Traces of a virus known to infect swine were found in a 57-year-old man from the state of Maryland who survived for two months with a heart transplanted from a genetically modified pig. The information is from the surgeon who performed the procedure, the first of its kind.
The revelation highlights one of the strongest objections to animal-to-human organ transplants: that the widespread use of modified animal organs can facilitate the introduction of new pathogens into the human population.
The presence of virus DNA in the patient may have contributed to his sudden deterioration more than a month after the transplant, said surgeon Bartley Griffith of the University of Maryland School of Medicine.
But, he said, there is no evidence that the patient developed an active infection of the virus or that his heart had rejected the porcine heart.
The patient, David Bennett Sr., was critically ill before the surgery and had several other complications after the transplant. He died on March 8.
Revealed by Griffith last month at a meeting of the American Transplant Society, the news of the viral traits found in the patient was first reported by the MIT Technology Review.
In an interview with the New York Times on Thursday, Griffith and his colleague, Muhammad Mohiuddin, scientific director of the heart xenotransplantation program at the University of Maryland Medical Center, said Bennett’s death saddened them, but that they have not given up on the goal of using animal organs to save human lives.
“What happened doesn’t give us any real fear about the future of this area, unless for some reason this isolated incident is interpreted as a complete failure,” said Griffith. “It was a learning experience. Knowing that this problem exists, it is likely that we will be able to avoid it in the future.”
Genetically modified so that its organs would not be rejected by the human immune system, the pig was provided by the regenerative medicine company Revivicor, based in Blacksburg, Virginia.
Representatives for the company declined to comment on Thursday, and representatives for the Food and Drug Administration (FDA), which gave surgeons the emergency authorization that made it possible to perform the surgery on New Year’s Eve, said they could not answer questions immediately. .
University officials said that although the pig had been examined several times for the presence of virus, the tests only pick up active infections, not latent infections, in which the virus can be hidden discreetly inside the animal’s body. (Tests were done with nasal swabs, but the virus was later detected in the pig’s spleen.)
According to Griffith, the latent virus may have reached the patient by hitchhiking in the transplanted heart.
Initially, the transplant was considered a success. Bennett showed no signs of rejecting the organ, and the pig heart continued to function for well over a month, passing a critical milestone for transplant patients.
A test indicated the presence in Bennett of porcine cytomegalovirus DNS for the first time 20 days after transplantation, but at such a low level that Griffith said he thought it might have been a laboratory error.
But about 40 days after the surgery, Bennett suddenly became seriously ill, and further tests revealed an alarming rise in viral DNA levels.
During the meeting, Griffiths told the other transplant scientists: “So we started to think that the virus that had already appeared on the 20th day as just a slight indication must have increased over time and may have been responsible for triggering all this.” .
Bennett’s health abruptly deteriorated on the 45th day after the transplant.
Doctors treated him with antiviral drugs and intravenous immunoglobulin, a product made from antibodies, but the transplanted heart filled with fluid, doubled in size and stopped working. Bennett ended up receiving extracorporeal perfusion.
Amid an acute shortage of donated human organs, Bennett’s transplant was one of several groundbreaking transplants performed in recent months that offer hope to tens of thousands of patients in need of new kidneys, hearts and lungs.
In October, surgeons in New York connected a kidney grown in a genetically modified pig to a brain-dead patient. The organ functioned normally and produced urine.
In January, surgeons at the University of Alabama at Birmingham reported transplanting kidneys from a genetically engineered pig into the abdomen of a 57-year-old brain-dead man.
But the possibility of unforeseen consequences, especially the potential to introduce animal pathogens into the human population, could dampen enthusiasm for the use of genetically modified organs.
Many scientists believe that the coronavirus that triggered the global Covid-19 pandemic originated from a virus transmitted from an unidentified animal to humans in China.
Translation by Clara Allain