Lauren Dempsey, MS in Biomedicine and Law, RN, FISM News
A patient who received an interspecies transplant has died just a few months post-operation.
David Bennett Sr., who had end-stage heart disease, was told that he would most likely not receive a human heart. However, an experimental surgical treatment option was available. Bennett’s doctors at the University of Maryland Medical Center would transplant a genetically modified pig heart.
To provide this risky and experimental surgery, the FDA granted “compassionate access” as Bennett would otherwise die from his heart disease and had previously exhausted all other treatment options. The pig heart used for the transplant was procured from Revivicor, a regenerative biomedicine company that creates human-compatible organs and tissues from animals. The genetic modifications are done to prevent rejection and other complications. The heart used had a total of ten genetic modifications. Unfortunately, not long after surgery, Bennett woke with symptoms of an infection, leading doctors to treat him with antibiotics and antiviral medications. Subsequently, Bennett’s new heart quit functioning properly.
After some investigating, it was discovered that the transplanted heart had a viral infection, known as porcine cytomegalovirus, which is part of a family of viruses that can cause respiratory illness and pregnancy complications in pigs. Human cytomegalovirus causes symptoms such as fever, sore throat, and fatigue, and the CDC estimates that one in three children have had the virus and over 50 percent of all adults have been infected by age 40. Usually, the virus does not cause complications in humans, but can occasionally lead to mononucleosis or hepatitis.
While porcine cytomegalovirus is not transmissible to humans, previous research has shown that the presence of this virus could cause the immune system to launch into overdrive. A 2015 study found that when organs were transplanted from pigs to baboons the transplanted organs failed quickly, lasting weeks to months regardless of whether the tissue was virus-free or not. The authors of this study suggested that a patient who received an infected heart would have very poor survival outcomes.
Dr. Bartley Griffith, Bennett’s physician, believes that this may have contributed to his surprising death. It does not appear to have been an active infection in the pig; however, this virus can lay dormant. Griffith describes it as a “hitchhiker” that can be “latent” for long periods. However, prior to the surgery, there was no indication that an infection was present, the donor pig appeared to be healthy and had passed all FDA-required testing and health checks. Joachim Denner of the Institute of Virology at the Free University of Berlin believes that more accurate testing would have detected the virus, which can be found in almost all animal tissues. He believes that the surgery was still a success for the medical field, especially since more people are waiting for organs than are available.
Researchers are still working to better understand what caused Bennett’s death so they can prevent future complications in interspecies transplants. Griffith said “This was a patient. It wasn’t an experiment to us. All he wanted to do was live.”