Gene therapy

Question 1

What is gene replacement?

Answer 1

Replace faulty genes with normal ones, corrects inherited genetic errors.
Adding back or restoring a missing function.
Monogenic diseases e.g cystic fibrosis, haemophilia, X-SCID.

Question 2

What is gene addition?

Answer 2

Deliver genes to provide a new function. Polygenic diseases such as cancer. Add a new ‘gene’:
Gene immunotherapy for cancer.
GDEPT.

Question 3

What is GDEPT? [5]

Answer 3

1. Virus encoding suicide enzyme enters target cell via transduction.
2. Suicide gene expression occurs.
3. Suicide enzyme converts non-toxic prodrug into active toxic drug,
4. Death of transduced tumour cells.
5. Death of neighbouring cells through bystander effects.
   (HSV, Transgene thymidine kinase)

Question 4

What is the perfect vector for gene therapy? [5]

Answer 4

1. Easily and cheaply produced.
2. Targeted
3. High Gene expression
4. Regulation of gene expression
5. No adverse/pathogenic effects.

Question 5

What non-viral vectors exist? [5]

Answer 5

1. Naked DNA
2. Lipoplexes (liposomes/DNA)
3. Polyplexes (polymer/DNA)
4. Lipopolyplexes (liposome/polymer/DNA)
5. Carboplexes (carbon nanotudes/DNA)

Question 6

What are lipoplexes?

Answer 6

Liposomes and DNA

Question 7

What are polyplexes?

Answer 7

Polymers and DNA

Question 8

What are lipopolyplexes?

Answer 8

Liposome/Polymer/DNA

Question 9

What are carboplexes?

Answer 9

Carbon nanotubes and DNA

Question 10

What viral vectors exist?

Answer 10

DNA viruses (adenovirus, adeno-associated, HSV)
RNA viruses (lentivirus, retrovirus.

Question 11

What DNA virus vectors exist?

Answer 11

Adenovirus, Adeno-associated virus, HSV.

Question 12

What RNA virus vectors exist?

Answer 12

Lentivirus, Retrovirus

Question 13

How do RNA viruses function as vectors?

Answer 13

Integrate into host DNA for transgene expression.
Adv: long-term expression of therapeutic gene.
Dis: cancer, disruption of cell cycle regulation.

Question 14

What are the advantages and disadvantages of RNA virus vectors?

Answer 14

Adv: long-term expression of therapeutic genes.
Dis: cancer, disruption to cell cycle regulation.

Question 15

How do DNA viruses function as vectors?

Answer 15

DNA expression without integration into host genome.

Question 16

What are the advantages of DNA virus vector use?

Answer 16

In-vivo.

Dis: short term expression as no integration. Repeated administration is needed. Can provoke immune reaction.

Question 17

What are some licenced gene therapy products?

Answer 17

1. Gendicine
2. H101
3. Glybera

Question 18

What does Gendicine treat?

Answer 18

Replication deficient adenovirus carrying p53.

Question 19

What does H101 treat?

Answer 19

Recombinant oncolytic Adenovirus targeting p53-deficient tumour cells.

Question 20

What does Glybera treat?

Answer 20

Alipogene tiparvovac - Adeno-associated virus delivering the lipoprotein lipase gene.

Question 21

What does Ex Vivo gene therapy involve?

Answer 21

1. Remove faulty cells from patient.
2. Transfect cells with therapeutic gene outside the body.
3. Return cells to the patient.

Question 22

What is In Vivo gene therapy?

Answer 22

Inject the DNA liposome or Recombinant virus etc into the body. Which it then infects cells of the body,

Question 23

What regulations govern the handling of gene therapy in viral vectors?

Answer 23

1. GMO (Contained Use) Regs 2014, HSE.

2. GMO (Deliberate Release) Regs 2002, DEFRA.

Question 24

What do the GMO (Contained Use) Regs 2014, HSE stipulate?

Answer 24

All possible barriers (physical, biological or chemical) are in place to limit contact of the GMOs with humans and the environment,

Question 25

What do the GMO (Deliberate Release) Regs 2002, DEFRA stipulate?

Answer 25

All appropriate measures are taken to avoid damage to the environment from the escape or release from human control of GMOs.

Question 26

What additional regulations apply to gene therapy clinical trials?

Answer 26

The protection of the patient must be the first priority.
Gene Therapy Advisory Committee (GTAC). Est. 1993, Department of Health. UK National research ethics committee (REC) for gene therapy.

Question 27

What is the GTAC?

Answer 27

Gene Therapy Advisory Committee (GTAC). Est. 1993, Department of Health. National research ethics committee (REC) for gene therapy.