10. Gene Therapy

Question 1

Which kind of genes are delivered + their function

Answer 1

• normal genes — to substitute the defective ones;
• abnormal genes — to block excessive replication (HIV)
• protective genes — to block abnormal development of cells with
  malignant potential

Function:
1. integrate in host DNA with stable and long term expression
- side effects: cell death in case they displace an important gene, activation of oncogenes or inactivation of tumor suppressor
2. not integrate
side effect – short term action

Question 2

• Ex and in vivo

- Somatic and germ cell therapy

Answer 2

Ex vivo — removing cells from the body and adding current vectors with therapeutic genes ->Engineered cells contains therapeutic genes are injected in body

In vivo — vector is injected topically to interested tissue

Somatic cell therapy:

• Therapeutic genes are transferred into somatic cells (bone marrow, blood, skin)
• Not inherited in next generations

Germ line cell therapy:

• Therapeutic genes are transferred into germ cells (eggs, sperms)
• Inherited in next generations

Question 3

Therapy involving viral transduction

Most commonly used

Answer 3

1. Cells are removed from patient
2. In the lab virus is altered so that it cannot reproduce
3. A gene is inserted into virus
4. Altered virus is mixed with cells from patient -> cells become genetically altered
5. Injected into patient
6. Genetically altered cells produce desired protein or hormone

Question 4

Gene therapy using adenovirus vector

Answer 4

1. Modified DNA contains new recombinant DNA and viral DNA is injected into vector
2. Vector binds to cell membrane -> endocytosis
3. In the cell vector is packaged into vesicles
4. Vesicles breaks down, releasing the vector
5. Vector injects new gene into nucleus
6. Cell produces protein using new gene

-> used for treatment of tumor cells in cancer therapy

Question 5

Vectors for gene therapy

Answer 5

• viruses (e.g. retrovirus, adenovirus)
• plasmids
• direct delivery/injection of therapeutic genes
• receptor-mediated endocytosis
• DNA packed in liposomes

Question 6

Direct delivery & cell-based Delivery

Answer 6

Direct Delivery:
-> therapeutic gene is packaged into a delivery vehicle such as retrovirus and injected into patient (in target organ)

Cell- based delivery:

1. Isolation and propagation of adult stem cells (in vitro)
2. Genetically modified embryonic cells are added to stem cells (->can block immune reaction from patient)
3. Therapeutic gene (packaged in delivery vehicle/retrovirus) is introduced in stem cells as well
4. Genetically modified cells are reintroduced into patient