In January 2022, David Bennett (57 years old), a worker with heart failure, underwent a highly experimental surgery at the University of Maryland medical center, where doctors transplanted the heart. genetically modified pigs to help David stay alive. At that time, the results of the surgery were considered as a remarkable advance in the medical field.
However, two months after the surgery, the patient died suddenly, caused in part by a virus in pigs called porcine cytomegalovirus. The full investigation into the cause of death is still underway to clear doubts about how much the virus contributed to this unfortunate incident.
Bartley Griffith, the surgeon who transplanted the patient’s pig heart, said the January trial may have encountered an unexpected error. Doctors believe that pigs bred to provide transplanted organs do not carry the virus, but the process of transplanting tissues between different breeds has the potential to introduce unwanted risks.
The biggest challenge in animal-to-human organ transplantation is the resilience of the human immune system. It can attack foreign cells, destroy tissues and transplant animal organs. This process causes infection and creates a harmful reaction for the patient afterwards.
Companies have been working on bioengineering pigs by removing and adding different genes to help mask their tissues from potential immune attacks. The heart used in David Bennett’s case came from a pig that had undergone 10 gene-editing runs by Revivicor, a biotech company.
Immediately after David’s surgery, doctors regularly monitored his recovery through various blood tests. In one of the tests, they found “a small blip” indicating the presence of cytomegalovirus in pigs. However, because its levels are so low, doctors are not concerned.
Since each special blood test took about 10 days, doctors did not know that the virus had begun to multiply rapidly. As a result, this may have caused a reaction known as a “cytokine burst,” a storm of immune responses that causes serious problems.
On the 43rd day of follow-up, doctors discovered that David was breathing heavily, showing signs of distraction and not talking to people. Suspecting the patient had an internal infection, the doctors injected David with globulin and cidofovir. The patient showed signs of recovery after 24 hours before returning to the worst condition. Shortly after, the patient did not survive.