Question

Explain any three different approaches used in the treatment of a person suffering from Adenosine Deaminase deficiency.

Hint:

Use bone marrow transplant, ADA injection (enzyme replacement) or gene therapy with a retroviral vector.

Answer 1

Step 1: What the disease is:
ADA deficiency is caused by deletion of the gene for the enzyme adenosine deaminase.
Without this enzyme the immune system of the child does not work properly.

Step 2: Approach 1: bone marrow transplantation:
Bone marrow from a matching donor gives the patient cells that carry a working ADA gene.
These cells make the enzyme, so the immune system can recover.

Step 3: Approach 2: enzyme replacement therapy:
Functional ADA enzyme is given to the patient by injection.
The effect is not permanent, so the injections must be repeated again and again.

Step 4: Approach 3: gene therapy:
Lymphocytes of the patient are taken from the blood and grown in a culture outside the body.
A functional ADA cDNA is introduced into them using a retrovirus vector.
The modified cells are returned to the patient. They need to be given again from time to time, as they are not immortal.
If the gene is put into marrow cells in early embryonic stages, it can give a permanent cure.

Final Answer:
Three approaches: bone marrow transplantation, enzyme replacement therapy (injecting ADA) and gene therapy (introducing a functional ADA cDNA into lymphocytes using a retroviral vector).