Cloning Promise and Peril
On Tuesday, executives at the British biotechnology firm PPL Therapeutics proudly carted out five cute piglets that their Virginia-based researchers recently succeeded in cloning. It’s a major achievement, marking the fourth kind of mammal ever to be cloned and moving scientists closer to growing pigs with gene-altered organs that can be transplanted into people.
Still, in its breathless enthusiasm PPL is making claims that the public, investors and government regulators should not simply accept--forgive us--whole hog.
First, to downplay ethical concerns about human cloning, recently banned in the United States and Britain, PPL managing director Ron James says his company’s success does not take us “a single step closer” to that. But in fact it does. Pigs are more biologically similar to humans than the three other mammals that have been cloned--mice, cattle and sheep. So scientists indeed are closer than ever to understanding how the process would work in humans, who share about 90% of pigs’ genetic makeup.
Most overblown and misleading is the PPL claim that with its success at cloning pigs, “all the known technical hurdles [to cross-species transplants] have been overcome.”
Actually, scientists are far from mastering the very complex procedures that will be necessary to prevent human immune systems from rejecting organs from pigs or any other species. Nor have scientists figured out how to prevent viruses from moving from pigs to humans. In recent years, some patients have survived their wait for a human organ by being hooked up to a pig organ kept outside the body, but many have since been shown to harbor errant pig cells that contain potentially troublesome viruses.
Fortunately, federal officials are taking steps to thwart the dangers that biotechnology firms like PPL often minimize. Just last month, for example, an FDA advisory panel recommended that people who have received cells or organs from other species, called xenotransplants, should not be allowed to donate blood or plasma because of the possibility that they might transmit disease-causing organisms to others through their blood products.
Xenotransplantation is one of many exciting new frontiers in genetic science, and PPL, which helped clone Dolly the sheep three years ago, has significantly advanced the field once again. But the technique is full of peril as well as promise and should be implemented carefully and thoughtfully.
