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I&I SC1 > Background of virology > Flashcards

Background of virology Flashcards

Lectures: -Week 2, day 1, lecture 1: Introduction, history of virology & viral families -Week 2, day 1, lecture 4: Acute viral infections - comparative pathology -Week 2, day 5, lecture 1: Emerging pathogens & pandemics -Week 3, day 5, lecture 2: Emerging pathogens & pandemics - Arboviruses

1
Q

What is the virome?

A

All the viruses a specific body part carries around (similar to microbiome for bacteria)

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2
Q

What is the definition of a virus?

A

An infectious, obligate intracellular parasite, comprising genetic material (DNA/RNA), often surrounded by a protein coat, sometimes by a membrane

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3
Q

Which two organic stages do viruses have?

A
  1. Virion
  2. Infected cell
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4
Q

What is a virion?

A

An infectious viral particle

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5
Q

True or false: viruses outnumber cellular life

A

True; viruses outnumber cellular life by at least 10:1 -> greatest biodiversity on earth

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6
Q

What are the 5 general steps of the infectious viral cycle?

A
  1. Attachment & entry
  2. Translation
  3. Genome replication
  4. Assembly
  5. Release
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7
Q

What is a (virus-)susceptible cell?

A

A cell that has a functional receptor for a given virus -> only implies viral attachment

This cell may or may not be able to support viral replication

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8
Q

What is a (virus-)resistant cell?

A

A cell without the entry receptor for a specific virus

This cell may or may not be competent to support viral replication

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9
Q

What is a (virus-)permissive cell?

A

A cell that has the capacity to replicate virus

This cell may or may not be susceptible to the virus

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10
Q

How can a virus-permissive cell be brought to produce virus, even when it does not have the required entry receptor?

A

It can be artificially transfected, after which the cellular machinery will produce virus

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11
Q

Which two factors does a cell need to have in order for a virus to be able to infect and replicate in the cell?

A
  1. Susceptibe -> right entry receptor
  2. Permissive -> right cellular machinery for viral replication
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12
Q

How is the infectious cycle often studied?

A

In cell cultures

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13
Q

What is cytopathic effect (CPE)?

A

Viral effects on a cell -> can be used to identify the presence of virus

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14
Q

How can viral infectivity be studied? (2 methods)

A
  1. Plaque assays (for viruses that create plaques)
  2. Endpoint dilution assays (for viruses that do not create plaques)
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15
Q

True or false: all particles produced by a virus-infected cell are infectious

A

False; often a majority of the particles is non-infectious and defective

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16
Q

How can the amount of infectious particles be measured in relation to the total number of particles?

A

Particle/PFU ratio -> total amount of particles/plaque forming units

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17
Q

What are reasons for viral particles to be unsuccesfull in infecting another cell? (3)

A
  1. Damaged particles
  2. Mutations
  3. Complexity of infectious cycle
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18
Q

What is the eclipse period of the infectious cycle?

A

The period in which no (new) viral particles are detected -> intracellular production of viral particles

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19
Q

What is the latent period?

A

The delay between intracellular viral particle production and release of particles

20
Q

What is MOI?

A

Multiplicity of infectious particles added per cell

= number of infected particles added per cell

21
Q

What are techniques that can be used to measure the presence of viral particles? (4)

A
  1. Hemagglutination
  2. Electron microscopy
  3. Viral enzymes
  4. Serology
22
Q

How can hemagluttination be used to measure viral particles?

A

Erythrocytes stick together when infected -> causes hemagluttination

So: hemagluttination shows presence of (infectious) viral particles

23
Q

How can viral enzyme activity be used to determine the presence and amount of viral particles?

A

Metabolism assays can determine the amount of enzyme, which can be extrapolated to the amount of viral particles

24
Q

How can serology be used to show the presence of viral particles?

A

Antibodies are used to label viral antigens -> titre can be determined

25
Q

How can PCR be used to determine the amount of viruses?

A

By limiting the amount of cycles, one can determine the original amount of virus present in a sample

26
Q

What is (+)-mRNA?

A

‘Ribosome ready’ mRNA -> can directly be translated to produce proteins

27
Q

What is (+)-DNA?

A

DNA of equivalent polarity to (+)-RNA

28
Q

What is Baltimore Classification group 1?

A

dsDNA -> can be directly transcribed into mRNA by RNA polymerase

29
Q

What is Baltimore Classification group 2?

A

(+)-ssDNA -> needs to be made into dsDNA before being transcribed

30
Q

What is Baltimore Classification group 3?

A

dsRNA -> have to copy the (-)-strand to produce a complementary (+)-RNA during replication

Need to produce their own RNA-polymerase -> human cells are unable to copy RNA from RNA

31
Q

What is Baltimore Classification group 4?

A

(+)-ssRNA -> needs an (-)-ssRNA intermediate before mRNA is produced

Needs a viral RNA polymerase to produce (+)- and (-)-RNA strands

32
Q

What is Baltimore Classification group 5?

A

(-)-ssRNA -> can directly be translated into (+)-ssRNA

Needs a viral RNA polymerase to produce (+)-RNA

33
Q

What is Baltimore Classification group 6?

A

(+)RNA, which gets copied into (-)-DNA, after which a complementary strand is synthesized

The dsDNA that gets synthesized is integrated into the host genome

34
Q

What is Baltimore Classification group 7?

A

Gapped dsDNA -> strands need to be completed before transcription can occur

35
Q

What is the virosphere?

A

All viruses on earth

36
Q

What is the advantage of DNA genomes over RNA genomes?

A

DNA genomes are stable, can be larger and are less prone to mutation

37
Q

What kind of viruses are most often dsDNA?

A

Bacteriophages

38
Q

How many of the novel (viral) diseases are zoonotic?

39
Q

Why are zoonoses from wildlife more common than from farm animals?

A

We have been co-evolving with our livestock for a long time -> our immune system is (somewhat) adapted to their pathogens
This is not the case for wildlife

40
Q

What are 3 drivers for the emergence of novel infectious diseases?

A
  1. 20-fold growth in wildlife trade over the last 50 years
  2. Enormous amounts of land use of agriculture/animal husbandry
  3. 10-fold growth in global trade over the last 50 years
41
Q

What is orthopathogenesis?

A

Pathogenesis in an animal reservoir

42
Q

What is neopathogenesis?

A

Pathogenesis of viruses in a new host

43
Q

Why would you want to study neopathogenesis (in humans) and compare it with the ortopathogenesis of a virus?

A

Differences between these provide clues about the mechanism for severe disease in humans

44
Q

What are the two possible strategies an organism can use to protect itself from infection?

A
  1. Resistance: detection and elimination of the invading pathogen by the immune system
  2. Tolerance: reduction of negative impacts of infection by tolerating the presence of the pathogen

I&I SC1 (20 decks)

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