Animal viruses a risk for humans

By Luis Fabregas

Tribune-Review

April 9, 2006

The potential of pig-to-human organ transplants begs the question: Could a pig organ transfer deadly animal viruses into humans?

That's been the top worry among critics of the controversial field of cross-species transplantation.

Their worries are justified. Pigs carry a virus known as porcine endogenous virus, or PERV. The virus, which some have likened to HIV, can infect human cells in the laboratory, according to British scientists.

But recent studies have shown PERV to be less of a threat that previously thought.

In 2004 scientists at Harvard Medical School transplanted human and pig cells into mice. After six months, tests showed PERV did not infect the human cells.

Still, the possibility of PERV or other viruses crossing species has weighed heavily on some groups.

The Campaign for Responsible Transplantation, based in New York, has lobbied forcefully against animal-to-human transplants. In 2000, it filed a lawsuit against the U.S. Food and Drug Administration, demanding documents on the side effects and deaths caused by human xenotransplantation trials.

The lawsuit produced several thousand documents that are still being reviewed by the group.

Some documents have shown that some xenotransplantation patients developed side effects such as tumors, says Alix Fano, the group's executive director.

"You can't make this technology safe at all," Fano says.

Fano's group worries that placing pig cells and organs in humans will foster the transmission of PERV and other unknown animal diseases they believe could remain dormant for years.

"Whatever you do, those (pig) cells carry the risk of infection not only to the patients, but their relatives and their health care workers. The pigs are laden with retroviruses, and we don't know all of them. In my mind, it's extremely dangerous and irresponsible," she says.

The transmission of animal diseases also has worried members of an advisory committee for the U.S. Department of Health and Human Services.

"You can't know for sure whether or not you are going to introduce an infectious disease through xenotransplantation," Dr. Jonathan S. Allan of the Southwest Foundation for Biomedical Research in San Antonio, said at the committee's last meeting in February 2004, according to meeting transcripts. "To suggest there is no risk, I don't think anybody would suggest there is no risk."

The advisory committee was disbanded in January after five years because there had been little activity in the field.

Dr. Sharon C. Kiely, a Pittsburgh internist who sat on the committee, says xenotransplantation will have difficulty moving forward unless tests show more consistent survival among those getting the organs.

"The public needs the reassurance of the scientists that the organs are safe," says Kiely, vice chairwoman of the department of medicine at Allegheny General Hospital in the North Side. "The public health implications are unknown. Whenever there's a new frontier, we need to be sure this is consistent with the public health culture of this country."

David Ayares, the president and chief executive officer of Revivicor, the biotech firm cloning pigs for xenotransplantation, says the company has talked with U.S. Food and Drug Administration officials about the matter.

All organs, he says, would be tested for PERV before they are transplanted.

Copyright © 2006 by The Tribune-Review Publishing Co.

This article posted May 7, 2006.