29 April 1998

Mutant Spuds Could Wipe Out Cholera

Cholera and other enteric diseases could become a thing of the past, thanks to a new method of administering vaccines through genetically modified potatoes. Ushering in a new era of grow-your-own edible vaccines, researchers at the Boyce Thompson Institute for Plant Research (BTI) hope to revolutionize the science of immunization - with far-reaching benefits for the developing world.

Results of the first-ever clinical trials of a vaccine against travellers' diarrhoea, published in the May issue of the journal Nature Medicine, represent a breakthrough in the biotechnology of transgenic implantation (transferring a particular gene from one species to another). Eating raw potatoes implanted with bacterial antigens was found to stimulate the production of antibodies in subjects - resulting in a much improved immune response (ten of the eleven volunteers who ingested the transgenic potatoes had fourfold rises in serum antibodies after immunization, and six of the eleven developed fourfold rises in intestinal antibodies). Caused by the E. coli bacterium, the diarrhoea results in some three million deaths each year, particularly among children in developing countries.

By using an E. coli gene that is similar to one from the bacterium that causes cholera, researchers hope the potatoes will provide broad cross-protection against both forms of the diarrhoea. There is also talk of developing plant-based vaccines to immunize against the Norwalk virus - another cause of severe diarrhoea epidemics throughout the world.

"This first trial is a milestone on the road to creating inexpensive vaccines that might be particularly useful in immunizing people in developing countries, where high costs and logistical issues, such as transportation and the need for certain vaccines to be refrigerated, can thwart effective vaccination programmes," says Regina Rabinovitch of the National Institute of Allergy and Infectious Diseases. "The hope is that edible vaccines could be grown in the developing countries where they would actually be used."

The next step is to engineer "tasty" alternatives, particularly bananas, that would appeal to children more than raw spuds. "American kids will also probably prefer being vaccinated by an edible vaccine rather than by a needle," says Charles Arntzen, president of BTI. The day when the dreaded TB jab is replaced by a banana split could be just around the corner.