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Doctor reveals reason behind pig heart transplant recipient’s death — Analysis

A transplanted heart infected by pig virus may have killed the recipient of pioneering treatment

Two months after receiving an interspecies pig heart transplant, a Maryland doctor confirmed that the man had died of complications from the pig virus. David Bennett Sr., a patient with end-stage heart disease, died March 2 months after receiving interspecies transplant surgery at University of Maryland Medical Center. While he had initially appeared to respond well to the procedure, the first of its kind, his recovery did not last, and a spokesperson for the hospital where he died initially said there was “no obvious cause” for his passing.

Bennett’s death from porcine cytomegalovirus was attributed to Dr. Bartley, Griffith who carried out the surgery. This preventable disease isn’t believed to have any human-to-human transmission. While the pig, supplied by biotech firm Revivicor, was supposed to be free of all pathogens, Griffith told the MIT Technology Review that doctors noticed a “Blip” suggesting the presence of the virus 20 days after the procedure, and the team believes the donor pig was infected.

While the doctors initially ignored the readings, claiming the level of cytomegalovirus was very low and attributing it to an error, Griffith noted that by the 43rd day after surgery his patient “Looked really cool” and had clearly fallen off the pathway to recovery. “It was an accident. It looked like he was infected. He was unable to pay attention, and he wouldn’t speak with us..”

Bennett’s death was not due to the cytomegalovirus. He had end-stage heart problems and treatment of an infection that could trigger the immune system to attack the pig’s heart required a delicate balance. His death might have been accelerated by the doctors giving Bennett human antibodies. These are blood products which could have caused damage to his pig organ.

While some doctors worry that xenotransplantation – surgically implanting an organ from one species into another – could set off a new type of pandemic, there was no evidence that the virus that attacked Bennett’s heart had spread to any of his human body parts, and Massachusetts General Hospital transplant specialist Jay Fishman said there was “No real danger to the persons” of the virus spreading beyond the donor organ.

However, the lack of a pig’s natural immune system, and the fact that the human recipient was on immunosuppressive medication to avoid him from rejecting the donation, means that non-human virus could continue to infect the transplanted organ, possibly causing further complications.

According to several doctors speaking to MIT Technology Review, other than the viral infection the operation was considered a success. The transplanted heart was not rejected by the recipient, which was critical to the outcome of this experiment. “It was amazing. He’s a gentleman with a big heart. Literally, he’s got a pig heart.,” Griffith, the surgeon who performed the operation, gushed – even while acknowledging that the surgery team was “Like a group blind squirrels” scurrying around in the dark to manage a condition they didn’t fully understand.

Total of 10 gene modifications were given to the donor pig, which included genes that might cause rapid organ rejection. To facilitate patient acceptance, it was also given human gene modifications. In the near future, several other biotech companies will likely develop their own pig to human transplants. 

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