Introduction to viruses Flashcards
(120 cards)
1
Q
viruses are obligate
A
intracelluar parsite
2
Q
are viruses living
A
no - inert particles
3
Q
if virus needs enzyme to replicate its genome, the virus must do what
A
provide it itself - certain enzymes virus needs for replication and the virus has to carry those in itself
4
Q
anything needed after stage of mRNA
A
virus doesn’t need to carry, ti will just happen
5
Q
virus will self ______ within host cell
A
assemble
6
Q
virus particle called
A
virion
7
Q
virus has to have
A
genome
8
Q
what kind of genome does virus have
A
DNA or RNA
9
Q
if DNA genome can be
A
linear or circular
single or double stranded
10
Q
RNA genome can be
A
linear or segmented
single or double stranded
11
Q
if single stranded rna genome what is important
A
polarity
12
Q
what are three possibilities for rna genome for virus
A
positive sense or negative sense or ambiesense (+ at one end - at one end)
13
Q
negative sense RNA
A
opposite to mRNA cannot be directly translated
need enzyme to make RNA
RNA dependent RNA polymerase
14
Q
all viral genoms have to be associated with what kind of proteins
A
capsid
15
Q
what are possible structures for capsid
A
helical capsid
icosahedral capsid
16
Q
capsid + nucleic acid is calld
A
nucleocapsid
17
Q
what is actually introduced into cytoplasm of cell
A
nucleocapsid
18
Q
minimal structure of virus
A
genome + capsid proteins
19
Q
some viruses will have add’l structures
A
envelope
peplomers
packaged enzymes
20
Q
envelope viruses will have
A
envelop
21
Q
what is envelope
A
part of membrane of cell that the virus affected and assembled in
lipid bilayer that surrounds nucleocapsid
22
Q
peplomers
A
viral glycoprotein spikes
targets for neutralizing antibodies
23
Q
what is important about peplomer
A
targets for neutralizing antibodies
24
Q
many viruses are designed to neutralize
A
peplomer
25
what does virus use to attach to specific receptor on host cell
peplomer (viruses block attachment!)
26
if virus needs enzyme the host cell can't provide ie needs
pakcaged enzyme
27
what are examples of packaged enzymes
replicases, proteases
28
viral proteins that make up virion are called
structural proteins
29
oms proteins made during replication cycle of virus - they don't become part of virus - they are called
non-structural proteins (not part of virion)
30
encoded enzymes a virus may need are not always packaged in
virion
31
ultimately virus needs to get to what stage on its own
mRNA
32
examples of helical enveloped virus
pox virus
rabies virus
HIV
33
how are viruses classified into order, family, etc (taxonomic classification)
how they replicate
*polarity/strand of genome
type of disease it will cause
34
most common route for infectious disease and true for virus
mucousal route (inhalation or ingestion)
35
once virus enters,once a virus enters,
limited replication then virus spreads
36
how can virus enter
repiratory, wounds, STD, fecal-oral
37
when virus enters there can be replication at
initial site it entered
38
incubation preriod
there can be asymptomatic period or prodrom period
39
dissemination may occur -
they may spread from primary to secondary site
40
some viruses spread to what site
tertiary
41
what is responsible for spreading HIV
dendritic cells
42
primary site replication can be spread to
secondary site
43
secondary site replication can be spread to
tertiary site
44
but not all viruses will spread correct?
yes
45
4 types of viral infection
abortive
productive - nonlytic
latent
productive - lytic
46
abortive
cell cannot survive replication of virus or virus itself is defective
47
productive (non-lytic)
the host cell is altered but not killed- permissive and productive
48
producive nonlytiic is often viruses that have
envelope
49
productive - lytic
host cell death and release of progeny viruses
- permissive and productive
cell is lysed during replication
50
producitve - lytic characteristic of what virus
no envelope
51
latent viral infection
viral genome persists inside host cell without production of virus particles
latent viruses can become reactivated
52
when latent viruses are reactivated lead to production of
virus particles
53
lytic infections mediated by
naked viruses (no evvelope)
54
budding is mediated by
envloped virus (during budding iti will aquire envelope)
55
regardless if relase is lytic or budding what are the steps
```
Adherence
Penetration
Replication
Assembly
Release
```
56
penetration
release nucleocapsid into cell
57
replication
synthesis of viral proteins
58
release
lysis or budding
59
transofrming virus e cause
cancer
60
do all transofrming viruses integrate
no
61
first step due o highly speicif reaction of
peptomer
62
specificity of peplomer receptor interaction determins
tropism (type of cell virus can affect)
63
tropism:
(type of cell virus can affect)
64
permissiveness
allows virus to enter and replciate
65
two main strains of HIV
T tropic
| M tropic
66
T tropic HIV straing primarlily affects
t lymphocyte
67
m tropic strain primarlily affects
macrophage
68
both strains HIV the receptor primarily binds to
CD4
69
once virus binds to CD4 what happens
it undergoes conformational change that allows it to bind to a coreceptor
70
coreceptor for m tropic strain of HIV
CCR5 (chemokine receptor)
71
coreceptor for t trophic strain
CXCR4 (chemokine receptor)
72
m tropic strain of hiv will not affect
t lymphocytes
73
t trophic strain of hiv will not affect
macrophage
74
influenza virus peplomer called
Haemagglutinin
75
HA stands for
Haemagglutinin
76
where does human flu replicate
airway epithelia
77
once it binds has to deliver
nucleocapsid into cell
78
can enevloped viruses fuse
yes - they can fuse with bilayer of host cell
79
where does fusion occur
often cell membrane but can be membrane inside cell like endosome
80
can naked viruses fuse
no b/c they just have coating of protein and own't fuse with lipid
81
adenovirus enduses induces
lysis of endosome once its taken up
82
main mechanisms virus can enter cell - draw out
pg 20
83
influenza virus will only fuse at
acidic pH
84
HIV virus will fuse at
neutral pH
85
neutral pH fusion takes place where
at surface of cell
86
acidic pH fuses wehre
endosome
87
fusion at acidic pH is also called
pH dependent fusion
88
poliovirus will form what in endosome
pore - it allows genome to be available for replication
89
adenovirus lead to what of endosome
lysis - then the nucleocapsid is delivered to where it replicates
90
what is function of spike glycoproteins
bind to receptor on surface of cell allowing the cell to become infected (they remain in membrane!)
they define where they are going to bud from cell by the spike glycoproteins
91
multinucleated giant cells are called
syncytia
92
influenza viruses taken up into endoxomes and then
it fuses - it needs the pH to drop
93
will syncytia formation happen during influenza
no
94
will ther be fusion at neutral pH for influenza virus
no - they cannot force fusion at the neutral pH it needs pH to drop
95
entry does not necesarilly require
fusion (naked virus!)
96
naked virus will not fuse with
lipid membrane
97
once nucleocapsid is delivered and uncoated what needs to happen
need to replicate
98
enzymes that carry ou replication are
host or viral enzymes (or both)
99
enzymes always made on host
ribosomes
100
once repplication happens there will be
assembly & release
101
naked virus released by
lysis
102
not naked virus released by
budding
103
large DNA viruses life cycle
wave of transcription
immediate early genes expressed followed by early genes, they encode proteins that regulate the transcription and replication of virus. they are made early on. many RNA virsuses don't have wave of transcription, most you just straigt away mke structural/nonstructural proteins
104
in macromolecule once genome made then
make what is needed to package enome
105
what are stages of macromolecular syntehssis and replciation
Transcription of Immediate Early and Early mRNA synthesis of nonstructural regulatory proteins
Replication of genome
Transcription of Late mRNA structural protein synthesis
106
when viruses are assembling they can give rise to
inclusion bodies
107
inclusion bodies
proteins falling out of solution - so many proteins being made
108
where will inclusion bodies be
wherever replication is taking places
109
what is period b/w addition of virus where amount of virus seems to decrease
eclipse period
110
why does amoutn of virus decrease once injected
b/c it is being taken up into cell
111
eclipse period
b/w infection and when more virus can be detected than what was added (length depends on virus)
112
RNA viruses encode
RNA-dependent RNA polymerase
113
permissivness =?
entry + replication
114
what are syncytia
multinucleated cells
115
pH independent fusion leads to the formation of what
syncytia (multinucleated cells)
116
what are chemokines
chemoattracts that a cells in our body make to tell immune system there is infection going on
117
HIV fuses with what membrane
plasma
118
enveloped viruses fuse with what
host cell membrane - often plasma membrane but isn't always
119
fusion at neutral ph is also called
ph independent fusion
120
what is the result of fusion at neutral pH
once nucleocapsid is released into cell, spike glycoproteins remain in the plasma membrane
the spike glycoproteins allows them to fuse with other cells with spike glycoproteins resulting in multinucleated cells
