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virology exam 1 > exam 1 > Flashcards

exam 1 Flashcards

1
Q

What is penetration by fusion

A

Attachment has envelope associated with plasma membrane of the host. plasma membrane fuses to lipid envelope

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2
Q

2 types of penetration for enveloped viruses

A

entry via endosomes, fusion with plasma membrane

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3
Q

what is entry via endosomes

A

particle brought in via endocytosis

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4
Q

acidification to allow for fusion in entry via endosomes is created by

A

proton pumping

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5
Q

how does influenza penetrate cell

A

gets inside with receptor mediated endocytosis. all 8 segments of genome go striaght into the cytoplasm. endosome gets close to nuclear pore, uncoats

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6
Q

from a one step growth curve where protein comes up first, what type of virus is that

A

positive sense because the rna virus genome can be read into proteins since it looks the same as our rna

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7
Q

how long is the infectious cycle of polio (picornavirus)

A

8 hours

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8
Q

how long is infectious cycle of herpes virus

A

> 40 hours

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9
Q

describe what type of virus polio is

A

+ ssRNA

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10
Q

name the 8 basic steps of the infectious cycle

A

attachment/adsorption, penetration, uncoating, replication, genome expression, assembly, release

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11
Q

what is adsorption

A

virus develops an attachment protein that can bind to the cell receptor

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12
Q

tropism

A

ability of a virus to replicate in particular cells or tissues

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13
Q

what two factors control tropism

A
  1. how the virus gained entry 2. interaction of a virus attachment protein with a specific cell receptor molecule
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14
Q

true or false, adsorption is temperature and energy independent

A

true

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15
Q

what is the cell receptor for poliovirus

A

ICAM-1

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16
Q

why is influenza called a recycling virus

A

it detaches from the cell in a hydrolysis reaction which allows it to leave the cell

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17
Q

what are the HIV attachment proteins

A

gp 120 and gp 41

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18
Q

how is adsorption different from penetration

A

penetration is energy dependent

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19
Q

how does HIV penetrate cell

A

fusion with the plasma membrane

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20
Q

how do naked viruses usually penetrate the cell

A

receptor mediated endocytosis and membrane pore formation

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21
Q

how does polio penetrate the cell

A

pore formation. vp1 interacts with cell receptor, when ph is low theres a conformational change, virion enters cell

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22
Q

name 2 unusual ways naked viruses can penetrate the cell

A

-entry across plasma membrane, -direct puncture of cell membrane

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23
Q

purpose of uncoating

A

makes genome available

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24
Q

what happens after uncoating

A

degradation of the capsid and genome is transported to site where transcription and replication will occur

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25
Q

what two events must occur for a virus to infect a cell

A
  1. synthesis of viral nucleic acid 2. synthesis of viral protein
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26
Q

where to dna viruses release their genome to rely on cellular machinery for transcription

A

nucleus

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27
Q

what do + rna viruses encode and package

A

RdRP, does not package it

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28
Q

what do - rna viruses encode and package

A

RdRP must package it

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29
Q

which rna virus looks like our mrna

A

+ sense

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30
Q

example of dsDNA

A

hsv, adenovirus, human pap

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31
Q

describe how ssdna viruses create protein

A

reverse transcriptase creates dsDNA, dsDNA creates ssRNA intermediate, reverse transcription back in -ssDNA, dna polymerase creates + ssDNA

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32
Q

are +ssRNA segmented

A

no they are unsegmented

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33
Q

examples of + ssRNA viruses

A

poliovirus, west nile, rhinovirus

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34
Q

What kind of genome does -ssRNA viruses have

A

segmented or nonsegmented

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35
Q

examples of -ssRNA viruses with nonsegmented genomes

A

rabies, ebola

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36
Q

examples of -ssRNA viruses with segmented genomes

A

influenza

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37
Q

how does HIV replicate

A

uses dsDNA intermediate, ssRNA is reverse transcribed into dsDNA

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38
Q

what is assembly

A

components are assembled into a particle

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39
Q

what stage does a virus become infectious

A

maturation

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40
Q

how do enveloped viruses leave the cell

A

budding

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41
Q

how do non enveloped viruses leave the cell

A

lysis

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42
Q

when does HIV go through maturation

A

viral protease cleaves budding and matures after leaving cell

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43
Q

what happens when a virus damages a cell or kills it

A

cell death can cause paralysis or death or increase mucus secretion

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44
Q

what stage of the infectious cycle is targeted by antiviral intervention

A

any!

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45
Q

what enzymes does chemotherapy often target

A

nucleic acid polymerase, protease, integrase, neuraminidase

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46
Q

what step would be targeted if the antiviral targets polymerases

A

replication

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47
Q

what drugs block were tested to see if they block RdRP during transcription

A

Remdesivir

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48
Q

how does covid penetrate cell

A

viral host membrane fusion or endocytosis

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49
Q

how does covid replicate

A

creates a -ssRNA with RdRP, transcribes this copy into + RNA

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50
Q

what might chloroquine do for covid

A

blocks cell receptor, might stop endosomal acidification and prevent formation of clathrin complexes

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51
Q

how might chemotherapy affect attachment

A

agents block cell receptors

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52
Q

explain how hiv could be blocked at attachment

A

add extra receptor

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53
Q

how might chemotherapy block penetration

A

block low pH needed for endosome membrane fusion

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54
Q

how might chemotherapy block uncoating

A

block ion transport

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55
Q

how might chemotherapy block replication

A

take advantage of high specificity of polymerases to block reverse transcription

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56
Q

example of drug action that blocks replication

A

azt looks like thymidine and gets incorporated into RT by rna polymerase and then stops transcription

57
Q

what RdRp drug is used against flu

A

favipiravir

58
Q

what are the targets for the best drugs to treat HIV

A

block maturation by targeting the proteases that clips the bud

59
Q

how might chemotherapy block release

A

a neuraminidase can block the release of viral proteins

60
Q

schemes for classifying viruses

A

host range, tissue infected, mode of transmission. now use basic structure and molecular biology

61
Q

who names viruses

A

international committee of taxonomy of viruses

62
Q

what are the ictv properties for classifying viruses

A
  1. order 2. family 3. subfamily 4. genus
  2. common names
63
Q

Several different criteria have been used to classify a virus. Which of the following is NOT among these criteria.
a. the type of nucleic acid that constitutes the viral genome.
b. the nature of the disease caused by the virus.
c. the metabolic activity of the virus outside of its host cell.
d. the replication strategy of the viral genome.
e. the mode of transmission of the virus.

A

c

64
Q

why must the skin be breached in order for it to be considered a place of entry

A

top layers are dead so there is no virus replication in dead cells

65
Q

what kind of inhibitory mechanism prevent viruses from infecting the respiratory tract

A

cilliated epithelium, mucus secretion, lower temepratre

66
Q

why is the gi tract a difficult place of entry

A

hostile environment

67
Q

why are the eyes an easy target for viral entry

A

easy to access and unprotected

68
Q

examples of viruses that enter through the skin

A

pap virus, HSV

69
Q

examples of viruses that enter through respiratory tract

A

rhinovirus, coranovirus, flu

70
Q

viruses that infect gastrointestinal tract

A

rotavirus, norovirus

71
Q

where do viruses most often cause symptoms

A

at the point of entry

72
Q

define latrogenic induction

A

infections generated by a physician

73
Q

type of virus that replicates at site of infection

A

localized infection

74
Q

type of virus that moves to another site in the host

A

systemic infection

75
Q

example virus of systemic infection

A

poliovirus, herpesvirus

76
Q

what are 3 mechanisms for spread

A

bloodstream (viremia), nervous system, lympthatic system

77
Q

how do viruses shed

A

usually leave through routes of entry

78
Q

what does a productive infection mean

A

entry into permissive cells followed by virion formation

79
Q

what does abortive infection mean

A

entry into non permissive cell, does not create virion

80
Q

restringent or restrictive infection means

A

transiently permissive and some virus is produced

81
Q

what type of infection is HSV

A

restringent

82
Q

why are persistent infections bad

A
  1. epidemic importance
  2. virus reactivation
  3. can act as precursor for another disease
  4. can cause cancer
83
Q

is rhinovirus persistent or non persistent and why

A

non persistent, gets completely cleared

84
Q

example of chronic infection

A

hiv

85
Q

example of slow infection

A

TSE

86
Q

what does it mean when a virus is in latency

A

there is no infectious virus present

87
Q

how does HSV latency work

A

HSV enters epithelial cell, then enters nerve cell, decides to just hang out there

88
Q

describe the model for establishin latency

A

1.virion attaches and penetrates the neuronal cell
2. loss of tegument proteins on axonal transport
3. enters viral genome by uncoating and circularizes
4. does not transcribe
5. forms chromatin
6. forms latent rna

89
Q

describe how hsv-1 starts as acute infection

A
  1. enters skin cell and uncoats
  2. genome enters nucleus
  3. viral mrna creates viral genome
  4. viral genome repackages and buds out
  5. goes up trigeminal ganglion
90
Q

advantages of being in a neuron

A
  1. no good immune surveillance
    2 non dividing
    3, pathway of axon allows virus to get back to epithileal cells
91
Q

what happens to t cells in aids

A

they all die

92
Q

what kind of virus is hep b and why is it improtant

A

dsDNA, chronic human infection

93
Q

3 conditions required for viral persistence

A
  1. infect some host cells without cytopathology
  2. mechanism for long term maintenance of viral genome
  3. must avoid detection of host defense systems
94
Q

explain what it means for viral persistence to require no viral cytopathology

A

-infection of non permissive cells
-infection of small number of permissive cells
-infection by virus variant that are less cytopathic

95
Q

explain what it means for viral persistence to require maintenance of viral genome

A

dna: integration into host chromosome
rna: continuous low level replication

96
Q

explain what it means for viral persistence to require escape from host defense system

A

-limited viral gene expression to avoid detection

97
Q

Which of the following are required for viral persistence?

a. Infect some host cells without cytopathology
b. Mechanism for long term maintenance of viral genome in host cells
c. Virus must avoid detection by host defense systems
d. All of the above

A

d

98
Q

what host changes can produce disease

A

age, immunity, immune supression

99
Q

what viral agent changes can produce disease

A

survival in environment, mode of transmission, evasion of host immunity

100
Q

what environment changes can produce disease

A

population density, climate, water

101
Q

what affects severity of infection

A
  1. virus genotype
  2. ammount of innoculum delivered to host
  3. host immune competence
102
Q

name some physical innate immunity

A
  1. skin
    mucous
    acid pH
103
Q

describe the virus specificity, time frame, range of effect, and general mode of action of interferons

A

specificity: non specific
time frame: within minutes or hours
range of effect: localized
mode of action: induce antiviral state to affect protein synthesis

104
Q

describe the virus specificity, time frame, range of effect, and general mode of action of antibodies

A

specificity: virus specific antiviral
timeframe: 7-10 days
range of effect: systemic
general mode: neutralize virus entry and destroy virus infected cells

105
Q

describe cellular altruism

A

when virus infects first cell, blocks protein synthesis and stops host from makign the repressor that silences interferon formation. then it sends the interferon signal to neighboring cells.

106
Q

what is considered the inducer for the interferon system

A

dsRNA (either enters virally like that or is an intermediate during ssRNA replication)

107
Q

what receptors binds to dsRNA to send off signal for interferons

A

rig-I or mda5

108
Q

how do you create an antiviral state

A

blcoking translation

109
Q

what 3 pathways create the antiviral state

A

oligoA intiviral response, PKR, RNAse L

110
Q

how does rnase L contribute to an antiviral state

A

kills infected cells by apoptosis and destroys viral mrna

111
Q

how does pkr contribute to the antiviral state

A

inhibits translation by phosphorylating a kinase rgar phosphorylates the initiation factors

112
Q

other examples of non specific defense

A

nk cells, phagocytes

113
Q

how are nk cells activated

A

activated by interferons

114
Q

examples of active evasion

A

adenovirus and hsv

115
Q

what does active evasion do

A

viral protein mediates blockage

116
Q

what molecule use immunosuppression as active evasion

A

HIV

117
Q

how does HIV evade the immune response

A

kills t cells via apoptosis

118
Q

how does ebola avoid the interferon response

A

virus attaches, penetrates, uncoats. dsRNA is made as replicative intermediate. this should signal interferon response, but vp35 binds to the ds rna and blocks it from rig I

119
Q

how does inhibition of cytokines work for active evasion

A

inhibits cytokine transcription, translation, and function

120
Q

how does a viroceptor block chemokines in active evasion

A

-competitively binds to chemokine and blocks signaling

121
Q

how does vck block chemokines in active evasion

A

mimincs cellular cytokine and blocks cytokine receptor

122
Q

how does vCkBP block chemokines in active evasion

A

binds to cellular chemokine to stop it from binding to receptor

123
Q

2 types of passive evasion

A

antigenic drift (mutation accumulate to make changes in the part of rna the immune system recognized), internal sanctuaries

124
Q

name several ways covid evades ifn response

A

blocks activation of rig-I, inhibits nfkb, blocks a lot. in neighboring cells, blocks transcription factors

125
Q

what type of virus is covid

A

+ ssRNA

126
Q

structure of covid

A

enveloped helical

127
Q

VAP and receptor of covid

A

spike protein and ace2 receptor

128
Q

how does covid produce a lot of proteins

A

ribsomal frame shifting, polyprotein, subgenomic rna

129
Q

what type of virus is HIV

A

+ssRNA

130
Q

structure of HIV

A

enveloped icosahedral

131
Q

what type of virus is VSV

A

-ssRNA

132
Q

what type of virus is polio

A

+ssRNA

133
Q

structure of polio

A

nonenveloped icosahedral

134
Q

how does polio enter the cell

A

pore formation

135
Q

structure of HSV

A

enveloped icosahedral

136
Q

what type of virus is flu

A

-ssRNA

137
Q

all viruses that -ssRNA are what structure

A

enveloped helical

138
Q

how does flu avoid the immune response

A

binds to reim25 and stops rig-i from starting interferon response

virology exam 1 (3 decks)

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