Gene therapy uses viruses that have been genetically engineered to carry a "normal" human gene to replace the missing function of an "abnormal", disease-causing gene in a patient's cells. A paper that will appear in the July issue of Nature Genetics highlights one of the possible dangers of this therapy: the viruses carrying the therapeutic gene can become inserted into other genes and damage them.
Adeno-associated virus (AAV) is one of viruses commonly used to carry therapeutic genes. Typically when this virus is injected into a cell it produces the therapeutic product without affecting the genetic material of the cell, but in a few cases copies of the virus genome become integrated into the cell's chromosomes. Hiroyuki Nakai and Mark Kay injected AAV in the livers of mice and showed that when the virus integrates it prefers to do so inside functioning genes, rather than in DNA that does not code for genes. This means that the virus has the potential to damage normal genes.
The Food and Drug Administration (FDA) has yet to approve any human gene therapy product. A major blow to gene therapy came in January of this year, when two children being treated for "bubble boy" disease in a French gene therapy trial developed leukemia from the treatment.
Mark Kay (Stanford University, CA, USA)
Tel: +1 650 498 6531
Also available online.
(C) Nature Genetics press release.
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