A generation ago, Guy Pearce might have been like the famous “bubble boy,” a Texas child born with an immune system so fragile, the best way to keep him alive was to seal him in a sterile plastic enclosure to protect him from the world’s germs.
Instead, Guy, a lively 6-year-old from Nottingham, England, lives a life that David Vetter, the U.S. child who battled severe combined immunodeficiency, or SCID, only imagined.
“He can do all of the things his friends can and more,” said Guy’s mother, Gaynor Harnden. “He is able to play football and ride a pony.”
Guy is among more than a dozen children, now aged 4 to 14, who lead nearly normal lives despite the disease thanks to an experimental treatment that appears to be a long-term success. In two papers published this week, researchers in Britain report that gene transfer therapy has kept SCID in check in young patients for nearly a decade, rivaling traditional transplant techniques.
“These are some of the sickest children you’ll see,” said Dr. Bobby Gaspar, a professor of pediatrics and immunology at Great Ormond Street Hospital for Children and the UCL Institute of Child Health in London. “Some were on a ventilator when we first saw them, others riddled with infection. Ten years later they live fully functional lives.”
In 2001, Gaspar and his team were among the first to attempt a still-controversial treatment to solve the riddle of SCID, in which children are born with virtually no immune system protection from ordinary germs. For them, the viruses, bacteria and fungi of daily life can be deadly.
That was the reason that David Vetter, of Shenandoah, Texas, was encased in a NASA-made bubble at a Texas hospital for his entire life. The boy, whose life inspired a movie starring John Travolta, died in 1984 at age 12 after complications from a bone marrow transplant from his sister.
Scientists fix genetic defect in cells
In the new research, involving 10 children with a form of SCID called SCID-X1, found only in boys, and six children with a form of SCID called ADA-SCID, the scientists took blood-forming stem cells from the youngsters, genetically fixed the underlying defect in the cells, and then returned the repaired cells to the patients.
More than nine years later, the disease has been halted in four of the six SCID-ADA patients and in nine of the 10 SCID-XI patients, all of whom have developed functioning immune systems of their own.
In the other two SCID-ADA children, gene therapy failed, but they received alternate treatment and are doing well. One SCID-X1 patient developed leukemia, but is now in remission, the papers published in the journal Science Translational Medicine report.
That’s a ground-breaking success in a world in which the record of treating SCID was mixed, said Dr. Donald B. Kohn, a professor of microbiology, immunology and molecular genetics and pediatrics at the University of California at Los Angeles.
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SCID is estimated to occur in between 1 in every 50,000 live births to 1 in every 100,000 births, though the true prevalence isn’t certain, Kohn said. Many children with SCID die, often undiagnosed, after infections in the first year or two of life.
“It really shows the proof of this research,” said Kohn, who wrote a commentary in the same issue of the medical journal. “The families that we’ve treated successfully, they have healthy kids because of this.”
SCID babies are best treated with transplants of hematopoietic stem cells from the bone marrow of matching siblings. Often, however, good matches can't be found. Unmatched donations from parents or other donors can be used, but they risk the development of graft-versus-host-disease, in which the transplanted cells attack the recipient’s body. Between 2,000 and 3,000 children have been treated in this way since the 1970s, Gaspar said, with about a 70 percent success rate.
“The main issue was that these children had few alternatives,” he said. “If we didn’t treat them, they would die. If we used a mismatched transplant, they had a 25 percent to 40 percent chance of dying as a result of the transplant.”
'We didn't really have a choice'
For some parents of children with SCID, gene transfer therapy offered their only hope. That was the case for Debra Crick of Leicester, England, whose son Jack was born in May 2004 and diagnosed with SCID the next September.
“He was snuffly as a newborn baby, which doctors put down to mucus build-up,” she recalled.
After the diagnosis and a stint in intensive care, doctors said Jack would need a bone-marrow transplant, but no match could be found. That’s when technicians suggested gene transfer therapy.
“By that point we didn’t really have a choice, because Jack had run out of available treatment options,” she said.
The blond boy is now an active schoolchild who plays English football and proudly sports the uniform of his favorite team, Manchester United. He still takes medications, but is otherwise "doing really well now both in school and socially," his mother said.
All told, fewer than 100 children in the world have undergone gene transfer therapy in the past decade in trials conducted in Italy, France, England and the U.S., Hohn estimated. The British trial demonstrates the first long-term success, but with such small numbers of patients studied, the technique is still regarded as experimental — and it’s not clear whether the children are cured.
“We still don’t know. We know that 10 years out, these patients are doing well clinically,” said Hohn.
More children are being diagnosed with SCID, especially after the United States added the condition to a core panel of 29 genetic disorders included in newborn screening tests last year. In California alone, seven children with SCID were diagnosed in the first year, Hohn said.
With their immune systems apparently rebuilt, there appears to be no reason that the SCID children, some of whom are now entering puberty, can’t pursue normal lives, including careers and families, Gaspar said.
The children themselves can’t really know what life would have been like without their disease — or their treatment, he said. But for parents of children like Guy Pearce and Jack Crick, the risk was worth it.
“He wouldn’t be here if it wasn’t for the option of gene therapy treatment,” said, Gaynor Harnden, Guy's mother.
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