Gene therapy

GENE THERAPY
S.RAM PRAKASH
IIIrdBSC BIOTECHNOLOGY, AYYA NADAR JANAKI AMMA COLLEGE, SIVAKASI, TAMIL NADU.

1. S.RAM PRAKASH 18UT38 IIIrd BSC BIOTECHNOLOGY GENE THERAPY (ANIMAL BIOTECHNOLOGY AND STEM CELLS)

2. What is Gene Therapy? Human gene therapy seeks to modify or manipulate the expression of a gene or to alter the biological properties of living cells for therapeutic use  . Gene therapy is a technique that modifies a person’s genes to treat or cure disease. Gene therapies can work by several mechanisms: Replacing a disease-causing gene with a healthy copy of the gene Inactivating a disease-causing gene that is not functioning properly Introducing a new or modified gene into the body to help treat a disease Gene therapy products are being studied to treat diseases including cancer, genetic diseases, and infectious diseases .

3. How Gene Therapy Works Gene therapy can be performed both inside and outside the body. This infographic illustrates in simple terms how gene therapy works inside the body.  Sometimes the whole or part of a gene is defective or missing from birth, or a gene can change or mutate during adult life. Any of these variations can disrupt how proteins are made, which can contribute to health problems or diseases. In gene therapy, scientists can do one of several things depending on the problem that is present. They can replace a gene that causes a medical problem with one that doesn’t, add genes to help the body to fight or treat disease, or turn off genes that are causing problems.

4. There are two different types of gene therapy depending on which types of cells are treated: Somatic gene therapy:  transfer of a section of DNA to any cell of the body that doesn’t produce sperm or eggs. Effects of gene therapy will not be passed onto the patient’s children. Germline gene therapy:  transfer of a section of DNA to cells that produce eggs or sperm. Effects of gene therapy will be passed onto the patient’s children and subsequent generations.

5. There are two types of gene therapies: I. Ex vivo gene therapy : This involves the transfer of genes in cultured cells (e.g., bone marrow cells) which are then reintroduced into the patient. II. In vivo gene therapy: The direct delivery of genes into the cells of a particular tissue is referred to as in vivo gene therapy.

6. Ex Vivo Gene Therapy: The ex vivo gene therapy can be applied to only selected tissues (e.g., bone marrow) whose cells can be cultured in the laboratory. The technique of ex vivo gene therapy involves the following steps (Fig. 13.2). 1 . Isolate cells with genetic defect from a patient. 2 . Grow the cells in culture. 3 . Introduce the therapeutic gene to correct gene defect. 4 . Select the genetically corrected cells (stable trans-formants) and grow. 5 . Transplant the modified cells to the patient. The procedure basically involves the use of the patient’s own cells for culture and genetic correction, and then their return back to the patient. This technique is therefore, not associated with adverse immunological responses after transplanting the cells. Ex vivo gene therapy is efficient only, if the therapeutic gene (remedial gene) is stably incorporated and continuously expressed. This can be achieved by use of vectors.

7. In Vivo Gene Therapy: The direct delivery of the therapeutic gene (DNA) into the target cells of a particular tissue of a patient constitutes in vivo gene therapy (Fig. 13.6). Many tissues are the potential candidates for this approach. These include liver, muscle, skin, spleen, lung, brain and blood cells. Gene delivery can be carried out by viral or non- viral vector systems. The success of in vivo gene therapy mostly depends on the following parameters i . The efficiency of the uptake of the remedial (therapeutic) gene by the target cells. ii. Intracellular degradation of the gene and its uptake by nucleus. iii. The expression capability of the gene. In vivo gene therapy with special reference to gene delivery systems (viral, non-viral) with suitable examples is described.

8. Risks Gene therapy has some potential risks. A gene can't easily be inserted directly into your cells. Rather, it usually has to be delivered using a carrier, called a vector. The most common gene therapy vectors are viruses because they can recognize certain cells and carry genetic material into the cells' genes. Researchers remove the original disease-causing genes from the viruses, replacing them with the genes needed to stop disease. This technique presents the following risks: Unwanted immune system reaction.  Your body's immune system may see the newly introduced viruses as intruders and attack them. This may cause inflammation and, in severe cases, organ failure. Targeting the wrong cells.  Because viruses can affect more than one type of cells, it's possible that the altered viruses may infect additional cells — not just the targeted cells containing mutated genes. If this happens, healthy cells may be damaged, causing other illness or diseases, such as cancer .

9. Infection caused by the virus.  It's possible that once introduced into the body, the viruses may recover their original ability to cause disease. Possibility of causing a tumor.  If the new genes get inserted in the wrong spot in your DNA, there is a chance that the insertion might lead to tumor formation. The gene therapy clinical trials underway in the U.S. are closely monitored by the Food and Drug Administration and the National Institutes of Health to ensure that patient safety issues are a top priority during research.