Quiz3 Flashcards
(301 cards)
1
Q
Which mechanism do the maximum viral mRNAs use to get translated?
A
5’-end dependent mechanism
2
Q
What happens to ribosomes in 5’ end independent mechanisms?
A
They bind to the IRES
3
Q
For ribosomes to bind to IRES, what do the IRES need?
A
RNA-binding proteins
4
Q
What do the + strand RNA genomes that lack caps and polyA tail need for protein synthesis?
A
Cap independent 3’ translational enhancer
5
Q
What do unusual translational mechanisms do?
A
Expand coding capacity of viral genomes and allow the synthesis of multiple polypeptides from a single genome
6
Q
What is common in virus-infected cells?
A
Alterations in the cellular-translational apparatus
7
Q
To which NT of the mRNA is the 5’-7-methylguanosine added and how?
A
2nd NT of the mRNA by 5’-5’ phosphodiester linkage
8
Q
What is the advantage of capping?
A
- Directs pre-mRNA to processing and transport pathways
- Required for efficient translation by 5’ end dependent mechanism
- Regulates mRNA turnover (determined by the rates of mRNA synthesis and mRNA degradation which jointly adjust the level of gene expression)
9
Q
What regulates mRNA turnover?
A
5’ capping
10
Q
What determines the mRNA turnover?
A
Rate of mRNA synthesis and degradation
11
Q
Parts of an eukaryotic mRNA
A
5’ cap
5’ UTR
Initiation codon AUG
Open reading frame
Stop codon
3’ UTR
Poly A tail
12
Q
What is the typical length of 5’ UTR?
A
50-70 NT; Some over 1000
13
Q
What aspects of the mRNA structure influences translational efficiency?
A
Length of 5’ UTR and secondary structures, poly (A) tail, 3’ UTR
14
Q
What can 3’ UTR regulate?
A
Translation initiation, mRNA stability, translation efficiency
15
Q
What is the eukaryotic ribosome?
A
80s
16
Q
What are the subunits of the 80s ribosome?
A
60s+ 40s
17
Q
What rRNA and proteins is the 60s subunit of the 80s ribosome composed of?
A
28S, 5.8S, 5S rRNA
50 proteins
18
Q
What rRNA and proteins is the 40s subunit of the 80s ribosome composed of?
A
18s rRNA
30 proteins
19
Q
What are the kinds of proteins involved in translational machinery?
A
Initiation eIF
Elongation eEF
Termination eRF
20
Q
Which mRNAs are translated by the 5’ end dependent initiation?
A
Intact mRNAs with 5’ cap and poly (A) tail
21
Q
What is the first step in the 5’-end dependent initiation pathway?
A
Recognition of the m7G cap by the cap binding protein eIF4E.
22
Q
Why is the preinitiation complex formed?
A
For scanning
23
Q
Where does the preinitiation complex reach?
A
AUG start codon
24
Q
What is the multifunction binding protein of the preinitiation complex?
A
eIF4G
25
What is the helicase of the preinitiation complex?
eIF4A
26
Why are hairpin structures not inhibitory in some RNAs?
Ribosomes bypass them by ribosome shunting
27
Is ribosome shunting dependent on viral proteins?
May be dependent/ independent of viral proteins
28
How does ribosome shunting start?
40S subunit binds to the mRNA by a cap dependent mechanism
29
How does ribosome shunting work?
40S subunit bypass regions of mRNA with secondary structures to reach the AUG start codon
30
What can direct ribosome movement in ribosome shunting?
Shunting elements such as viral or cellular proteins
31
What are the shunting elements?
Loops, viral or cellular proteins
32
What is shunting predicted to decrease dependence on?
Dependence on the EIF4F of mRNAs during initiation is reduced by reducing the need for unwinding
33
Which viruses use ribosome shunting?
Plant pararetroviruses
Adenovirus mRNAs
Sendai virus
34
What is an internal ribosome entry site?
RNA element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis
35
Why are IRES sequences used?
To express two proteins from a single promoter in an expression construct or a transgenic construct
36
How many RNAs are produced with IRES?
A single RNA, but a second translational start on the same mRNA
37
What is the organization of plasmids for the expression of two genes?
Promoter -> First gene -> IRES -> Second gene
38
What mechanism is used by the first gene translated in a two-gene-expression plasmid?
5'-end dependent mechanism
39
How is the second gene translated in a two-gene-expression plasmid?
Internal ribosome entry
40
What is initiation on IRES type I and II dependent on?
C terminal fragment of EIF4G to recruit the 40S ribosomal subunit via its interaction with the eIF3.
41
How does EIF4G bind to the IRES?
Directly
42
What is IRES initiation not dependent on?
The presence of a cap structure
43
What is the hepatitis C virus IRES dependent on for the initiation of translation?
The 40s ribosomal subunit is not dependent on translation initiation proteins. eIF3 binds to the IRES, necessary for the recruitment of 60S ribosomal subunit.
44
How many tRNA binding sites are are on the ribosome and what are they?
Three tRNA binding sites:
1. Peptidyl (P site)
2. Aminoacyl/acceptor (A site)
3. Exit (E site)
45
How does the processing map of protein encoded by picornavirus/poliovirus genome look like?
One long precursor polyprotein from a mRNA; processed by viral proteases 2Apro and 3Cpro to form viral proteins
46
How does the processing/cleavage map of protein encoded by flavivirus genome look like?
Flavivirus precursor polyprotein cleaved by Host signal peptidase and/or viral serine protease NS3.
47
How many start sites are there in the Sendai virus C protein?
Four
48
How many proteins can be formed from the P open reading frame of sendai virus and what are they?
4. P, V, W, X.
49
How are the different proteins formed from the P open reading frame in sendai virus?
mRNA editing.
50
How many proteins are formed from a single mRNA of sendai virus P/C gene/ paramyxoviridae
8
51
What is the process of different proteins being formed from the C open reading frame of Sendai virus?
Leaky scanning
52
What are the translation termination proteins?
eRF1 and eRF3
53
What do the translation termination proteins recognize?
They recognize all three stop codons, UGA, UAA, UAG
54
What other than the translation terminations proteins can recognize the stop codons?
Charged-tRNA misreading, charged suppressor tRNA (e.g. selenocysteine for UGA)
55
What does normal translation and termination produce in retroviruses like rous sarcoma virus in ORFs that have gag and pol proteins in reading frames that overlap by -1?
Only the gag proteins are produced
56
How is the gag-pol fusion protein made in rous sarcoma virus?
Ribosomal frameshifting to the -1 frame
57
When does the slippage of the two tRNAs occur?
After the aminoacyl-tRNA enters the A site but before peptidyl transfer
58
What does slippage allow the tRNA to do?
Form only two base pairs with the mRNA
59
What are miRNAs?
They are small, non-coding RNAs found within the viral/cellular genome
60
How is the miRNA transcribed?
By either pol-II or pol-III as 60-70 nt pre-miRNA
61
How is the pre-miRNA processed?
To a ~21-NT miRNA
62
How many miRNAs are found so far?
>1000
63
What does miRNA regulate
~60% of the protein coding genes
64
How do miRNA control gene expression?
mRNA degradation, repression of translation
65
Where of the 3'-UTRs do the miRNA bind?
About 15-NT after the ORF
66
What determines whether the mRNA is degraded or translated?
Complementarity to the 3'-UTR
67
What structure do miRNA form while binding to mRNA?
Bulge
68
What does miRNA complex with to function?
AGO, Dicer, TRBP to form miRNP
69
What are the two ways that miRNA regulate translation?
Initiation block and elongation block
70
How does miRNP block initiation of translation?
It inhibits cap recognition by eIF4E, or it inhibits the joining of 60S subunit
71
How does miRNP block elongation of translation?
Slowed translation, causing ribosome drop off
72
What is an example of a liver specific miRNA?
miR-122
73
Why is miR-122 necessary?
HCV replication
74
What do miRNAs target?
Viral or cellular genes needed for viral replication
75
What miRNA is induced during enterovirus infection?
miR-141
76
What does miR-141 inhibit?
Translation of eIF4E mRNA
77
Four functions of viral miRNAs
1. Block apoptosis
2. Facilitate immune escape
3. Prevent cell cycle arrest
4. Promote latency
78
How many viral encoded miRNA in herpesviridae
>200
79
How many viral encoded miRNA in polyomaviridae
>4
80
How many viral encoded miRNA in baculoviridae
4
81
How many viral encoded miRNA in adenoviridae
2
82
How many viral encoded miRNA in ascoviridae
1
83
How many viral encoded miRNA in retroviridae
?
84
What are the three host defenses?
Intrinsic, Innate, Acquired
85
What are some physical and chemical defenses of the host?
Skin, low pH, tears, mucus, surface cleansing
86
What are examples of some intrinsic immune defenses?
Autophagy, apoptosis, RNA silencing, antiviral proteins
87
When is the intrinsic immune defense present?
Always in the uninfected cell
88
How does innate immune system start?
Induced by infection
89
Property of adaptive immune system
Tailored to pathogen
90
Where is RNAi against viral genomes present?
Plants and invertebrates.
RNAi present in mammals, but not sure if it's against viruses
91
Which of the APOBEC3 proteins can encapsidate into HIV virions?
APOBEC3D, APOBEC3F, APOBEC3G, APOBEC3H
92
What is the function APOBEC3 proteins?
Deamination of cytosine to Uracil upon reverse transcription of the viral RNA in target cells.
93
What kind of mutations happen due to the deamination activity of APOBEC3 proteins?
Guanine-to-Adenine mutation
94
What leads to the Guanine-to-Adenine mutation through the activity of APOBEC3 proteins?
Cytosine deaminated to Uracil, which was previously going to template Guanines. But since deaminated to Uracils, they template Adenine.
95
What is the ultimate fate of the proviral cDNAs with guanine-to-adenine mutation?
Degradation
96
What is the example of a protein that restricts the immune defense by APOBEC3 proteins for HIV-1 infections?
Vif proteins
97
What is the mechanism of action of the Vif proteins for overcoming the APOBEC3 restriction block?
Vif binds CBF proteins recruiting E3 ubiquitin ligase complex.
E3 ubiquitin ligase complex polyubiquitylates APOBEC3 proteins and target them for degradation by 26S proteasome.
98
Among the producer and target cell, where does Vif proteins overcome the APOBEC3 restriction block?
Producer cell
99
What is autophagy?
The process of self-digestion by a cell through the action of enzymes originating within the same cell
100
What are the different steps of autophagy?
Phagophore -> Autophagosome -> Fuse to lysosome -> Degradation
101
What is apoptosis?
A type of cell death where the cell uses specialized cellular machinery to kill itself
102
What does apoptosis (a cell suicide mechanism) allow the animals to do?
Control cell number and eliminate cells that threaten the animal's survival
103
What are the steps of apoptosis?
Apoptosis begins -> Apoptotic bodies are formed -> Taken up by macrophages
104
What are examples of some innate immune defenses?
Sentinel cells (Dendritic cells, NK cells, macrophages), cytokines, complement
105
When is the innate immune system activated?
Minutes to hours after infection
106
What happens when the Pattern recognition receptors cannot recognize the pathogen?
No innate immune response
107
What happens in adaptive immune response?
1. Pathogen structure evaluation
2. Fine tuning response
3. Clonal expansion of B and T cells
4. Memory
108
Who identified the toll gene and when?
1980, Nusslein-Volhard and Wieschaus
109
What does the toll gene do in drosophila embryos?
Establish the dorsal-ventral axis
110
What was found out about the toll gene related to flies in 1996
Toll have role in immunity of fly to fungal infections
111
When did Nusslein-Volhard and Wieschaus get the nobel prize
1995
112
When was toll-like receptors identified in mammals?
1997
113
What are the parts of a Toll-like receptor, TLR?
Leucine rich repeats and the TIR (Toll/Interleukin-1 receptor) domain
114
What binds the drosophila toll ectodomain?
spaetezie
115
What are the TLRs concerned to viruses?
Tlr3, Tlr7, Tlr8, Tlr9
116
What pattern does Tlr3 recognize?
DSRNA
117
What pattern does Tlr7 recognize?
SSRNA
118
What pattern does Tlr8 recognize?
SSRNA
119
What pattern does Tlr9 recognize?
CpG DNA; unmethylated CpG oligonucleotides
120
What are the helicases that recognize RNA viruses?
MDA-5 and RIG-1
121
What kind of RNA genomes do the helicases MDA-5 and RIG-1 recognize?
DSRNA
122
What do the helicases MDA-5 and RIG-1 bind to start the signaling cascade?
Mitochondrial CARD, through the MAVS/IPS1/VISA/CARDIF proteins
123
What does the RNA helicase signaling cascade activate transcription factors for?
Inflammatory cytokines
124
What happens in sensing DNA?
DNA is recognized in the cytoplasm by
- "IFI16" and "DDX41", that would activate cGAS. cGAS would utilize ATP and GTP to produce cGAMP, which would bind to STING, and start the signaling pathway of many phosphorylations, nfkb activated, they will go to the nucleus, and stimulate transcription of inflammatory and immune genes
125
What is sensing DNA mechanism similar to?
GPCRs and their signaling pathways through recognition of hormones
126
What are examples of cytosolic multiprotein oligomers of the innate immune system?
Inflammosomes
127
What are the roles of inflammosomes?
To produce caspace-1
128
What are two examples of inflammosomes?
AIM2 and NLRP3
129
Which inflammosome detects DSDNA?
AIM2
130
What do the caspaces produced by inflammsomes activate?
Inflammatory interleukins 1beta and 18.
131
Who discovered interferons and when?
Issac and Lindenmann; 1957
132
How were interferons discovered?
Chicken cells exposed to non-infectious influenza produce substance that interfered with infection of other cells
133
Which cells produce interferons and what triggers its release
Virus-infected cells and uninfected sentinel cells produce interferons in response to products released from the cell (i.e. viral nucleic acid)
134
Who are the producer cells of IFN-alpha and IFN-beta
Most if not all nucleated cells
135
What induces the production IFN-alpha and IFN-beta
Viral infection
136
Who are the producers cells of IFN-gamma
T cells, NK cells
137
What induces the production IFN-gamma
T cell activation, IL-2 and IL-12
138
What are the receptors of Type I interferons?
IFNAR1 and IFNAR2
139
What are the receptors of Type II interferons?
IFNgR1 and IFNgR2
140
What kind of pathway does IFN binding to its receptors activate?
JAK-STAT signaling pathway
141
What does IFN binding to its receptors stimulate the synthesis of?
ISGs, >1000 cell proteins
142
When does IFNalpha/beta decline?
Within 10 hours
143
When is IFNalpha/beta produced?
Within hours of infection
144
What physiological consequences do large quantities of IFN have?
Fever, chills, nausea, malaise
145
What are the sentinel cells?
Macrophages, dendritic cells, NK cells
146
What do the sentinel cells do?
They patrol all our tissues looking for signs of change.
147
What causes the common flu-like symptoms?
Interferon production
148
How does the classical cascade begin?
When a pathogen is detected by C1q
149
How many classical detector systems are there?
Two except the detection by C1q.
C1r, C1s
150
Explain the classical complement system
C1q detects the virus particle, opsonizes/binds to the antigen antibody complex -> C3 convertase takes the b subunit of C4 and a subunit of C2 and form C4b2a (bound to cell surface) -> Activates C3 -> C3B subunit bound to C4b2a (C4b2a3b) ; a subunit (mediator of inflammation) -> C5 targeted, C5a (mediator of inflammation), C5b bound to membrane -> C6, C7 bound to C5b (C5b67) -> Activates C8 and C9 and they form the membrane attack complex
151
What is the membrane attack complex?
C5b6789
152
Which subunits are mediators of inflammation?
C3a and C5a
153
How many functions of complement and what are they?
Four functions:
1. Opsonization
2. Cytolysis
3. Inflammation
4. Solubilization
154
What is cytolysis?
Make holes in the infected cells if they have bound antibody or have unusual proteins on their surface
155
What is inflammation
Activation by cytokines
156
What is opsonization
Coat virus particles to facilitate uptake by macrophages
157
What is solubilization
Solubilization of the immune complexes (antigen antibody complexes)/ breaking them up which can damage the organs
158
How does infection lead to inflammatory response?
Infection -> Cytokines produced -> Inflammation -> Increased capillary permeability, increased blood flow, influx of phagocytic cells, Tissue damage -> Redness, heat, swelling, pain (Four classic signs of inflammation)
159
What are the four classic signs of inflammation?
Redness, heat, swelling, pain
160
What are the three classes of cytokines?
Proinflammatory, anti-inflammatory, chemokines
161
What is the activity of proinflammatory cytokines?
Promote leukocyte activation
162
What is the activity of anti-inflammatory cytokines?
Suppress activity of proinflammatory cytokines, return system to "circulate and wait" state
163
What is the activity of chemokines?
Recruit immune cells during early stages of immune response
164
Examples of proinflammatory cytokines
IL-1, TNF, IL-6, IL-12
165
Examples of anti-inflammatory cytokines
IL-4, IL-10, TGF-B
166
Example of chemokine
IL-8
167
How do the cytokines function initially?
Locally in antiviral defense
168
How can cytokines enter circulation and what can they do?
In large quantities cytokines can enter circulation and have global effects (sleepiness, lethargy, muscle pain, nausea, no appetite)
169
Which viruses do not effectively activate the adaptive immune response
Non-cytopathic viruses
170
How do non-cytopathic viruses work?
Do not stimulate inflammatory response, cells are not damaged, no apoptosis/no necrosis -> Low/ineffective innate immune response
171
What are persistent infections?
Rarely/inefficiently cleared
172
Which viruses cause persistent infections?
Non-cytopathic viruses
173
What does the classic inflammatory response reflect?
Communication between innate and adaptive immune system
174
When is inflammation-stimulating adjuvants used?
For non-infectious vaccines
175
What is the workflow from innate to adaptive immunity?
Virus binds to epithelial cells -> Replication and local spread of infection -> Cytokines released -> Immature dendritic cells mature -> Travel to lymph node -> Then the circulatory system -> Adaptive immunity takes over
176
What can packaging of the genome be coordinated with?
It can be coordinated with the assembly of the capsid/nucleocapsid
177
What can be coordinated in the enveloped viruses?
Acquisition of the envelope can be coordinated with assembly of the internal components (i.e. retroviruses)
178
What are the common steps of assembly reactions?
Structural units formed -> Assembly of the protein shell by appropriate and sometimes variable interactions among structural units -> Selective packaging of the viral genome and virion components -> Acquisition of envelope -> Release from host cell -> Maturation of the virion
179
What determines how a virus is formed?
The structure of a virus particle
180
What host cell machinery is assembly dependent on?
Nuclear import and export machinery, transports, secretory pathway, cellular chaperones
181
What are the concentrated viral components called?
Viral components factories or inclusions
182
Where does poliovirus concentrate proteins?
Internal membranes
183
What are the concentrated components of rabies virus called?
Negri bodies
184
What are the built in structures for membrane targeting?
Signal sequences and fatty acid modifications
185
What kind of localization signal does SV40 T antigen have?
Simple (Hydrophobic- Basic - Hydrophobic)
186
What kind of localization signal does nucleoplasmin have?
Bipartite (Basic -X10 - Basic)
187
How many strategies are there to make sub-assemblies of viral structural units?
Three
188
What are the strategies of sub-assembling viral structural units?
1. Assembly from individual protein molecules
2. Assembly from a polyprotein precursor
3. Chaperone-assisted assembly
189
Which virus sub-assembles from individual protein molecules?
Simian virus 40
190
What does the simian virus 40 sub-assembly look like?
SV40 pentamer from VP proteins
191
Which virus sub-assembles from polyprotein precursor?
Poliovirus
192
What is the poliovirus sub-assembly called and how is it formed?
5S structural unit. It is formed from the processing of folded P1 protein by 3CDPro
193
Which virus sub-assembles using chaperone proteins?
Adenovirus type 2
194
What chaperone protein does adenovirus type 2 use?
L4 100-kDa protein
195
What does the L4 100-kDa chaperone protein form?
AD2 hexon trimer
196
In the poliovirus assembly, when does the transition from provirion to virion occur?
Due to the cleavage of Vp0 to Vp2 and Vp4
197
What are the different structures formed sequentially during poliovirus assembly?
3CDpro cuts the folded P1 -> 5S structural unit -> 5 of 5S structural unit come together to form the 14S capsid pentamers -> 75S empty capsid -> 150S Provirion -> Cleavage of Vp0 to Vp2 and Vp4 -> 150S Virion
198
When does the 135S structure happen in poliovirus life cycle?
When it's on the membrane/receptor of a new cell -> undergoing conformational change and uncoating
199
What are the late steps in T4 assembly?
Head -> Tail -> Tail fiber
200
What does assembly line concept ensure?
Orderly formation viral particles and virion subunits. Formation of discrete intermediate structures. Can't proceed unless the previous structure is formed.
201
Examples of self-assembled virus particles
gag - retrovirus
HA - influenza
VLP - HBV
202
Example of a virus undergoing concerted/sequential assembly
Influenza A virus
203
Where does the assembly of influenza A virus take place
The membrane during budding
204
What happens in influenza A assembly?
It's a -SSRNA. Gets to the nucleus. Gets replicated. mRNA is transcribed. mRNA leaves nucleus, translates M1 and NEP proteins, they get inside nucleus, they bind to the -SSRNA replicated genome, they transport to the membrane. Some other mRNA gets translated in the ribosomes attached to the ERs (HA, NA, M2), through golgi they reach membrane, assemble, bud
205
How is cellular DNA/RNA distinguished from viral DNA/RNA during packaging?
Packaging signals in the viral genome
206
Where is the adenovirus (AD5) packaging signal located?
Near left inverted repeat and origin of replication and E1A transcription unit
207
What is the adenovirus packaging signal?
Set of repeated sequences overlapping with the enhancers that stimulate late transcription
208
Who recognizes the adenovirus packaging signal?
Viral protein IVA2 (also a transcriptional activator)
209
Where is the simian virus packaging signal located?
After the enhancer, in the SP1 binding sites, before the origin of replication and early transcription unit
210
If the packaging mechanism was random, what would be the particle to pfu ratio of segmented genomes?
1 infectious particle per 400 assembled
211
Where are the signals for influenza virus RNA packaging located?
Signals at the coding and non-coding sequences at the 5' and 3' ends.
212
What does the structure of the RNPs look like during budding for influenza?
A distinct pattern, perpendicular to the membrane
213
How does the packaging of the φ6 virus look like?
Serial dependence of packaging, 3 DSRNA, first the small (S) goes in, medium goes in if (S) is present, and large (L) goes in if (M) is present
214
What is the particle to pfu ratio of φ6 virus
~1
215
When do most enveloped viruses gather envelop?
After assembly of internal structures
216
How many budding strategies are there?
Four
217
What are the budding strategies
1. Envelope glycoproteins + capsid proteins
2. Capsid proteins + matrix proteins
3. Envelope proteins
4. Matrix proteins drive budding but additional components (glycoproteins, RNP) needed for efficiency
218
What is an example of a virus that uses the envelope glycoproteins and capsid proteins for budding?
Alphaviruses
219
What is an example of a virus that uses the internal matrix proteins and capsid proteins for budding?
Retroviruses
220
What is an example of a virus that uses the glycoproteins for budding?
Coronaviruses
221
How do viruses leave infected cells?
1. Release from the cell by budding or lysis
2. Move from cell to cell
222
What does the assembly of some large icosahedral proteins require?
Scaffolding or chaperone proteins
223
What is an assembly line mechanism well suited for?
Orderly formation of some virus particles
224
What must the virus genome do to survive?
It must establish itself in a host population
225
What is virus infection with no obvious disease called
Inapparent
226
In how many years did West Nile Virus spread?
4, From 1999 to October 2004, 1 million cases in US (Antibody positive)
227
How many of the infected people had febrile illness for WNV?
20%
228
How many had neuro-invasive disease for WNV?
1%
229
Why can't a WNV epidemic be stopped?
It can't be recognized early
230
What is pathogenesis
Process of producing a disease
Chain events leading to that disease
The development of a disease
231
What are the two components of viral disease?
Effects of viral replication on the host
Effects of host response on the virus and the host
232
What are thee requirements of a successful infection?
Enough virus, cells should be accessible, susceptible, permissible, local antiviral defense absent or overcome
233
How do the viruses that are sensitive to heat, drying, sunlight (UV) overcome this restriction?
By producing large number of virions
234
What are the properties of viruses that are stable in low pH or stable to proteases?
They survive in gut, they spread by fecal-oral transmission (water borne)
235
Which viruses never experience the environment?
Insect and arachnid vectors
236
How do the infections spread by physical contact?
Bodily fluids, those viruses are not stable outside for long
237
How many sites of entry are there for viral infection in human body?
A limited spectrum
238
How are the virions that land on skin are inactivated?
By desiccation, acids, low pH - 5.5, or by other inhibitors formed by our cells or by commensal micoorganism (Antimicrobial peptide)
239
How much mucus does a normal individual produce per day in nasal cavity, lungs
20-200ml
240
How much liquid is transferred from lungs to esophagus through muco-ciliary escalator
1cm/minute
241
How is the virus swept to esophagus and what happens to it
Through ciliary action, where it is swallowed 30 times per hour
242
Where are virus particles filtered?
Sinuses
243
What do the lower regions of respiratory tract have?
Immune cells, antibodies
244
What kind of barrier does the small intestine have?
Selectively permeable
245
What kind of epithelial cells do the small intestine have?
Polarized, enterocytes and M cells
246
What is the small intestine in direct contact with
Outside world and also the nervous system and the immune system
247
What part of eyes are most vulnerable to viral infections?
Bulbar conjunctiva and sclera
248
What is one viral infection of the eye?
Subconjunctival bleed
249
What is disseminated viral spread?
When it spreads beyond the primary site
250
What is systemic viral spread?
If many organs are infected
251
What is a localized virus?
Spreads within the epithelium, contained by tissue structure and immune system
252
Example of a neurotropic virus
West nile virus
253
What can west nile virus do?
Can cause encephalitis or paralysis
254
Example of a virus with tropism for CD4 T cells
HIV
255
What can HIV do
Immunodeficiency
256
What is tropism
The capacity of a virus to infect/damage specific cells/tissues/species
257
What is the capacity to induce disease dependent on for viruses?
Dependent on the cell and tissue infected
258
Tissue tropism
The tissues where the viruses like to replicate
259
Three tissue tropism examples
Enterotropic (Intestine)
Neurotropic (Nervous system)
Hepatotropic (Liver)
260
What is a pantropic virus?
It has tropism for multiple organs
261
What are the determinants of tissue tropism?
Susceptibility, permissibility, accessibility, defense
262
What is virus shedding
Process that occurs when a virus is present in bodily fluids or open wounds and thus can be transmitted to another person
263
What are the exceptions to virus shedding?
Germline
Blood supply
Vectors
264
What are examples of virus shedding
Respiratory secretions, nasal secretions, urine, semen, blood, skin lesions
265
What are respiratory secretions?
Aerosol produced by coughing, speaking, sneezing
266
What are the three kinds of aerosols and how far do they spread
Large infectious droplets (1-3 ft)
Small infectious droplets (3-5 ft)
Infectious droplet nuclei (5-160+ ft)
267
What is required to maintain the chain of infection?
Spread of infection from one susceptible host to another
268
How many general patterns are there for transmission of infection and what are they?
Direct, human - human
Indirect, through a vector
269
What is transovarial transmission
The transmission of an infectious agent from parent to offspring via infection of the developing egg which subsequently results in infectious adult arthropods
270
How are non-enveloped virions spread
Fomites, fecal-oral routes, transmitted respiratory
271
How are enveloped virions spread
Aerosols or secretions, vectors, injections, organ transplantation
272
What is the transmission type when activity of the healthcare worker leads to infection of patient
Iatrogenic
273
What is the transmission type when individual is infected in hospital or healthcare facility
Nosocomial
274
What is the transmission type when infection is transferred from parent to offspring
Vertical
275
What is germline transmission
Agent is transferred as part of the genome (Proviral DNA)
276
Chikungunya virus classification
Family (Togoviridae)
Genus (Alphavirus)
277
How is chikungunya virus spread
Through Aedes aegypti
278
Symptoms of chikungunya virus infection
Rash, joint pains
279
Where was chikungunya virus first identified
Tanzania
280
When did chikungunya virus spread from Kenya to India
2004
281
When and where, the first case of chikungunya in europe
2007, Italy
282
What is associated with the recent chikungunya virus infections?
A. albopictus
283
Recent chikungunya virus infection structural change?
One amino acid change in viral E1 glycoprotein
284
Rubella and Influenza seasonality
Nov - July
285
Poliomyelitis seasonality
North pole- Towards the end of the year
South pole- Towards the beginning of the year
286
Seasonality of influenza according to humidity
Low % humidity, higher transmission as droplet nuclei form
287
What is incidence
New cases/ Defined time period
288
What is prevalence
Number of cases at a given time
289
Mortality rate
Deaths / Total infections
290
Morbidity rate
Illness/ Total infections
291
Case fatality ratio
Deaths/ Total with disease
292
What is the scaffolding protein for adenovirus type 5?
L1 52/55 kDa-proteins
293
What is the function of L1 52/55 kDa proteins?
Present in immature, not mature particles
May be required for encapsidation
Necessary for formation of capsid
294
What is a chaperone protein for African Swine Fever Virus?
CAP80
295
What is the function of CAP80
Productive folding of the major capsid protein p73
296
What is a protein that works as both scaffold and chaperone for HSV1
VP22a
297
Function of VP22a
Scaffold: Forms a scaffold like structure that organizes the assembly of empty nucleocapsid
Chaperone: Formation of VP5 pentamers
298
What is a chaperone protein for Simian Virus 40?
LT antigen
299
What is the function of LT antigen?
N-terminal J domain necessary for assembly of virus particles
Binds and stimulates the activities of cellular Hsc70 proteins
300
What is a scaffolding protein for Adenovirus-associated virus type 2?
Assembly activating protein (AAP)
301
What is the function of assembly activating protein?
Interacts with common C terminus VP1, VP2, VP3; promotes capsid assembly; forms high molecular weight oligomers
