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Friday, 13 September, 2002, 23:33 GMT 00:33 UK
Gene therapy treats 'whole body' disease
The treatment managed to prevent the onset of disease
For the first time, gene-manipulating therapy has been used to successfully treat a disease which affects organs and tissues throughout the body.

The breakthrough, in dogs, affected by a rare disease, provides the strongest evidence yet that gene therapy could work against many different diseases.

However, there are still many hurdles to be overcome before scientists can be convinced that such treatments could be safe and effective in humans.

The treatment involved dogs with a rare disorder called mucopolysaccharidosis VII, which involves a lack of a body enzyme.

This leads to clouding of the corneas of the eye, heart problems and bone abnormalities.

If the disease were allowed to progress naturally, the dogs would generally become immobile by the age of six months.

The disease does happen in humans, affecting one in every 27,000 babies born, and leading to similar problems.

It is normally treated by regular and expensive enzyme replacement injections.

Single gene

The source of the problem is a single defective gene in the liver.

Doctors at the University of Pennsylvania School of Veterinary Medicine, and the Washington University School of Medicine in the US attempted to prevent the development of symptoms by altering this gene early in life.

They treated newborn dogs with the gene defect with therapy designed to insert a new, correct gene into liver cells.

They did this by using a modified virus designed to infect the liver cells - then insert the new gene into the right point in the cell's DNA.

Chemical produced

At this point in the dog's life, liver cell growth is incredibly rapid, so the change should be picked up, passed on, and the liver cells start secreting the vital enzyme.

This seemed to be the case - the newborn dogs maintained near-normal mobility throughout the 17-month study and showed little evidence of any other signs of the disease.

They were not cured, however - and the defect was not eradicated from their genetic "germ-line" - meaning they could still in theory pass it on to their offspring.

Dr Mark Haskins, who led the study, said: "While gene therapy has been used previously in dogs, this the first use to treat a disorder affecting multiple organ systems throughout the body.

"Like many diseases that we might eventually like to treat with gene therapy, this one has complex, multisystemic effects."

He said that in theory, the principle might be applied to other systemic diseases such as haemophilia.

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