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Gene Therapy
Phung Nguyen
Brief Overview
1. What Gene Therapy Is
a. The Different Methods of Gene Therapy
i. Ex vivo: indirect injection
i. Types of tissue removed and process
i. Viral and Non-viral
ii. In vivo: direct injection
1. Viral and Non-Viral
2. Uses and Costs of Gene Therapy
What is Gene Therapy?
• Purpose: treating genetic disorders with the
use of vectors to introduce healthy DNA in a
host with damaged DNA.
Viral
o
Retrovirus
o Murine leukemia virus
o RNA to DNA
o Tends to cause cancer
o
Lentivirus
o Made from more dangerous viruses
o Ebola, HVI, and others.
o Can effect non-dividing cells
o
Adenovirus
o Such as the common cold virsus
o Requires readministration
o
Adeno-associated virus
o Not lethal to human
o Can infect dividing and non-diving cells alike
Adeno-associated virus
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Has not been found to cause illness in humans.
o No immune response from humans
Has been shown to infect chromosome 19 with a 100%
success rate with the help of a rep gene.
o Makes the infection more predictable and lessen
chances of complications
Has a very low uptake frequency
o Usually does not combine with host genome
Needs a helper virus to replicate
o A lysogenic pathway unlikely without that helper virus
Non-Viral
• Naked DNA
o DNA simply goes into cell (much like transformation)
 Safest method but least efficient
• Lipid Carriers
o Genetic information shuttled in a liposome
• Gene Gun
o Genes covered and gold and shot into the body
• Electroporation
o Shock of electricity to cause pores to form in cell
Lipid Carriers (lipoplex)
• Most commonly used are cationic lipids
o Have a positive charge to compact negative DNA
 Forms complex with DNA
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• Lipoplex
Promotes Endocytosis
Protects DNA from degradation
Mechanism of Infection
• Lipoplex
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Enters host cell through Endocytosis
Lipoplex is degraded and DNA is released
DNA is taken up into the nucleus
Recombination occurs and DNA is in genome
• Adeno-associated virus
o Binds to receptors on cell membrane
o Virus particles injected into cell
 (process not fully understood)
o Gene is expressed by host cell
 But usually not taken up into genome
Lipoplex
Cationic lipid
complex with DNA
(Lipoplex)
Adeno-associated virus
Practical Uses and Cost
• Has already been implemented in many
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clinical trials all around the world since 1990.
Has been shown to treat cystic fibrosis,
cancer, arthritis, Parkinson’s, and other
illnesses caused by genetic mishaps.
Cost is not yet known.
o Not readily available to the masses
o Mostly still only seen in clinical trails
 No Bioshock quite yet
o Ethical Cost?
Alternative Methods
• Protein Therapy
oSimply injects needed protein into
patients body
oTemporary Solution
oDifficult to deliver proteins into
cells
Hard to get proteins into cell
The Future of Gene Therapy?
Citations
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Verma, Inder M. and Nikunj Somia. "Gene therapy - promises, problems, and prospects." NATURE 389 (1997): 239-242.
Lovejoy, Katherine. "JYI Volume Five Features: Gene Therapy: Techniques of Cell Transfection." Journal of Young
Investigators. Feb. 2002. Web. 24 Apr. 2012.
<http://www.jyi.org/volumes/volume5/issue5/features/lovejoy.html>.
Miller, Dusty A. and Carol Buttimore. "Redesign of Retrovirus Packaging Cell Lines To Avoid." Molecular and Cellular
Biology 6.8 (1989): 2895-2902.
Clare E. Thomas, Anja Ehrhardt and Mark A. Kay. "PROGRESS AND PROBLEMS WITH THE USE OF VIRAL VECTORS
FOR GENE THERAPY." Nature 4 (2003): 346-359.
T Niidome and L Huang. "Gene Therapy Progress and Prospects: Nonviral Vectors." Nature.com. Nature Publishing Group,
2002. Web. 24 Apr. 2012. <http://www.nature.com/gt/index.html>.
Mueller, C., and T. R. Flotte. "Clinical Gene Therapy Using Recombinant Adeno-associated Virus Vectors." Gene Therapy
15.11 (2008): 858-63. Print.
Carter, B. "Adeno-associated Virus Vectors." Current Biology 2.12 (1992): 644. Print.
Gonçalves, Manuel AFV. "Adeno-associated virus: from defective virus to effective vector." Virology Journal 2.43
(2005): 1-17.
Ghosh, S. "Liver-directed Gene Therapy: Promises, Problems and Prospects at the Turn of the Century." Journal of
Hepatology 32 (2000): 238-52. Print.
Kotin, R. M. "Site-Specific Integration by Adeno-Associated Virus." Proceedings of the National Academy of Sciences 87.6
(1990): 2211-215. Print.
Friedmann, T., and R. Roblin. "Gene Therapy for Human Genetic Disease?" Science 175.4025 (1972): 949-55. Print.
Wagner, Darcy E., and Sarit B. Bhaduri. "Progress and Outlook of Inorganic Nanoparticles for Delivery of Nucleic Acid
Sequences Related to Orthopedic Pathologies: A Review." Tissue Engineering Part B: Reviews (2011): 110906083848008.
Print.