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

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

Flashcards in Virus replication, structure, and classification (complete) Deck (90):
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

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)