An American man who died two months after receiving the first-ever human heart transplant from a pig may have been the victim of a pig virus infection, a new report said.
David Bennett, 57, died from no clear causes on 8 March at the University of Maryland Medical Centre after his condition began deteriorating several days earlier.
The 57-year-old had undergone a ground-breaking experimental surgery in January in which doctors replaced his heart with one from a gene-edited pig.
Scientists had modified the pig to remove the animal’s genes that could trigger hyper-fast organ rejection and added human genes to help the body accept the organ.
A few days after the surgery was performed, Mr Bennet’s heart was “working” and looked “normal,” his doctors had said in a statement.
About two months later, however, his condition began deteriorating and he died. It is not yet clear whether his heart had failed, and if so, why.
A spokesperson said in a statement released by the university in March that there was “no obvious cause identified at the time of his death,” adding that a full report was pending.
Mr Bennett’s heart was possibly infected by a pig virus called porcine cytomegalovirus, a preventable infection linked to devastating effects on transplants, the MIT Technology Review reported on Wednesday.
“We are beginning to learn why he passed on,” said University of Maryland School of Medicine (UMSOM) transplant surgeon Bartley Griffith.
BREAKING: The heart used in pioneering University of Maryland xenotransplant experiment was infected by a pig virus--may have contributed to patient's death after 60 days. https://t.co/iiHfbpgIDY
— Antonio Regalado (@antonioregalado) May 4, 2022
The virus “maybe was the actor, or could be the actor, that set this whole thing off,” Dr Griffith added.
The pig, whose heart was transplanted into Mr Bennet, was reportedly raised by biotech company Revivicor, which altered the pig’s genome to reduce the risk of rejection.
Scientists had noted early in March that as part of attempts to decrease the risk of infection, the donor pig was raised in a disease-free laboratory environment and screened for many known pig pathogens before being brought to the laboratory.
While all pigs are known to have an endogenous porcine virus, researchers said they had not detected any transmission of this virus to humans or to non-human primates in earlier studies.
But previous studies testing the techniques for pig-to-human transplants in baboons have shown that kidney grafts failed about four times faster when the porcine cytomegalovirus was present.
Another study from 2020 carried out in baboons had found pig-to-baboon heart transplants free of the virus could last more than six months while those with infected organs failed much more quickly with extremely high levels of the virus.
The study’s authors had said the transplanted hearts showed extremely high levels of the virus likely due to the intentional inhibition of the baboon’s immune system for transplantation or due to the absence of the pig’s immune system that may have been more suited to suppress the pig-specific virus.
Researchers had also noted that the high virus levels in the recipient baboon caused rejection of the transplant by disrupting the production of immune system molecules called cytokines which protect against infection.
They noted in the study that a human receiving a similar porcine cytomegalovirus-infected heart may show “a similar reduction of survival time”.
Speaking to MIT Technology Review, Dr Griffith wondered if Mr Bennett was hit by a similar syndrome that was previously seen in baboons that received infected pig hearts.
“Although the evidence is lacking, there is a definite concern of porcine pathogens causing disease in humans,” Muhammad M Mohiuddin, Professor of Surgery at UMSOM, had said in March.
If a virus did lead to Mr Bennet’s death, it could mean future transplants would need better screening processes to ensure infection-free organs.
“Infectious disease complications are always a concern in the field of organ transplantation, whether it is infections related to the recipient or the donor, which in this case remarkably happens to be a pig,” Kapil Saharia, Chief of Solid Organ Transplant Infectious Diseases Service at the University of Maryland Medical Centre, had said in a statement in early March.
Revivicor declined to comment to MIT Technology Review and has not immediately responded to a request for comment from The Independent.