The uses
Gene therapy research and trials are being conducted to treat a number of conditions:
- inherited disorders such as severe combined immunodeficiency syndrome (SCID), diabetes, thalassaemia, haemophilia and cystic fibrosis,
- cancers of different types,
- heart disease, and
- age-related diseases, including arthritis and dementia.
Mending a broken heart
Heart attacks cause damage to the muscle cells of the heart. Scar tissue forms which disrupts the heart's electrical system and weakens the heart.
Recently, researchers have been able to reprogram the scar tissue to behave like heart muscle cells.
The researchers at the Children's Medical Research Institute in Sydney, in collaboration with Children's Hospital Westmead, added two extra genes to the cells.
The first gene programs the cell to be excitable like a muscle cell, the second gene allows the cells to communicate with each other, passing on the electrical pulse of the heart.
Trials
In 1990, a four-year-old American girl Ashanthi DeSilva, became the first person to be treated with gene therapy for severe combined immunodeficiency (SCID) syndrome. This is a disease which affects the immune system so that children born with it are very susceptible to any infectious diseases. Because they are kept in germ-free environments such as a plastic enclosure, SCID is sometimes referred to as 'Bubble Boy disease'.
This girl's cells were provided with genes to produce an infection-fighting enzyme that she lacked. Doctors removed white blood cells from her body, let the cells grow in the lab, inserted the missing gene into the cells using a viral vector, and then infused the genetically modified blood cells back into her bloodstream.
This procedure is not a cure; the genetically treated white blood cells only work for a few months, and the process must be repeated every few months. Since that trial, more than 3,000 people have received this treatment in human clinical trials
Gene therapy is still an experimental procedure and has suffered a number of major setbacks since this first trial.
In 1999, 18-year-old Jesse Gelsinger died from multiple organ failure only four days after beginning gene therapy to help cure him of an inherited disorder. It is believed that his death was the result of a severe immune response to the viral vector and since then other problems with the trial have been identified.
In early 2003, a temporary halt was placed on all United States-based gene therapy trials using viral vectors in blood cells. This occurred after two children developed leukaemia-like conditions after being treated by gene therapy for SCID.
Future techniques may be better able to guarantee the safety of the techniques and deliver the correct gene to the correct cells in the correct tissues.
There are currently about 3,000 trials being carried out worldwide.
A list of Australian gene therapy trials is on the National Health Medical Research Council's web site: http://www.nhmrc.gov.au/about/committees/expert/gtrap/documents.htm#2
There is also a list of reports of serious adverse events resulting from gene therapy trials: http://www.nhmrc.gov.au/about/committees/expert/gtrap/sae.htm