It was a special first when David Bennett, 57, became the first-ever human to receive a pig heart in January after an eight-hour operation at Maryland University Hospital in Baltimore, USA.
Bennett was seriously ill, too ill even to qualify for a donation of a human organ. He agreed to an experimental donation made by surgeon Bartley Griffith. The operation was successful, but Bennett died two months later.
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Now a pig virus appears to have been present in the donor heart. Porcine cytomegalovirus (cmv), a type of herpes virus. The virus probably played a role in the man’s death, says surgeon Griffith.
Ian Alwayn, professor of Transplant Surgery at the LUMC, finds it remarkable that this virus was present in the heart. “Pigs used for transplants are screened, especially for this specific virus. You should be able to find that, so I’m surprised it hasn’t been picked up in advance.”
no medicines
Cytomegalovirus also occurs in humans, but that is a different variant than in pigs. Humans have no resistance to the pig variety, and there are no medicines for it, explains Alwayn.
In addition, patients who receive a donor organ are given drugs to suppress their immune system. This prevents the organ from being rejected. “As a result, those patients are extremely susceptible to infections,” Alwayn says.
“In this case, the infection could not be treated and the patient was not resistant to it. So the virus most likely contributed to his death. And that could have been prevented.”
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The pigs used for these types of transplants are not only extensively screened, they are also bred in special conditions, such as a germ-free environment, precisely to prevent animal viruses from being transplanted.
Alwayn: “Apparently something went wrong. That does not mean that it was also a danger to the environment, because people cannot transmit such a virus, but it is annoying for the person who is infected.”
Not the last try
Still, Alwayn doesn’t think Bennett will be the last patient to get a pig heart transplant. “This experience is very instructive, and once again emphasizes the importance of handling these organs very carefully, and testing accurately for these types of viruses.”
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“Don’t forget: this man was very ill and functioned with a pig’s heart for two months. That is very special,” says the professor. “The heart has been genetically modified in ten points, among other things to prevent rejection. That seems to have worked. If you can prevent an infection like this, a human with a donor heart from a pig could live a long time.”
Hopefully suitable alternative
According to Alwayn, Bennett’s death is not a ‘show stopper’ for research into animal donor organs. “It is difficult to predict how quickly and how often such an operation will take place, but it will certainly be looked at further. In the US, but also in Germany, they have already come a long way with this kind of research.”
“We can learn more from that. And hopefully pig organs will soon offer an alternative for patients who otherwise die while they are on the waiting list for a donor organ.”
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