A new yet experimental treatment, known as T-cell therapy, aims to cope with that vulnerable period, the months during which the body is rebuilding its natural defenses.
By:
AFP
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When a person’s immune system is affected by a genetic disease, a bone marrow transplant can cure it, but with a major disadvantage: during the first months, the defenses of the recipient become severely weakened. The slightest infection can take you to the hospital.
A new yet experimental treatment, known as T-cell therapy, aims to cope with that vulnerable period, the months during which the body is rebuilding its natural defenses. After two decades of clinical trials, the technology has been perfected and is being used to treat more and more patients, many of them children.
Johan is one of them.
Today he is a naughty and smiling little boy who never tires of chasing the family’s puppy, Henry. Nothing in it reveals the medical and emotional roller coaster that his family, who lives in a comfortable suburb of Washington, spent three years.
It all started with a pregnancy test: Johan was not planned. “It was a shock, I cried,” says his mother, Maren Chamorro, 39.
She knew from childhood that she carried a gene that causes an often fatal disorder before the age of ten: chronic granulomatous disease (EGC). His brother died at age seven. And the laws of genetics indicated that he had a chance among four of transmitting it.
For her first children, she and her husband, Ricardo, had chosen in vitro fertilization, which allowed a genetic test of the embryos before implantation.
His twins Thomas and Joanna were born seven and a half years ago without the disease. But a genetic test confirmed that Johan had EGC.
After contacting Washington Children’s Hospital, the couple made one of the most important decisions of their lives: Johan would receive a bone marrow transplant, a risky procedure that allowed healing.
“The fact that Maren lost her younger brother to this disease played an important role,” says Ricardo.
Bone marrow is our factory of red and white blood cells. Johan’s produced white blood cells unable to respond to bacteria and fungi. In it, a bacterial infection could get out of control.
Fortunately, his six-year-old brother Thomas was a compatible donor. In April 2018, doctors “cleaned” Johan’s bone marrow with chemotherapy. Then they took a small amount of Thomas’s, taking it out of the bones of his pelvis with a needle.
They extracted “supercells,” as Thomas says, stem cells, which re-injected into Johan’s veins to gradually nest in his bone marrow and produce normal white blood cells.
The same immune system as the brother
The second step was preventive cell therapy, in an experimental program led by immunologist Michael Keller. The part of the immune system that protects against bacteria is rebuilt in a few weeks, but for viruses it takes more than three months.
From Thomas’ blood, doctors extracted specialized white blood cells (T cells) that had already found six viruses. Keller multiplied them for 10 days in an incubator, creating an army of hundreds of millions of specialized T cells. The result: a white fluffy substance contained in a small glass jar.
Then, the T cells were injected into Johan, immediately ensuring protection against these six viruses, preventively.
“He has his brother’s immune system,” says Keller.
His mother confirms it: now when Thomas and Johan catch a cold, they have the same symptoms, of the same duration. “It’s great to have the same immunity as your older brother,” says Maren.
The stimulation of the immune system from donor cells, or from the genetically modified cells themselves, is called immunotherapy.
The main application of this is for cancer, but Keller hopes it will soon be available against viruses, for immunosuppressed patients like Johan.
The obstacle remains technical complexity and cost, which currently restricts the procedure to some thirty centers in the United States.
For Johan, a year and a half after the transplant, everything indicates that it worked perfectly.
“It’s great to see him play in the mud,” says Maren, whose only concern now is that, when Johan gets sick, the rest of the family gets the same germ.
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