Gene therapy seeks to mend cystic fibrosis.

British molecular biologists have boosted the promise of gene therapy as a treatment for cystic fibrosis by correcting a similar genetic defect in specially bred mice. But they and other experts caution that these results do not prove the approach will work in humans, and a few scientists express doubts about the data.

Cystic fibrosis (CF), an inherited disease, affects one in 20,000 babies born in the United States, few of whom live past age 30. They suffer from mutations in a gene that normally directs the production of a tunnel-shaped protein. That protein helps channel chloride ions out of the cells that line the lungs and other organs. If the protein doesn't work right, thick mucus builds up in the lungs, and the pancreas releases excess enzymes.

Last year, several research groups created genetically engineered strains of mice that contain this defective gene (SN: 9/5/92, p.154).

In their report in the March 18 NATURE, Stephen C. Hyde of the University of Oxford in England and his colleagues describe how they squirted the correct gene - encased in a lipid envelope called a liposome - into the airways of six of these mice. They then measured electrical currents caused by the movement of ions across cell membranes. Defective mice typically lack such currents, but in four of the six treated mice, "they were completely back to normal" says Oxford collaborator Deborah R. Gill.

"This is the first time there is a purported correction, but the numbers [of mice treated] are very small," comments Robert J. Beall at the Cystic Fibrosis Foundation.

Richard C. Boucher, who works with CF mice at the University of North Carolina at Chapel Hill, worries that because of underappreciated complexities in ion transport in these mice, we don't know if it's corrected or not," he told Science News.

Other researchers, including those in the United States planning to try gene therapy next month on CF patients, use altered adenoviruses, which cause cold symptoms. They transfer genes much more efficiently than liposomes. Boucher says he has been unable to show conclusively that gene transfer via virus corrects the defect in the engineered mice.

But Bob Williamson, a molecular geneticist at the University of London, hopes to try liposomes in gene therapy for CF patients sometime next year and finds the Oxford results very encouraging. "It must raise hopes that gene therapy will work," he says.