According to the scientific journal, Science, published on 11 July 2013, three children suffering from late infantile metachromatic leukodystrophy and three other children with Wiskott-Aldrich’s syndrome improved following novel gene therapy. The first group developed speaking and walking problems between the ages of 1 and 2 years and were expected to die soon, between 3 and 10 years of age. The second group developed "a combined immune deficiency, eczema and thrombopenia". In order to carry out their studies, scientists collected samples of haematopoietic stem cells (HSCs) from patients suffering with the afore-mentioned conditions and then "used a partly inactivated, lentiviral [HIV-derived] carrier to introduce the therapeutic gene into the cells". Finally, “genetically modified HSCs […] were reinjected into the patients".
As for patients suffering from Wiskott-Aldrich syndrome, they were given their own cells carrying the WAS functional gene. "Their condition improved or symptoms of the disease such as recurrent eczema infections disappeared" 20 to 32 months after gene therapy. Following both these studies, no lentiviral gene therapy triggered "carrier integration profiles which could increase the risk of leukaemia, […] a major concern with gene therapy using retroviral carriers".