A modified version of the virus that causes Aids could become the basis of a prenatal gene therapy for cystic fibrosis, new research has suggested.

British scientists have discovered that a form of HIV, adapted to be harmless, is a promising vector for ferrying replacement genes into the lungs of affected foetuses. Experiments at University College London have already shown that the modified virus can infect the lung tissue of unborn mouse pups, suggesting it could be used to correct the genetic defects that cause cystic fibrosis.

The virus could potentially be engineered to carry working copies of the gene which, when it goes wrong, causes the devastating lung condition. It would then be used to infect foetuses known to be affected by the disease before they were born.

The UCL team, led by Suzy Buckley, has won a prize from the British Society for Gene Therapy, which will fund them to collaborate with a group in Australia that has developed a mouse model of cystic fibrosis.

They are now working on modifying HIV further so it can carry the genetic material needed to treat the disease.

Simon Waddington, a colleague of Dr Buckley’s at UCL, said it would be at least five years before the gene therapy could begin clinical trials. If it is shown to work, such foetal gene therapy could have significant advantages over similar treatments.

“Some genetic diseases kick in before birth, and if you’re going to try to address these by gene therapy, it may already be too late to reverse some of the damage if you wait until a baby has been born,” Dr Waddington said.

Foetal gene therapy also has other advantages. Foetuses’ immune systems are less likely than those of children and adults to reject the modified virus, and the virus is also likely to reach stem cells from which other tissues are grown.

The HIV vector is a profoundly disabled version of the virus, and its surface proteins have also been modified so that it primarily infects lung cells rather than the immune system cells that it usually targets.

Its surface proteins now resembled those of the flu virus, Dr Waddington said.

Previous research has also shown that a different type of foetal gene therapy has promise for curing a form of haemophilia, and experiments using macaque monkeys are soon to begin in Singapore.

Gene therapy involves attempting to treat diseases caused by genetic errors by introducing working copies of the DNA that has gone wrong. It is usually done using genetically modified viruses, which effectively write both their own DNA and the added therapeutic package into the genomes of the cells they infect.

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