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Microbiology > Viruses II: Animal Viruses > Flashcards

Viruses II: Animal Viruses Flashcards

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Biology 101 flashcards
1
Q

What is an animal virus

A

A virus that infects eukaryotic

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2
Q

Five-steps infection

A
  1. Attachment
  2. Penetration and Uncoating
  3. Synthesis
  4. Assembly
  5. Release
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3
Q

Attachment of animal viruses (step one)

A
  • Bind to receptors on the plasma membrane

- Specific receptors required

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4
Q

Through what structure do animal viruses attach to the host cell

A

Spikes

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5
Q

What are the two methods of penetration and uncoating (step 2)

A
  1. Fusion

2. Endocytosis

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6
Q

T/F uncoating is specific to animal viruses

A

True, anything specific to animal viruses can be used as a target for antiviral drugs

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7
Q

What is the basic definition of uncoating

A

removal of the capsid, allows DNA or RNA to enter into the host cell cytoplasm.

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8
Q

T/F Naked virus can use either endocytosis or fusion

A

False, cannot use fusion process for entry since the envelope is required

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9
Q

Fusion definition

A

The entire nucleocapsid enters the cell, not just the RNA/DNA

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10
Q

Endocytosis definition

A

Human cell membrane grows around the entire virus, engulfing the entire virus and taken inside with the receptors in the form of a vesicle

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11
Q

Steps of fusion (5)

A
  1. Adsorption: spikes of virion attach to specific host cell receptors
  2. Membrane fusion- envelope of virion fuses with plasma membrane
  3. Nucleocapsid released into cytoplasm- Viral membrane remains part of the plasma membrane
  4. Uncoating- nucleic acid separates from capsid
  5. Fusion of virion and host cell membrane
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12
Q

Steps of Endocytosis (4)

A
  1. Adsorption- attachment to receptors triggers step 2
  2. Endocytosis- Plasma membrane surrounds the virion forming an endocytic vesicle
  3. Release of vesicle- envelope of virion fuses with the endosomal membrane
  4. Uncoating- nucleic acid separates from capsid
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13
Q

Synthesis (step 3) basics

A
  • the viral genome is duplicated
  • some enzymes from the host, some carry their own
  • synthesis of multiple copies of viral genome
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14
Q

What are the three general replication strategies used in synthesis step

A
  1. DNA viruses
  2. RNA viruses
  3. Reverse Transcribing viruses
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15
Q

Replication of DNA viruses (step 3)

A
  • In nucleus

- DNA polymerase (enzyme) is found in the nucleus

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16
Q

Replication of RNA viruses (step 3)

A
  • majority ss-RNA
  • in cytoplasm
  • Requires virally encoded RNA polymerase (replicase)
    • comes from virus typically
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17
Q

What is the difference between +/- RNA

A

+ RNA can be used as mRNA to make proteins

-RNA cannot be directly used as mRNA

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18
Q

What is the importance of the RNA polymerase (replicase) for replication of RNA viruses

A

Lacks proofreading ability which could cause antigenic drift

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19
Q

What is antigenic drift

A

the mistakes made in replication and cannot correct these mistakes, causes the emergence of a new strain of virus because of mistakes made.

Drift away from the original strain. Ex. Influenza virus

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20
Q

Replication of reverse-transcribing viruses (step 3) (4 points)

A
  • Encode reverse transcriptase which makes DNA from RNA
  • synthesizes single strand DNA
  • Complementary strand is synthesized
  • dsDNA is integrated into the host cell chromosome as either productive or latent
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21
Q

T/F Retroviruses have ss (-) RNA genome

A

False, retroviruses like HIV have ss (+) RNA which they can directly use as mRNA to make proteins

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22
Q

What is the enzyme involved in the replication of reverse-transcribing viruses

A

reverse transcriptase

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23
Q

Assembly (step 4)

A
  • Protein capsid forms; genome packaged

- Needed to make a mature virion

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24
Q

What are the two options for release of an animal virus and which is more common?

A 
1 Budding (more common)
2. Apoptosis
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25
Q

What is the mechanism for budding

A

The viral spike proteins that are embedded into the host membrane where the assembled nuclear capsid attaches resulting in the formation of the bud

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26
Q

What is a way that the budding process can be affected by antiviral drugs?

A

The release of the virus can be blocked by getting rid of the enzyme needed to produce the budding process

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27
Q

Budding extrusion process

A
  • viral proteins insert into host cell membrane and the nucleocapsids are extruded
  • Covered with lipid envelope
28
Q

What is the source of the lipid envelope in the budding process and what makes it different from the host cells membrane

A
  • It can obtained the envelope from organelles
  • Also from the lipid layer from the host cell membrane, still different from host cells by the presence of spike proteins
29
Q

How are naked viruses released?

A
  • When the cell dies, often by apoptosis

- Initiated by either the virus of the host

30
Q

How does the human immune cells tell a difference from viruses and host cells

A

By the presence of the spikes since the lipid membrane is identical

31
Q

H1N1, what does the N stand for

A

The type of enzyme (nueroimidase) needed to release the capsid

32
Q

What are the two categories of animal viruses?

A
  1. Acute

2. Persistant

33
Q

What are two examples of persistent infections

A
  1. Chronic

2. Latent

34
Q

Describe an acute infection

A
  • rapid onset
  • short duration
  • Virus reaches the maximum level at the peak
  • As the curve increases (chart) the virus is multiplying
35
Q

T/F if you recover from an acute infection, you will have long-lasting immunity

A

True

36
Q

Describe a persistant infection

A
  • Continue for years of lifetime
  • May or may not have symptoms
  • Some viruses exhibit both chronic and latent infections (HIV)
37
Q

T/F in a chronic infection, the viruses are continuously increasing

A

False, the viruses are not increasing in number, but there is steady production in low numbers

38
Q

What is the state of virus in a chronic infection

A

After the initial infection with or without disease symptoms, infectious virus is released from host with no symptoms

39
Q

What is the state of virus in a latent infection

A

After initial infection, virus is maintained in neurons in non-infectious state. Virus is activated to produce new disease symptoms
-cannot be eliminated and can later be reactivated

40
Q

What is the example of a latent infection

A
  • Chicken pox and reoccurrence of shingles

- Cold sores

41
Q

What are examples of chronic infections from the chart

A

Hep B, Hep C

42
Q

What are examples of latent infections from the chart

A
  • Herpes simplex virus type 2
  • Vericella zoster (chx pox and shingles)
  • Epstein Barr virus
43
Q

What is the importance of viral oncogenes

A
  • can interfere with host control mechanisms, thus inducing tumors
  • When viruses introduced these viral oncogenes to the human cell, its function is compromised, interfering with the proper growth of that cell
    ex. HPV
44
Q

What have been the methods used to cultivate and quantify animal viruses

A
  1. Historically- inoculated live animals
  2. Embryonated (fertilized) chicken eggs * most common method
  3. Cell culture or tissue culture
45
Q

T/F Viruses grow in an artificial medium

A

False, they must be grown in the appropriate host

46
Q

Cell culture/ tissue culture method and drawbacks

A
  • can process animal tissues to obtain primary cultures
  • A virus can be so specific that it can’t be grown in chicken eggs or animal livers, need human liver cells
  • Drawback: cells divide only limited number of times
47
Q

Why are tumor cells often used to cultivate animal viruses

A

-they multiply indefinitely, considered immortal (HeLa)

48
Q

True/False: Viruses multiply only inside living cells

A

True

49
Q

Which are easier to cultivate host cells to grow virus, bacteria or animal host cells

A

Bacterial host cells

50
Q

What is the purpose of a plaque assay

A

used to quanitate phage particles in samples

51
Q

Describe the process of use of a plaque assay

A
  • soft agar inoculated with bacterial host and specimen
  • poured over the surface of agar in Petri dish
  • Bacterial lawn forms
  • continuing plaque forming units (PFU) yields titer
52
Q

What is a plaque

A

zones of clearing from bacterial lysis, circles will be the clearings and blue will be considered the growth the bacteria

53
Q

Viroids- description and structure

A
  • small single-stranded RNA molecules
  • 246-375 nucleotides long
  • 1/10th the size of the smallest RNA virus
54
Q

What are viroids resistant to that typical RNA isn’t

A

very resistant to heat and RNAase, so not easily destroyed

55
Q

Where are viroids typically found

A
  • only found in plants enter though their wound sites
  • typically found in tomatoes or peaches
  • also causes the potato spindle disease
56
Q

T/F humans and animals van be infected by viroids

A

Somewhat false, we don’t know if they can or not

57
Q

What does the name prion stand for

A

proteinaceous infectious agents

58
Q

What are prions made of

A

solely proteins

-made up of the same amino acids that ours are made of

59
Q

T/F prions do not contain nucleic acids

A

True

60
Q

What are the basics of diseases caused by prions

A
  • linked to slow, fatal human diseases and animal diseases

- Usually transmissible only within species

61
Q

Where do prion proteins accumulate and what happens

A
  • Accumulate in the neural tissues
  • Neurons die
  • Tissues develop holes
  • Brain function deteriorates
62
Q

What is the general term for all prion diseases and how did this term come up

A

The characteristic appearance gave them the name ‘transmissible spongiform encephalopathies’

63
Q

Is there any treatment for prion diseases

A

No

64
Q

What is the reason that prion proteins can’t denature

A

their unusual folding patterns

65
Q

Describe the effects on infectious prion proteins on the normal form

A
  • PrP(c) is the normal prion protein form that is cellular
  • PrP(SC) is the infectious prion protein, scrapie
  • hypothesized that PrP(SC) converts PrP(C) folding to the PrP(SC) form
  • the prion protein will bind to the normal protein and induce the misfolding in the normal protein
  • eventually makes the normal proteins unfunctionable
66
Q

What is specific to the PrP(SC) infectious prion

A
  • Resistant to proteases; become insoluble and aggregate

- Unusually resistant to heat and chemical treatments

Microbiology (7 decks)

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