Gene therapy used in cystic fibrosis treatment

Adelaide researchers have made progress on the development of a new gene therapy technique for cystic fibrosis, utilising a naturally occurring detergent in combination with a retroviral delivery vector.

The researchers, at the Women's and Children's Hospital, used the technique to deliver the correcting gene for cystic fibrosis to cells in the nose of mice with cystic fibrosis. The cells in the nasal airways were 'conditioned' with a natural detergent, lysophosphatidylcholine (LPC), prior to using the human immunodeficiency virus-1 based vector containing the corrective gene.

The inserted gene, CFTR, was found to substantially correct the cystic fibrosis defect in the mouse model, and more significantly, the effect was found to last for at least 110 days.

"Airway cells are replaced every three months so our findings are particularly exciting because they imply we are in fact targeting airway stem cells through this approach -- some of the therapeutic gene must have been passed on from these parent stem cells to their daughter cells for the effect to persist beyond three months," said project leader Dr David Parsons from the Pulmonary Medicine department at the Women's and Children's Hospital in Adelaide.

Nasal airway cells were used as they behave similarly to human lung cells, he explained. "This enables us to use the nose airways in mice to easily develop and test out gene therapy treatments," he explained.

According to Parsons, the use of the detergent came from earlier work by the researchers, which used a synthetic detergent and adenovirus vectors. But adenovirus gene therapy vectors do not give persistent expression, so the researchers switched to retroviral vectors.

Dr Don Anson, the molecular biologist responsible for engineering the HIV-1 based vector, said there was a long history of using retroviral vectors for gene therapy. In general, he noted, vectors containing only the necessary gene functions are designed.

Parsons said that the use of the detergent was an important step in the technique, as it made the surface of the airways more permeable to the vector. LPC normally occurs in the lung at very low levels.

"The detergent temporarily opens the junctions between the cells which probably allows the virus to get down to layers which are likely to contain stem cells," he explained. "The potential is that we are affecting adult stem cells in situ."

Parsons noted that very little was known about adult stem cells in the lung. Part of the next phase of research will attempt to identify the cells that the vector infects.

The researchers also plan to further investigate dose optimisation parameters in their mouse model, including the dose of detergent, timing of application, possibility of simultaneous delivery, and vector titres. Parsons said that it would be at least five to 10 years before the approach was suitable for clinical trials in human patients.