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25 Cards in this Set

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Germ-line Genetic Therapy
Genetic manipulation of germinal or reproductive cells
Therapeutic effect is permanent and transmissable.
Somatic Gene Therapy
Insertion of genes into diploid cells of an individual where the genetic material is not passed to its progeny
Modifies specific cells or tissues
Ex vivo Delivery
Transfer of genetic material into cells outside of body and then re-implanted
Advantanges of Ex vivo delivery
Lack of Immune Response
Enhanced efficacy of vector delivery in vitro
Disadvatages to Ex vivo delivery
A small number of re-implanted cells remain viable (applicable to some diseases)
In situ delivery
Administering genetic material directly to the desired tissue when cells cannot be easily removed or reimplanted (brain cell)
Advantages to In situ delivery
Effective Targeting
Disadvantages to In situ delivery
Low efficiency of transduction
In vivo delivery
Genetic material is administered systemically
Advantages to in vivo delivery
Potentially the most useful
Disadvantages to In vivo delivery
Insufficient targting (prepared outside the body and the liver elimates most material on first pass)
Retroviral Vectors
Most widely used delivery vehicles
Relatively nonpathogenenic (exceptions include HIV)
Use RNA as their genetic material
Can infect a variety of cells and can integrate their genome into a single RANDOM site (possible to develop side effects since you can't specify where you want it to go)
Integration is only possible in dividing cells since membrane is permeable during cell division
-Can incorporate about 8kb of transgene DNA
Advantages to Retroviral Vectors
Stable and efficient integration into the genome
Disadvantages to Retroviral Vectors
Integrate randomly into the host genome possibly near a proto-oncogene leading to tumor formation
Difficult to produce in high concentrations
Induce an immune response
Adenoviruses
Most common DNA virus used for gene therapy
Target both dividing and nondividing cells but unable to integrate into host genome.
Do not produce serious illnesses
Can cause upper respiratory tract infections
Virus is eliminated from nucleus over time -->repeated dosing in necessary
-Most have a transgene capacity of 7kb newer versions can hold 35kb "gutless or pseudo"
Advantages of Adenoviral Vectors
They can produce a high titer of purified particles
Can infect a variety of cells
Especially good for lung cells and have ben used to treat cystic fibrosis
Disadvantages of Adenoviral Vectors
Highly immunogenenic which limits their repeated dosing
Adeno-Associated Viral Vectors (AAV)
No known pathogeneic effect on humans
Single stranded DNA - need an adeno or herpes helper virus to replicate
Integrates on a chromosome 19q with no noticeable effects on other genes
Weak immunogens in most tissues
Advantages to AAV's
Selective integration into host genome and no risk of insertional mutagenesis
Long-term expression
Disadvantages to AAV's
The production of the viral partilces is a complicated process
Limited capacity
Lentiviruses
Specialized retroviruses that can infect both dividing and nondividing cells
Integrate into host genome at a random site
Human HIV is the basis for most lentiviral vectors
Advantages to Lentiviruses
Long-term expression
Infection of nondividing cells
Disadvantage to Lentiviruses
Risk of insertional mutagenesis
Herpes Simplex Viral Vectors (HSV)
Complex, double stranded DNA viruses
Viral genome does not integrate into host genome
Can establish life long latency in sensory ganglia
Advantages to HSV Vectors
Specially suited for CNS treatment due to long term expression
Can express large transgenes
No risk of insertional mutagenesis