Gene Therapy 1990 – A New Generation of Treatments for Genetic Diseases

Various characteristics, such as our eye colour and susceptibility to many diseases, cancer and asthma, result from defects in our genes. For example,  sickle cell anaemia, which produces abnormal red blood cells, results from a single faulty change in a gene's  DNA  sequence.

Gene therapy is a new discipline involving the insertion, replacement or removal of genes in human cells to treat diseases. 

One form of gene therapy involves using a virus engineered to contain a useful human gene. The virus inserts this gene into a defective human cell (usually at a random location in the host's DNA), and the new gene produces a properly functioning protein. If a sperm or egg is altered, the change will be passed to offspring. This would have profound ethical consequences for the human race. 

The first approved gene therapy procedure in the United States was performed in 1990 to treat a four-year-old girl with a rare immune disorder known as adenosine deaminase (ADA) deficiency, which left her vulnerable to infections. American researcher W. French Anderson and his team treated white blood cells taken from the girl's body with the gene she lacked. They then returned these cells to her body, hoping that they would produce the target enzyme. Unfortunately, although the target enzyme was produced, healthy cells could not be produced. 

Gene therapy was subsequently used successfully to treat ADA deficiency, other forms of severe immune deficiency (such as "bubble boy" disease), AIDS (by genetically altering T cells to resist HIV viruses) and Parkinson's disease (by reducing symptoms). 

However, in some cases gene therapy can carry risks. Many children in the immune deficiency study developed leukaemia, because viral insertion of genes into the host cell can sometimes disrupt normal gene function. In addition, viral gene carriers (or cells containing the newly implanted gene) can be attacked by the host's immune system, making treatment ineffective. At worst, a powerful immune attack can cause the patient's death.

Description of the article image: Haemophilia results from a mutation in a single gene on the X chromosome. People with haemophilia lose large amounts of blood when injured. The image shows Queen Victoria of the United Kingdom (1819–1901), who passed this mutation to many people of royal descent.

Historical figures mentioned in the article: William French Anderson (b. 1936)

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