Researchers trying to learn what killed the first person to receive a heart transplant from a pig have discovered that the organ harboured an animal virus but cannot yet say if it played any role in the man’s death.
Maryland resident David Bennett died in March, two months after the groundbreaking experimental transplant.
University of Maryland doctors said on Thursday they found an unwelcome surprise — viral DNA inside the pig heart. They did not find signs that this bug, called porcine cytomegalovirus, was causing an active infection.
A major worry about animal-to-human transplants is the risk that they could introduce new kinds of infections to people.
Because some viruses are “latent”, meaning they lurk without causing disease, “it could be a hitchhiker”, said Dr Bartley Griffith, the surgeon who performed the transplant.
Still, development of more sophisticated tests is under way to “make sure that we don’t miss these kinds of viruses”, said Dr Muhammad Mohiuddin, scientific director of the university’s xenotransplant programme.
The animal virus was first reported by MIT Technology Review, citing a scientific presentation Dr Griffith gave to the American Society of Transplantation last month.
For decades, doctors have tried using animal organs to save human lives without success.
Bennett, who was dying and ineligible for a human heart transplant, underwent the last-ditch operation using a heart from a pig genetically modified to lower the risk that his immune system would rapidly reject such a foreign organ.
US man gets a genetically modified pig heart in a world-first transplant
The Maryland team said the donor pig was healthy, had passed testing required by the Food and Drug Administration to check for infections and was raised at a centre designed to prevent animals from spreading infections.
Revivicor, the company that provided the animal, declined to comment.
Dr Griffith said his patient, while very ill, had been recovering fairly well from the transplant when one morning he woke up worse, with symptoms similar to an infection.
Doctors ran numerous tests to try to understand the cause, and gave Bennett a variety of antibiotics, antiviral medication and an immune-boosting treatment. But the pig heart became swollen, filled with fluid and eventually quit functioning.
“What was the virus doing, if anything, that might have caused the swelling in his heart?” Dr Griffith asked. “Honestly we don’t know.”
The reaction also did not appear to be a typical organ rejection, he said, noting the investigation still is under way.
Meanwhile doctors at other medical centres around the country have been experimenting with animal organs in donated human bodies and are anxious to attempt formal studies in living patients soon. It is not clear how the pig virus will affect those plans.
