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The genetic defect adenosine deaminase (ADA) deficiency may be cured permanently by
A
Enzyme replacement therapy
B
Periodic infusion of genetically engineered lymphocytes having functional ADA cDNA
C
Administering adenosine deaminase activators
D
Introducing bone marrow cells producing ADA into cells at early embryonic stages
Detailed Solution
ADA deficiency is caused by the deletion of the gene for adenosine deaminase, an enzyme crucial for the immune system to function.
Enzyme replacement therapy (injecting functional ADA) and bone marrow transplantation are not completely curative.
In gene therapy, lymphocytes from the patient's blood are grown in culture, a functional ADA cDNA is introduced into them using a retroviral vector, and they are returned to the patient. Since these cells are not immortal, the patient requires periodic infusion of such lymphocytes; so this is not a permanent cure either.
However, if the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
Hence the permanent cure is introducing bone marrow cells producing ADA into cells at early embryonic stages.
Enzyme replacement therapy (injecting functional ADA) and bone marrow transplantation are not completely curative.
In gene therapy, lymphocytes from the patient's blood are grown in culture, a functional ADA cDNA is introduced into them using a retroviral vector, and they are returned to the patient. Since these cells are not immortal, the patient requires periodic infusion of such lymphocytes; so this is not a permanent cure either.
However, if the gene isolated from marrow cells producing ADA is introduced into cells at early embryonic stages, it could be a permanent cure.
Hence the permanent cure is introducing bone marrow cells producing ADA into cells at early embryonic stages.