A newly designed viral vector has shown promise for effectively delivering genes into the cells of patients with sickle cell disease.

Sickle cell anaemia is when a faulty gene causes the structure of haemoglobin to mutate and distort the shape of red blood cells, significantly hindering the transport of oxygen around the body. It is significantly more common in African-descended populations. Gene therapy holds huge potential for sickle-cell treatment as if the healthy haemoglobin gene can be edited into the cell, its oxygen carrying capacity would be restored.

The current method for treating sickle cell using gene therapy involves harvesting blood producing stem cells from the patient, gene editing of the cells using viral vectors and then transplanting the edited cells back into the patient. However, the gene editing stage is far from optimised.

The β-globin gene is essential to restore haemoglobin function in sickle-cell but it must be inserted alongside intron-2, which promotes its expression. However, Intron-2 gets ‘clipped out’ during the gene editing process if the gene is left in the natural forward direction. Editing the gene in the backwards direction results in a lower proportion of cells being successfully edited, lowering treatment efficacy.

The new viral vector enables the β-globin gene to be read forward, without disrupting intron-2. It displayed four-to-ten times higher transduction efficiency, although more vectors were required to infect each cell. The edited stem cells successfully produced β -globin. The new vectors displayed long term efficacy, remaining in cells four years after transplantation. They can also be produced more rapidly and at larger scales than conventional vectors, which is ideal for mass manufacture.

Sickle cell affects 100,000 people in the US alone and an effective gene therapy treatment could permanent relief to this disease.