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DMD 5245 > Virus replication, structure, and classification (complete) > Flashcards

Virus replication, structure, and classification (complete) Flashcards

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1
Q

how do viruses replicate

A

by assembly of subunits in infected cells

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2
Q

What are the steps for viral replication

A
  1. attachement
  2. penetration
  3. uncoating
  4. early transcription
  5. early translation
  6. replication
  7. late transcription
  8. late translation
  9. assembly
  10. release
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3
Q

What are the two ways that viruses can kill

A

causing an overactive immune system (angry macrophages)

inhibiting the immune system

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4
Q

what is the primary example of a virus that kills by causing an over active immune system

A

influenza

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5
Q

what is the primary example of a virus that kills bu inactivating the immune system

A

Ebloa (also HIV)

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6
Q

What is the main difference between positive and negative RNA virus replication

A

a positive strand is just like mRNA so it is immediately translated, negative strand mRNA has have a complementary strand made, then have that one translated

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7
Q

although positive and negative RNA virus replication is different, what is one important similarity

A

they both create double stranded RNA

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8
Q

why is double stranded RNA so important

A

it is the signal that induces the synthesis of interferon

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9
Q

can viruses resist interferon action

A

yes

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10
Q

what is a retrovirus

A

an RNA virus that goes from RNA to double stranded DNA.

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11
Q

what is needed by a retrovirus, and can be the target of antiviral drugs

A

RT

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12
Q

What is the main target of antibodies against viruses

A

antibodies against particles on the viral envelope, this prevents them from binding to the cell

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13
Q

What are the different outcomes of a viral infection for the cell

A
  1. Abortive infection
  2. Latent infection (can become a productive infection)
  3. productive infection (can lead to cell death or a persistent infection)
  4. apoptosis
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14
Q

What are the four immune mechanisms that fight viruses and what do they cause

A
  1. interferon - blocks infection, kills infected cells
  2. NK cells - kill infected cells
  3. B cells/antibody - neutralizes viruses, enhance phagocytosis
  4. Cytotoxic T-cells - kills infected cells
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15
Q

What are the TLRs that are important to antiviral activity

A

TLR 3, 7, 8, and 9

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16
Q

What does TLR3 recognize and result in

A

TLR 3 recognizes DsRNA and produces IFN-beta

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17
Q

what do TLR 7, and 8 recognize and result in

A

they recognize viral ssRNAand produce IFN-1 alpha

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18
Q

What does TLR 9 recognize and result in

A

it recognizes unmethylated CpG, and results in IFN-alpha

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19
Q

what type of cell produces the most IFN-alpha

A

plasmacytoid dendritic cells

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20
Q

what is the sequence of events from TLR recognition to IFN production

A
  1. TLR recognition
  2. signal pathway
  3. transcription factors
  4. Interferon production
  5. Release of interferon
  6. protection of non-infected cells
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21
Q

What is type 1 interferon

A

IFN alpha and beta

produced by immune cells and infected cells

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22
Q

what is type 2 interferon

A

antiviral and defense against intracellular bacteria and parasites
produced by immune cells only

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23
Q

What are the three ways in which interferons work

A
  1. they inhibit all translation (type 2 IFN only does this)
  2. they degrade mRNA and rRNA
  3. they inhibit transcription, and viral assembly
    (type 1 IFN does all three)
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24
Q

What does STAT do?

A

it causes IFN to be produced

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25
how can viruses evade antiviral defenses
- Influenza NS1 binds to dsRNA - Ebola prevents dsRNA from inducing IFN release - Ebola inhibits RNA silencing - adenovirus blocks STAT1 from functioning - Vaccinia prevents IFN from attaching
26
What are the two ways that a virus can initiate apoptosis
extrinsic (death by instruction) | intrinsic (death by stress)
27
how is apoptosis carried out
activation of caspases, which basically chew everything in the cell up, then they are and ingested by phagocytes
28
is apoptosis good or bad for the virus inside the cell
it can be both. Some viruses initiate apoptosis, others prevent it so the cell will stay live and produce more virus
29
What is a latent viral infection
the viral genome is present, but there are no infectious viral particles
30
What is lysogeny
when a viral genome integrates into the host genome
31
what is an episomal viral genome
when a viral genome isn't entered into the host chromosome (like a bacterial plasmid)
32
which viruses cause chronic inflammation
Hep B and C
33
which viruses can cause cancer
Hep B and C
34
what is a viral oncogene
cancer causing genes in sarcoma and leukemia viruses
35
What is tropism
the increased ability of a virus to replicate in certain cells or tissues
36
what controls tropism
1. viral antireceptor 2. viral receptor 3. route of infection 4. transcription factors 5. immune system response
37
What happens to a host with a viral infection
IL-1 - causes fever, somnolence, anorexia, lowers libido, lowers pain threshold IFN - causes nausea, vomiting, fever, chills, fatigue, malaise, asthenia, myalgia, leukopenia TNF-alpha - causes inflammation, cachexia, fever, cell lysis
38
What are acute viral infections
rapid onset, rapid resolution (virus is cleared)(influenza)
39
what are chronic viral infection
slow onset, slow resolution, cells die, infection spreads (HBV, HIV)
40
what are persistent infections
virus stay with the host, infected cells live (retroviruses)
41
what are latent infections
virus stays with the host, reactivation episodes occur (HSV) start and end as acute infections
42
What is a subclinical viral infection
an infection with no signs or symptoms, but infectious virus is produced and transmittable
43
What is a virus
a very small non-cellular parasite of cells.
44
What are the parts of a virus
a DNA or RNA genome a Capsid (protein coat) sometimes an envelope
45
are there parts of our genome that are retroviral sequences
yes, our genome is about 8% retroviral
46
What is the newest theory on origin of viruses
that viruses preceded cellular organisms
47
What is a virion
an infectious virus particle
48
can viruses sustain themselves and replicate
no, they are obligate intracellular parasites (they can't produce energy or synthesize ribosomes)
49
What is a capsid
a protective protein shell for the viral genome, composed of capsomers
50
what are capsomers
the structural components (bricks) of the capsid, they are made of protomers
51
what are protomers
the building blocks that make up capsomers
52
What are the functions of viral proteins
1. structural 2. protect genome 3. attachment to host cell 4. fusion with cell membrane 5. Enzymes 6. primers 7. immune interference
53
how are capsids build
they self-assemble, due to reactions with large free energy that proceed to near completion
54
are all of the components made by viruses for replication used to make new viruses
no, probably not even close, but enough are that the virus still successfully replicates
55
what is a virion composed of
it is the infectious virus particle, that is composed of RNA or DNA, proteins, and sometimes an envelope
56
where is the envelope a virus sometimes has obtained from
from a modified cell membrane
57
What are the two main structures of capsids
helix and icosahedron
58
what are the functions of the capsid
1. protect the genome from nucleases and other hostile things 2. necessary for the infectivity of virions 3. in naked viruses it serves as the attachment protein 4. it is antigenic and invokes an immune response
59
how many capsid layers do viruses have? any excpetions
1 | yes, reoviridae has 3 capsid layers
60
what is the helical structure of capsids like
it looks like a stack of washers. it is a long tightly coiled protein
61
What are the shapes that a capsid with helical symmetry can make
sphere bullet Rod thread
62
What is the capsid of rhabdovirus (rabies) like
helical capsid tight envelope bullet shaped
63
What is the capsid of the influenza virus like
helical capsid loose envelope sphere shaped
64
What is an icosahedra
a structure with 20 equilateral triangles 30 edges 12 verticies
65
how many axis of symmetry do icosahedra have
3 5 fold 2 fold 3 fold
66
what is the minimum number of subunits that can make up a face in an octahedron
3
67
what is the minimum number of subunits a whole icosahedra can have
60 (3 per face x 20 faces)
68
how do you get larger icosahedra
by adding more subunits per face, not by making larger subunits
69
What can you have external to the capsid
an envelope (sometimes you do, sometimes you don't, that depends on the virus)
70
Which virus has a brick shaped capsid
poxvirus
71
What are the 4 different types of viral capsids we study
1. naked icosahedral 2. envelopped icosahedral 3. naked helical 4. envelopped helical
72
what are the 4 different types of viral genomes
1. single stranded RNA 2. double stranded RNA 3. single stranded DNA 4. double stranded DNA
73
what shapes do the viral genomes take
circular or linear
74
what other modifications can viral genomes have
they can be incomplete double stranded | they can be segmented (more than one piece)
75
What is a positive strand RNA
one that has the same polarity as mRNA (5'-3')
76
what is a negative strand RNA
one that has the opposite polarity as mRNA (3'-5')
77
What are the three different types of viral DNA genomes
1. double stranded with open ends 2. double stranded with closed ends 3. single stranded
78
what are the 4 different types of viral RNA genomes
1. single stranded + 2. single stranded - 3. double stranded 4. single stranded, segmented
79
Which strand, positive or negative, ssRNA needs to bring its own RNA dependent RNA polymerase
the negative strand RNA, this way it can make its own complementary copy
80
How are viruses classified
1. DNA or RNA 2. Icosahedral or Helical 3. Naked or Envelop 4. Double Stranded, Single Stranded 5. + or -
81
What are the characteristics of the influenza virus (orthomyxo)
1. RNA 2. Helical 3. Enveloped 4. Single Stranded (8 SEGMENTS) 5. Negative
82
What are the characteristics of the paramyxo virus
1. RNA 2. Helical 3. Enveloped 4. Single Stranded (non-segmented) 5. Negative
83
What are the characteristics of the Filo (ebola) virus
1. RNA 2. Helical 3. Enveloped 4. Single Stranded (non-segmented) 5. Negative
84
What are the characteristics of the Corona virus (sore throats)
1. RNA 2. Helical 3. Enveloped 4. Single Strand 5. Positive
85
What are the characteristics of the Picorna virus (common cold)
1. RNA 2. Icosahedral 3. Naked 4. Single Stranded 5. Positive
86
What should we remember about helical DNA viruses
there are no helical DNA viruses that affect humans
87
What are the characteristics of the herpes virus
1. DNA 2. Icosahedral 3. Enveloped 4. Double Stranded (linear)
88
What are the characteristics of the hepadna virus (HEP B)
1. DNA 2. Icosahedral 3. Enveloped 4. Double Stranded (circular - gapped)
89
What are the characteristic of the Adeno (upper respiratory) virus
1. DNA 2. Icosahedral 3. Naked 4. Double stranded (linear)
90
What are the characteristics of the Papilloma virus (HPV)
1. DNA 2. Icosahedral 3. Naked 4. Double Stranded (circular)

DMD 5245 (15 decks)

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