Your next immunization could be a little easier to swallow. In the July issue of the Journal of Infectious Diseases, researchers report that a vaccine built into an ordinary potato can trigger an immune response against a virus that causes food poisoning. The study has encouraged scientists hoping to produce vaccines in edible form for a host of infectious diseases.
Currently, there are no good vaccines for the world's most devastating diseases, such as AIDS, malaria, and tuberculosis. But if they should become available, immunizing entire populations is often difficult. Vaccine injections are expensive; they require syringes, needles, and usually refrigeration; and they must be delivered by trained health care professionals. That's why researchers are engineering plants to produce key parts of viruses and bacteria, in the hope that the human body will take them for invaders and start producing antibodies against the organisms. But until now, no one has produced an edible vaccine that prompts such a response in humans.
The team, led by Charles Arntzen, president of the Boyce Thompson Institute for Plant Research in Ithaca, New York, engineered potatoes to produce a protein that makes up the structural shell of the Norwalk virus, a common cause of gastroenteritis. After being fed the modified potatoes, all but one of the 20 healthy adult volunteers had an increase in the number of antibody-secreting cells, and six of them had started secreting into the digestive system more antibodies that recognize the Norwalk virus structure.
The vaccine clearly triggered the immune system, says Arntzen, "but we need more vaccine per potato" to protect against an infection. And potatoes, while a convenient starting point, are not the vehicles of choice for future vaccines; they have to be eaten raw, which causes indigestion. Currently, most researchers are betting on bananas, which are easily grown in many developing countries, are commonly eaten raw, and can be fed to young children when immunization is most desired.
A Chiquita against cholera may be a ways off, says plant biotechnologist Peggy Lemoux of the University of California, Berkeley, but "this is an important landmark." For a long time, "people were not convinced you could do it, period," says Lemoux. "This shows that it's certainly workable."
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at the Boyce Thompson Institute for Plant Research
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