Gene therapy is a form of genetic treatment where a functional version of a gene is introduced into a person’s cells to replace or supplement a faulty gene. It aims to correct the underlying genetic cause of a disease rather than just treating the symptoms.

There are two main types:

• Somatic therapy: Targets body cells (not inherited by offspring)
• Germline therapy: Targets gametes or early embryos (inheritable - currently illegal in humans)

The Problem:

• CF is caused by a mutated CFTR allele, resulting in a faulty chloride ion channel. (As this allele is recessive, 2 copies have to be inherited for the individual to have CF).
• Chloride ions can't leave the cell → water doesn’t follow by osmosis → thick, sticky mucus builds up in lungs and digestive system.

The Solution: Gene Therapy

Goal: Deliver a healthy copy of the dominant CFTR allele to epithelial cells lining the airways. This is an example of somatic gene therapy.

Delivery Methods:

Method	How It Works
Adenovirus vector	Engineered virus carries the healthy CFTR allele into respiratory epithelial cells.
Liposomes (lipid vesicles)	CFTR gene is packaged into a liposome spray, inhaled into the lungs, and moves into epithelial cells across the phospholipid bilayer.

In both methods, the new gene is inserted into the target cells, enabling production of the correct CFTR protein, which restores chloride ion transport and reduces mucus thickness.

Challenges and Limitations

• Effects are longer lasting than other treatments but still temporary - airway cells are constantly replaced by new cells, so repeated treatments are needed.
• Immune response to viral vectors can limit effectiveness.
• It's difficult to get the gene into enough cells to produce a strong therapeutic effect.
• The individual would still pass on the faulty, recessive allele to offspring as their gametes will be unchanged by the treatment.