Gene Therapy;Boon Or Adversary To Humanity


Published on

Published in: Health & Medicine, Technology
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Gene Therapy;Boon Or Adversary To Humanity

  1. 1. GENE THERAPY; Boon or adversary to humanity Dr. shahnawaz Ah. Bhat MVSc scholar IVRI Izatnagar India
  2. 2. Genes <ul><li>Are carried on a chromosome </li></ul><ul><li>The basic unit of heredity </li></ul><ul><li>Encode how to make a protein </li></ul><ul><ul><li>DNA  RNA  proteins </li></ul></ul><ul><li>Proteins carry out most of the </li></ul><ul><li>functions of life. </li></ul><ul><li>When there is a mutation in the gene, change the conformation & function of the protein Diseases. </li></ul>
  3. 3. What is Gene Therapy? <ul><li>It is an experimental technique for correcting defective genes that are responsible for disease development </li></ul><ul><li>Approaches: </li></ul><ul><ul><li>A normal gene inserted to compensate for a nonfunctional gene. </li></ul></ul><ul><ul><li>An abnormal gene is replaced for a normal gene </li></ul></ul><ul><ul><li>An abnormal gene repaired through selective reverse mutation </li></ul></ul><ul><ul><li>Change the regulation of gene. </li></ul></ul><ul><li>5. Researchers are also experimenting with introducing a 47 th artificial chromosome to the body </li></ul>
  4. 4. How It Works <ul><li>A vector delivers the therapeutic gene into a patient’s target cell. </li></ul><ul><li>Functional proteins are created from the therapeutic gene causing the cell to return to a normal state </li></ul>
  5. 5. <ul><li>In general, a genetic material(DNA or RNA) is inserted into a person’s cell using a carrier, or vector. Vector systems can be divided into: </li></ul><ul><li>Viral Vectors </li></ul><ul><li>Non-viral Vectors </li></ul>
  6. 6. Types of Gene Therapy <ul><li>Germ line gene therapy </li></ul><ul><li>germ cells, i.e., sperm or eggs, are modified by the introduction of functional genes, </li></ul><ul><li>the change due to therapy would be heritable and would be passed on to later generations. </li></ul><ul><li>permanent therapeutic effect for all who inherit the target gene eliminating some diseases from a particular family, and ultimately from the population, forever. </li></ul>
  7. 7. <ul><li>Somatic gene therapy </li></ul><ul><li>The therapeutic genes are transferred into the somatic cells of a patient. Any modifications and effects will be restricted to the individual patient only. </li></ul><ul><li>In other words, the therapeutic effect ends with the individual who receives the therapy. </li></ul><ul><li>viewed as a more conservative, safer. </li></ul><ul><li>All gene therapies to date on humans has been directed at somatic cells. </li></ul>
  8. 8. Methods adopted <ul><li>ex vivo , where cells are modified outside the body and then transplanted back in again . </li></ul>
  9. 9. <ul><li>in vivo , which means interior where genes are changed in cells still in the body. </li></ul>
  10. 10. Vectors for gene therapy <ul><li>Viral Vectors </li></ul><ul><li>Adenoviral vectors. </li></ul><ul><li>Adeno-associated viral vectors. </li></ul><ul><li>Retroviral vectors. </li></ul><ul><li>Alpha viral vectors. </li></ul><ul><li>Herpes virus vectors. </li></ul><ul><li>Vaccinia Viral Vectors. </li></ul>
  11. 13. A comparison of different viral vectors in use for gene therapy
  12. 14. Retroviral vectors <ul><li>genetic material of the virus inserted in the host cell genome. </li></ul><ul><li>host cell divides later, its descendants will all contain the new genes. </li></ul><ul><li>problems using retroviruses is that the integrase enzyme can insert the genetic material of the virus into any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. </li></ul>
  13. 15. Adenoviral Vectors <ul><li>Have double stranded DNA genome </li></ul><ul><li>that cause respiratory, intestinal, and </li></ul><ul><li>eye infections in humans </li></ul><ul><li>The inserted DNA is not incorporated </li></ul><ul><li>into genome </li></ul><ul><li>Not replicated though. </li></ul><ul><ul><li>Has to be reinserted when more cells divide </li></ul></ul><ul><ul><li>This vector system has been promoted for treating cancer and indeed the first gene therapy product to be licensed to treat cancer, Gendicine, is an adenovirus. Gendicine, an adenoviral p53-based gene therapy was approved by the Chinese FDA in 2003 for treatment of head and neck cancer. </li></ul></ul>
  14. 17. Adeno-Associated Viral Vectors <ul><li>Can also insert genetic material at a specific point on chromosome 19. </li></ul><ul><li>Causes no known disease and doesn't trigger patient immune response in humans. </li></ul><ul><li>Low information capacity. </li></ul><ul><li>hemophilia treatments, for example, a gene-carrying vector could be injected into a muscle, prompting the muscle cells to produce Factor IX and thus prevent bleeding. </li></ul><ul><ul><li>(Wilson and Kathy High University of Pennsylvania) </li></ul></ul><ul><ul><li>AAV vectors are used to deliver genes to the brain. This is possible because AAV viruses can infect non-dividing (quiescent) cells, such as neurons. </li></ul></ul>
  15. 18. Herpes virus es <ul><li>Herpes Simplex Virus is a human neurotropic virus </li></ul><ul><li>unique features of HSV derived vectors are the very high transgenic capacity. </li></ul><ul><li>the ability of HSV vectors to invade and establish lifelong non-toxic latent infections in neurons from sensory ganglia from where transgenes can be strongly and long-term expressed. </li></ul>
  16. 19. Risk Factors associated with viruses . <ul><li>Viruses can usually infect more than one type of cell. </li></ul><ul><li>the n ew gene might be inserted in the wrong location in the DNA, possibly causing harmful mutations to the DNA or even cancer especially retroviruses. </li></ul><ul><li>DNA could unintentionally be introduced into the patient’s reproductive cells. If this happens, it could produce changes that may be passed on if a patient has children after treatment. </li></ul><ul><li>transferred genes could be over expressed, producing so much of the missing protein as to be harmful. </li></ul><ul><li>the viral vector could cause an immune reaction. </li></ul>
  17. 20. <ul><li>virus could be transmitted from the patient to other individuals or into the environment. </li></ul><ul><li>However, this basic mode of gene introduction currently shows much promise and doctors and scientists are working hard to fix any potential problems that could exist. They use animal testing and other precautions to identify and avoid these risks before any clinical trials are conducted in humans. </li></ul>
  18. 21. Non-Viral Vectors <ul><li>Naked DNA </li></ul><ul><li>Oligonucleotides </li></ul><ul><li>Lipoplexes </li></ul><ul><li>Polyplexes </li></ul><ul><li>Receptor mediated endocytosis. </li></ul><ul><li>Dendrimers. </li></ul>
  19. 22. <ul><li>Naked DNA </li></ul><ul><li>simplest method of non-viral transfection. </li></ul><ul><li>intramuscular injection of a naked DNA plasmid or naked PCR product. </li></ul><ul><li>expression has been very low in comparison to other methods of transfection. </li></ul><ul><li>Research into more efficient methods for delivery of the naked DNA such as electroporation , sonoporation , and the use of a &quot; gene gun &quot;, which shoots DNA coated gold particles into the cell using high pressure gas. </li></ul>
  20. 25. <ul><li>A gene gun or a biolistic particle delivery system is a device for injecting cells with genetic information. The payload is an elemental particle of a heavy metal coated with plasmid DNA. </li></ul><ul><li>This technique is often </li></ul><ul><li>simply referred to as </li></ul><ul><li>bioballistics . </li></ul>
  21. 26. Oligonucleotides <ul><li>To inactivate the genes involved in the disease process. </li></ul><ul><li>As antisense specific to the target gene to disrupt </li></ul><ul><li>the translation of the faulty gene. </li></ul><ul><li>As small molecules of RNA called siRNA to signal the cell to cleave specific unique sequences in the mRNA transcript of the faulty gene, disrupting translation of the faulty mRNA, and therefore expression of the gene. </li></ul><ul><li>Double stranded oligodeoxynucleotides as a decoy for the transcription factors that are required to activate the transcription of the target gene. </li></ul><ul><li>Oligonucleotides can also form a triple helix with DNA and alter transcription. </li></ul>
  22. 29. Use of siRNA Dicer is an endoribonuclease that cleaves double-stranded RNA (dsRNA) into short double-stranded RNA fragments called small interfering RNA(siRNA) about 20-25 nucleotides long, initiates formation of the RNA-induced silencing complex (RISC), whose catalytic component is an endonuclease capable of degrading messenger RNA (mRNA) whose sequence is complementary to that of the siRNA guide strand .
  23. 31. Lipoplexes/liposomes <ul><li>Aqueous compartments enclosed by lipid bilayer membranes; also known as lipid vesicles. </li></ul><ul><li>Protect the DNA from undesirable </li></ul><ul><li>degradation during the transfection process. </li></ul><ul><li>Plasmid DNA can be covered with lipids in an organized structure like a micelle or a liposome. </li></ul><ul><li>3 types anionic (negatively charged), neutral, or cationic (positively charged). </li></ul><ul><li>Cationic lipoplexes more stable & easy to produce. </li></ul><ul><li>the transfection efficiency is very low due to the lack of ability in terms of “endosomal escaping”. </li></ul>
  24. 35. Polyplexes <ul><li>Complexes of polymers with DNA are called polyplexes </li></ul><ul><li>Most polyplexes consist of cationic polymers like poly(l-lysine). </li></ul><ul><li>polyplexes cannot release their DNA load into the cytoplasm so co-transfection with endosome-lytic agents such as inactivated adenovirus must occur. </li></ul><ul><li>polymers such as polyethylenimine have their own method of endosome disruption as does chitosan and trimethylchitosan. </li></ul>
  25. 36. <ul><li>Polyplexes can also be combined with a receptor specific ligand to target specific cells. </li></ul><ul><li>Ligand covalently binds to polycation. </li></ul><ul><li>DNA binds to the polycation by ionic interactions. </li></ul><ul><li>DNA conjugate complex internalised into specific cells. </li></ul><ul><li>Ligands like asialorosomucoid for asialoglycoprotien receptors of liver cells, anti-CD3 antibody ligand for C-kit receptors of hematopoietic stem cells. </li></ul>
  26. 39. Dendrimers <ul><li>A dendrimer is a highly branched macromolecule with a spherical shape. </li></ul><ul><li>Nanomolecules, can be used as vehicles to deliver genetic material into the cells. </li></ul><ul><li>Positively charged dendrimers can be used more efficiently. </li></ul><ul><li>Biodegradable . </li></ul>
  27. 41. The Beginning… <ul><li>In the 1980s, Scientists began to look into gene therapy. </li></ul><ul><ul><li>They would insert human genes into a bacteria cell. </li></ul></ul><ul><ul><li>Then the bacteria cell would transcribe and translate the information into a protein </li></ul></ul><ul><ul><li>Then they would introduce the protein into human cells </li></ul></ul>
  28. 42. The First Case……. <ul><li>The first gene therapy was performed on September 14 th , 1990 at the U.S. </li></ul><ul><li>National Institutes of Health by </li></ul><ul><li>W. French Anderson and his </li></ul><ul><li>colleagues. </li></ul><ul><li>Ashanti DeSilva was treated </li></ul><ul><li>for SCID </li></ul><ul><ul><ul><li>Sever combined immunodeficiency </li></ul></ul></ul>
  29. 43. What they did….. <ul><li>Doctors removed white blood </li></ul><ul><li>cells from the child's body, let </li></ul><ul><li>the cells grow in the laboratory, </li></ul><ul><li>inserted the missing gene into </li></ul><ul><li>the cells, and then infused the </li></ul><ul><li>genetically modified blood cells </li></ul><ul><li>back into the patient's </li></ul><ul><li>bloodstream. </li></ul><ul><li>As of early 2007, she was </li></ul><ul><li>still in good health, and she </li></ul><ul><li>was attending college. </li></ul>
  30. 44. Failures……… <ul><li>FDA USA hasn’t approved any human gene therapy product for sale </li></ul><ul><li>Reasons: </li></ul><ul><li>In 1999 , 18-year-old Jesse Gelsinger died from multiple organ failure 4 days after treatment for omithine transcarboxylase deficiency. </li></ul><ul><ul><li>Death was triggered by severe immune response to adenovirus carrier Within hours after doctors shot the normal OTC gene attached to a therapeutic virus into his liver, Jesse developed a high fever. His immune system began raging out of control, his blood began clotting, ammonia levels climbed, his liver hemorrhaged and a flood of white blood cells shut down his lungs. </li></ul></ul>
  31. 45. <ul><li>January 2003 , halt to using retrovirus vectors in blood stem cells because 4/20 children developed leukemia-like condition after successful treatment for X-linked severe combined immunodeficiency disease </li></ul><ul><li>July 2007 Jolie Mohr, a 36-year-old woman with rheumatoid arthritis died, while participating in a gene-therapy clinical trial. sudden infection raged through her body and caused her organs to fail just after the experimental treatment was injected into her right knee, which raised suspicion that her death was linked to the therapy. </li></ul>
  32. 46. Success story…….. <ul><li>Between 2001 and 2002 , surgeons at San Diego's University of California placed genetically modified tissue into the brains of eight Alzheimer's patients. Memory tests suggest the gene therapy has slowed cognitive decline by as much as 50%. Brain scans also show that the patients' brains were more active than before. </li></ul><ul><li>Gendicine , an adenoviral p53-based gene therapy was approved by the Chinese FDA in 2003 for treatment of head and neck cancer. </li></ul>
  33. 47. <ul><li>In 2003 at University of California, Los Angeles research team inserted genes into the brain using liposomes coated in a polymer called polyethylene glycol(PEG). The transfer of genes into the brain is a significant achievement because viral vectors are too big to get across the &quot;blood-brain barrier&quot; This method has potential for treating Parkinson's disease. </li></ul><ul><li>Scientists at the National Institutes of Health Maryland have successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells. This study constitutes the first demonstration that gene therapy can be effective in treating cancer. </li></ul>
  34. 48. <ul><li>18 May 2007 - Researchers at London’s Moorefield Eye Hospital made the world’s first successful attempt at using gene therapy to treat a visual disorder due to a defect in a gene called RPE65, which stops the photoreceptor cells in the retina at the back of the eye from detecting light. </li></ul>
  35. 49. <ul><li>September 2009 , the journal Nature reported that researchers at the University of Washington and University of Florida were able to give trichromatic vision to squirrel monkeys using gene therapy, a hopeful precursor to a treatment for color blindness in humans. </li></ul><ul><li>October 2009 , Toronto researchers put harvested lungs in a domed chamber that maintained body temperature and pumped them with oxygen and nutrients, then inserted a gene that induced the lungs to produce the immune molecule IL-10, which has helped reduce inflammation. </li></ul>
  36. 51. <ul><li>30 October 2009 , source: Science Daily Born with a retinal disease that made him blind, the nine-year-old boy used to sit in the back of the classroom, relying on the large print on an electronic screen and assisted by teacher. Now, after a single injection of genes that produce light-sensitive pigments in the back of his eye, he sits in front with classmates and participates in class without extra help. </li></ul><ul><li>8 November 2009 , the journal Science reported that researchers succeeded at halting a fatal brain disease, adrenoleukodystrophy, using a vector derived from lenti virus to deliver the gene for the missing enzyme . </li></ul>
  37. 52. Future prospects…..
  38. 54. Gene therapy in India……… <ul><li>Tata Cancer hospital has initiated gene therapy studies specifically for oral cancer. </li></ul><ul><li>In 2001, Metro Heart Institute in Noida used about 20 persons with a certain heart condition for a trail on VEGF (vascular endothelial growth factor), a genetic protein but without any authorization & without the consent from patients. </li></ul><ul><li>(THE TIMES OF INDIA NEWS SERVICE 21 April 2001) </li></ul><ul><li>A cell-based gene therapy to treat renal cell carcinoma, colon, breast, and lung cancer, has been given permission to be used in Indian patients by the country's regulator, The Indian Department of Biotechnology. Mologen, the Berlin-based biotech company has developed the treatment. India is the first country to give the go-ahead to such a gene therapy. </li></ul>
  39. 55. Problems with Gene Therapy <ul><li>Short Lived </li></ul><ul><ul><li>Would have to have multiple rounds of therapy </li></ul></ul><ul><li>Immune Response </li></ul><ul><ul><li>New things introduced leads to immune response </li></ul></ul><ul><ul><li>Increased response when a repeat offender enters </li></ul></ul><ul><li>Viral Vectors </li></ul><ul><ul><li>Patient could have toxic, immune, inflammatory response </li></ul></ul><ul><ul><li>Also may cause disease once inside </li></ul></ul><ul><li>Multigene Disorders </li></ul><ul><ul><li>Heart disease, high blood pressure, Alzheimer’s, arthritis and diabetes are hard to treat because it needs to introduce more than one gene. </li></ul></ul><ul><li>Induce tumor if integrated in a tumor suppressor gene because of insertional mutagenesis. </li></ul>
  40. 56. Ethical issues surrounding gene therapy <ul><li>How can “good” and “bad” uses of gene therapy be distinguished? </li></ul><ul><li>Who decides which traits are normal and which constitute a disability or disorder? </li></ul><ul><li>Will the high costs of gene therapy make it available only to the wealthy? </li></ul><ul><li>Could the widespread use of gene therapy make society less accepting of people who are different? </li></ul><ul><li>Should people be allowed to use gene therapy to enhance basic human traits such as height, intelligence, or athletic ability? </li></ul>
  41. 57. Conclusion <ul><li>All inventions start with failures. </li></ul><ul><li>As the technique </li></ul><ul><li>is still in its </li></ul><ul><li>infancy restricted to clinical </li></ul><ul><li>trials. So with the </li></ul><ul><li>development of better </li></ul><ul><li>delivery system & certain </li></ul><ul><li>other technical modifications </li></ul><ul><li>gene therapy will be really </li></ul><ul><li>a boon to human kind in future. </li></ul>
  42. 58. Thanks