Interferon Flashcards
1
Q
Which gene is key to the interferon induction pathway? What does deficiency in this lead to?
A
IRF-7
lack of IFN-alpha
2
Q
IRF-3 gene does what?
A
Influences IFN resposne
3
Q
IRF-7 gene does what?
A
key to the interferon induction pathway
4
Q
3 levels of virus immunity and examples?
A
- Intrinsic – skin, mucous, all barriers that keep viruses out of the body
- Innate – fast acting and non-specific which is switched on when viruses are detected. Is what makes you feel ill because it switches on inflammatory chemokines and cytokines
- Acquired – takes a longer time to respond and remembers the virus for the future.
5
Q
What inside host cells decides if a nucleic acid is self or pathogenic
A
ZAP
6
Q
What does ZAP do and where is it
A
Inside host cells decides if a nucleic acid is self or pathogenic
7
Q
What indicates to ZAP that a nucleic acid is foreign
A
If it has a lot of CpG (CG dinucleotides)
8
Q
3 functions of IFN?
A
- Induce antimicrobial state in infected and neighbouring cells
- Modulate innate response to promote antigen presentation and natural killers but inhibit pro-inflammation
- Activate the adaptive immune response (by enhancing B and T cells)
9
Q
What are type 1 IFNs?
A
alpha and beta
10
Q
What cells secrete IFN beta
A
All
11
Q
What cells have IFN-alpha receptors
A
All
12
Q
What triggers IFN-beta induction
A
IRF3
13
Q
What cells secrete IFN-alpha
A
plasmacytoid Dendritic cells
14
Q
How many types of INF alpha and beta are there
A
- One gene for IFN- so only one type, 13/14 isotypes of IFN-
15
Q
What triggers IFN-alpha induction
A
IRF-7
16
Q
What is T2 IFN?
A
IFN-gamma
17
Q
What produces IFN-g
A
- Produced by activated T cells and NK cells
18
Q
What type of cells do IFN-lambda signal through
A
Epithelial
19
Q
Where is IFN-lambda important (2)
A
Epithelial surfaces and liver
20
Q
Epithelial cells make what interferons
A
IFN-lambda, and IFN-alpha or IFN-beta
21
Q
How do we differentiate self from non-self (mention 2 key things - what differentiates us, and how do we notice this different thing)
A
- Pathogen Associated Molecular Patterns (PAMPs) are things that all viruses have that our own cells do not have
- Pattern Recognition Receptors (PRRs) see these viral PAMPs
22
Q
3 PRR examples?
A
RLR, TLR, NLR
cytoplasmic RIG-I like receptors RLRs (sitting in the cytoplasm to bind to viruses in the cytoplasm) , endosomal Toll like receptors TLRs (membrane proteins), cytoplasmic nucleotide oligomerization domain receptors NLRs
23
Q
Examples of a DNA sensor?
A
cGAS
24
Q
What is cGAS an example of?
A
DNA sensor
25
What downstream molecule do PRRs interact with which causes phosphorylation of IRF3 or IRF7
MAVS
26
What activates MAVS
PRRs
27
What does MAVS cause
phosphorylation of IRF3 (or IRF7 in the plasmacytoid dendritic cells)
28
What causes phosphorylation of IRF3
MAVS
29
What causes phosphorylation of IRF7
MAVS
30
Where is IRF7 found
in plasmacytoid dendritic cells
31
Describe the pathway taken for IFN to be produced starting from virus entering cell
enters a cell and produces RNA (for the purpose of this example it is an RNA virus)
- The RNA is recognised by a PRR in the cytoplasm, e.g. RIG-I
- Upon binding viral RNA, PRRs change shape, unfold and interact with a downstream molecule called Mavs
- Mavs sends a signal through other pathways which ends up phosphorylating IRF3 (or IRF7 in the plasmacytoid dendritic cells)
- IRF3 then moves into the nucleus and sits on the promotor of the IFN- gene
- This causes production of IFN- and the desired response
32
What does MAVS stand for
mitochondrial associated viral signaller
33
where do TLRs sit (2)
mitochondrial associated viral signaller
34
What do TLRs recognise
- TLRs will see single stranded RNA inside the endosome/cell surface
35
what does activation of a TLR do (does X by Y Z)
y is a verb
- TLRs will see single stranded RNA inside the endosome/cell surface, activate and send a signal into the nucleus of a cell
- This will switch on the expression of the IFN- gene by phosphorylating IRF3
36
What does cGAS signal through
STING
37
Where is cGAS found
In the cytoplasm of a cell
38
What does cGAS bind to
DNA PAMPs
39
What does cGAS synthesise once bound to a DNA PAMP
cGAMP
40
what does cGAMP bind to
STING
41
What binds to STING
cGAMP
42
What synthesises cGAMP
cGAS
43
Where is STING found
On the rER in the cytoplasm
44
Describe the cGAS detection of DNA
- Sensors (cGAS) in the cytoplasm which sense and bind the DNA PAMPS, and synthesise a small molecule dinucleotide called cGAMP
- cGAMP binds to STING (which sits on the membrane of the rER), and STING is phosphorylated and uses the IRF3 dimerisation pathway
45
What happens to STING when cGAMP binds to it
STING is phosphorylated and uses the IRF3 dimerisation pathway
46
What type of signalling does IFN do
Autocrine and paracrin
47
What does IFN bind to and what does this cause
- It can act on IFN- receptors on other cells, causing their dimerization
- This will cause phosphorylations which make a new dimer, and a subsequent trimer which moves to the nucleus of the cell to bring about transcription/translation of interferon stimulated (IS) genes
48
Describe type 1 IFN signalling
- IFN- gene cause translation of the IFN- protein
- This protein will be secreted from the cell to do autocrine and paracrine signalling
- It can act on IFN- receptors on other cells, causing their dimerization
- This will cause phosphorylations which make a new dimer, and a subsequent trimer which moves to the nucleus of the cell to bring about transcription/translation of interferon stimulated (IS) genes
- These genes code for antiviral signal proteins and mean that viruses from the original cell can’t spread to neighbouring cells
49
Examples of IFN stimulated genes? (7)
- (PKR) Protein Kinase R inhibits translation, this stops new viral products being made, but also means that the host cell is likely to die
- 2’5’OAS activates RNAse L that destroys ss RNA (including mRNA, not just viral RNA)
- Mx inhibits incoming viral genomes
- ADAR induces errors during viral replication
- Serpine activates proteases
- Viperin inhibits viral budding
- IFITM3 Restricts virus entry through endosome, they stop the virus being able to leave the endosome
50
What does PKR do
inhibits translation, this stops new viral products being made, but also means that the host cell is likely to die
51
What does 2’5’OAS do
activates RNAse L that destroys ss RNA (including mRNA, not just viral RNA)
52
What does Mx do
inhibits incoming viral genomes
53
What does ADAR do
induces errors during viral replication
54
What does Serpine do
activates proteases
55
What does viperin do
inhibits viral budding
56
What does IFITM3 do
Restricts virus entry through endosome, they stop the virus being able to leave the endosome
57
what gene mutation causes more severe influenza
IFITM3
58
What gene product inhibits viral budding
- Viperin
59
What gene product inhibits incoming viral genomes
- Mx
60
What gene product activates RNAse L that destroys ss RNA (including mRNA, not just viral RNA)
- 2’5’OAS
61
What gene product activates proteases to kill viruses
- Serpine
62
What gene product induces errors during viral replication
- ADAR
63
What gene product activates Restricts virus entry through endosome, they stop the virus being able to leave the endosome
- IFITM3
64
What gene product inhibits translation, this stops new viral products being made, but also means that the host cell is likely to die
- (PKR) Protein Kinase R
65
What virus does Mx1 inhibit
Influenza
66
What virus does Mx2 inhibit
HIV
67
- Mx can form multimers which .....
wrap around the nucleocapsids of incoming viruses
68
how long does an IFN response last
few hours
69
How does an IFN response get suppressed
- SOCS (suppressor of cytokine signalling) genes turn off the response
70
What genes suppress IFNs
- SOCS (suppressor of cytokine signalling) genes turn off the response
71
7 ways viruses evade IFN response?
1. Avoid detection by hiding the PAMP
2. Interfere globally with host cell gene expression and/or protein synthesis
3. Block IFN induction cascades by destroying or binding components of the cascade
4. Inhibit IFN signalling
5. Block the action of individual IFN induced antiviral enzymes
6. Activate SOCS
7. Replication strategy that is insensitive to IFN because they’re so quick that neighbouring cells haven’t had the time to respond to interferon.
72
How does hep C evade the IFN response
NS3/4 protease acts as an antagonist to interferon induction by cleaving MAVS from the mitochondria so it can no longer start a signal
73
What virus has NS3/4 protease which acts as an antagonist to interferon induction by cleaving MAVS from the mitochondria so it can no longer start a signal
Hep C
74
How does influenza evade the IFN response
NS1 (non-structural 1) protein acts as an antagonist to interferon induction by binding to RIG-I /TRIM25/RNA complex and preventing activation of signalling pathway, and also prevents nuclear processing of newly induced genes
75
What virus has NS1 (non-structural 1) protein which acts as an antagonist to interferon induction by binding to RIG-I /TRIM25/RNA complex and preventing activation of signalling pathway, and also prevents nuclear processing of newly induced genes
Influenza
76
How does POX virus evade the IFN response
POX viruses encode soluble cytokine receptors (vaccinia virus B18) which mops up cytokines - being developed as possible future immunoregulatory therapies
77
Which viruses encode soluble cytokine receptors (vaccinia virus B18) which mops up cytokines - being developed as possible future immunoregulatory therapies
POX viruses
78
How does ebola virus evade the IFN response (2)
Encode these proteins:
VP35 is a protein which blocks RIG-I and MDA5 signalling to the nucleus of infected cells
VP24 blocks the signal from the IFN receptor into the nucleus so no ISGs are made
79
2 ways we end up with viral pathology
We can end up with viral pathology because of damage of infected cells by virus OR damage of infected and bystander cells by the immune response
80
What can cause a cytokine storm
Viruses modulating the immune response
81
What does the protective/immunopathological effects of IFN response depend on
Concentration of IFN, if you give too much IFN or if a virus stimulates a lot of production of IFN, you get a pro-inflammatory IL-6 response
82
Describe the events leading to a cytokine storm
- So virus gets into cell, triggers IFN-β release, but this doesn’t help kill the virus due to evasion mechanisms so escapes, finds another cell, IFN released and this causes cytokine storm.
83
6 mediators of a cytokine storm?
- TNF, type I and II IFN. IL1-β, IL6 and other chemokines (CCL2 and CXCL10).
84
What does a cytokine storm result in
- This makes endothelium leaky resulting in hemorrhaging, huge inflammatory responses and pulmonary fibrosis
85
RoA of IFN for IFN therapy
has to be injected
86
What is necessary of a virus before it can be used in vaccines?
- Viruses deficient in control of IFN are attenuated in IFN competent cells
87
How can viruses be used in cancer therapy?
Oncolytic viruses take advantage of the IFN deficient state of cancer cells We hope to be able to engineer oncolytic viruses to cure cancers
88
IFN response of cancer cells?
Cancer cells don’t make healthy IFN responses
