Cystic Fibrosis

Inheritance	Autosomal recessive
Occurrence	1 in 3,300 Caucasians; 1 in 9,500 in Hispanics; frequency varies with ethnic group
Description	A disease caused by defective chloride transport that leads to high levels of mucus in the lungs and pancreas, high sweat chloride levels, and other digestive and respiratory problems.
Gene and Location	The gene is known as CFTR and is found on chromosome 7. Carrier testing is available.
Treatment	Many treatments are available that treat the symptoms of the disease. These treatments, although improving the quality of life, are not a cure and have only served to extend the life span of an individual with CF. In 1993 the first trials of gene therapy were begun. It is hoped that gene therapy may provide not only effective treatment but also a cure.

Gene Therapy

Cystic Fibrosis is one of the most common genetic diseases. Among Caucasians the chance of being a carrier is 1 in 23. This activity is to introduce students to recombinant DNA technology and gene therapy.

Cystic Fibrosis (CF) is caused by a dysfunctional CFTR gene. There are many treatments to help the symptoms, but there is not a cure. Gene therapy holds the promise of someday providing a cure to CF. Gene therapy is based on the premise that the only way to cure CF is to give affected individual new copies of the CFTR gene. How do they do that? Adapt this to teach your class how to genetically engineer a vector (in this case a modified adenovirus or common cold virus) and treat a disease like CF. The following discussion is a very simple overview of how one would go about gene therapy. This is oversimplified for the express purpose of introducing the big picture concept to your class.

(2) Choose an appropriate vector that will work to infect the appropriate cells in the body. With CF the adenovirus has been chosen for the first few clinical trials.

(3) Using restriction enzymes, insert the CFTR gene into the adenovirus. Now the common cold virus is set to infect individuals with the new CFTR gene.

(4) Give a CF patient this cold virus. This is usually done through an inhaler (like for asthma) filled with the adenovirus.

(5) Once in the body the adenovirus inserts itself into the cells and gives those cells a new copy of the CFTR gene.

In most clinical trials patients have shown dramatic improvement as the new CFTR gene begins working. Unfortunately, these improvements last for only a few weeks. Eventually the body attacks and destroys these infected cells (just as it would attack a real cold) and these patients are left once again with cells having the old defective CFTR gene.