Did a virus kill the first pig heart transplant recipient?

Earlier this year, American surgeons announced they had performed the first successful transplant of a genetically modified pig heart into a human. Unfortunately, the patient died two months later. According to more recent analyses, a pig virus is probably the cause of death.

A great first Tainted

David Bennett, 57, with a terminal heart condition, has been ruled unsuitable for a conventional heart transplant. As a last resort, the team at the University of Maryland Medical Center, where he was admitted, attempted a pig heart transplant last January. The procedure was exceptionally approved by the Food and Drug Administration (FDA) due to the lack of other treatment options.

Some people have already received pig heart valves as replacements. Whole heart transplantation, however, had none never been tempted. For the operation, Dr. Bartley P. Griffith of Maryland Medical School with Dr. Muhammad M. Mohuiddin, inventor of the Cardiac Xenotransplantation Program. They used a genetically engineered heart developed by Revovicorn, a Blacksburg-based regenerative medicine company.

In detail, the animal had developed with it a dozen genetic modifications. Four genes had been deactivated, including one that codes for a molecule that triggers an aggressive rejection reaction in humans. A growth gene was also inactivated to prevent the pig heart from continuing to grow after implantation. Finally, six human genes were integrated into the genome of the donor pig to make the organ more tolerable for the immune system.

Overall the process went well. The heart was beating violently and the patient appeared to recover within the first month (a critical stage for transplant recipients). However, while still in the hospital, his condition rapidly worse early March. The patient is finite died in Marchabout two months after the operation.

Credits: University of Maryland School of Medicine

An avoidable death?

After several weeks of analysis, the medical team is now of the opinion that the porcine cytomegalovirus may have played a key role in this death. In fact, she had found evidence of porcine cytomegalovirus in the patient’s system just twenty days after the operation. However, since the detected levels were very low and the pig was guaranteed virus-free, the doctors initially thought it could be a test error. Finally, weeks later, a postmortem heart biopsy showed that the organ was likely damaged by an infection.

Although porcine cytomegalovirus cannot infect human cells, it can cause complications with the heart itself triggered an immune response dangerous.

This discovery will obviously have important implications for the future of transplantation between species (xenotransplantation). Ethical questions are also raised again insofar as the transplantation of an infected organ should normally have been avoided.

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