Lesson 8 of 12 · 6 min
Gene therapy
NCERT §10.2.2
In the paediatric ward, a doctor tells Kavya about a child whose immune system had never worked properly. 'She was missing one gene,' he says.
The lesson in notes
In short
Gene therapy is a set of methods for correcting a gene defect diagnosed in a child or an embryo. It treats disease by putting genes into the person's cells and tissues.
A normal gene is delivered into the person or embryo to take over the function of the non-functional gene and compensate for it.
The first clinical gene therapy was in 1990: the patient, a girl aged 4, had adenosine deaminase (ADA) deficiency.
ADA is an enzyme crucial for the immune system to work. The disorder arises from deletion of the gene for ADA.
Some children with ADA deficiency can be cured by bone marrow transplantation; others receive enzyme replacement therapy, injections of working ADA. Neither approach is completely curative.
In gene therapy, lymphocytes from the patient's blood are grown in culture outside the body, a functional ADA cDNA is introduced into them using a retroviral vector, and the cells are returned to the patient.
These lymphocytes are not immortal, so the patient needs periodic infusions of the engineered cells.
Putting the ADA gene, isolated from marrow cells, into cells of an early embryo could cure the disorder permanently.