In a move into a market potentially worth hundreds of millions of pounds a year, Axis Genetics of Cambridge has commissioned the American company Ag-Tec International to grow potatoes containing extra genes that make a vaccine against the hepatitis B virus.
The potatoes will be used in clinical trials in the US to test how well their vaccine works in humans. But because the experimental plants have not yet been approved for public use, the scientists who developed them are not allowed to eat them - unless they are participating as subjects in the trial.
Future products could exploit tomatoes, carrots, corn or lettuce, said Paul Rodgers, the commercial director of Axis Genetics. "Fundamentally, there are no barriers to genetic modification of any plant species," he said yesterday. "But potatoes are particularly easy because they propagate as clones, so you can cultivate from an initial one without sexual crossing, which can lose the desired genes."
Ag-Tec brings expertise in the mass production and processing of potatoes, he said. Trials in Britain and Europe will follow in a couple of years.
The development of vaccine-making potatoes marks a new generation of transgenic foods and plants. The first, such as Calgene's "Flavr Savr" tomato, were engineered to keep fresh longer by deleting a gene that caused decay. The second generation, typified by Monsanto's transgenic soya, which is resistant to weedkiller, also offered benefits to food producers, but none directly to the person eating them.
However, "pre-vaccinated" potatoes are developed specifically for their effect on the person who eats them. The extra genes mean the vaccine is produced within the potato as it grows. Eating the raw or cooked product encourages the body to build up defences against the virus, which causes liver disease and cancer.
Trials in the US last year showed the same technique is effective with modified potatoes which prompt immunity to the virus that causes travellers' diarrhoea. In addition, it bolsters defences in the gut, where the virus is most likely to attack. Injections tend to boost the body's blood-borne defences.
Eventually, though, the edible vaccine would probably take the form of a tablet containing potato extract, rather than a supermarket display of "superpotatoes". "It means you can regulate the dose precisely," said Mr Rodgers, "and there's no problem about it going past a sell-by date."
The commercial prospects for edible vaccines are highly promising. Hepatitis B vaccinations are already a $1bn (pounds 606m) annual market, although only a minority of those at risk are vaccinated, he said.Reuse content