ON A PIG AND A PRAYER

By Christine Gorman

Transplanting a pig's heart into a human being sounds like an experiment only a mad scientist would dream up. But researchers at Duke University Medical Center in North Carolina believe they are quite sane -- and getting closer to making such a bizarre operation possible. In the journal Nature Medicine last week, they reported overcoming some of the obstacles that Mother Nature has put in the way of transplanting organs between species. By altering the genetic makeup of a strain of pigs, Duke's team, led by Dr. Jeffrey Platt, was able to fool the immune systems of three baboons into accepting pig hearts almost as their own-at least for a short period of time. Platt predicts that he may be ready to transplant porcine hearts into humans in two years.

Many physicians had written off this kind of organ swapping between species back in 1984, when Dr. Leonard Bailey of Loma Linda University Hospital in California transplanted a baboon's heart into a two-week-old infant known as Baby Fae. Three weeks after the operation, the child died of kidney failure, and Bailey was heavily criticized for experimenting on a human with little chance of success.

But the persistent shortage of organs from human donors has motivated some researchers to reconsider the possibility of transplants from animals. In the U.S. alone, there are 40,000 people on the national transplant waiting list and only 5,000 donors a year. As a result, about one-fifth of the people who need a heart transplant, for example, die before one becomes available.

By using drugs that partly suppress the immune system, doctors can prevent the body from rejecting transplants of human origin. When organs from one species are placed in another, however, the recipient reacts even more violently and quickly-usually attacking the foreign tissue within a matter of minutes or hours.

To get around that problem, scientists at Nextran, a biotech firm in Princeton, New Jersey, re-engineered the genes of several litters of pigs so that their tissue would have some of the immunological markings that are found in humans. After these so-called transgenic animals had grown to full size, Platt and colleagues at Duke transplanted the pigs' hearts into baboons. Ordinarily, such hearts would have stopped beating within 90 minutes. Instead, all three transgenic hearts survived for at least several hours -- one lasted more than a day. Because people and baboons are so closely related genetically, the human markings on the implanted pig hearts protected the transplants from swift rejection by the baboons. Even so, the Duke team had to use drugs to curb the longer-term rejection response.

There are several more complications to clear away before surgeons can start stitching pig hearts into people. For one thing, viruses that normally attack only swine might literally piggyback a ride into people during transplant surgery, leading to new diseases in humans. Yet transplant doctors are optimistic that such technical obstacles can be surmounted. Then it will be up to the patients to decide how they feel about having a pig's heart beating in their breast. --Reported by Alice Park/ New York

With reporting by Alice Park/New York