Question

What is meant b y ADA deficiency? How is gene therapy a solution to this problem? Why is it not a permanent cure? What can be done for this?

Answer 1

Adenosine deaminase deficiency (also called ADA deficiency or ADA-SCID[1]) is an autosomal recessive[2] metabolic disorder that causes immunodeficiency. It occurs in fewer than one in 100,000 live births worldwide. It accounts for about 15% of all cases of severe combined immunodeficiency (SCID).[3] ADA deficiency may be present in infancy, childhood, adolescence, or adulthood.[1] Age of onset and severity is related to some 29 known genotypes associated with the disorder.[4] Pathophysiology ADA deficiency is due to a lack of the enzyme adenosine deaminase. This deficiency results in an accumulation of deoxyadenosine,[5] which, in turn, leads to: a buildup of dATP in all cells, which inhibits ribonucleotide reductase and prevents DNA synthesis, so cells are unable to divide. Since developing T cells and B cells are some of the most mitotically active cells, they are highly susceptible to this condition. an increase in S-adenosylhomocysteine since the enzyme adenosine deaminase is important in the purine salvage pathway; both substances are toxic to immature lymphocytes, which thus fail to mature. Because T cells undergo proliferation and development in the thymus, affected individuals typically have a small, underdeveloped thymus.[6] As a result, the immune system is severely compromised or completely lacking. Treatments include: bone marrow transplant gene therapy ADA enzyme in PEG vehicle On September 1990, the first gene therapy to combat this disease was performed by Dr. William French Anderson on a four-year-old girl, Ashanti DeSilva, at the National Institutes of Health, Bethesda, Maryland, U.S.A. In April 2016 the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed and recommended for approval a stem cell gene therapy called Strimvelis, for children with ADA-SCID for whom no matching bone marrow donor is available.

Answer 2

The full form of ADA is adenosine deaminase deficiency. Adenosine deaminase enzyme plays an important role to maintain the function of the immune system. Due to the lack of T- lymphocytes fails to overcome the infecting pathogens.

If children are suffered with ADA deficiency are cured by enzyme (ADA) replacement.

In the latest gene therapy techniques, Lymphocytes are taken from the affected body bone marrow in gene therapy techniques and retrovirus is used to introduce the normal gene for ADA into the lymphocytes. Then reintroduces the cells into the affected body.  But the patient requires a periodic infusion of such lymphocytes because these cells are not immortal. Hence, it is not a permanent cure.