SOME ideas, no matter how good they look on paper, should never be tried in practice. One of these is the notion of producing drugs or vaccines in genetically engineered food crops. Why? Because the risk of these potent chemicals finding their way into the human food chain is just too high.
So we are pleased to note the decision by one of the world鈥檚 authorities on 鈥減harming鈥�, as this idea is called, to replace food crops with a relative of the tobacco plant. Charles Arntzen of Arizona State University is a pioneer of edible vaccines: foods that are genetically engineered to contain a vaccine. However, fears that the modified crop 鈥� or the altered gene within it 鈥� could find its way into the food of unsuspecting people have convinced Arntzen to think again. He has devised a different model for making edible vaccines (see 鈥淲hy vaccination by potato got chopped鈥�).
Using food crops is risky for several reasons. Pollen containing the gene may fertilise strains of the crop intended for the table. Seeds from a pharm crop left in the field after harvesting may grow the following season, something that has already happened when GM corn plants came up in soybean plots in Iowa and Nebraska. If harvested crops are not properly segregated, modified versions could easily get mixed up with food crops. This too has happened before, when Starlink, a variety of GM corn meant only for animal feed, turned up in foods across the US. Then there is theft, which has also taken place. In China, researchers from Beijing University buried a batch of experimental GM tomatoes to prevent their seeds spreading. But local farmers dug up the fruit and ate them or planted the seed.
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There are ways to limit some of these risks, such as engineering modified plants to be sterile. But the only foolproof way to prevent accidents is not to use food plants at all. Agribiotech companies will complain that food crops grow fast, produce lots of protein and are what they know most about. But these are poor excuses. Breeding a few fast-growing high-yielding non-food crops and getting to know their genomes would be a small price to pay for public confidence.
One other argument used by agribiotech companies to defend their corner is that even if a protein from a drug or vaccine did get into the food chain it would be destroyed in the human gut. Arntzen鈥檚 work with potatoes modified to produce a hepatitis B protein casts doubt on this, too. More than half the people who ate the potato produced large numbers of antibodies to hepatitis B. Why take the risk?
