In the news

Correct mutations in the adenosine deaminase (ADA) gene to alleviate the symptoms of X-linked severe combined immunodeficiency (SCID) 

10 children with X-SCID aged between 4 and 46 months were treated with blood stem cells (that give rise to immune cells) that had been treated with a viral-based gene therapy vector containing healthy copies of the interleukin-2 receptor gamma chain (IL2RG) gene. 

The children were followed over a median period of 80 months (some for longer) and showed restoration of normal cell-mediated immune function, though only partial restoration of humoral (antibody mediated) immune function, such that some needed ongoing antibody therapy. One child developed leukaemia as a result of the gene therapy, which went into remission following chemotherapy. The other children remained well. 

These findings support earlier reports of successful gene therapy for SCID (see previous news); although there were more cases of leukaemia in the other study, in combination the two trials show a 95% survival rate to date. Improved, safer gene therapy vectors have been developed and are entering clinical trials 

A second paper by the same authors [Gaspar HB et al. (2011)] also reports successful gene therapy for another, less common form of SCID caused by mutations in the adenosine deaminase (ADA) gene; four out of six patients showed recovery of immune function with a median follow-up of 43 months and no adverse events. Together, these papers show steady progress towards effective treatments for a majority of patients with severe genetic forms of immune deficiency, and lessons learned will aid the development of gene therapy for other diseases.  

Of note, these therapies are apparently most effective in the youngest patients, suggesting that improvements in early diagnosis of genetic disorders (for example, faciltated by whole genome sequencing technologies) may be an important factor for successful treatment.