Question

In gene therapy of Adenosine Deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes because:

• A. Retroviral vector is introduced into these lymphocytes
• B. Gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages
• C. Lymphocytes from patient’s blood are grown in culture, outside the body
• D. Genetically engineered lymphocytes are not immortal cells.

Answer 1

Answer: (D)

Genetically engineered lymphocytes are not immortal cells.

Answer 2

In some children ADA deficiency can be cured by bone marrow transplantation; in others it can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. But the problem with both of these approaches is that they are not completely curative. As a first step towards gene therapy, 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 periodic infusion of such genetically engineered lymphocytes.