Government Issues Rules on Cross-Species Transplants Involving Humans

By Jeffrey Brainard

Source: The Chronicle of Higher Education

(Washington) The federal government issued final guidelines on Monday for researchers who seek to transplant animal organs and tissues into humans to treat illnesses. The rules are meant to reduce the risk that patients will be unwittingly exposed to serious diseases that are found in animals but not in humans.

The Department of Health and Human Services spent more than four years refining the guidelines after complaints that the risk of such a disease transfer is unknown, and the consequences potentially too calamitous to warrant such experimentation. The final version was published in Monday's Federal Register.

Researchers have yet to move ahead with plans to transplant entire organs, such as hearts and livers, to patients whose organs are failing. But scientists hope the procedure -- known as xenotransplantation -- will help the thousands of patients who die each year because the demand for transplanted organs exceeds the supply. Researchers expect to begin such operations within a few years. Already, researchers are transplanting fetal pig cells into small numbers of patients with Parkinson's disease as an experimental therapy.

Under the guidelines published Monday, researchers are encouraged to reduce the risk of disease by taking special care when raising donor animals. For example, they should come from "closed" herds, which are not exposed to outside animals, to prevent the introduction of infectious animal diseases. And the animals should be delivered by cesarean section, when possible, to reduce the transmission of infections to newborns.

In addition, the health of human participants involved in xenotransplantation research should be monitored for the rest of their lives to detect diseases of animal origin -- an unusually restrictive criteria, as clinical trials go. Also, sponsors of the studies would have to store tissue specimens from the involved humans and animals for at least 50 years, so that researchers could track the origins of any animal diseases that slowly emerged in humans many years after transplantation.

A similar version of the guidelines was published last year, and already researchers have begun to comply with them, said Jonathan Allan, a virologist at the Southwest Foundation for Biomedical Research, in San Antonio.

Mr. Allan said the final guidelines are a useful reference for controlling the risk of disease. "Over all, they've done a lot better job than the original version," he said.

But he worries that the final version still does not go far enough. He had hoped, for example, that it would contain an outright ban on xenotransplantation studies involving nonhuman primates, like chimpanzees. Scientists believe that the genetic similarities between humans and these primates make it more likely that disease could be transferred through transplantation. Some researchers believe that H.I.V. originated in chimpanzees before being transferred to humans.

The Food and Drug Administration issued a separate policy in 1999 that discourages transplants involving nonhuman primates because of the unknown risk of disease.

Some advocates oppose any xenotransplantation. A better alternative would be to encourage more people to donate their organs, and to work harder to reduce diseases that cause organ failure, said Neal D. Barnard, president of the Physicians Committee for Responsible Medicine. The group supports a stronger emphasis on proper nutrition and preventive medical care.

"Our fear is that under the guise of caution, this is really a green light for more xenotransplantation experiments," he said of the guidelines.