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Virology > Chapter 6 > Flashcards

Chapter 6 Flashcards

1
Q

Toxicity

A

Difficult to separate viral metabolism from cellular metabolism

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2
Q

Toxicity example problem: NRTI

A

Nucleoside analogs for HIV treatment

NRTIs lack a 3’-hydroxyl group on the deoxyribose moiety.
As a result, following incorporation of an NRTI, the next incoming deoxynucleotide cannot form the next 5’-3’ phosophodiester bond needed to extend the DNA chain
Thus once an NRTI is incorporated, viral DNA synthesis is halted = chain termination
NOTE: nucleoside analogs are preferentially incorporated by viral reverse transcriptase (compared with host cell DNA polymerase)
PROBLEM: host mitochondria encode their own DNA polymerase, which is not as selective as to which nucleoside it incorporates = toxicity

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3
Q

Current antiviral drugs – approaches by life cycle

A
  1. Before cell entry
  2. During viral synthesis
  3. Assembly
  4. Release
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4
Q

Block Viral Synthesis

A

Reverse transcription
Integrase
Genome replication/protein production

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5
Q

Protein production

A

Nucleic acid based approaches
Oligonucleotides
Ribozymes
RNA interference

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6
Q

Aciclovir

A
  • Effective against HSV and to a lesser extent VZV
  • Prodrug
  • HSV (dsDNA virus) produces a thymidine kinase
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7
Q

Oligonucleotides

A

Decoy oligonucleotides
Antigene inhibition
Antisense inhibition

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8
Q

Decoy Oligonucleotides

A

Copies of viral DNA or RNA regulatory sequences
Compete with viral genome or mRNA for binding -> regulatory protein will bind decoy sequence and be unavailable to bind actual genome or viral mRNA

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9
Q

Antigene Oligonucleotides

A
  • Produce a ssDNA molecule complementary to genomic viral DNA
  • Produces a triple helix
  • Blocks ability for regulatory proteins to bind, and gene transcription
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10
Q

what is Antisense Inhibition

A

Design an RNA molecule that is complementary to the viral mRNA or RNA genome sequence
Binds viral mRNA or genomic RNA -> dsRNA

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11
Q

Innate Immune Stimulants

A
  • Potential for broad-spectrum antiviral therapies

- Type I IFN therapy

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12
Q

what is Innate Immune Stimulants used to treat

A 
Hepatitis B
In combination with a nucleoside analog drug
Hepatitis C
In combination with ribavirin
SARS during Toronto outbreak
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13
Q

4 classes of HIV antivirals (antiretrovirals)

A
  • Reverse transcriptase inhibitors
  • Integrase inhibitors
  • Protease inhibitors
  • Entry inhibitors
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14
Q

Limitations of Antiviral Drugs (3)

A
  1. No broad spectrum antiviral drugs
  2. Many of the drugs can’t cure the infection.
    HIV, herpesviruses, papillomaviruses
  3. Symptoms do not correlate with infection
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15
Q

Beneficial Uses of Viruses

A

Understanding biological systems

  1. Gene therapy
  2. Cancer prevention and control
  3. Control of harmful or damaging organisms
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16
Q
  1. Gene Therapy
A
  • Use genes to treat or prevent disease

- DNA encoding the gene must be packaged within a vector, which is used to get the DNA inside the cell

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17
Q

what are the delivery systems

A

Ex vivo somatic
In vivo somatic
germ line

18
Q

Ex vivo somatic

A

Ex vivo = ‘out of the living’, somatic = non-germ cells

Collect somatic cells from a patient, treat them and reintroduce

19
Q

In vivo somatic

A

Introducing the DNA/vector to the patient, somatic cells altered within patient

20
Q

Germ line

A

Introducing the gene into germ line cells
Allow therapy to be heritable and passed onto later generations
Not currently used for human therapy

21
Q

Approaches

A
  1. Insertion of a functional gene

2. Gene targeting

22
Q

what does Gene targeting

do?

A
  • Can delete a gene, remove exons, add a gene, introduce point mutations
  • Uses homologous recombination or engineered nucleases
23
Q

what are Gene Therapy Vectors

A

non viral or viral therapy vectors

24
Q

Advantages of AAV?

A
  • Low immunogenicity (restricted to generating neutralizing antibodies)
  • Lack of pathogenicity Needs a helper virus to produce infectious particles
  • Integration of gene into a specific site of host genome (AAVS1)
  • Specific to LPD, AAV targets muscle cells, the most important tissue contributing to a healthy LPL protein production
25
Q

3 virus-based strategies to treat or prevent cancer:

A
  1. Vaccines
  2. Oncolytic viruses
  3. Viral vectors for therapeutics
26
Q

Prophylactic (preventive) vaccine

A

Vaccine to prevent infection of a virus that causes cancer
Ex. hepatitis B vaccine (associated with hepatocellular carcinoma)
Ex. human papillomavirus (associated with cervical cancer)
Both subunit vaccines

27
Q

Oncolytic Viruses

A
  • Viruses can preferentially infect and kill cancer cells
  • Are also immunogenic, recruit immune cells to site of infection/cancer cell killing = enhanced anti-tumor immune response
28
Q

what are the two strategies

Oncolytic Viruses

A

Use recombinant DNA technology to engineer tumor selectivity into viruses that are pathogenic to normal cells

Use inherent tumor selectivity of naturally oncolytic viruses
Just beginning to understand how this selectivity works

29
Q

Viral Vectors for Therapeutics

A
  • Using a cancer cell tropic virus to deliver a therapeutic to cancer cells specifically
  • In phase III clinical trials for chemotherapy- resistant metastatic sarcoma, pancreatic cancer, and breast cancer
30
Q

Ex. Rexin-G

A 
Retrovirus core:
Surface proteins that are selective for cancer cells
a dominant negative human G1 cyclin
Arrests cancer cells in G1
Cells die by apoptosis.
31
Q

Virus-mediated Pest Control

A
  • Specificity

- Long-lasting effects

32
Q

Problems with Virus-derived Pest Control

A
  • High specificity
  • Slow effects
  • Environmental stability
  • Viruses don’t like dry, heat
  • pesticide companies
33
Q

Baculoviruses

A
  • Infect insects and other arthropods
  • Can be used to treat butterfly and moth larvae and sawfly larvae infestations
  • Use of the baculovirus-insect cell expression system to produce recombinant proteins
34
Q

Baculoviruses vaccines advantages

A 
post-translational modifications  closer to humans (vs. yeasts)
improved solubility
higher protein yield
could release VLPs
reduced serum sickness  development
less chance of cross-species  infections
35
Q

Capsid/Subunit vaccines diaadvantages

A

Expensive (cell medium, purification
Time consuming (clone gene, transfect cells, wait for protein buildup)
Glycosylation sites are different from those made in human cells

36
Q

Bacteriophage Therapy is

A

Killing a pathogen with its own pathogen

Viruses infecting bacteria
Very target-specific
Most numerous viruses on the earth

37
Q

Bacteriophage Therapy life cycles?

A

Lytic cycle

Lysogenic cycle (latency): phage  genome is integrated into the  bacterial chromosome.
Inserted DNA = prophage
38
Q

Bacteriophage discovered by?

A

Frederick Twort by accident
named by Felix d’Herelle

Made filtrates from the patients’ fecal samples and found that the fecal filtrates inhibited growth of Shigella dysenteriae in vitro

“Phage Therapy”

39
Q

Advantages of Phage Therapy

A
  1. Specificity means less side effects
  2. Using replicating phage means you can use low doses
  3. Phage replicate only at site of infection
  4. Phage are unaffected by antiobiotic resistance
  5. Free of gross toxicity
  6. Simple and fast to manufacture
  7. Can adapt to counter bacterial resistance
40
Q

Disadvantages of Phage Therapy

A
  1. Not accessible for intracellular infections
  2. Need to identify pathogenic bacteria before treatment and ensure it is responsible for disease
  3. Difficult to administer
  4. Limited systemic use  detected by the host immune system
  5. Facilitate horizontal gene transfer between bacteria 
    increased chance of resistance
41
Q

Phage Therapy

A

Use bacteriophage to eliminate bacterial infections

Alternative to antibiotic treatments

Virology (6 decks)

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