A DNA spray has shown significant success in tackling the symptoms of cystic fibrosis.

The research brings an easy-to-administer treatment for the disease one step closer.

The gene responsible for cystic fibrosis was discovered in 1989.

Since then scientists have tried to find a successful way of replacing the defective gene with a healthy one - gene therapy.

This research is proof that gene therapy can work.

Widespread condition

The Cystic Fibrosis Trust says the disease is the UK's most common life-threatening inherited disorder.

It affects approximately one child in every 2,500 born, or one a day, the trust says.

The disease is inherited and affects the lungs and digestion.

It is caused by a genetic abnormality that affects the way chloride ions are transported across cell membranes.

This combines with an increase in sodium absorption to cause excessive mucus secretion in the lungs and digestive tract, increasing the risk of infections.

Aerosol delivery

Researchers at the National Heart and Lung Institute and Royal Brompton Hospital, London, found the spray restored some of the ability to transport the chloride ions correctly.

Professor Eric Alton led the team, which published its results in The Lancet on Friday.

The researchers administered the healthy gene - cystic fibrosis transmembrane conductance regulator - to patients via an aerosol.

CFTR was combined with a lipid oil, which allowed it to be absorbed by cells.

Eight patients with cystic fibrosis were given the gene-lipid complex via a nasal spray.

Restored ability

Following the treatment, those patients had a 25% restoration of normal chloride transport.

A comparison group of eight patients did not receive the gene spray. They showed no such improvement.

However, no such improvement was seen in reversing the over-absorption of sodium among those who received the gene spray.

The researchers recorded some temporary side effects - flu-like symptoms and breathing problems - in those who received the gene therapy.

"We have shown a significant correction of the basic electrophysiological defect in cystic fibrosis," the researchers wrote.

"Gene therapy for cystic fibrosis continues to make steady progress towards becoming a realistic therapeutic option for the disease."