced antibodies to the toxin. The antibodies block the toxin from attaching to cells in the gut, the scientists explain.

“This paper is another step ahead in proving that plant vaccines will work in humans,” says molecular biologist William Langridge of Loma Linda University in California, who earlier this year reported breeding potatoes that elicit anticholera antibodies in mice. “Probably the only thing really lacking is to demonstrate protection from a challenge with the pathogen itself,” he says.

Arntzen says his ultimate goal is to get this technique to work in what he considers the ideal vaccine vehicle in tropical countries: the banana—widely eaten, popular with babies, and unlike potato, good raw.

Plant-based vaccines should hit the market in just a couple of years, predicts Langridge.

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