Which of the following is a common vector used for introducing a DNA fragment into human lymphocytes?

Retrovirus

In 1990, the first clinical gene therapy was administered to a 4-year-old girl who had adenosine deaminase (ADA) deficiency, a condition essential for the proper functioning of the immune system. This deficiency arises due to the deletion of the gene responsible for producing ADA. While bone marrow transplantation and enzyme replacement therapy can partially address ADA deficiency in some cases, they are not fully curative.

As an initial step toward gene therapy, lymphocytes from the patient's blood are cultured outside the body. Functional ADA complementary DNA (cDNA) is then introduced into these lymphocytes using a retroviral vector. Subsequently, the modified lymphocytes are infused back into the patient. However, since these cells are not immortal, the patient requires periodic infusions of genetically engineered lymphocytes to maintain the effect.

Alternatively, for a more permanent cure, if the gene responsible for producing ADA is introduced into cells during early embryonic stages, it could result in a lasting solution. This approach aims to correct the genetic defect early in development, offering the potential for a lifelong and complete cure for ADA deficiency through gene therapy.