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Pig Organ Breakthrough Raises Infection Fears

January 04, 2002|From Associated Press

WASHINGTON — As science moves closer to using pig organs for human transplants, some experts caution that the technique could transfer deadly swine viruses. Ethicists question the whole idea of using animals to make spare parts for people.

Two research teams announced this week that they have cloned piglets that lack one of two genes that prompt the human immune system to reject swine tissue. The next step is breeding or cloning that would eliminate the gene entirely from a strain of pigs.

In a world where more than 5,700 people in need of transplants die each year because of the shortage of donated organs, many researchers view pigs as a potentially unlimited supply source. By removing a gene that causes a swift and powerful rejection by the human immune system, researchers hope that pig organs could be made available to people.

But some experts caution that the whole field of xenotransplantation--transplanting tissue from one species to another--is fraught with infection risks, to the transplant recipients and perhaps to other humans.

Pigs are known to contain what are called porcine endogenous retroviruses, which evolved with the swine over millions of years and now are part of the animals' genes.

The viruses do not affect the pig, but what would happen if the animal's organs are transplanted into humans? Perhaps nothing, or perhaps it could lead to a whole new disease, say some experts.

"This is a recipe for disaster," said Alix Fano, head of the Campaign for Responsible Transplantation, an organization of scientists and doctors opposed to xenotransplantation. "Pigs are a reservoir of viruses, and we have no idea what their organs would do if transferred to humans."

Others agree that swine viruses are a serious, complex problem with no clear solution, but they believe science will find a way.

"That is a genuine concern. There is a risk," said George J. Agich, chairman of bioethics at the Cleveland Clinic. "The ethical question is whether there is a risk to the general population from a procedure that would benefit a single individual. But we have at our disposal scientific means to determine if that risk is reasonable."

Until then, he said, "we should be extremely cautious. We may be talking about decades before we can roll out this technology [xenotransplantation]."

Some studies in which humans were exposed to pig cells have suggested that the viruses do not infect human cells. But critics say there are many other examples showing that some retroviruses that are harmless in one species become virulent killers when transplanted into other humans.

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