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S2 Case 3 - asthma & COPD > Gene Therapy > Flashcards

Gene Therapy Flashcards

1
Q

What is gene therapy?

A

Use of nucleic acid polymers as a drug to treat disease by therapeutic delivery into the cells of a patient

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2
Q

When does reverse transcription occur?

A

Used by virus
RNA virus
Specialised enzymes convert back to DNA

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3
Q

What are the gene therapy approaches?

A

Replace non-functional gene
Swap abnormal gene
Selective reverse mutation
Gene regulation

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4
Q

What are the methods of vector delivery?

A

In vivo
Ex vivo

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5
Q

What is in vivo?

A

Directly into the body

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6
Q

What is ex vivo?

A

Cell type taken out + modified then put back into the body

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7
Q

What are the choices of gene delivery vectors?

A

Viral
Non-viral

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8
Q

What are examples of viral vectors?

A

Retrovirus
Adenovirus
Adeno-associated virus
Herpes simplex virus

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9
Q

What are examples of non-viral vectors?

A

Liposome
DNA-polymer conjugates
Naked DNA

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10
Q

What characteristics would an ideal vector system have?

A

Undetectable by immune system
Non-inflammatory
Safe
Efficiency sufficient
Long duration of expression

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11
Q

What is the objective of non-viral gene therapy?

A

Insertion of normal gene to replace abnormal

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12
Q

Describe the non-viral approach: direct delivery

A

Direct introduction of DNA into target cells
Restriction to certain tissues
Large amount of DNA required

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13
Q

How is non-viral direct approach done?

A

Electroporation = electric charge across membranes = open up
Sonoporation = sound waves
Magnetofection = magnets change the charge

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14
Q

What are the pro of non-viral gene therapy?

A

Possible to work with large pieces of DNA
Non-toxic
No immune response

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15
Q

What are the cons of non-viral gene therapy?

A

Inefficient
Limited to accessible cells

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16
Q

What is a liposome?
Non-viral vectors

A

Artificial lipid sphere with aqueous core, carrying therapeutic DNA
= can pass through membrane + deliver gene

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17
Q

What is receptor-mediated endocytosis?
Non-viral vectors

A

DNA molecule encapsulated in delivery device
Then endocytosed into cell

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18
Q

Describe the viral approach of gene therapy

A

Carrier molecule (vector) used to deliver DNA
Viruses

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19
Q

What happens to the virus in viral approach of gene therapy?

A

Virus genome modified to deliver therapeutic gene

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20
Q

What are the requirements for viral vector?

A

Cell-specific
Immune evasion
Non-immunogenic
Safe
Express for long as required

21
Q

Describe retroviral vectors

A

Creates DNA via reverse transcription
DNA integrates into host chromosome via integrase

22
Q

What are the advantages of retroviral vectors?

A

Long term expression
Low toxicity
High capacity
Low immunity allowing repeat administration

23
Q

What are the problems of retroviral vectors?

A

Lack of cell specificity
Only infect dividing cells

24
Q

What is an example of retroviral vectors?

A

Treat CF by injections directly into bronchial lining

25
Q

What are X-SCID patients?

A

Immuno deficiency

26
Q

What happens to patients with X-SCID?

A

Cannot make T lymphocytes their B lymphocytes fail to make essential Abs for fighting infections

27
Q

What do X-SCID patients need?

A

Bone marrow transfer

28
Q

What is X-SCID caused by?

A

Mutations in X-linked gene

29
Q

Describe gene therapy of X-SCID patients

A

Stem cells taken out
Genetically manipulated
Put back into patient
= express T + B cells
Gene therapy via injection of retrovirally transduced stem cells

30
Q

Describe adenoviral vectors

A

Viruses with dsDNA genome = double stranded
Remains in episome in cells
DNA transcribed

31
Q

Why are adenoviral vectors widely used in gene therapy?

A

High transfection efficiencies
Large quantities possible

32
Q

What are the cons of adenoviral vectors?

A

More likely to be attacked by immune system
Trigger inflammatory response = NO repeat administration

33
Q

Describe adeno-associated vectors (AAVs)

A

ssDNA = single stranded
DNA integrates into single site
Infect many cell types

34
Q

What are the pros of AAVs?

A

Non-toxic
Don’t trigger immune response
NO inflammation

35
Q

What are the disadvantages of AVVs?

A

Small = carry only 2 genes
Difficult to make in large quantities

36
Q

Describe herpes simplex viral (HSV) vectors

A

Gene transfer in nervous system

37
Q

What are the advantages of HSV vectors?

A

Large genome = larger genes
Infect wide range of tissues

38
Q

What are the disadvantages of HSV vectors?

A

Relatively untested
Stigma due to “herpes”

39
Q

What are the disadvantages of gene therapy?

A

Short-lived nature
Immune response
Viral vectors = toxicity, immune response
Multi-gene disorders = difficult to treat
Insertional mutagenesis

40
Q

What is insertional mutagenesis?

A

Virus may target wrong cells

41
Q

What is Glybera?

A

Treatment for lipoprotein lipase deficiency
Introduce normal, healthy LPL gene

42
Q

What is CF?

A

Autosomal recessive disease

43
Q

Why is CF an ideal candidate for gene therapy?

A

Single gene defect
Recessive condition
Main pathology = lung = accessible
Progressive = at birth normal phenotype

44
Q

What does gene delivery for CF involve?

A

Large vol of vector-containing fluid to lung via the nose

45
Q

What is the problem with gene delivery for CF?

A

Safety problems = aspiration
Large vol = enhanced alveolar exposure

46
Q

What is another way for gene delivery for CF?

A

Oral inhalation of corticosteroid

47
Q

What is the problem with oral inhalation for gene delivery for CF?

A

Small particles enhance delivery to peripheral airways
= undesirable for gene vector delivery
= adverse effects

48
Q

What is success of CF gene delivery restricted by?

A

Airways well defended

49
Q

How does the covid-19 vaccine work?

A

Raise immune response to spike protein
mRNA in liposome then injected into patient
= encode for spike protein
mRNA degraded = NOT long lasting in genome

S2 Case 3 - asthma & COPD (25 decks)

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