(CNN) — When Kaitlyn Sinnamon was 20 weeks pregnant with her second child, doctors told her her baby would be born with a heart defect that would require surgery early in life.
Easton Sinnamon was born at Duke University Hospital with single ventricle heart disease, which meant his heart had only one ventricle, rather than two, to pump blood to the rest of the body.
Ivy Sinnamon holds her brother, Easton, who needed a heart transplant due to a congenital condition.
After two heart operations failed to correct a leaky heart valve related to his congenital heart disease, it became clear to his surgical team that Easton would need a new heart. But the transplant would require Easton to take immunosuppressive drugs for the rest of his life so his body wouldn’t reject the new organ.
These drugs can increase the risk of cancer and be toxic to the kidneys, as well as making patients more susceptible to serious infections.
Easton Sinnamon four days after the transplant operation.
But doctors ran into another problem while Easton awaited the heart transplant. After repeated infections, further tests revealed that she had a deficiency in a specific type of immune system cell called a T cell. T cells mature in the thymus, an organ located in front of the heart.
Easton’s poor immune function meant his body didn’t naturally produce T cells, which are also often responsible for the body rejecting and attacking a transplanted organ when it doesn’t recognize it.
“It was a fluke that Easton needed a heart transplant and that he also had very poor immune function,” Dr. Joseph Turek, chief of pediatric cardiac surgery at Duke University and a member of Easton’s surgical team, said in an email. a press conference on Monday.
This made Easton a candidate for a novel surgery to receive both a new heart and a processed thymus from the same donor. This combination of procedures had never been performed on a human.
For Easton’s parents, Kaitlyn and Brandon Sinnamon, the decision to put their baby through such a critical procedure was not an easy one, especially considering the risks that come with transplant surgery. When Easton’s second operation failed, Turek discussed the options with the Sinnamons.
“I think one of the things that stuck with us the most is that he told us, ‘I want to give you your child back, and the only way to do that is through a transplant,'” Kaitlyn Sinnamon told CNN. “If it works, it will not only help Easton, but it will help millions of people. And besides, we managed to make a big difference. And if it doesn’t work, at least we tried.”
According to Turek, Duke University is the only place in the Western Hemisphere that performs cultured thymus transplants, in which cells from the donor’s thymus are incubated and grown in a laboratory before being implanted into the recipient.
In a healthy immune system, immature immune cells enter the thymus, where they learn to identify what is “self” and what is foreign. The thymus culturing process removes any mature immune cells from the donor, leaving a thymus scaffold for the recipient to grow their own immune cells.
“The idea that the thymus grows in the same environment as the new transplanted organ is what allows it to recognize it as ‘its own’. If only the thymus were used and not cultured, there would be cells that would start rejecting it,” Turek said. to CNN.
Easton’s immunodeficiency meant that he would be able to develop one aspect of his immune system, T cells, as his body got used to his new heart. This double transplant from the same donor could even eliminate the need for dangerous immunosuppressive medication for life.
In August, at 6 months old, Easton received his heart transplant and began immunosuppressive medication. Two weeks later, after the donor thymus cells had completed their culturing process, she, too, had her thymus implanted.
“It’s bittersweet to be excited about your son getting a transplant, because you can bring him home, but someone else is losing theirs,” Sinnamon said.
Shortly after the operation, Easton was released from the intensive care unit, signaling to his parents that he was recovering well.
Six months after the transplant, tests showed that Easton’s new thymus was properly developing T cells and that his body had not rejected his new heart. These results are promising, and Easton’s medical team hopes to wean him off immunosuppressant medication within a year if tests confirm that his T-cells recognize his transplanted heart as their own.
“The idea of being able to get a transplant and not have to take these drugs is really a game changer for organ transplant patients,” Turek told CNN.
A member of the Duke transplant team holds tissue from the donor’s thymus.
Turek also said that the success of this procedure could mean that the transplanted heart can live longer.
Currently, transplanted hearts typically survive only 10 to 15 years due to minor rejection episodes in the years after the operation. These episodes can usually be treated by increasing the dose of immunosuppressive medication, but over time they can ruin the integrity of the heart. Therefore, creating an immune system tolerant to heart transplantation could increase the durability of that heart.
Turek sees this as opening the door to the future of transplant medicine. The next step is to test whether this procedure could be successful in someone with a healthy immune system who needs an organ transplant.
“I think if that happens, this is going to be the way most transplants are done in the future, and that’s going to be for all organs,” Turek told CNN.
However, T cells are only part of the immune system’s response to transplanted organs, said Dr. Reshma Biniwale, an associate professor of cardiac surgery and director of pediatric heart transplantation at UCLA.
Easton Sinnamon is now a happy and spirited one year old.
“I would be very hesitant to say that the child will be completely free of all immune suppression, because this technique is only dealing with T cells, thymic cells,” said Biniwale, who was not involved in Easton’s surgery. “Immunity is also mediated by humoral cell antibodies, which require an entirely different mechanism of immune suppression.”
B cells, also known as humoral cells, are a type of immune cell that makes antibodies and is produced in the bone marrow.
“This can be a great short-term solution, but it doesn’t provide a lifetime solution,” Biniwale told CNN.
It’s not yet clear whether this procedure would be feasible in an adult patient, according to Turek, because the thymus shrinks as people age and the bone marrow becomes responsible for making T cells.
“That’s one of the things we’re looking at in the lab, as well as figuring out what the right age of donors is. We think you’re probably at some point in early adulthood where you still have a viable thymus to the transplant,” Turek said.
There is even the possibility that transplants of cultured thymus may accompany xenotransplantation, which is when organs are transplanted from animals to humans.
A man who was the first to receive a genetically modified pig heart transplant He died on Tuesday, two months after his intervention. Turek says that a cultured thymus transplant could eliminate the need for high doses of the immunosuppressive medication that the man needed.
Seven months after his own surgeries, Easton celebrated his first birthday and “is thriving at home,” according to Sinnamon.
“When we brought him home, he couldn’t even hold his head up. We had to carry him like a newborn, and now he walks around the house and laughs and plays with his sister on the floor,” she said. “If you were to look at him now, you would have no idea that he went through everything he went through.”