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Hepatitis C Flashcards

(88 cards)

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1
Q

Hepatitis C baltimore classification?

A

Group IV

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2
Q

Hepatitis C genome?

A

+ssRNA

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3
Q

Hepatitis C infection leads to chronic infection in how many cases?

A

60-80%

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4
Q

Hepatitis C early infection symptoms?

A

No symptoms

Asymptomatic

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5
Q

HCV can be cured by?

A

Anti-viral drugs

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6
Q

Family?

A

Flaviviridae

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7
Q

Genus?

A

Hepacivirus

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8
Q

How many ORFs?

A

A single ORF

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9
Q

1 ORF encodes?

A

A polyprotein

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10
Q

The polyprotein results in how many proteins?

A

10

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11
Q

How are 10 proteins made from the polyprotein?

A

Viral encoded and host cell encoded proteases

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12
Q

The genome is flanked by?

A

5’ and 3’ NTR

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13
Q

HCV genome structure?

A

+ssRNA
1 ORF
Flanked by 5’ and 3’ UTR

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14
Q

5’ UTR includes a?

A

IRES

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15
Q

IRES?

A

Internal Ribosomal Entry Site

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16
Q

Structural proteins encoded?

A

Nucleocapsid C

E1 and E2 glycoproteins

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17
Q

Non-structural proteins encoded?

A

P7, NS2, NS3, NS4A, NS5A, NS5B

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18
Q

NS2/3?

A

Autoprotease

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19
Q

NS3/4A?

A

Autoprotease

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20
Q

NS5A?

A

Responsible for creating the membranous web

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21
Q

NS5B?

A

RNA dependent RNA polymerase

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22
Q

E1 function?

A

Fusion

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23
Q

E2 function?

A

Attachment to the cell

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24
Q

NS2/3 mediates cleavage of?

A

NS2/NS3

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25
NS3/4A mediates cleavage of?
NS3/NS4A NS4A/NS4B NS4B/NS5A NS5A/NS5B
26
NS4A is a?
Cofactor of the NS3 protease activity
27
NS3/4A can also cleave cellular factors included?
Adaptor proteins essential for signal transduction
28
NS3/4A can cleave which adaptors?
TRIF and MAVS
29
TRIF is an adaptor in which signalling pathway?
All TRLs apart from TLR3 use the Myd88 signalling adaptor TLR3 uses TRIF NS3/4A can cleave TRIF
30
How does NS3/4A interrupt with TLR3 signalling?
Cleaving TRIF
31
TLR3 signalling leads to?
Activation of IRF-3 and NF-kB required for IFN-b production
32
MAVS is also known as?
Cardif
33
How does NS3/4A interfere with RIG-I/MDA-5 signalling?
Cleaving MAVS | MAVS is an adaptor that the RLRs- rig like receptors bind to, in order to drive IRF-3 activation and NF-kB
34
RIG-I senses?
Short dsRNA
35
MDA-5 senses?
Long dsRNA
36
NS3 can also inhibit TBK1 which causes which effects?
TBK1 is essential for phosphorylation and activation of IRF-3 in response to cytosolic DNA (DAMPs...)
37
How does NS3 disrupt TBK1?
Directly interferes with the binding of TBK1 to IRF-3 and prevents activation of IRF-3 via phosphorylation
38
NS5B has which function?
RdRP | RNA dependent RNA polymerase
39
NS5A has which function?
Formation of the membranous web
40
P7 is?
An ion channel
41
P7 function?
Required for viral assembly and release
42
Why is HCV so genetically diverse?
Due to RNA polymerase- no proof-reading ability
43
HCV is a genetically diverse virus that can be classified into how many genotypes
7
44
Virion structure?
E1 and E2 glycoproteins form the envelope | Inside the envelope there is an icosahedral core
45
E1 mediates?
Fusion
46
E2 mediates?
Cell attachment
47
The virion of HCV is a?
Lipoviroparticle
48
Lipoviroparticles contain?
Low density and very low density lipoproteins
49
Replication of HCV occurs in?
Liver hepatocytes
50
What determines the tropism of this virus?
Presence of miRNA-122 in the hepatocytes determines the tropism of the virus, it is required for viral replication
51
Replication of HCV occurs where?
In the cytoplasm
52
What is the first receptor HCV binds to?
Low affinity receptor | LDLs- low density lipoprotein receptor
53
What high affinity receptor does HCV then bind to?
SR-B1
54
Interaction with SR-B1 causes?
Conformational changes in viral envelope glycoprotein E2
55
SR-B1 is what type of receptor?
A scavenger receptor
56
Binding to SR-B1 causes?
A conformational change in E2 causing it to bind to CD81
57
CD81 along with tight junction proteins such as?
Claudin-1 and occludin
58
CA81 along with claudin-1 and occludin (tight junction proteins) complex results in?
Triggers HCV to be internalised via receptor mediated endocytosis
59
Low pH within the endosomal compartment triggers?
Fusion via glycoprotein E1
60
Overview of entry?
Low affinity binding to the low density lipoprotein (LDL) receptor Binding to SR-B1 which triggers a conformational change in E2 and causes binding to CD81 CD81 complex with tight junction proteins (claudin-1 and occludin) triggers clathrin mediated endocytosis of the virion Low pH in the endosomal compartment triggers a change in the E1 glycoprotein which mediates fusion +ssRNA then released into the cytoplasm
61
+ssRNA can be directly?
Translated
62
Translation occurs where?
ER | Endoplasmic reticulum
63
How is translation initiated?
CAP independent manner
64
How does IRES initiate translation?
Direct binding of IRES to the 40S subunit of the eukaryotic ribosome
65
miR-122 an miRNA is expressed in high levels where?
In the hepatocytes
66
What is the function of miR-122?
It binds in two places in the 5'UTR upstream of IRES and stabilises the genome allowing translation to occur
67
What determines the tropism of HCV?
miR-122 presence
68
Translation yields?
A single protein- polyprotein
69
How is the polyprotein processed?
By cellular signal peptidase and signal peptide peptidase | By viral proteins
70
How is the polyprotein processed by viral proteins?
NS2/NS3 processed by NS2/NS3= autoprotease | NS3/4A processes: NS3/NS4A, NS4A/NS4B, NS4B/NS5A, NS5A/NS5B...= autoprotease
71
How is the polyprotein processed by cellular proteases?
Cleavage of E1, E2, nucleocapsid C and P7 is mediated by signal (peptide) peptidases
72
The proteins that are produced are not free-floating they are?
Membrane associated
73
RNA replication takes place in?
A membranous web
74
Membranous web is formed by?
NS5A
75
Membranous web is mostly composed of?
Double membrane vesicles containing HCV non-structural proteins
76
How does replication occur?
+ssRNA --> -ssRNA intermediate --> +ssRNA
77
What may be the function of the membranous web?
To protect the viral RNA from being detected by the immune system
78
Newly synthesised +ssRNA can be used for?
- Packaging into viral particles - In translation to make more proteins - As a template for more rounds of replication
79
Why is the mutational rate of HCV very high?
NS5B is an RdRP | It has no proofreading ability and is very error prone
80
Assembly and release?
Core protein from ER membrane to lipid droplets- cytoplasmic organelles HCV RNA relocated from the membranous web to lipid droplets where they are encapsulated - viral capsid takes a bit of the lipid droplet with it
81
Why do the HCV particles often differ in size?
Due to the lipids incorporated into the virion- LVP= lipoviroparticle
82
HCV subgenomic replicon was created in?
1999
83
The HCV subgenomic replicon structure?
IRES and 5'UTR of HCV Neo- neomycin phosphotransferase gene IRES of EMCV NS3-NS5
84
What has been removed?
C,E1,E2,P7,NS2
85
All of the structural proteins were removed so therefore?
No infectious particles can be made
86
How can selection occur?
Apply to Huh-7 cells on G418 medium (antibiotic) The antibiotic will kill any cells not expressing the neomycin phosphotransferase which confers resistance to certain antibiotics
87
Which cells will survive?
The cells in which the replicon is self-amplifying
88
Advantages of the system?
Non-infectious means it can be worked with at the lowest biosafety levels Can be used in drug research Helps us to study replication

MM- Viruses (13 decks)

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