Potential Risks of Biopharming in Plants
Although the field of biopharming offers great promise, the use of food crops for this purpose is controversial. Corn is by far the most popular biopharma plant, followed by soybeans, tobacco, and rice. Non-food crops, such as tobacco or duckweed, are harder to manipulate. Biopharmed tobacco may also have to be processed green, as drying may change the nature of the desired protein. Other factors that influence the choice of pharma crop include the availability of patents for specific plants and technologies.
Critics of biopharming have noted because plants process proteins differently than animals or humans, the body might recognize a “human” protein produced in plants as foreign, triggering an allergic reaction. Opponents have also warned that GM crops containing transgenes for bioactive or toxic substances could contaminate the human food supply through the dispersal of seeds or pollen. Pollen spreads on the wind, and seeds can be carried long distances by birds or animals, farm equipment, and trucks transporting grain. “Volunteers,” or unharvested seeds that sprout in a field the next year, are also difficult to control.6 For these reasons, a 2004 report by the National Academy of Sciences concluded that containing transgenes coding for pharmaceuticals and other foreign proteins is virtually impossible.
Pharma crops also pose potential risks to useful insects (such as honeybees) that consume their pollen, and to wildlife that eat corn and other engineered crops, particularly as scientists modify such plants to produce drugs and chemicals in higher concentrations.
Focus on Corn
Corn is an attractive crop for biopharming because it produces large amounts of protein that is easy to purify, and because the structure of the corn genome is well understood and relatively easy to engineer. Yet the use of corn for this purpose is controversial because it is a staple food crop that openly pollinates. Corn pollen can travel for over a mile on the wind, and insects can fertilize conventional corn with pollen from GM corn.
Gene-containment measures, such as male sterility and chloroplast transformation, are not foolproof and have been known to “leak” genetic material. For example, a supposedly male-sterile variety of biopharm corn that was used to grow the pharmaceutical Avidin turned out to have partially or fully fertile pollen in 18 percent of tested plants. Containment of pharma crops in sealed greenhouses is also not practical when they are grown on a commercial scale.
Even with biosafety precautions, the risk remains that pollen containing a transgene for a biologically active protein could cross with a nearby corn crop being grown for human consumption, causing it to produce harmful substances. This is of particular concern with biopharmaceuticals, which are potent at low doses and may be toxic at higher doses. The 2002 ProdiGene incident (next slide) illustrates the risk of genetic contamination, which will increase as companies scale up from trials involving a few acres to commercial plantings of hundreds of acres.6