A small study using an experimental gene therapy to correct defects in DNA has transformed the lives of six boys with a deadly immune disorder, researchers report.

Wiskott-Aldrich syndrome is a rare genetic disorder that affects up to 10 children in every million born, and occurs almost exclusively in males. 

The syndrome is characterised by eczema, low platelet counts in the blood, which results in bruising, and a compromised immune system that leaves people vulnerable to a suite of recurring and potentially deadly infections such as pneumonia. People with the condition can also suffer severe nose bleeds and bloody diarrhea.

In the two years since the treatment was administered, there has been a significant decrease in the number of infectious complications that often arise with the illness, and the average number of days spent in hospital for the study participants has dropped from 25 per year in the two years before the treatment to zero days in the two years following.

"This study demonstrated the feasibility of the use of gene therapy in patients with Wiskott-Aldrich syndrome," the researchers noted.

The findings, which were published in the Journal of the American Medical Association, could revitalise interest in gene therapy, which involves functional genes being inserted into cells to correct defects and help reverse genetic diseases. 

But the researchers also caution that, "controlled trials with larger numbers of patients are necessary to assess long-term outcomes and safety."

As James Gallagher from the BBC explains, the syndrome "stems from an error in the genetic code that contains the building instructions for a key element in the immune system - a protein called WAS."

Current treatment options involve bone marrow transplants, whereby hematopoietic stem cells from a donor can help restore some level of immune function.

But these transplants are only viable when there's a prospective donor with a close tissue match, and even then, researchers say there's usually a high rate of complications involved.

So researchers in the UK and France have begun investigating a gene therapy option, which they say could be more effective and safer.

With this technique, researchers use stem cells from the sick individual rather than from a donor. These cells are extracted and modified - or infected, rather - with an advanced lentiviral vector, which is derived from HIV.

These vectors have become an important tool for gene delivery to cells, and are promising for gene therapy because they can infect both dividing and non-dividing cells, and can change the expression of their target cell's gene for long periods of time.

In a trial that took place at the Great Ormond Street Hospital in the UK and Necker Children's Hospital in France, researchers administered this gene therapy to seven male patients with severe Wiskott-Aldrich syndrome between 2010 and 2014. These patients ranged in age from about eight months to 16-years-old.

While one of the seven patients passed away from a pre-existing infection, the results for the surviving patients seem encouraging.

In the 24 months following treatment, researchers reported that infectious complications related to the illness were resolved in all six patients, with three of them able to stop taking preventative antibiotics.

Furthermore, severe eczema was cured in all affected patients, as were signs and symptoms of autoimmunity.

Patients have also recorded no severe bleeding episodes after treatment, and have seen a remarkable decline in hospital visits.

"I think it is very significant, it is another clear and powerful demonstration that a gene therapy approach is an effective one." study co-author and immunologist, Adrian Thrasher, from Great Ormond Street Hospital, told the BBC. 

"What we hope, and the evidence is certainly suggestive of this, is that the therapeutic effect will last for a very substantial amount of time, such that the patients should not need another treatment and so therefore we hope that it will be lifelong."

Source: BBC