The version used in Maryland comes from a pig with 10 genetic modifications developed by Revivicor, a subsidiary of United Therapeutics.
Monitoring promising tests of such pig organs in baboonsthree U.S. transplant teams have launched the first human studies since late 2021. Surgeons at the University of New York and the University of Alabama attached pig kidneys to people with brain deaths, but the University of Maryland went a step further when Griffith sewed a pig heart into Bennett’s chest. in early January.
The transmission of swine viruses to humans is worrying – some fear that xenotransplantation could trigger a pandemic if the virus adapted within the patient’s body and then spread to doctors and nurses. The concern could be serious enough to require lifelong follow-up of patients.
However, a specific type of virus found in Bennett’s donor heart is not believed to be capable of infecting human cells, says Jay Fishman, a specialist in transplant infections at Massachusetts General Hospital. Fishman believes that “there is no real risk for people” from its further spread.
Instead, the problem is that swine cytomegalovirus has been linked to reactions that can damage the organ and the patient – with disastrous results. Two years ago, e.g. German researchers they reported that pig hearts transplanted with baboons lasted only a few weeks if the virus was present, while organs without infection could survive more than half a year.
The researchers said they found “astonishingly high” levels of the virus in the hearts of pigs removed from baboons. They think that the virus could pass not only because the baboon’s immune system was suppressed by drugs, but also because the pig’s immune system was no longer there to keep the virus under control. “It seems very likely that the same could happen to people,” they warned at the time.
Joachim Denner of the Institute of Virology at the Free University of Berlin, who led the study, says the solution to the problem is more accurate testing. The American team seems to have tested the pig’s snout for the virus, but it often lurks deeper in the tissues.
“It’s a latent virus and it’s hard to detect,” says Denner. “But if you test the animal better, it won’t happen. The virus can be detected and easily removed from pig populations, but unfortunately they did not use a good test and did not detect the virus, and that was the reason. The donor pig was infected and the virus was transmitted through a transplant. ”
Denner says he still thinks the experiment was a “great success”. For example, the first human-to-human heart transplant, in 1967, lasted only 18 days, and two years later, one in Germany lasted only 27 hours.
Denner says the virus alone cannot be blamed for Bennett’s death. “This patient was very, very, very ill. Don’t forget that, “he said. “The virus may have contributed, but that was not the only reason.”
Cause of death?
Benett’s cause of death is important, because if his heart fails as a result of immune rejection, researchers may have to return to the drawing board. Instead, companies like United Therapeutics and eGenesis, or academics working with them, are now expected to launch clinical trials of their pig organs within a year or two.
Bennett was offered a pig heart after Griffith applied to the U.S. Food and Drug Administration for special permission to test the animal organ in a one-time transplant. He was considered a good candidate for a brave attempt because he was approaching death from heart failure and was not entitled to a scarce human heart for transplantation due to a history of neglect of medical advice.