Question

Explain gene therapy, with reference to the treatment of SCID.

Answer 1

Gene therapy with respect to SCID: Gene therapy is the insertion of desired genes into an individuals cells and tissue to treat genetic diseases.

SCID is severe combined immunodeficiency due to the deficiency of the enzyme adenosine deaminase (ADA). This disorder is caused by the deletion of the gene for adenosine deaminase.

The enzyme is crucial for the immune system to work properly. The deficiency leads the individual
susceptible to many infections due to impairing the immune system.

The first clinical gene therapy was given in 1990 to a 4-year-old girl with ADA deficiency.
During this procedure, the lymphocytes from the blood of the patient are grown in a culture outside the body.

• A functional ADA, cDNA (using a retroviral vector) is then introduced into these lymphocytes, which are subsequently returned to the patient.
• However, as these cells are not immortal, the patient requires the periodic infusion of such genetically engineered lymphocytes.
• However, if the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.