单选题 Most of us can't remember our first vaccination, a common practice of preventing us against diseases. Chances are, it was a shot filled with a drug formula—just enough to produce a mild infection but not the full-blown disease. Immunizing, or preventing people against some diseases in this way has worked reasonably well for more than a century, but scientists think they can do better by using genetically engineered plants.
We all know that eating fruits and vegetables is good for us, but within the next decade we could be eating as a way to deliver drugs that keeps off epidemic diseases or that treat various chronic conditions. "The idea of vaccinating people with edible plants is very new," says Dwayne Kirk of the Boyce Thompson Institute for Plant Research in Ithaca, New York, "But it's a lot friendlier than injections."
Potatoes and tomatoes seem for now to be the most efficient vehicles for the new approach. Instead of mixing viral or bacterial DNA in a formula for injection, for example, scientists could insert it into soil bacteria. When the bacteria are taken-up by the plant, the DNA material gets into the plant. Another method of getting genes into plants is to coat tiny particles of metals such as gold with foreign DNA, then shoot the particles directly into plant cells. Either way, the plant's cells start to produce whatever proteins the new genes are designed to make. Immunization begins when the plant or its fruit is eaten, prompting the body to produce the appropriate antibodies.
The technique does not have to be limited to infectious diseases, however. It may even be useful for conditions such as Type I diabetes. For such patients, eating genetically engineered plants could eventually train the body's defenses, all without the bother—or risk—of a needle.
Plant-based vaccines are particularly attractive for Third World countries, where storage and distribution of drugs are a problem. Eventually, people in these areas may inoculate themselves against diseases simply by growing a crop of genetically engineered fruits or vegetables and eating a few several times a year.