540 - Drug Delivery Systems - Exam Iv - Gene Therapy

Front 1

Describe what is meant by "Gene Therapy."

Back 1

Gene Therapy is the treatment or prevention of disease by gene transfer. This may entail, for instance, the replacement of missing or altered genes with healthy genes, or the inserting genes into cancer cells in order to make them more sensitive to chemotherapy, radiation therapy, or other treatments.

Front 2

Describe the mechanism through which "suicide genes," introduced into a patient's cancer cells, are utilized.

Back 2

The "suicide gene" encodes enzymes capable of activating a prodrug to create a toxic product that causes targeted death.

Front 3

What are the advantages of adenovirus vectors?

Back 3

Wild-type infections are common and have low pathogenicity in humans; moderate efficiency but high titers (>10^12) yield high tranduction rates; broad host and cell range; insert (no more than 30 kb for gutless vectors)

Front 4

What are the disadvantages of adenovirus vectors?

Back 4

Inflammatory cellular immune response triggered by low-level viral protein expression and/or antigenic processing of viral proteins; transient expression due to destruction of transduced cells; limited DNA insert capacity (no more than 8 kb) for 1st and 2nd generation vectors

Front 5

What are the advantages of AAV vectors?

Back 5

Non-cytotoxic and non-immunogenic; stable transduction with long-term expression; potential for site-specific integration; small size facilitates spread and distribution within the brain; broad host and cell range

Front 6

What are the disadvantages of AAV vectors?

Back 6

High viral vector titers possible but this makes packaging difficult; potential for random integration; very limited DNA insert capacity (no more than 5 kb)

Front 7

What are the advantages of HSV vectors?

Back 7

Indefinite presistence in latent state as circular episomal molecule; broad host range; large DNA insert capacity

Front 8

What are the disadvantages of HSV vectors?

Back 8

Cytotoxicity and immunogenecity due to antigenic processing or low-level protein expression in recombinant vectors; potential reactivation of latent HSV-1; contaminated stocks and/or reversion to wild-type virus might lead to HSV-1-induced encephalitis and death

Front 9

What are the advantages of retrovirus vectors?

Back 9

Low pathogenicity in humans; stable long-term expression; useful for ex vivo gene therapy; selective transduction for dividing cells enables brain tumors to be targeted; moderate insert capacity; broad host cell range

Front 10

What are the disadvantages of retrovirus vectors?

Back 10

Risk of insertional mutagenesis and oncogenic transformation due to random integration into host genome; low titers; requirement for mitosis is order to integrate and achieve stable expression precludes use for most CNS applications

Front 11

What are the advantages of lentiviral vectors?

Back 11

Ability to transduce post-mitotic cells; pseudotyped vectors can show strong neuronal tropism; efficient transduction and stable long-term expression; moderate insert capacity

Front 12

What are the disadvantages of lentiviral vectors?

Back 12

Concerns over safety with HIV-derived lentiviral vectors; risk of insertional mutagenesis and oncogenic transformation due to random integration; potential reversion to wild-type virus; low titers

Front 13

What is Severe Combined Immunodeficiency (SCID)?

Back 13

SCID is a genetic disorder in which both B-cells and T-cells of the adaptive immune system are impaired due to a defect in one of several possible genes.

Front 14

The most common genetic form of SCID became the first human diseae to be successfully treated by gene therapy. What form is it and how does it the production of natural killer cells, T-cells, and B-cells?

Back 14

X-linked SCID is the most common form. Patients having X-linked SCID do not make natural killer cells or T-cells and their B-cells are functionally impaired due to a faulty IL2RG gene that encoded interleukin 2 receptor gamma chain.

Front 15

Describe the gene therapy utilized to treat infants having X-linked SCID.

Back 15

Infants with X-linked SCID receive an infusion of autologous bone marrow cells corrected by IL2RG gene transfer via retroviral vectors.

Front 16

What complication is associated with the gene therapy used to treat infants having X-linked SCID?

Back 16

2 of 10 children later develop leukemia about 2.5 to 3 yrs later due to random integration of the gene and uncontrolled proliferation of mature T cells.

Front 17

What major problems must scientists overcome before gene therapy becomes a common technique for treating diseases?

Back 17

The problems associated with gene therapy relate to precision, efficiency, specificity. In other words, the ideal vector will consistently deliver the gene to a precise location in the patient's DNA in every specifically targeted cell throughout the body.

Front 18

List three advantages of Viral Gene Delivery.

Back 18

1) Highly Efficient, 2) Built in Targeting, & 3) Long Term Expression

Front 19

List two disadvantages of Viral Gene Delivery.

Back 19

1) Immunogenic / Pathogenic & 2) Expensive / Difficult Production

Front 20

List four advantages of Non-Viral Gene Delivery.

Back 20

1) Nonpathogenic / Nonimmunogenic, 2) Can be made to target, 3) Easy production, & 4) Non-toxic

Front 21

List two disadvantages of Non-Viral Gene Delivery.

Back 21

1) Inefficient Transfection & 2) Transient Expression

Front 22

List seven attrributes of PEG as a biocompatible inert coating of a non-viral gene delivery vehicle.

Back 22

1) Reduced immunogenicity, 2) Reduced interaction with other macromolecules, 3) Prevents particle aggregations, 4) Alters pharmacokinetics, 5) Enhances stability and solubility, 6) Nontoxic and FDA approved, & 7) Available in a range of molecular weights (MW) and functionality

Front 23

List four properties of polyethylenimine (PEI) as a an inert coating of a non-viral gene delivery vehicle.

Back 23

1) Available in a wide variety of MW (molecular weights), 2) Branched or Linear Structures, 3) Polydisperse (contains a wide range of MWs), & 4) Non-biodegradable

Front 24

By what three mechanisms does chloroquine enhance the transfection activity of polyplexes?

Back 24

1) pH buffering of endocytic vesicles, 2) protection of DNA against enzymatic degradation, & 3) displacement of polycations from DNA in the polyplexes

Front 25

Contrast PEI of high and low molecular weights with respect to "efficiency," the complexing of DNA, and cytotoxicity. Which of the two is not biodegradable?

Back 25

High MW PEI is "relatively efficient," while low MW PEI has "low efficiency / transfection." High MW PEI strongly complexes DNA, while low MW PEI complexes DNA poorly. High MW PEI has a cytotoxic IC50 of 15 micrograms/mL, while low MW PEI has, and I quote, an "IC10 > 50 micrograms/mL in C2C12" [Whiskey Tango Foxtrot!!?] High MW PEI is not biodegradable.

Front 26

Which type of vectors, viral or non-viral, have most clinical trials involved?

Back 26

Most clinical trials have involved viral vectors.