Virus replication, structure, and classification (complete) Flashcards Preview

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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

What is lysogeny

when a viral genome integrates into the host genome