Viral Vectors and Gene Therapy - Whitt

Question 1

What is somatic gene therapy?

Answer 1

ivolves the manipulation of gene expression in cells so as to be corrective for the patient, but these corrections will not be inherited by the next generation

Question 2

What is germline therapy?

Answer 2

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

Question 3

What types of gene therapies have been approved in the US for treatment?

Answer 3

none. All gene therapy is currently in various stages of clinical or preclinical trials

Question 4

What are therapeutic strategies?

Answer 4

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

Question 5

What is cytolytic strategy?

Answer 5

vector is designed to destroy or eliminate a diseased cell or tissue. Example shows a virus carrying the gene for thymidine kinase (TK) from herpes simplex virus. Expression of TK converts the prodrug gancyclovir to the toxic product gancyclovir phosphate.

Question 6

What are the steps in development of genetic therapy?

Answer 6

identify the gene or genes responsible for a particular disease state.
Find a way dto deliver the genetic material to the appropriate cells
Find a way to ensure controlled gene expression
Understand the host immune response.

Question 7

What types of vectors are commonly used in gene therapy?

Answer 7

adenovirus, adeno-associated virus, herpesvirus, liposomes/naked DNA, and retroviruses. All of these have distinct advantages and disadvantages

Question 8

What are adeno-associated virus vectors (AAV)?

Answer 8

viruses that infect cells that are simultaneously infected with adenovirus. By themselves harmelss. Do not stimulate inflammation, antibody response, can enter non-dividing cells and integrate successfully into one spot in the genome of host.

Question 9

What do most of the current gene therapy trials focus on curing?

Answer 9

majority focus on cancers.

Question 10

What are the properties of adenovirus?

Answer 10

episomal, high transduction efficiency, infects replicating and non-replicating cells, elicits an immune response, insert capacity of 8-36 kb

Question 11

What are the properties of adeno-associated virus?

Answer 11

integrates genome into specific region on chromosome, low immunogenicity, no associated disease, infects both dividing and non-dividing cells, limited insert capacity ~5kb

Question 12

What are the properties of herpesvirus?

Answer 12

large insert capacity, broad host range, infects both dividing and non-dividing cells

Question 13

What are the properties of liposomes/naked DNA?

Answer 13

no size limit of genes, low immunogenicity, poor levels of ene transfer

Question 14

What are the properties of retroviruses?

Answer 14

non-pathogenic in humans, only infect dividing cells, inserts genome into host cells DNA, long term expression, insert capacity of 8kb, inactivated by human complement system

Question 15

Which vectors illicit immune responses?

Answer 15

adenovirus

Question 16

Which vectors can target non-dividing cells?

Answer 16

adenovirus, adeno-associated virus, herpesvirus

Question 17

Which vectors require dividing cells?

Answer 17

retrovirus

Question 18

If you have an exceptionally large gene that needs to be entered, what vector is best?

Answer 18

liposomes/naked DNA because it has no size limit.

Question 19

Do adenoviruses integrate into host chromosome?

Answer 19

no. the therapeutic effects will eventually be lost.

Question 20

Do liposomes integrate into host chromosome?

Answer 20

no

Question 21

How are retrovirus vectors made?

Answer 21

using a producer cell and packaging vectors of virus. virus vectors made lack the ability to replicate so they are one-shot then dead