Flashcards in Virus replication, structure, and classification (complete) Deck (90)
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1
how do viruses replicate
by assembly of subunits in infected cells
2
What are the steps for viral replication
1. attachement
2. penetration
3. uncoating
4. early transcription
5. early translation
6. replication
7. late transcription
8. late translation
9. assembly
10. release
3
What are the two ways that viruses can kill
causing an overactive immune system (angry macrophages)
inhibiting the immune system
4
what is the primary example of a virus that kills by causing an over active immune system
influenza
5
what is the primary example of a virus that kills bu inactivating the immune system
Ebloa (also HIV)
6
What is the main difference between positive and negative RNA virus replication
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
7
although positive and negative RNA virus replication is different, what is one important similarity
they both create double stranded RNA
8
why is double stranded RNA so important
it is the signal that induces the synthesis of interferon
9
can viruses resist interferon action
yes
10
what is a retrovirus
an RNA virus that goes from RNA to double stranded DNA.
11
what is needed by a retrovirus, and can be the target of antiviral drugs
RT
12
What is the main target of antibodies against viruses
antibodies against particles on the viral envelope, this prevents them from binding to the cell
13
What are the different outcomes of a viral infection for the cell
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
14
What are the four immune mechanisms that fight viruses and what do they cause
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
15
What are the TLRs that are important to antiviral activity
TLR 3, 7, 8, and 9
16
What does TLR3 recognize and result in
TLR 3 recognizes DsRNA and produces IFN-beta
17
what do TLR 7, and 8 recognize and result in
they recognize viral ssRNAand produce IFN-1 alpha
18
What does TLR 9 recognize and result in
it recognizes unmethylated CpG, and results in IFN-alpha
19
what type of cell produces the most IFN-alpha
plasmacytoid dendritic cells
20
what is the sequence of events from TLR recognition to IFN production
1. TLR recognition
2. signal pathway
3. transcription factors
4. Interferon production
5. Release of interferon
6. protection of non-infected cells
21
What is type 1 interferon
IFN alpha and beta
produced by immune cells and infected cells
22
what is type 2 interferon
antiviral and defense against intracellular bacteria and parasites
produced by immune cells only
23
What are the three ways in which interferons work
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)
24
What does STAT do?
it causes IFN to be produced
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
