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THE CUTTING EDGE

Harvesting Medicine

June 10, 1996|JENNIFER OLDHAM

Imagine tobacco plants producing medicine for lung cancer victims. It's not as far-fetched as you might think. A Vacaville, Calif.-based firm, Biosource Technologies Inc., is testing a process that genetically modifies tobacco to manufacture proteins that can be made into drugs. Known as "pharming," the procedure is cheaper than the current means of synthesizing drugs and produces greater quantities of medicine. A look at how Biosource scientists "pharm" tobacco fields in Kentucky in attempts to produce an antibiotic called Defensin and a vaccine for malaria:

1. In a laboratory, scientists slice open pieces of the tobacco mosaic virus and insert a gene programmed to instruct the plant to produce protein for a certain drug. Scientists first weaken the virus, which is endemic in many tobacco farms, so it is unlikely to infect the plant itself.

2. Workers drive tractors through tobacco fields, positioning themselves about two feet from the plants. They blast the plants' leaves with a pressurized spray containing the virus, boring tiny holes into the leaves. The virus enters the plant through these holes.

3. The virus invades the plant's cells and causes them to produce the protein the gene holds instructions for. The protein collects in the plants' tissues. Since the gene is engineered to affect the cell only and not the plant's DNA, it is not passed on to the plant's seeds or pollen and dies out with that generation of tobacco.

4. The tobacco leaves are harvested and ground up in a press. The proteins are filtered out of the green juice extracted from the plants. Biosource plans to use drugs produced in tobacco plants in clinical trials sometime in the next year.

* Sources: Biosource Technologies Inc., New Scientist, wire reports

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