New gene therapy treatment for cystic fibrosis?

The inherited lung disorder cystic fibrosis (CF) could be treated using parts of two viruses to deliver a therapeutic gene, US researchers say. A team based at the University of Pennsylvania says that it has successfully used a 'hybrid' of the viruses that cause HIV (human immunodeficiency virus) and Ebola to deliver test genes to the lungs of monkeys. Now, according to a report in New Scientist magazine, the scientists are planning a more extensive monkey trial to convince the Food and Drug Administration (FDA) that the technique would be safe to use in people.

CF is a progressive, life-threatening condition that mainly affects the lungs and digestive system. It is caused by a mutation in the cystic fibrosis transmembrane conductor (CFTR) gene. Researchers have been trying to develop gene therapy treatments for CF for several years, but their efforts have been plagued by difficulties in delivering enough copies of the working CFTR gene to the affected tissues. The Pennsylvania team have tried to overcome this problem by combining elements of two different viruses to create a more efficient 'gene delivery system', or vector. Since the Ebola virus is very effective at targeting lung surface cells, the researchers took a surface protein from Ebola and added it to HIV - one of several viruses that reproduces by copying its own genetic information into that of the host cell. They then used the new hybrid virus to deliver a test gene to the lungs of monkeys, and found that after two months the gene was active in around 20 per cent of the lung cells.

The results, which are currently being prepared for publication, suggest that the hybrid virus is more efficient at delivering the CFTR gene than vectors used previously. Although it uses parts of two potentially deadly viruses, the researchers are confident the hybrid virus would be safe to use in humans.

However, US gene therapy researcher Ray Pickles, who was not involved in the study, told New Scientist that he has abandoned similar research because he thinks that opposition from a fearful public will prevent the method being used. In addition, because the approach targets lung surface cells, which die off after a few months, patients would require repeated treatments. UK expert Steve Hyde, of Oxford University, also expressed reservations about using the virus. 'The body generates antibodies to it', he told BBC News Online, adding 'the therapy works the first time but it's not guaranteed to work the second time, or subsequent times'.