A second patient in a gene therapy trial taking place at Great Ormond Street Hospital in London has been successfully treated, his parents and doctors announced last week. Christopher Reid, now two years old, received gene therapy for the immune system disorder X-linked severe combined immune deficiency (X-SCID) in December 2001. His treatment followed that of toddler Rhys Evans, whose recovery from the life-threatening illness was announced in April 2002.
Children affected by X-SCID have a faulty gene that means they have no working immune system, so their bodies cannot fight infections. Unless they can be given a matched bone marrow transplant, children with X-SCID face a lifetime living in a sterile bubble. 'Without gene therapy Christopher would not have lived to see his first birthday' said Rachel Reid, Christopher's mother. 'Even if we had decided to opt for a bone marrow transplant he could have become a casualty'. To treat Rhys and Christopher, the gene therapy researchers, lead by consultant paediatric immunologist Adrian Thrasher, first harvested bone marrow from the boys. They then isolated white blood stem cells from the bone marrow, which they infected with a virus carrying a working gene, before returning the cells to the boys' bodies.
Blood samples taken from Christopher last week revealed that his immune system is now working perfectly. 'The gene therapy has now restored most of his immune system, he takes protective drugs but can visit soft play areas and mother and toddler groups' said a hospital spokesperson. Rachel said her son has gone from being 'an unsettled, miserable baby into a happy confident toddler with a wonderful sense of humour'.
Christopher's parents decided to go public because of their concern about the 'negative coverage' of gene therapy over recent months. Concerns over the safety of the technique were raised earlier this year, when a second child in an X-SCID gene therapy trial at the Necker Hospital in Paris developed leukaemia. Investigations revealed that the virus used to deliver the therapeutic gene had inserted itself into or close to another gene called LMO2, previously linked to leukaemia. Similar trials in several countries were temporarily suspended, but restarted recently in both the UK and US. After weighing up the benefits and risks of the treatment, the UK's Gene Therapy Advisory Committee (GTAC) decided that 'it would be unethical to withdraw its approval of the UK X-SCID study'. The Great Ormond Street Hospital trial is funded by the charity 'Jeans for Genes', which runs an annual appeal to raise money for children affected by genetic disorders. The next 'Jeans for Genes' day will be held on 3 October 2003.