The patched code
Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.
More posts by Christiane Fux All content is checked by medical journalists.A tiny twist in the genetic code can trigger fatal hereditary diseases. Researchers all over the world are trying to replace the diseased genes with healthy ones. But the method still carries great risks
Felix Ott is five years old. A perfectly normal little boy with dark blond hair and long eyelashes. A child who enjoys going to kindergarten and romping around with friends. Two years ago his life was different. Back then, every shock, every fall could cause life-threatening bleeding. If a virus flew through the air, the boy was guaranteed to catch it, he was always sick. "To put him in bed in the evening and not know whether he would wake up again in the morning was sheer horror," remembers Felix mother. Her son suffered from the rare Wiskott-Aldrich syndrome (WAS), a blood disorder caused by a single altered gene on the X chromosome.
Rare and destructive
Orphanet Germany reports that the disease affects only 1 to 9 out of 1 million children. The syndrome is one of the "orphan diseases", the rare diseases. Characteristics are a lack of blood platelets, which are also too small, eczema and frequent infections. Wiskott-Aldrich syndrome weakens the immune system and disrupts blood clotting. So far, the disease could only be treated with a blood stem cell donation. "If left untreated, children usually die before the age of ten," explains Prof. Christoph Klein, Director of the Clinic for Pediatric Hematology and Oncology at the Hanover Medical School in an interview with .
Last hope gene therapy
Felix initially seemed to have had bad luck. There was no suitable donor for him, not in his family and not in the large, internationally networked donor database. But then the tide turned. Experts at the Medical University of Hanover were able to help him. With gene therapy.
Klein's team first took blood stem cells from the boy's bone marrow. All blood cells and all cells of the immune system arise from them. Then the researchers smuggled healthy genes into the stem cells. They use so-called retroviruses as transporters for the genetic component.
Viruses as gene taxis
Viruses are ideally suited as gene taxis. In the course of evolution, they have developed a way of introducing their own genetic material into host cells. Then they use their reproduction program for their own reproduction. Gene therapy makes use of precisely these abilities. To do this, the scientists clean the viruses of all the genes that cause disease and then load them with healthy genetic components. The virus does the rest of the work: it "infects" the cells with the healthy gene.
The virus transfer was successful at Felix. Today the genetically modified blood stem cells work perfectly in his body: They produce healthy blood and immune cells. "We no longer have to treat him like a raw egg," says the father, relieved.
Progress in triple steps
In monogenic diseases such as Wiskott-Aldrich syndrome, a single change in a genome is responsible for the development of a disease. Such diseases are suitable candidates for gene therapy because only a single gene has to be exchanged - namely the "broken" one.
In the case of more complex diseases, the situation is much more difficult. For example with cancer or the major common ailments such as diabetes, cardiovascular diseases, Alzheimer's and depression. Too many genes are involved in the disease process, and we do not know all of them. There are also external factors, for example lifestyle, which are also important. "Even with the help of gene therapy, we will not get rid of the suffering," says Klein. However, one day it may be possible to help many people. "We still have a long way to go," says the scientist.
Bright spots and setbacks
In addition to the bright spots, such as Felix's successful therapy, there are always bitter setbacks. Gene therapy has its pitfalls. "On the one hand, we do not know whether the success of the treatment is permanent," explains Klein. If you are unlucky, the introduced genes stop working after a while.
Even more threatening, however, is the possibility that gene therapy could spark cancer. "The genes jump into the chromosome. It can happen that they also activate neighboring genes," explains Klein. If further mutations are added, the balance in the genetic material slips - leukemia can develop. At the moment the devil is still being driven out with the Beelzebub.
This is shown by the example of Felix little fellow patient in Hanover. He is one of nine boys who treated Klein and his team. Worldwide only around 50 seriously ill people have received gene therapy because of various ailments. With him, too, the therapy had so far been uncomplicated. Three weeks earlier everything seemed to be in perfect order. "The leukemia must have broken out very quickly," reports Klein. Now the child has to undergo cancer therapy. "It's like a shadow over us all."
Risky rescue
As with any therapy, benefits and risks have to be weighed against each other with gene therapy - and these are currently still very high. "At the moment, such an intervention is only an option if there is no other way to control the disease." In the case of Felix and his fellow patients, the alternative would almost certainly have been death. In the future, researchers hope to be able to reduce the risk of leukemia with modified virus ferries. You learn from every setback. "We are only at the very beginning," says Klein.
Every three weeks, Felix and his fellow fates are examined very carefully - including for signs of leukemia. Everything is going well with Felix now. The parents are convinced that it will stay that way. It was not for nothing that they called their son "Felix". In German it means "the lucky one".
More info:
Orphanet Germany, Internet: www.orphanet.de (accessed: November 24, 2010);
German Society for Gene Therapy, Internet http://www.dg-gt.de/ (accessed: November 24, 2010);
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