Is bone marrow transplantation and enzyme replacement therapy are same as gene therapy or they are some other therapy??
Both the process you mentioned are not same as gene therapy.
Bone marrow transplantation is carried out in the patient whose bone marrow has been damaged and is replaced with the healthy bone marrow. In case of patients suffering from leukemia bone marrow is replaced with healthy bone marrow. Post bone marrow transplantation, infusion of genetically modified lymphocytes are carried out to protect the individual from pathogen and cancer for longer duration of time, so that memory T cell can be generated for long term immune protection.
Enzyme replacement therapy involves intravenous infusions of a particular enzyme which is deficient and due to which there occurs accumulation of a particular product, this leads to the appearance of symptoms and disease. Example: Gaucher disease.
Though some of the enzyme deficiency can be treated by gene therapy. Example:
Adenosine deaminase (ADA) is an enzyme crucial for immune system. Its deficiency is caused due to the deletion of the gene coding for adenosine deaminase.
The transplantation of bone marrow is not the permanent cure for ADA deficiency because this method may require repeated application and it is difficult to find the exact match. Also, it is associated with complications like infections, graft versus host disease and lack of engraftment.
A permanent cure for ADA deficiency is to introduce genes isolated from marrow cells that produce ADA into cells of patient at early embryonic stages.