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24 Cards in this Set
- Front
- Back
What is gene therapy?
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An approach to treating disease by adding, augmenting, or repairing genes
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What are some diseases that may be treated with gene therapy?
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Cystic fibrosis, sickle cell anemia, muscular dystrophy, cancer, AIDS
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What are the two modes of gene delivery?
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Ex vivo - the gene is put into isolated cells
In vivo - the gene is put directly into patients Gene delivery may also be viral or non viral |
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What are the characteristics of an ideal vector for gene therapy?
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Safe
Sufficient capacity for size of therapeutic DNA Non-Immunogenic Allow re-administration Ease of manipulation Efficient introduction into target cells/tissues Efficient and appropriate regulation of expression Level, tissue specificity, transient, stable? |
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What are the non viral methods of gene delivery? Why are non viral methods difficult?
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Microinjection, electroporation, or complexing with a carrier (liposomes, cationic lipids). It's difficult because naked DNA or RNA cant enter cells!
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What is a viral vector?
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A virus that has been adapted to serve in gene delivery. They include retroviruses, adenoviruses, lentiviruses, and adeno-associated viruses (AAV)
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How can you use in vivo viral gene therapy to cure a mouse with muscular dystrophy?
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Create viral vectors with the dystrophin gene. Inject the virus into the mouse. Muscle cells pick up the DNA, incorporate it into their genome, and can produce dystrophin.
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How and why did gene therapy for hemophilia B (AAV vector used in liver cells) fail? How will future studies remedy this problem?
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Some patients treated with gene therapy produced factor IV and normal levels, but only transiently. Eventually, the patient's immune response destroyed the liver cells containing the therapeutic gene. In future studies, patients will be given immunosuppressive treatment to prevent the destruction of these cells.
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Are there risks associated with viral gene therapy?
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Yes. One patient received high doses of the virus, had a massive infammatory response, and died a few days later.
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Are problems in bone marrow treated without gene therapy?
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You can do a bone marrow transplant with healthy cells, say from a brother or sister.
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What is a complication of bone marrow transplants from relatives?
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Graft Versus Host disease, where the body rejects the new tissue
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How can you restore hematopoietic stem cells without facing the complications of graft versus host disease?
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Take out the patients own hematopoietic stem cells, fix the genetic defect, then reimplant it in the patient
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How do retroviral vectors work in gene therapy?
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Take the retrovirus RNA, replace the proliferation genes with your gene of interest, and let it integrate into your patient's tissues. This way it doesn't spread, but still let's your gene of interest incorporate into your patient's genome.
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What is SCID? What gene mutation is associated with SCID? Can ADA enzyme function be restored with gene therapy?
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SCID, severe combined immuno deficiency, or bubble boy disease, is a syndrome where infants are born without a functioning immune system (they lack all lymphocytes and suffer from opportunistic infections). The ADA gene, which codes for a protein required for immune cell survival. It appears that the enzyme can be restored with gene therapy, over time.
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Was gene therapy for XSCID patients successful? How is the gene therapy technique being modified?
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Gene therapy treatment for XSCID restored most of the patient's immunes systems. However, 1/4 of patients developed a leukemia-like disorder in 2-3 years. This is due to the potent retrovirus promoter activating oncogenes. Future studies will attempt using a less powerful promoter.
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What is a current treatment of sickle cell disease? What would gene therapy treatment involve?
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The current treatment is transplanting HSC from a healthy individual to the patient. Gene therapy would involve inserting an "anti-sickling" gene, as seen in fetal hemoglobin, into patient HSC genome
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What is the molecular basis of sickle cell disease?
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An amino acid substitution, caused by a point mutation, resulting in the polymerization of hemoglobin and the cells to develop a "sickle" shape
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How do sickle cell patients with higher amount of fetal hemoglobin levels compare to those with lower amount of fetal hemoglobin?
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Patients with fetal hemoglobin live longer and less severe symptoms
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What genetic factors affect susceptibility to HIV? What happened with the HIV patient who received a bone marrow transplant from a CCR5 mutation donor?
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The CCR5 receptor protein is an important cellular protein involved in the initial step of HIV infection. When this protein is mutated, susceptibility to HIV is decreased. For the patient who received a bone marrow transplant, the HIV became undetectable
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What gene therapy treatments are available for HIV patients?
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Inserting a gene for an inhibitory RNA gene, which interferes with CC35 protein translation.
Introducing a double strand break in DNA using gene-specific zinc finger nucleases, and letting the cell repair the DNA imperfectly, which disrupts the CCR5 gene |
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What gene therapy treatments are available to cancer patients?
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T cells recognize and attack tumor cells based on recognition of foreign surface proteins. Take the T cell receptor genes from a patient who has beaten cancer and insert them into a cancer patient to re engineer their immune system.
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What is one mechanism of gene repair?
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Introducing a double stranded break using zinc finger endonucleases, then relying on homologous recombination to repair the gene
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What are some advantages gene correction has over gene addition?
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In gene correction, the therapeutic gene is already in the normal location, so expression should be normal. It also avoids problems of genes inserting semi-randomly throughout the genome, which may lead to activation of nearby genes.
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How can gene therapy be used to generate healthy patient HSCs from a skin biopsy, per se?
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Tissue samples, such as a skin biopsy, can be taken from a patient. Gene addition or correction is done to this cell. It is then de-differentiated to a pluripotent stem cell, which can then be differentiated into a HSC. The HSC is now transplanted into the patient.
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