Gene therapy

Question 1

What is gene therapy?

Answer 1

novel approach to teating diseases baseed on modifying the expression of a person’s genes toward a therapeutic goal

Question 2

What is somatic gene therapy?

Answer 2

involves the manipulation of gene expression in cells so as to be corrective for the patient, but this correction is not inherited by the next generation

Question 3

What is germline gene therapy?

Answer 3

involves genetic modification of germ cells that will pass the seleccted change on to the next generation

Question 4

What is required for gene identification and cloning?

Answer 4

must have identified the gene (genes) responsible for a particular disease state and have demonstrated concordance of disease state with a defect in the particular gene or gene product

Question 5

What is the first task of any gene therapy strategy?

Answer 5

delivery of genetic material to the appropriate cells of patients in a way that is specific, efficient and safe

Question 6

What is an ex vivo strategy of gene therapy?

Answer 6

cells are removed from the body and treated with a gene vector that take up the selected gene then reintroduced back into the body

Question 7

What is the in vivo strategy for gene therapy?

Answer 7

direct injection of viral vector into the body

Question 8

What was the first ex vivo gene therapy trial used?

Answer 8

ADA deficiency

Question 9

What was the first in vivo gene therapy used to treat?

Answer 9

treat cystic fibrosis

Question 10

What are the most widely used indications for gene therapy?

Answer 10

cancer

genetic deficiencies (LPL deficiency)

viral infections

autoimmunity

diseases in which several genes and environment interact

Question 11

What is the therapeutic strategy for gene therapy applications?

Answer 11

vector carries a gene that encodes a protein that is either defective or that is not present due to mutation(s) in the patients’ endogenous gene(s)

Question 12

What is the cytolytic strategy for gene therapy applications?

Answer 12

vector is designed to destroy or eliminate a diseased cell or tissue

example=> virus carrying the gene for thymidine kinase from herpes simplex virus

Question 13

What is the drawback from the cytolytic strategy?

Answer 13

difficulty in targeting the specific cell

Question 14

Delivery of gene therapy requires vectors. What are the most important factors?

Answer 14

most vectors are based on attenuated or modified versions of viruses => challenge to remove the disease-causing components of virus and insert recombinant gene

utiliz non-viral vectors => a) liposome transfection, b) gene gun technology

Question 15

What is important about controlling gene expression?

Answer 15

making the correct amount of therapeutic protein at the right time

maintaining long-term expression of the gene

Question 16

What is important wrt the host immune response and gene therapy?

Answer 16

use of vectors that give minimal or no adverse immune resonses

ability to give multiple doses of vector

Question 17

For vector systems, what are the properties of adenovirus?

Answer 17

episomal

high transduction effeciency

infects replicating and non-replicating cells

elicits an immune response

insert capacity 8-36kb

Question 18

What are the properties for adeno-associated virus vectors?

Answer 18

integrates genome into specific region on human chromosome 19

low immunogenicity

no associated disease

infects dividing and non-dividing cells

limited insert capapcity of 5kb

Question 19

What are properites of herpesvirus vector?

Answer 19

large insert capacity

broad host range

infects dividing and non-dividing cells

Question 20

What is the liposomes/naked DNA virus vector?

Answer 20

no liit to size of genes that can be delivered

low immunogenicity

poor levels of gene transfer

Question 21

What is the properties of the retrovirus vector?

Answer 21

non-pathogenic in humans

stably transduces dividing but not non-dividing cells

inserts genome into host cell’s DNA

long term expression

insert capacity of 8kb

inactivated by human complement

Question 22

How is a retrovirus used?

Answer 22

1. reverse transcriptase codes RNA back to DNA
2. integrase integrates DNA into host chromosome

only dividing cells

Question 23

How is a adenovirus used?

Answer 23

is uses DNA but does not integrate into the host chromosome

both dividing and non dividing cells

Question 24

How do you make a retroviral vectors?

Answer 24

insert packaging signal in viral genome (virus must be killed after delivery)

gene is placed on a plasmid onto a packaging cell line to finally get a producer cell

Question 25

what are the most used viral vectors?

Answer 25

adeno virus and retroviruses

Question 26

What are the steps to initiate a gene therapy trial?

Answer 26

involves internal institutional reviews

external government reviews

Question 27

What are problems that must be solved before gene therapy can be used?

Answer 27

avoid immune response in patient (inflammation or Abs)

get genes into non-diving cells like liver, muscle, neurons

get gene integrated so that it will be replicated and expressed indefinitely as needed

Question 28

Describe adeno-associated virus (AAV)

Answer 28

often found in cells that are simultaneously infected with adenovirus

generally harmless

Question 29

What are the main ways that AAV is not like adenovirus?

Answer 29

does not stimulate inflammation in host

does not elicit Abs against itself

integrates ssuccessfully into one spot in genome of host (chromosome 19 in humans)

can enter non-dividing cells

Question 30

What are factors influencing future development of gene therapy?

Answer 30

optimizing vector safety to reduce adverse event risks

overcoming the technlogical obstables

analysis of human genome

expansion of diagnostic industry

public acceptance of gene therapy