http://seattlepi.nwsource.com/national/53187_pigs04.shtml

 

Alarms raised on pig-organ transplants

Advances for human use made; virus risk -- as in AIDS -- noted

Friday, January 4, 2002

By PAUL RECER
THE 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, citing the example of the virus that causes AIDS.

Ethicists question the 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 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.

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

Pigs are known to contain what are called porcine endogenous retroviruses or PERVs -- viruses that 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," 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 now, but they believe science will find a way.

"That is a genuine concern. There is a risk," said George 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 PERVs 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 humans.

The most notable example, said Jonathan Allan of the Southwest Foundation for Biomedical Research, is HIV, the virus that causes AIDS. The retrovirus is thought, by some, to have lived harmlessly in the green monkey and became deadly only when it jumped to humans.

Allan said studies have shown that a virus that was a harmless part of the genes of the langur monkey became a serious pathogen when it infected the Rhesus monkey.

Before pigs can be considered for the source of human organs, he said, much research will be needed to develop a level of confidence that the viral risk has been settled.

Dr. Randall Prather of the University of Missouri, a member of one of the teams that cloned the genetically altered piglets, said the problems can be addressed, but only if pigs are developed whose organs would not be rejected by the human immune system.

Prather is co-author of the study appearing today in the journal Science.

Science: www.scienceexpress.org

Xenotransplantation: www.transplant.ca/xeno.htm

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