The heart from a genetically modified pig transplanted to a Maryland patient in January in a pioneering, acclaimed, and widely critiqued surgery appears to have carried an unwanted passenger.
A porcine cytomegalovirus (PCMV) in the heart had gone undetected before the operation and may or may not have been instrumental in David Bennett’s death 2 months later, describes a report published May 4 in MIT Technology Review.
“The issue is now a subject of wide discussion among specialists, who think the infection was a potential contributor to Bennett’s death and a possible reason why the heart did not last longer,” states the article, written by staff journalist Antonio Regalado.
As described in the story, the xenotransplant saga’s new twist comes from the surgeon who performed the operation, Bartley P. Griffith, MD, University of Maryland School of Medicine, Baltimore, who related the PCMV finding in an April 20 online presentation hosted by the American Society of Transplantation.
Bennett’s initially promising but later turbulent clinical course, described by his surgeons and widely reported upon his death, included repeated skirmishes with infection and retaliatory adjustments to his immunosuppressant regimen. Those episodes were thought to have contributed to his death, the actual cause of which is undetermined or at least not yet reported.
“We are beginning to learn why he passed on,” Griffith says in Regalado’s article, acknowledging further that the porcine virus “maybe was the actor, or could be the actor,” that set off the events leading to Bennett’s death.
Xenotransplant specialists know that PCMV is a potential problem with pig organs and know to test for it before attempting the procedure in animal models, notes the article. It refers to a published a series of pig-heart transplants to baboons in Germany. The hearts ” lasted only a couple of weeks if the virus was present, while organs free from the infection could survive more than half a year.”
The heart Bennett received had been extensively screened for bacteria, viruses, and other issues that could potentially have threatened the organ and Bennett, but the effort apparently fell short. In the MIT Technology Review story, the first author of the German baboon series speculates on how the University of Maryland team might have missed PCMV.
“The US team appears to have tested the pig’s snout for the virus, but often it is lurking deeper in the tissues,” says Joachim Denner, PhD, Institute of Virology, Free University of Berlin, in the article. The virus, he contends , “can be detected and easily removed from pig populations, but unfortunately they didn’t use a good assay and didn’t detect the virus.”
That PCMV escaped detection before the operation “could now factor into some people’s questions over whether the experiment should have taken place at all,” the MIT Technology Review article proposes. “It’s a big red flag,” bioethicist Arthur Caplan, PhD, New York University, New York City, says in a quote, adding: “If doctors can’t prevent or control infection, ‘then such experiments are tough to justify’.”