Doctors have found signs of a virus known as "porcine cytomegalovirus" in the patient who survived for two months after receiving the first-ever pig heart transplant, reports Antonio Regalado for MIT Technology Review.
David Bennett, a 57-year-old man with heart failure, received a genetically-altered pig heart in January 2022. He appeared healthy for several weeks, but his condition began deteriorating after about 40 days.
“He looked really funky. Something happened to him. He looked infected,” the surgeon, Dr. Bartley Griffith of the University of Maryland School of Medicine, tells MIT Technology Review. “He lost his attention and wouldn’t talk to us.”
Bennett died on March 8 from unidentifiable causes. MIT reports Dr. Griffith discussed the presence of the porcine virus in an American Society of Transplantation webinar on April 20.
“We are beginning to learn why he passed on,” Dr. Griffith reportedly said in the webinar, “[the virus] maybe was the actor, or could be the actor, that set this whole thing off…If this was an infection, we can likely prevent it in the future.”
The donor pig was raised by the biotech company Revivicor, reports the New York Times’ Roni Caryn Rabin. It had been genetically altered to minimize the chance of rejection from Bennett’s body and had been screened several times for pathogens.
“It was surprising. That pig is supposed to be clean of all pig pathogens, and this is a significant one,” Mike Curtis, CEO of eGenesis, a competing company also breeding pigs for transplant organs, tells MIT. “Without the virus, would Mr. Bennett have lived? We don’t know, but the infection didn’t help. It likely contributed to the failure.”
The tests conducted on the pig were done in its snout, and only could detect active infections, per the Times. The virus was later found lurking in the pig’s spleen.
“It’s a latent virus and hard to detect,” Joachim Denner of the Institute of Virology at the Free University of Berlin, who led a study on pig hearts transplanted into baboons, tells MIT. “But if you test the animal better, it will not happen. The virus can be detected and easily removed from pig populations, but unfortunately they didn’t use a good assay and didn’t detect the virus, and this was the reason. The donor pig was infected, and the virus was transmitted by the transplant.”
Denner says the patient was sick before the transplant, which also played a role in his death.
“This patient was very, very, very ill. Do not forget that,” he tells the publication. “Maybe the virus contributed, but it was not the sole reason.”
Transmission of viruses from animals to humans is a concern for such transplants, reports the Times. If a virus adapts inside a patient and spreads to doctors and nurses, some fear it could trigger another pandemic, per MIT. But experts believe the type of virus found in Bennett’s donor is incapable of infecting human cells, the publication reports.
Despite Bennett’s death, the transplant was largely considered a success, and researchers plan to continue studying how to use animal organs to save lives.
“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,” Dr. Griffith tells the Times. “It is just a learning point. Knowing it was there, we’ll probably be able to avoid it in future.”