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Sunday, 13 October, 2002, 23:05 GMT 00:05 UK
Safer gene therapy developed
Lab
Gene therapy has great potential
Scientists have developed a new form of gene therapy that appears to be less risky than current techniques.

It is hoped the technique will lead to new ways to treat diseases in several different human organs including skin, retina, blood, muscle and lung.

The breakthrough follows news that a gene therapy trial in France was stopped after a child developed a leukaemia-type illness.


This work is extremely interesting, and I hope that the lab findings are rapidly translated into new treatment

Professor Norman Nevin
The new technique is able to introduce genetic material into a host in a more precise way. It also does away with the need to use a virus to transport genetic material into the body.

Researcher Dr Michele Calos, of the University of Stanford, said: "Our approach provides an alternative that didn't exist before."

The goal of gene therapy is to insert a healthy copy of a gene into a cell where it can take over for a faulty version.

If the therapeutic DNA does not integrate into the human chromosome, it produces its protein for a short time before being turned off or broken down within the cell.

For a long-term cure, the gene has to wedge itself into a chromosome where it remains indefinitely integrated, getting passed on when the cell divides.

Random positions

Current gene therapy approaches use a virus to carry the therapeutic DNA into the host cell.

However, the DNA inserts itself into the chromosome at random positions.

This means there is a chance that if the DNA lodges in the wrong position it may trigger changes in the body that can lead to disease.

This is what is thought to have happened in the French leukaemia case.

The new technique avoids this potential pitfall by inserting the DNA at known locations.

It can also handle genes - such as that for Duchenne's muscular dystrophy - that are too large to fit into a viral package.

The technique is based on mechanism used by a virus called a bacteriophage that infects bacteria.

It does this by producing a protein that guides its DNA to a specific site on the bacteria chromosome.

Natural process

The researchers have mimicked the process by inserting a gene that stimulates production of the same protein alongside the therapeutic gene.

This means the protein is on hand to guide the therapeutic gene to the right position on the host's chromosome.

The researchers tested the technique using a gene that makes Factor IX - a protein missing in the blood of people with a form of haemophilia.

Within a week mice that received the Factor IX gene and the gene for the guide protein made 12 times more Factor IX than mice given the similar gene therapy, but without the guide protein gene.

Dr Calos's group are now testing the technique on different tissue types to ensure that using the guide protein will not trigger off the formation of cancer.

Translate

She hopes to start human trials for the technique in a fatal childhood skin disease called recessive dystrophic epidermolysis bullosa, which she has already treated in mice.

Professor Norman Nevin, chairman of the government's Advisory Committee on Gene Therapy, told BBC News Online that although the research was still at an early stage, it was potentially a "very exciting development".

He said: "One of the big problems in gene therapy at present is the targeting of therapeutic genes to the right region of the genome.

"This work is extremely interesting, and I hope that the lab findings are rapidly translated into new treatments. It certainly augers well."

The research is published in the journal Nature Biotechnology.

See also:

03 Oct 02 | Health
03 Oct 02 | Health
10 Oct 02 | Health
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