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Viruses II: Animal Viruses 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
What is the mechanism for budding
The viral spike proteins that are embedded into the host membrane where the assembled nuclear capsid attaches resulting in the formation of the bud
26
What is a way that the budding process can be affected by antiviral drugs?
The release of the virus can be blocked by getting rid of the enzyme needed to produce the budding process
27
Budding extrusion process
- viral proteins insert into host cell membrane and the nucleocapsids are extruded - Covered with lipid envelope
28
What is the source of the lipid envelope in the budding process and what makes it different from the host cells membrane
- 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
How are naked viruses released?
- When the cell dies, often by apoptosis | - Initiated by either the virus of the host
30
How does the human immune cells tell a difference from viruses and host cells
By the presence of the spikes since the lipid membrane is identical
31
H1N1, what does the N stand for
The type of enzyme (nueroimidase) needed to release the capsid
32
What are the two categories of animal viruses?
1. Acute | 2. Persistant
33
What are two examples of persistent infections
1. Chronic | 2. Latent
34
Describe an acute infection
- rapid onset - short duration - Virus reaches the maximum level at the peak - As the curve increases (chart) the virus is multiplying
35
T/F if you recover from an acute infection, you will have long-lasting immunity
True
36
Describe a persistant infection
- Continue for years of lifetime - May or may not have symptoms - Some viruses exhibit both chronic and latent infections (HIV)
37
T/F in a chronic infection, the viruses are continuously increasing
False, the viruses are not increasing in number, but there is steady production in low numbers
38
What is the state of virus in a chronic infection
After the initial infection with or without disease symptoms, infectious virus is released from host with no symptoms
39
What is the state of virus in a latent infection
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
What is the example of a latent infection
- Chicken pox and reoccurrence of shingles | - Cold sores
41
What are examples of chronic infections from the chart
Hep B, Hep C
42
What are examples of latent infections from the chart
- Herpes simplex virus type 2 - Vericella zoster (chx pox and shingles) - Epstein Barr virus
43
What is the importance of viral oncogenes
- 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
What have been the methods used to cultivate and quantify animal viruses
1. Historically- inoculated live animals 2. Embryonated (fertilized) chicken eggs * most common method 3. Cell culture or tissue culture
45
T/F Viruses grow in an artificial medium
False, they must be grown in the appropriate host
46
Cell culture/ tissue culture method and drawbacks
- 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
Why are tumor cells often used to cultivate animal viruses
-they multiply indefinitely, considered immortal (HeLa)
48
True/False: Viruses multiply only inside living cells
True
49
Which are easier to cultivate host cells to grow virus, bacteria or animal host cells
Bacterial host cells
50
What is the purpose of a plaque assay
used to quanitate phage particles in samples
51
Describe the process of use of a plaque assay
- 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
What is a plaque
zones of clearing from bacterial lysis, circles will be the clearings and blue will be considered the growth the bacteria
53
Viroids- description and structure
- small single-stranded RNA molecules - 246-375 nucleotides long - 1/10th the size of the smallest RNA virus
54
What are viroids resistant to that typical RNA isn't
very resistant to heat and RNAase, so not easily destroyed
55
Where are viroids typically found
- only found in plants enter though their wound sites - typically found in tomatoes or peaches - also causes the potato spindle disease
56
T/F humans and animals van be infected by viroids
Somewhat false, we don't know if they can or not
57
What does the name prion stand for
proteinaceous infectious agents
58
What are prions made of
solely proteins | -made up of the same amino acids that ours are made of
59
T/F prions do not contain nucleic acids
True
60
What are the basics of diseases caused by prions
- linked to slow, fatal human diseases and animal diseases | - Usually transmissible only within species
61
Where do prion proteins accumulate and what happens
- Accumulate in the neural tissues - Neurons die - Tissues develop holes - Brain function deteriorates
62
What is the general term for all prion diseases and how did this term come up
The characteristic appearance gave them the name 'transmissible spongiform encephalopathies'
63
Is there any treatment for prion diseases
No
64
What is the reason that prion proteins can't denature
their unusual folding patterns
65
Describe the effects on infectious prion proteins on the normal form
- 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
What is specific to the PrP(SC) infectious prion
- Resistant to proteases; become insoluble and aggregate | - Unusually resistant to heat and chemical treatments

Microbiology (7 decks)

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