Viral Structure And Replication Flashcards
1
Q
Virus size is
A
Small
2
Q
Viruses are _____ _____cellular
A
Obligate intracellular
3
Q
Viruses don’t have ____
A
Sub cellular organelles
4
Q
Viruses can only ____ in living cells because they ___
A
Replicate
Rely on host cell protein synthesis machinery
5
Q
Does a virus divide and proliferate
A
No, new virions are assembled
6
Q
What is a virus made of
A
Nucleic acid
Protein shell
Envelope
7
Q
What does the nuceleic acid provide
A
Genome
Either DNA or RNA
8
Q
The genome and enzymes make
A
Core
9
Q
What does the protein shell makeup
A
Capsid
10
Q
A capsid can be ____ or ____
A
Helical
Icosahedral
11
Q
Core + capsid =
A
Nucleocapsid
12
Q
Nucleocapsid math
A
Genome + enzyme = core
Core + capsid = Nucleocapsid
13
Q
What is the envelope of a virus
A
Lipid bilayer derived from the host membrane WITH viral encoded glycoproteins
14
Q
Nucleocapsid aka
A
Naked capsid virus
15
Q
Envelope math
A
Nucleocapsid + glycoproteins and membrane
16
Q
We use the ___ classification system
A
Baltimore
17
Q
Baltimore classification system is based off of
A
Genome and replication strategy
18
Q
The ______ dictates replication strategy
A
Type of Nucleic acid
19
Q
ssDNA viruses =
A
Noneveloped —> icosahedral —> PARVOVIRIDAE
20
Q
How do viruses infect cells
A
Attachment
Entry/uncoating
Macromolecular synthesis
Assembly and release
MAAE
21
Q
How does attachment work
A
Viruses bind and infect
If it can’t bind it is USELESS
22
Q
How does entry/uncoating work
A
The genome needs to be released into the cell
23
Q
What two steps are crucial for the virus to infect
A
Attachment and entry
24
Q
How does macro molecular synthesis work
A
Viral proteins get transcribed/translated
Genome gets replicated!
25
How does assembly and release work
New viral particles assemble
Released thru lysis or budding
26
Review the picture as to how viruses infect
9 steps
Week 8
27
DNA genome can _____ like eukaryotic cells
Persist over time
28
Where does the DNA virus genome live
In the nucleus
29
The DNA viruses nucleus can utilize
The hosts cell chromosome
Or
Exist as a separate plasmid thing
30
DNA viruses can utilize ____ to copy Nucleic acid
Host polymerases
31
RNA virus has to make its own
Polymerases
RNA dependent RNA polymerase
32
Which mutates more, why
RNA viruses
Because RNA polymerases make more mistakes, it picks up more point mutations
33
DNA viruses and retroviruses are more _____ which can cause ___
Stable
Latent infections
34
Which turns into a cancer cell
DNA viruses and retroviruses
35
RNA Virus genome key characteristic
Labile/not long lasting/can’t just hang out
36
RNA virus genome lives where
Cytoplasm
37
Why do RNA have immune escape variants
They’re not as stable
The variability is changing the antigenicity
38
Quasi-species
Variability of RNA virus
Think of Quasimodo, he had lots of variable features
39
Helical vs iscosehedron shape
H= spiral
I = 20 sided shape
40
No human viruses that are ____ and _____
Naked and helical
41
Function of a capsid
Protect the genome
Help attachment - proteins on capsid bind to receptors on cell
Help entry/uncoating - capsid needs to fall apart to release genome
Help assembly
42
Assembly w/o capsid
Not infectious bc there is no genome incorporated
43
Naked icosahedral virus wet or dry, which means?
Dry = retain infectivity
44
Naked, icosahedral virus acidic virus or not
Survive acidic conditions of GI bc
45
A viral particle that is not infectious has ____
No genome in it
46
Naked, icosahedral viruses in response to temp and detergents
They are resistant to
extreme temps
detergents
poor sewage treatments
47
How are naked, icosahedral viruses released
Usually by cell lysis
48
Bc N, Ico are dry that means
Transmits through fomites
And
Really hard to disinfect surfaces
49
Bc N, Ico survive in acid
This means they can transmit vis fecal/oral route
They are responsible for most cases of viral gastroenteritis
50
Bc N, Ico released through lysed cells that means they are
Cytopathic
51
Viral envelope is from
Host cell
52
The viral envelope includes
Viral encoded glycoproteins
53
Glycoproteins in the envelope
Matrix proteins
Surface glycoproteins
54
Matrix proteins helps virus infect through
Assembly
It’s a bridge btw capsid and bilayer
55
Surface helps virus infect through
Viral attachment
Virus-cell fusion - fusing the bilayers
Antibody????
56
Envelope virus properties
Must stay wet
Acid and heat labile
Detergents destroy it - respond to disinfecting
Released by budding
57
The budding of enveloped viruses means
Virus release over extended periods of time
More persistent
Slowly it will kill host off
58
When N, Ico lyse out of the cell what does it do to the cell
Kills it
59
Because enveloped viruses must stay wet that means
Transmitted through droplets, secretion, resp, blood, organ transplants
60
Because enveloped viruses are acid/heat labile
They can live in GI and cant be passed fecal/oral
61
How do enveloped viruses attach
Surface glycoproteins
62
How do naked viruses attach
Capsid proteins
63
____ is key for tropism
Attachment style and viral receptors
64
What are the different types of viral receptors
Enzymes
Hormone
Cytokine
Complement receptor
Molecules involved in cell-cell interactions
65
Virus has evolved to take advantage of ____
Host receptors
66
How do enveloped viruses enter a cell
Fusion event
67
Describe fusion event
What viruses does it happen to
A hydrophobic domain/fusion peptide on the attachment protein of the virus is EXPOSED after it binds to a receptor on the host cell
Fuses to host cell and releases capsid
ENVELOPED
68
Describe how N, Ico enters cell
Hydrophobic interactions create a channel through the membrane and the RNA is let into the cytoplasm
69
pH dependent endocytosis
Involves clathrin proteins
And dynamin
1.Virus enters and turns into endosome
2.Endosome becomes acidic and fuses with lysosome
3.The acidic pH or lysosomal proteases activate fusion activity
70
pH independent endocytosis
Involves caveolin protein
a lipid raft
1.virus internalized at an invagination with a lipid raft that has caveolin
2.caveolin vesicles fuse with caveosome
3.no lysosomes or acidification involved
4.viral fusion protein active a neutral pH can fuse without acidic environment
71
What pH do you need to utilize for pH dependent entry?
Depends on the virus. Can utilize high or low pH
72
Describe endocytosis of N, Ico viruses
1. Capsid proteins form a pore through endosomal membrane
2. Viral capsid proteins lyse membrane
3. Confo Chang in capsid protein
to either
uncoat
or
create a pore
73
Uncoating means
Release of genome
74
RNA uncoating is in
Cytoplasm
75
DNA uncoating is in
Nucleus
76
Uncoating coincides with entry refers to what kind of virus
RNA
77
Triggers for uncoating
Binding to a receptor
Change in pH
Proteolytic degration
78
DNA viruses travel on what to get to the nucleus
MICROTUBLES
dynein
79
Steps in taking over the host cell
1: control transcription
2: replicate genome
3: control protein synthesis
80
Early transcripts vs late transcripts
Early: this is allll the stuff you need to shut down the host
late: now you’ve shut down the host, you can encode viral structural proteins
81
Where does transcription and translation occur in DNA viruses
Nucleus
82
DNA genome is ____ for mRNA
Template
83
Most DNA viruses use ______ encoded polymerases to replicate genome
Virally
84
Most DNA viruses use ______ polymerases to transcribe viral mRNA
Cellular
85
Positive strand RNA virus genome can function as
MRNA
86
Positive strand is the equivalent of the ____ strand
Coding
87
+ strand RNA aka
+ssRNA
88
What happens after the +ssRNA is dumping into the cell
1: translated to polyprotein
2: cleaved into viral proteins
3: on specific viral protein made is the RNA dependent RNA polymerase (RDRP)
4: the RDRP copies + strand to - strand
5: the - is a template to make more + ssRNA
6: those +ssRNA made turn into viral proteins
or Nucleocapsid
the viral proteins also eventually go to Nucleocapsid
89
What is located inside the polyprotein
A protease
90
-ssRNA is the ____ strand
Complement
91
The - strand is the _____ for mRNA
Template
92
When the -ssRNA enters a cell what does it need to bring with it
RDRP
93
What is a core protein and who encodes it
RDRP
Negative strand RNA
94
When - enters with RDRP what happens next
1: can either make (a)mRNAs or (b)+ssRNA
(A) then they make viral proteins
which then go to nucleoplasmids
(b)they then make more copies of viral genome
which then go to nucleoplasmid
95
A ___ strand copy of the genome is the template for genomic RNA
+
96
Reoviruses aka
dsRNA
97
Genome is segmented for
dsRNA
98
Segmented genome means
Diff proteins on diff pieces of RNA
99
RDRP is incorporated in
dsRNA and +/- ssRNA
100
____ strand RNA is transcribed into DNA =
+
Retrovirus
101
What is the core enzyme in retrovirus
RNA dependent DNA polymerase (RDDP)
102
____ travels to the nucleus where it integrates into the host cell
Provirus
103
The DNA provirus of retrovirus goes on to do what
It’s transcribed to make mRNA and genomic RNA
104
See retrovirus pic
Yub yub
105
Capsids ____ assemble
Self
106
____ determine site of budding for _____
Matrix proteins
Enveloped viruses
107
Viral budding can happen at the ___ or the _____
Plasma membrane or at the ER membrane
108
Antiviral therapy targets 3 things
Disrupt viral structure
Block virus specific activity
Avoids interfering with host
109
How does an antiviral disrupt viral structure
Detergents inactivate enveloped virus
110
How does an antiviral block virus specific activity
Target polymerases(this one is common), proteases, and attachment proteins
Targets steps in replication that only viruses use
111
Productive vs nonproductive
P: actively making virus particles
permissive
NP: not making viral particles
non permissive
112
Types of productive infection
Lytic
Persistent/chronic
Persistent with Lytic virus
113
What kind of infection produces changes to a cell and what is that called
Lytic
Cytopathic effect (CPE)
114
Virus buds with no lysing
Continual shedding
Chronic/persistent
115
At tissue or organ
Some cells lysed but not all
Persistent infection with Lytic virus
116
What are the types of CPE
Syncytial formation
Cell rounding or vacuolization
Inclusion bodies
117
MEGA cell is what
Syncytia formation = fusion of cytoplasm of adjacent cells making mega cells
118
Areas within a cell with lots of replication going on. Can be seen on a stain
Inclusion bodies
119
____ can help clinical virologists identify virus
CPE
120
Non reproductive infection
Abortive
Latent
121
Virus is dormant within host cell
Latent infection
122
_____ occurs in retroviruses or DNA viruses ____ RNA viruses
Latent
NOT
123
Why can’t our immune system detect latent infection
Bc the cell is not making any viral protein, so there is nothing for us to act on
124
In latent infection there are _____ for antiviral drugs to act on
No targets
125
Viral genomes usually integrate into the chromosome in _____ infections
Transforming
126
Transformed cells are ____
Immortalized
127
Immortalized cells may or may not become ____
Tumor cells
128
Mechanism for transforming cells
1: inactivate growth-regulatory proteins
2: provide or up-regulate genes involved in cell progression through the cell cycle
129
What growth reg proteins does transformation effect
P53
Retinoblastoma gene product
130
What are some consequences of transformation
Uncontrolled cell growth
Increased growth rate
Alteration of morphology and metabolism
Loss of contact inhibition of growth
just continual divisions
131
See nice map of viral replication
Yub yub
132
Acute infection remains ___
Localized
133
What type of infection is cleared by immune response
Acute
134
Acute disease leads to
Symptomatic illness
135
Where do acute infections enter host
Mucosal surfaces
136
When a host has a subacute / sub clinical infection what does that mean
They are asymptomatic BUT they are still shedding active virus
137
___ provides protection against actue infection
IgA response
138
Localized infection starts acute then ____ through _____
Disseminates
Blood
139
Where do you see symptoms of a localized infection
Replication at the secondary site
140
A disseminated infection means people are _____ before _____ is recognized
Infectious
Illness
141
Time period between exposure and symptoms show up
Incubation period
142
Prodrome
Nonspecific or flu-like symptoms during dissemination
143
___ is important for immunity of disseminated infections
IgG
144
Chronic infections could be _____ or ______
Productive or nonproductive
145
Cellular level vs tissue level productive chronic infections
C = host cell is not destroyed by infection
T = only a few cells in the population are infected at any one time
146
Non reproductive chronic infection latency vs transformation
L = reactivating of latent virus results in productive infection
T = cells are altered
147
a person is ___ during ______ but not during ______ or a nonproductive chronic infection
Infectious
Reactivating
Latency
148
When the cells are altered during nonproductive chronic infection that means they are ____ and not _____
Transforming
Infectious
149
Latency to deactivation steps
1: primary infection - local or disseminated, symptomatic or asymptomatic
2: latent infection -asymptomatic
3: reactivating - secondary infections cleared more rapidly than primary
150
Why are reactivated infections cleared more rapidly than priamary
Cuz or our memory in our immune system
151
Course of infection pic
Yub yub
152
Getting a disease depends on
Whether or not the pathogen can overwhelm the immune response
153
Balance between pathogenicity and immune response =
Whether or not you’ll get a disease
154
Symptoms of a disease are from
Our immune response
Or
Results of virus infecting and killing a cell
155
Disease pic
Yub yub
156
Transmission determines
Site of entry
157
Inoculum size influences
Severity
158
Tissue tropism determines
Site of pathology
159
Viral virulence factors =
Mech to control host cell protein synthesis
Mech to evade immune response
Mech to directly damage cells
160
If you have an acute viral infection you are treating the
Symptoms
161
Current antivirals do what
Inhibit actively replicating virus, not latent infections
162
The ____ the better with antivirals because __
Earlier
The viral replication may precede symptoms
163
Define chemoprophylaxis
Using antiviral to prevent disease from even starting
