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A donor stem cell transplant has kept two patients with neuromyelitis optica relapse-free for 15 years without ongoing medication.
NMO is a rare autoimmune disorder in which the immune system attacks the spinal cord and optic nerve, causing vision loss, paralysis and other severe symptoms.
Researchers say the treatment may have worked by replacing the patients’ immune systems and restoring immune tolerance.
Scientists remain cautious because the study involved only two patients and the procedure carries serious risks, including infections and other complications.
A stem cell transplant has kept two patients with neuromyelitis optica (NMO) — a rare, aggressive autoimmune disease — relapse-free for 15 years without the need for continuing medication, according to a study by researchers at San Raffaele Hospital in Milan. The stem cell transplant successfully replaced their immune systems entirely with someone else’s.
In NMO, the immune system mistakenly attacks the spinal cord and the optic nerve, which connects the eye to the brain. The disease can trigger episodes of eye pain, vision loss, vomiting and paralysis that may last for days, weeks or even months. There is currently no cure for NMO. Existing drugs can help suppress attacks, but patients usually need to remain on medication indefinitely. For some, even these treatments do not work.
Both patients in the study had severe disease that had not responded to standard therapies. As a last resort, doctors tried a procedure that had not previously been used for NMO: an allogeneic haematopoietic stem cell transplant, in which donor stem cells replace the recipient’s immune system.
The first patient, a man, received stem cells from his sister in 2009. The second patient, a woman, received stem cells from an unrelated donor in 2010. Each received a single infusion.
Before the transplant, both patients underwent chemotherapy to wipe out their existing immune systems, including the B cells producing the antibodies that were driving the disease. The immune system that grew back was from the donor rather than the patient.
The disease-causing antibodies became undetectable after the transplant and have remained so. The male patient resumed a normal life and went on to have two children. The female patient regained the use of her arms and no longer needs medication.
The study offers a possible explanation for why the procedure worked. Researchers found that the transplanted immune system showed an expansion of regulatory T cells, a type of immune cell that helps the body tolerate itself rather than attack its own tissues.
This could help explain how immune tolerance was restored. Researchers say the finding may also have implications for other autoimmune diseases, though further work is needed.
But with a sample size of just two patients, the scientific community is still cautious. Both also developed complications, including swollen lymph nodes and antibody deficiency. One patient developed bladder cancer, a known risk after stem cell transplants.
The procedure itself carries serious risks, including potentially fatal infections, and finding suitable donors can be difficult.
In an article published by Nature on the study, Jiao Jiao Li, a biomedical engineer at the University of Technology Sydney, said: “I don’t think we can say it’s a cure, but then again, it has addressed the problem the disease has caused over this very long period of time.”
The study’s authors said the findings provide “proof of concept” that allogeneic haematopoietic cell transplantation can achieve deep and potentially curative disease modification in selected NMO cases.
They said further studies are needed to better define which patients may benefit, how safe the procedure is and whether the long-term benefits outweigh the risks.
