Mention the cause of ADA deficiency in humans. How has genetic engineering helped patients suffering from it?

Adenosine deaminase also known as ADA enzyme.

ADA enzyme is vital for proper functioning of the immune system.

The ADA enzyme deficiency is mainly caused due to deletion of ADA gene. That is ADA enzyme deficiency is caused due to mutation in ADA gene.

The adenosine deaminase enzyme deficiency is a genetic disorder.

This deficiency is autosomal recessive disorder mainly found in children very rarely.

ADA enzyme acts upon Deoxyadenosine, which is toxic substance produced in the body. The Deoxyadenosine kill the T and B lymphocytes which are immunogenic cells. So the patient with ADA enzyme deficiency lacks resistance to fight against pathogens.

The ADA enzyme deficiency in turn causes SCID (Severe Combined Immune Deficiency) in infants.

The cure with the help of genetic engineering is as follows:

Gene therapy is made used for curing ADA deficiency. Gene therapy is a genetic engineering technique used to replace faulty gene with normal and healthy gene.

ADA deficiency is treated by enzyme replacement therapy where functional ADA is given to the patient by injection.

In the affected patient, the lymphocytes from bone marrow are collected with the help of biotechnology. Then in the laboratory by culturing ADAcDNA is inserted in the lymphocytes, i.e., genetically engineered lymphocytes are produced. Then these genetically engineered lymphocytes are inserted back into the bone marrow of patient using retroviral vector. These genetically engineered lymphocytes has functional ADA gene which now forms adenosine deaminase and maintains the immunity.

But these cells are mortal i.e., dies, hence requires periodic infusion of genetically engineered lymphocytes. So this is not a permanent cure.

If the genetically engineered lymphocytes containing functional ADA gene is introduced in embryonic stage then this can be permanent cure.