Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

OD2 S1 > M: Virology 2 - Week 11 > Flashcards

M: Virology 2 - Week 11 Flashcards

1
Q

What is the eclipse period?

A

the time between infection by (or induction of) a bacteriophage, or other virus, and the appearance of mature virus within the cell; an interval of time during which viral infectivity cannot be recovered.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the latent period?

A

the period between infection with a virus or other microorganism and the onset of symptoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define Uncoating

A

The release of viral nucleic acids/genome from the capsid that covers them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the one-step growth curve?

A

Describes the production of progeny virus over a period of time following infection under one-step conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When do one-step conditions exist?

A

When all cells are infected simultaneously so as to prevent secondary cycles of infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is a viral plaque?

A

a visible structure formed within a cell culture, demonstrating a region of cell destruction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a plaque forming unit (PFU)?

A

A measure of the number of particles capable of forming plaques per unit volume, such as virus particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens to PFU during the Eclipse Period of viral replication? (in one-step growth curve of the unenveloped virus)

A

No change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens to PFU during the Latent Period of viral replication?

A

No change for most of it, then a logarithmic increase near the end

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to PFU during the Uncoating Phase of viral replication?

A

No change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens to PFU during the Synthetic Phase of viral replication?

A

logarithmic increase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

In the one-step growth curve for viral replication, at what times after viral absorption do the following periods/phases occur?
- Eclipse
- Uncoating
- Latent
- Synthetic

A

Eclipse: 0-12 hours
Uncoating: 0-12 hours
Latent: 0-16 hours
Synthetic: 12-16 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In the one-step growth curve: what happens to the virus 16 hours after viral absorption?

A

extracellular bursting out of new viruses (happens for the next 28 hours until hour 44)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Name the 6 steps of viral replication

A

Attachment/Adsorption
Penetration
Uncoating
Replication
Assembly
Release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do viruses attach?

A

Viral attachment protein binds specifically to a receptor on the cell plasma membrane

This interaction defines and limits the host species as well as the type of cell that is infected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What receptors might the cell plasma membrane have for viruses? (2) Provide an example for each

A

Protein (e.g. ICAM-1 for most rhinoviruses)
Carbohydrate (e.g. sialic acid for influenza)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Can viruses use multiple different receptors on the same host cell?

A

Yes. Some viruses do that

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is referred to as the “one-two punch” for viruses to get into the cell

A

Some viruses use 2 different receptors on the same host cell: for initial attachment, then a coreceptor for closer attachment and entry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do viruses penetrate the cell membrane? (2)

A

The coat of enveloped viruses may fuse with the host cell membrane and release the virus nucleocapsid into the host cytoplams
Alternatively,
other viruses may enter the cell via “endocytosis”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does viral endocytosis involve?

A

invagination of the cell membrane to form vesicles in the cell cytoplasm which becomes acidified

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the purpose of viral uncoating?

A

enables the nucleic acid to be transported within the cell and transcribed to form new progeny virions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is direct fusion?

A

is when viruses initiate fusion and penetration of their core or nucleocapsid directly through the cell’s surface (plasma) membrane at neutral or alkaline pH

Several viruses do this.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Name 2 examples of viruses that undergo direct fusion

A

Paramyxoviruses (e.g. measles)
Retrovirus HIV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How do paramyxoviruses undergo direct fusion?

A

via a fusion (F) glycoprotein on their envelope

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How does retrovirus HIV undergo direct fusion?

A

gp120 binds sequentially to 2 receptors: CD4 receptor and CCR5 (chemokine co-receptor)
- this exposes gp41, which drives fusion of envelope and plasma membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the steps involved in the entry of HIV-1 by membrane fusion

A
  1. Native trimer: Attachment through non-specific cell receptors
  2. CD4 binding: structural changes in gp120 after binding CD4 receptor
  3. Coreceptor binding: binding to newly exposed chemokine coreceptor sites promotes gp41 fusion peptide insertion
  4. Membrane fusion: structural rearrangement of gp41 trimers drives membrane fusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

In the entry of HIV-1, which chemokine coreceptor sites become exposed? (2) Which chemokine is predominantly used during the process of transmission?

A

CCR5 and CXCR4. CCR5 is the predominantly used on for transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does the entry and uncoating of influenza viruses require? (2) Why?

A

requires endocytosis and acidification - to induce a conformation change in HA that reveals a fusion domain on HA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is HA? What does it stand for? (in relation to influenza virus)

A

Influenza Haemagglutinin. is a homotrimeric glycoprotein found on the surface of influenza viruses and is integral to its infectivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe the assembly phase of the viral life cycle

A

proteins assemble around the nucleic acids to form new viral particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Where do DNA viruses replicate? Are there any exceptions?

A

in the nucleus. (poxyviruses are an exception)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Where do RNA viruses replicate?

A

in the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What does mRNA encode?

A

viral proteins that are translated by the host cel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Where is mRNA transcribed from?

A

viral DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Where is mRNA formed directly from?

A

some RNA viruses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the difference between transcription and translation? (2)

A

Transcription: the synthesis of RNA from a DNA template where the code in the DNA is converted into a complementary RNA code

Translation: the synthesis of a protein from an mRNA template where the code in the mRNA is converted into an amino acid sequence in a protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Are “early” viral proteins structural or non-structural? What about “late” viral proteins?

A

early: usually non-structural
late: structural

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What do “early” viral proteins assist with?

A

replication (e.g. polymerases)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Provide one example for “early” and “late” viral proteins?

A

early: polymerases
late: capsid proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Name 3 viruses that can directly translate their genome to proteins. Why can they do this?

A

Picornaviridae
Togaviridae
Flaviviridae

Can do this because their genome is m(+)RNA. This is needed before we can translate but since these viruses already have it there is no need to undergo transcription to get it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Can negative sense viral RNA act as mRNA?

A

No. Only positive-sense do that (i.e. only positive sense can act as mRNA to be translated into protein in the host cell)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What does RDRP stand for? What does it do?

A

RNA-dependent RNA polymerases. Enzyme that produces complementary strands from the template

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Which of the following contains a RNA-dependent RNA polymerase in its capsid?
- Positive sense ssRNA or Negative sense ssRNA?

A

Negative-sense

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

How do (+)ssRNA viruses overcome their inherent lack of RNA-dependent RNA polymerase?

A

they use their genome as an mRNA to make an RNA-dependent RNA polymerase (or REPLICASE) upon infection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

How does replication of ssRNA work when starting with (+)ssRNA? What if we start with (-)ssRNA?

A

Minus strands are copied form plus strands, then more plus strands from the minus strand template

(vice-versa if starting with (-)ssRNA)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is the replicative intermediate?

A

refers to the complex formed when RNA-dependent RNA polymerase produces the complementary strand for ssRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

How do (-)ssRNAs make mRNA?

A

They use their replicase (i.e. rna-dependent rna polymerase) to make mRNA using the -ve sense genome as a template

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Can DNA viruses make DNA?

A

Yes. They have a DNA genome so they can just transcribe and make RNA

49
Q

True/False: Most dsDNA viruses have viral enzymes within them

A

False. They make viral enzymes when they arrive from the copy of DNA genome

50
Q

ds DNA viruses use cellular enzymes in the nucleus for what purpose? (2)

A

to express mRNA
to replicate DNA

51
Q

What do DNA viral proteins modulate?

A

normal cellular control mechanisms to favor virus replication

i.e. DNA viruses will have proteins that greatly favour the replication of viral proteins

52
Q

Name 4 DNA viruses

A

Adenovirus
Herpes virus
Pox virus
Papo virus

53
Q

What do ssDNA viruses need to do to further their genome replication?

A

They need to make a copy of the second strand

54
Q

How and where is translation of structural and non-structural proteins carried out?

A

Carried out by ribosomes in the host cell cytoplasm

55
Q

Once translated, what do the translated proteins almost invariably undergo?

A

Post-translational cleavage of polyproteins or trimming of structural proteins

56
Q

What does post-translational cleavage of polyproteins or trimming of structural proteins require?

A

virus-coded proteases

57
Q

Where does glycosylation of envelope glycoproteins occur? (2)

A

RER and Golgi vesicles

58
Q

What are viral structural proteins designed to assemble into?

A

Capsids

59
Q

What might the virus particle require to induce the final capsid conformation?

A

Proteolytic cleavage

60
Q

Where do virions accumulate following assembly? (2) and where are they released? (1)

A

Accumulate in the cytoplasm or nucleus and are released by lysis

61
Q

How may virus particles be released following assembly? (3)

A

Particles may be released from the cell by:
movement through the ER (exocytosis),
breakdown of the cell,
or by budding

62
Q

Which method of viral release from the cell is the main method for enveloped viruses?

A

By budding

63
Q

What is viral budding?

A

Nucleocapsids assembled or in the process of being built induce formation of a membrane curvature in the host cell membrane and wrap up in the forming bud which is eventually pinched off by membrane scission to release the enveloped particle

64
Q

Are enveloped or non-enveloped viruses released by exocytosis after assembly?

A

Can be either. However most often tends to be non-enveloped viruses

65
Q

What is viral exocytosis?

A

Viral progeny are synthesized within the cell and the host cell’s transport system is used to enclose them in vesicles; the vesicles of virus progeny are carried to the cell membrane and then released into the extracellular space.

66
Q

Does viral exocytosis (via movement through ER) kill the infected cell?

A

No

67
Q

What is the primary mode of viral exit from the cell for non-enveloped viruses?

A

cell lysis (to violate the integrity of the bilayer). This kills and ruptures the cell obviously

68
Q

Name 2 drugs that target the attachment of viruses

A

Maraviroc
Fuzeon

69
Q

Name 1 drug that targets the uncoating of viruses

A

Amantadine

70
Q

Name 2 drugs that target the genome replication of viruses

A

Acyclovir herpesviruses
Zidovudine (AZT)

71
Q

Name 2 drugs that target the RNA synthesis of viruses

A

Ribavirin
Interferons

72
Q

Name 3 drugs that target the protein synthesis of viruses

A

Interferons
Saquinavir
Darunavir

73
Q

Name 2 drugs that target the release of viruses from the cell

A

Tamiflu
Relenza

74
Q

Name the 3 classes of Interferons

A

IFN-alpha
IFN-beta
IFN-gamma

75
Q

What is the role of interferons?

A

induce proteins (IRPs) that inhibit viral replication or modify immune responses

76
Q

Describe the antiviral actions of interferons

A

Wide variety of antiviral actions - block viral protein synthesis

77
Q

Are interferons active against DNA viruses?

A

No. Not very active

78
Q

Do Interferons cause side effects? If so, how broad?

A

Yes. Wide ranging effects

79
Q

How many phosphate groups do nucleosides have? What about nucleoside analogues

A

none for both

80
Q

What is the substrate for DNA polymerisation?

A

Nucleoside triphosphate

81
Q

What is Acyclovir?

A

A guanosine analogue used to treat herpesviruses

82
Q

Why aren’t nucleoside analogues able to form a DNA polymer?

A

they lack the 3’ hydroxyl group required

83
Q

What does the synthesis of acyclovir monophosphate require? (1)

A

thymidine kinase (which adds a phosphate group to acyclovir)

84
Q

What is Ribavirin?

A

Guanosine analogue

85
Q

What is the function of Ribavirin?

A

Inhibits replication of many DNA and RNA viruses in vitro

86
Q

How does Ribavirin work? Describe its forms and what function each have (3 + 2)

A

Intracellular phosophorylation gives it mono-, di- and tri-phosphate forms.
Mono-phosphate form: reduces nucleic acid synthesis
Tri-phosphate form: alters viral mRNA formation

87
Q

Name 4 conditions you can use Ribavirin for

A

Use for:
respiratory syncitial virus bronchiolitis + pneumoniae
influenza
haemorrhagic fevers
hepatitis C

88
Q

How do you administer Ribavirin for treatment of influenza and respiratory syncitial virus bronchiolitis and pneumoniae?

A

Aerosolised, IV (intravenous)

89
Q

How do you administer Ribavirin for treatment of hemorrhagic fevers? (2)

A

oral or IV

90
Q

How do you administer Ribavirin for treatment of hepatitis C?

A

oral; in combination with interferon

91
Q

Describe the HIV replication cycle (3)

A

HIV is an RNA virus
HIV consists of an enzyme inside the particle – the enzyme converts the 2 copies of (+) viral RNA and reverse transcribes them into a double-stranded copy of DNA
The double-stranded DNA is taken into the nucleus and gets stitched into the host cell DNA to form pro-virus DNA

92
Q

Name 4 targets in the HIV replication cycle for anti-retroviral therapy

A

Fusion/Entry inhibitors
Reverse Transcriptase inhibitors
Integrase inhibitors
Protease inhibitors

93
Q

What is Zidovudine?

A

A reverse transcriptase inhibitor

94
Q

What are reverse transcriptase inhibitors (RTIs)? What can they be used to treat? (3) What is reverse transcriptase required for? (2)

A

are a class of antiretroviral drugs used to treat HIV infection or AIDS, and in some cases hepatitis B. RTIs inhibit activity of reverse transcriptase, a viral DNA polymerase that is required for replication of HIV and other retroviruses.

95
Q

What does NRTI (or NARTI) stand for? Name one example

A

Nucleoside analogue reverse-transcriptase inhibitors; a type of reverse-transcriptase inhibitor

e.g. Zidovudine

96
Q

What type of nucleoside analogues can NRTIs be? (3)

A

Analogues of:
Thymidine
Cytidine
Guanine

97
Q

How are NRTIs incorporated into the viral DNA? (so that they can inhibit reverse-transcriptase)

A

In order to be incorporated into the viral DNA, NRTIs must be activated in the cell by the addition of 3 phosphate groups to form NRTI triphosphates

98
Q

How are NRTIs phosphorylated?

A

via intra-cellular kinase enzymes

99
Q

Can reverse-transcriptase inhibitors eliminate HIV virus completely?

A

No. They can reduce the infection of new cells but cannot eliminate the virus completely

100
Q

When might you use combination therapy with reverse-transcriptase inhibitors?

A

When you have drug resistant mutant viruses

101
Q

What nucleoside analogue is Zidovidine?

A

a Thymidine analogue

102
Q

What does NNRTI stand for? Do NNRTIs have close structural similarity to nucleosides?

A

Non-nucleoside reverse-transcriptase inhibitors. No they do not!

103
Q

What type of anti-HIV drugs have a close structural similarity to the amino acid recognition sequence?

A

Protease inhibitors

104
Q

What features of a virus in general help confer drug resistance? (2)

A

High replication rate
High mutation rate (RNA>DNA)

105
Q

How does viral drug resistance typically emerge? How can we overcome this?

A

by “selective pressure”. Overcome by using combination therapy

106
Q

What is a “pre-existing” viral mutant

A

is a viral resistance mutation that exists before the patient has had any kind of treatment

107
Q

How often do “pre-existing” viral mutations occur? (in comparison to non-pre-existing)

A

often

108
Q

What is HAART?

A

Refers to any HIV treatment that uses a combination of 2 or more drugs

109
Q

What are the advantages of HAART? (3)

A

Synergistic potency
Durable anti-viral response
Minimise development of drug resistance

110
Q

Define Viral hepatitis

A

“inflammation of the liver”. a viral infection that causes liver inflammation and damage.

111
Q

Is viral hepatitis acute or chronic?

A

Can be either (Acute = weeks to months) (Chronic = years to lifetime)

112
Q

How does acute viral hepatitis present? [symptoms] (3)

A

non-specific, flu-like symptoms
jaundice
dark urine

113
Q

How does chronic viral hepatitis present? [symptoms] (3)

A

general malaise
cirrhosis
liver cancer

114
Q

In what body fluids is the concentration of blood born viruses high? (3)

A

blood (obviously)
serum
wound exudates

115
Q

In what body fluids is the concentration of blood born viruses moderate? (3)

A

semen
vaginal fluid
saliva

116
Q

In what body fluids is the concentration of blood born viruses low? (5)

A

urine
faeces
sweat
tears
breastmilk

117
Q

What proteins were used in HIV treatment a few years ago and are being phased out? Why are they being phased out?

A

Interferons (IFNs). They are being phased out because they made the treatment unpallatable.

Now we have IFN-free DAA combination treatment

118
Q

What does DAA stand for?

A

Direct acting antivirals

OD2 S1 (47 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions