The heart swap was a major test of xenotransplantation, the process of moving tissues between species. Photo / Getty Images
The heart swap was a major test of xenotransplantation, the process of moving tissues between species. Photo / Getty Images
The first person to receive a pig heart transplant may have died from complications from a swine virus, in what experts have called a "big red flag" for the future of animal-to-human transplants.
David Bennett was given the organ by US doctors in January, in a medical first that offered hope to patients around the world suffering from failing organs.
The 57-year-old handyman, who suffered from heart failure, underwent highly experimental surgery at the University of Maryland Medical Centre. However, he died eight weeks later.
In a statement released by the university in March, a spokesman said there was "no obvious cause identified at the time of his death" and that a full report was pending.
In a recent web seminar, Dr Bartley Griffith, who performed the procedure, revealed that the pig's heart was infected with a virus known as porcine cytomegalovirus, which may have contributed to Bennett's death.
The MIT Technology Review described cytomegalovirus as a preventable infection that is linked to devastating effects on transplants.
"We are beginning to learn why he passed on," Dr Griffith told a conference of the American Society of Transplantation. "[The virus] maybe was the actor, or could be the actor, that set this whole thing off."
He said there was no evidence that the patient's body had rejected the heart.
Bennett had been extremely ill before the surgery and suffered numerous other complications after the transplant.
"If this was an infection, we can likely prevent it in the future," Dr Griffith said.
The heart swap was a major test of xenotransplantation, the process of moving tissues between species. However, because the special pigs raised to provide organs are supposed to be virus-free, it now appears that the experiment was compromised by an "unforced error".
The version used in Maryland came from a pig with 10 gene modifications developed by Revivicor, a biotechnology company. It declined to comment and has made no public statement about the virus.
"It was surprising. That pig is supposed to be clean of all pig pathogens, and this is a significant one," said Mike Curtis, the chief executive of eGenesis, a rival company that is also breeding pigs for transplant organs.
"Without the virus, would Bennett have lived? We don't know, but the infection didn't help. It likely contributed to the failure," he told the MIT Technology Review.
David Bennett Jr, right, stands next to his father's hospital bed in Baltimore. Photo / AP
"It's a big red flag," said Dr Arthur Caplan, a bioethics expert at New York University, who added that if doctors cannot prevent or control infection, "then such experiments are tough to justify".
Tackling human organ shortage
Amid a shortage of human organs for transplants, scientists have long been trying to develop techniques on how to use animal organs instead.
However, previous attempts failed after patients' bodies rapidly rejected the animal organs.
In 1984, an infant patient in California known as "Baby Fae" lived for 21 days after having a baboon heart transplanted.
Pigs are considered ideal donors because of their size, rapid growth and large litters, and because they are already raised as a human food source.
For the most recent attempt, doctors used a pig heart from an animal in a herd that had undergone gene editing. That involved removing a particular sugar from cells that, in previous attempts, triggered a strong immune response and led to a quick rejection of transplanted organs.
Dr Griffith, however, did not see it as a reason not to proceed with other similar transplants.
"This doesn't really scare us about the future of the field unless for some reason this one incident is interpreted as a complete failure. It is just a learning point. Knowing it was there, we'll probably be able to avoid it in future."
