Gene therapy.

The therapeutic delivery of nucleic acid into patient's cells as a drug to treat genetic diseases.

1. DAVANGERE UNIVERSITY SEMINAR TOPIC : SOMATIC CELL GENE THERAPY.

2. CONTENTS Introduction Types of gene therapy Somatic cell gene therapy Germ line gene therapy Types of somatic cell gene therapy Ex-vivo gene therapy In-vivo gene therapy Antisense gene therapy Advantages and Disadvantages of gene therapy Summary Conclusion References

3. INTRODUCTION Gene therapy is an experimental technique that uses genes to treat or prevent disease. To treat a disorder by inserting a gene into a patient’s cells instead of using drugs or surgery. The first attempt at modifying human DNA was performed in 1980 by Martin Cline, but the first successful nuclear gene transfer in humans was approved by the National I nstitutes of Health (NIH) in may 1989.

4. Somatic cell gene therapy: In somatic cell gene therapy(SCGT), the therapeutic genes are transferred into any cell other than a gamete, germ cell, gametocyte, or undifferentiated stem cells. Any such modifications affect the individual patient only, and are not inherited by offspring. Somatic gene therapy represents main stream basic and clinical research, in which therapeutic DNA is used to treat disease. 2 . Germ line gene therapy: In germ line gene therapy, germ cells i.e., sperm or ovum, are modified by the introduction of functional genes, which are integrated into their genomes. This would allow the therapy to be heritable and passed on to later generations.

5. TYPES OF SOMATIC CELL GENE THERAPY Ex-vivo Gene Therapy In-vivo Gene Therapy Antisense Gene Therapy

6. Ex-vivo Gene Therapy Collect cells from an affected individual. Correct the genetic defect by gene transfer. Select and grow the genetically corrected (remedial) cells. Either infuse or transplant them back into the patient.

7. Ex-vivo Gene Therapy

8. Genetic map of a typical retrovirus Genetic map of a two – gene retroviral vector

9. Positive negative selection In addition to remedial gene it consists " selectable" genes whose products permit cells to live or cause them to die in the presence of a particular drug. The two most common selectable genes used in gene targeting are the neomycin resistance ( neo r ) gene, which allows cells to survive in the presence of the antibiotic neomycin, G418 (Positive selection). The thymidine kinase ( TK ) gene from the herpes virus. Cells with this gene die in the presence of the antiviral agent ganciclovir (Negative selection). The   neo r  and  TK  genes are generally used together for maximum selection .

10. In-vivo Gene Therapy

11. Adenovirus Adenovirus is a double stranded DNA virus that can carry >30Kb of insert DNA as a low pathogenicity in humans. An adenovirus packaging cell line can produce mixed population of viruses that consists of those containing viral DNA and those that carry the cloned genes on the viral vector eg :Duchenne muscular dystrophy. Herpes simplex virus Tissue specific viruses could be used as vehicles to bring genes to a defined region of the body. For eg: HSV recognize the nerve cells at their axonal terminal ends and is transported internal to the neuronal cell body. Where it is maintained. eg: Alzhemier’s disease.

12. Retroviral vector Researchers have also developed a novel cancer treatment that utilizes a retroviral vector system. Retrovirus can only infect dividing cells and that infective particles are released only after integration of a retroviral vector from packaging cell line technique. In this case, a retroviral vector containing the herpes simplex virus gene for thymidine kinase was introduced into a packaging cell line. eg: Brain tumor

13. Antisense Therapy

14. Advantages of Gene Therapy Gene therapy has the potential to eliminate and prevent hereditary diseases such as cystic fibrosis, ADA-SCID etc. It is a possible cure for heart disease, AIDS and cancer. The virus is replication deficient, so its safe and is suitable for the treatment of a variety of diseases. They can be modified so that they can’t replicated and destroy cells. It can be used to eradicate diseases from the future generation.

15. Disadvantages of Gene Therapy Immune response is of stimulated that reduces gene therapy effectiveness which is always a potential risk. Viruses used as vectors for gene transfer may cause toxicity, immune responses, and inflammatory reactions in the host. Disorders caused by defects in multiple genes can’t be treated effectively using gene therapy. They can carry a limited amount of genetic material. therefore, some genes may be too big to fit into some viruses. Random insertion can disrupt normal genes

16. SUMMARY Once a normal version of a gene for a human disease has been cloned, the possibility exists that it can be used to correct the defect in individuals that have a mutant form of the gene. When this form of treatment is applied to non-germ line cells, it is called somatic cell gene therapy. There are three therapeutic approaches: Ex-vivo gene therapy , In-vivo gene therapy, and antisense therapy.

17. CONCLUSION Theoretically, gene therapy is the permanent solution for genetic diseases. But it has several complexities at its current stage, it is not accessible to most people due to its huge cost. Gene therapy have the potential to revolutionize the practice of medicine . Overcoming all its hurdles it would change our lives forever.

18. REFERENCES Freshney R. I., (2010), Culture Of Animal Cells, 6 th e dn , John Wiley and Sons, Inc., pp 732 . Pasternak J. J ., and Glick R. B.,(1994), Molecular Biotechnology, 1 st e dn , Panima Publishing Corporation, New Delhi, pp 484 . Reichsman F , and Fitzgerald- hayes M.,(2010), DNA and Biotechnology, 3 rd e dn , Academic Press, USA, pp 390. Ramadass P.,(2008), Animal Biotechnology, MJP Publishers, Chennai, pp 494 .