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Gene Therapy and Cystic Fibrosis.

Gene Therapy = helping people with mutated or faulty genes to alleviate the symptoms of their disease.

People who have cystic fibrosis (CF) have a faulty gene in their cells. This gene codes for a carrier protein in the cell membrane called CFTR.

This protein helps Chlorine ions (Cl-) leave the cell taking water with them by osmosis.

In CF patients not enough water leaves the cell and the mucus made by the cells becomes very thick. This thick mucus has a particular effect in the cells of the lung. It stops gas exchange in the alveoli and blocks all bronchi and bronchioles. This makes the sufferer cough, liable to chest infections and reduces their breathing rate.

The mucus may also block sperm tubes in male patients and fallopian tubes in females. It can also upset digestion of food in the stomach.

Most sufferers of CF die before reaching 30 years of age.

Scientists looked to treat CF patients by cloning normal CFTR genes and inserting them into the sufferer. To work the CFTR gene would need to be inserted into the chromosomes of the sufferers cells via a vector.

 

The vectors used so far are either viruses or liposomes in sprays inhaled into the nose or lungs.

 

1. Viruses

These are attenuated (killed/made harmless) viruses that do not cause disease but carry the CFTR gene.

The viruses are capable of inserting the recombinant DNA into the hosts DNA so that the vital CFTR protein can be produced in the cells.

However, the donor DNA has not proved able to insert itself and remain stable in the hosts DNA. Regular treatments are needed.

Some patients have also had severe side affects to the viruses used and the treatment.

2. Liposomes

These are microscopic fluid filled droplets made of oil and water. They contain the recombinant CFTR plasmids in the centre of the droplet. These liposomes can be coated in sugars as receptor molecules to allow them to be taken up by the lung cells. However, although many of the liposomes are taken up and some CFTR protein is found to be translated, very few of the CFTR genes seem capable of recombining with the DNA in the nucleus of the cells.

So treatment needs to be repeated regularly to ensure the CFTR protein is produced in the sufferers cells.

So in summary :-

A. The treatment needs to be repeated regularly. The patient is not cured for life.

B. Treatment is expensive and not widely available.

C. There has been little real success in trials so far.

D. There is much controversy over whether it is right to try to insert normal/correct genes into humans. Many are worried we will not just stop at diseases and move onto other characters we may want to improve!