Human Health - Gene Therapy

The technique of treating genetic disorders by correcting defective genes in somatic cells is called gene therapy.

Gene therapy is a biotechnological technique used to treat genetic disorders by inserting a normal, functional gene into an individual's cells to compensate for a defective or absent gene, thereby correcting the disorder at the molecular level. It may be applied to somatic cells (non-heritable correction) or, in principle, germ-line cells (heritable correction).

Based on Target Cell

Based on Therapeutic Strategy

Defective gene identified

↓

Healthy gene isolated & inserted into vector (usually retrovirus)

↓ 

Patient's target cells (e.g., lymphocytes) extracted 

↓ 

Vector introduces healthy gene into extracted cells (ex vivo) 

↓

Modified cells cultured and multiplied

↓

Cells reinfused into patient's bloodstream

↓

Functional gene expressed → therapeutic protein produced

Ex vivo delivery: Cells are removed from body, modified, then reintroduced (used in ADA-SCID treatment).

In vivo delivery: Vector carrying the gene is directly introduced into the patient's body/tissue.

Condition: Adenosine deaminase (ADA) deficiency causes severe combined immunodeficiency (SCID), where the immune system fails to function.

Procedure:

1. Lymphocytes extracted from patient's bone marrow
2. Functional ADA gene inserted using a retroviral vector
3. Genetically corrected lymphocytes cultured and reintroduced into the patient

Limitation: Lymphocytes are not permanent cells, so the procedure needs periodic repetition. A permanent cure may be possible only if gene correction is performed in early embryonic stages (germline) – raising ethical concerns.

Alternative treatments: Bone marrow transplantation and enzyme replacement therapy.

• Severe Combined Immunodeficiency (SCID) – ADA deficiency
• Haemophilia
• Cystic Fibrosis
• Certain cancers
• Select cardiovascular and neurological disorders (emerging research)

Technical Challenges

• Low efficiency of gene delivery vectors
• Risk of immune reaction against viral vectors
• Non-permanent correction (cells with limited lifespan need repeated therapy)
• Difficulty targeting only the intended cells

Ethical Challenges

• Germ-line therapy raises concerns about altering heritable traits
• Potential misuse for non-therapeutic genetic enhancement
• Accessibility and cost barriers for patients

• Gene therapy is the treatment of diseases by replacing, altering, or adding genes to correct genetic defects.
• It is used to treat genetic disorders such as haemophilia, cystic fibrosis, sickle cell anaemia, and thalassaemia.
• Genes can be delivered into cells by ex vivo (outside the body), in vivo (inside the body), or using vectors like viruses and liposomes.
• There are two types: germ-line therapy (affects future generations, not used in humans) and somatic cell therapy (affects only the patient and is commonly used).
• Gene therapy has applications in treating genetic diseases, cancer, and improving immune response, but it involves technical and ethical challenges.