Scientists have worked for 20 years to perfect gene therapy for the treatment of cystic fibrosis, which causes the body to produce dehydrated, thicker-than-normal mucus that clogs the lungs and leads to life threatening infections.
Now University of North Carolina at Chapel Hill School of Medicine scientists have found what may be the most efficient way to deliver a corrected gene to lung cells collected from cystic fibrosis patients. They also showed that it may take this high level of efficiency for cystic fibrosis (CF) patients to see any benefit from gene therapy.
Using parainfluenza virus, one of the viruses that causes common colds, the UNC scientists found that delivery of a corrected version of the CFTR gene to 25 percent of cells grown in a tissue culture model that resembles the lining of the human airways was sufficient to restore normal function back to the tissue.
"This is the first demonstration in which we've been able to execute delivery in an efficient manner," said Ray Pickles, Ph.D., associate professor of microbiology and immunology at the UNC Cystic Fibrosis Research and Treatment Center. "When you consider that in past gene therapy studies, the targeting efficiency has been somewhere around 0.1 percent of cells, you can see this is a giant leap forward."
"We discovered that if you take a virus that has evolved to infect the human airways, and you engineer a normal CFTR gene into it, you can use this virus to correct all of the hallmark CF features in the model system that we used," Pickles said. For instance, the experiment improved the cells' ability to hydrate and transport mucus secretions.
Now the researchers must work to ensure the safety of the delivery system. In a pleasant surprise, simply adding the CFTR gene to the virus significantly attenuated it, potentially reducing its ability to cause inflammation. But the scientists may need to alter the virus further.
"We haven't generated a vector that we can go out and give to patients now," Pickles said, "but these studies continue to convince us that a gene replacement therapy for CF patients will some day be available in the future."
In addition to Pickles, UNC co-authors are Liqun Zhang Ph.D, research associate, CF Center; Brian Button Ph.D., assistant professor, CF Center; Sherif E. Gabriel Ph.D., associate professor, pediatrics); Susan Burkett, research analyst, CF Center; Yu Yan, research specialist, CF Center; Yan Li Dang, research specialist, CF Center; Tristan McKay Ph.D., postdoctoral fellow, CF Center; and Richard C. Boucher M.D., Kenan Professor of Medicine, director, CF Center.
Other co-authors are April Mengos of the Mayo Clinic College of Medicine, as well as Mario H. Skiadopoulos, Ph.D., Leatrice N. Vogel and Peter L. Collins Ph.D., all of the National Institute of Allergy and Infectious Diseases, National Institutes of Health.
The research was funded by the National Institutes of Health and the Cystic Fibrosis Foundation.
- Zhang L, Button B, Gabriel SE, Burkett S, Yan Y, et al. CFTR Delivery to 25% of Surface Epithelial Cells Restores Normal Rates of Mucus Transport to Human Cystic Fibrosis Airway Epithelium. PLoS Biology, July 21, 2009; 7(7): e1000155 DOI: 10.1371/journal.pbio.1000155
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