Long-term success of gene therapy for X-linked severe combined immunodeficiency

12 May 2005

An international team of researchers has reported that four out of five baby boys treated by gene therapy for X-linked severe combined immunodeficiency (SCID) have remained healthy for two years after treatment [Hacein-Bey-Abina, S. et al (2002) N Engl J Med 346, 1195-1193]. X-linked SCID is caused by mutations in the gene encoding a common protein segment which forms part of five different cell-surface receptors that are essential for normal development of T cells and natural killer cells in the immune system. The boys were treated by removing their bone marrow cells and transducing them with a viral vector containing a normal copy of the defective gene. The cells were then infused back into the patients. In the four boys who responded to the treatment, T cells and natural killer cells containing the transduced normal gene were found in the blood within four months, and in higher numbers than are observed when affected babies are treated by bone marrow transplantation from tissue-matched donors. The boys also developed normal numbers of B cells, enabling them to mount near-normal antibody responses so that they could be successfully vaccinated against severe childhood diseases and did not need continuing immunoglobulin treatment.

Comment: This paper builds on the initial success in treating X-linked SCID that was reported by the same researchers in 2000 [Cavazzana-Calvo, M. et al (2000) Science 288, 669-672 (Abstract)]. Treatment by gene therapy appears to offer several advantages over treatment by bone marrow transplantation, and may become the treatment of choice for this disease. An accompanying editorial by Rosen gives useful background information about genetic immunodeficiency diseases and the history of attempts to treat them by bone marrow transplantation and gene therapy. (19/4/02)

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