Pig transplants prompt cautionary advances

Boston-

The successful pig-to-human transplant of a genetically altered heart is within the foreseeable future, but that doesn't necessarily appease all scientists, according to experts.

Pigs' genes are undergoing modifications to "humanize" their organs, a process known as xenotransplantation, to serve as an alternative to transplants from human cadavers.

Immerge BioTherapeutics and PPL Therapeutics both claim to have created pigs that are lacking one of two copies of a gene that makes alpha-1-galactose sugar, which lines pig blood vessels. Because it resembles a bacterial sugar, the human immune system fights it, almost instantly destroying pig organ transplants.

Dr. David Cooper, Massachusetts General Hospital, says he sees the cloning efforts as"a major step forward" but not flawless.

He and Dr. Fritz H. Bach, transplant scientist, Boston Beth Israel Deaconess Medical Center, recently spoke at a conference of the American Association for the Advancement of Science. They predict transplants could occur within five to seven years, if the kinks can be ironed out.

Solution effects new problem

A concern is that the organs may carry pig viruses that could be harmful to people, especially if spread to others.

All pig cells carry a so-called retrovirus that is harmless to them, but experts do not yet know its potential effect on humans.

Cooper says the decision should be left to regulatory agencies, which can balance the highly opposing technical arguments.

In fact, the Food and Drug Administration has already taken a stance to transplants currently taking place.

In a recent proposal, FDA urges U.S. blood banks to defer blood donors who have animal tissue transplants. Additionally it wants to ban such donations from close contacts of transplant donors.

The administration is mulling the policy due to the risk that xenotransplantation could infect potential donors with viruses and bacteria that blood banks would be unable to screen. The donor could then possibly pass such agents onto a blood recipient.