" GENE THERAPY "

Gene therapy is to replace 'a faulty gene' by a normal healthy functional gene. Gene therapy is a collection of methods which permits the correction of a gene defect which has been diagnosed in a child/embryo. In gene therapy normal genes are inserted into individual or embryo to take over the function and compensate for non-functional gene.

Show of Gene therapy in patient of SCID :👇🏻

Types of therapy :--👇🏻

(1) Germ line gene therapy. It leads to modification of germ cells i.e. sperms or eggs. This is done by introducing functional genes which are integrated into their genomes. This type of therapy is inheritable.

(ii) Somatic cell gene therapy. It leads to modification of somatic cells by introducing concerned gene in body cells. It removes symptoms of disorder temporarily.

Under gene therapy, hereditary diseases like sickle cell anaemia to killer diseases like SCID (Severe combined immuno deficiency). SCID occurs due to defect in the gene for enzyme adenosine deaminase (ADA) which is essential for the normal functioning of the lymphocytes of immune system. Such patients bear non-functional T-lymphocytes. As a result, they fail to mount immune responses against attacking pathogens. The first clinical gene therapy was given to a 4 year girl in 1990 with ADA deficiency. The ideal approach for SCID treatment is to provide functional ADA which breaks down toxins. The defect is caused due to deletion of gene for ADA

synthesis. It is cured in children by two methods: 

(i) Bone marrow transplantation.

(ii) Enzyme replacement therapy.

However by applying above methods, disease is not completely cured.

Lymphocytes, a kind of white blood cells are extracted from bone marrow of a SCID sufferer. A good copy of human gene encoding this enzyme is introduced into such cells. This is done by gene therapy in which lymphocytes from blood are grown in culture outside the body. A functional ADA CDNA (using a retroviral vector) is introduced into such cells. They are reinjected into SCID sufferers.

Usually patients need regular infusion of genetically engineered lymphocytes. Because such cells are not immortal. But if a better gene is introduced into bone marrow cells at an early embryonic stage, a permanent cure can be achieved.

Clinical trials of diseases that are being considered for using somatic gene therapy.

1. Colon cancer

2. Haemophilia

3. Cystic fibrosis

4. Hypercholestromia

5. Acute myeloid leukaemia

6. Leukaemia

7. AIDS

8. Liver cancer

9. SCID

10. Lung cancer

11. Breast cancer

12. Osteoporesis

13. Atherosclerosis

14. Sickle cell anaemia

* MOLECULAR DIAGNOSIS : 👇🏻👇🏻

For any disease, an early diagnosis by knowing symptoms, pathophysiology etc., is required. Recombinant DNA molecules and some techniques like Polymerase Chain Reactions have proved very rewarding in this regard. PCR technique has already been discussed in Chapter 11.

PCR involves following steps:

(i) A single stranded DNA or RNA strands islabelled with radioactive probe.

(ii) It is hybridized to its complementary strand in a clone of cells.

(iii) Detected using autoradiography

(iv) If no complementary pairing, it indicates mutations of the gene.

In ELISA (Enzyme linked immunosorbant assay) cloned genes are expressed to produce recombinant proteins help in developing sensitive diagnostic techniques.

* Note -👇🏻👇🏻 /--

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