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Virology > Host Response/Immune Evasion > Flashcards

Host Response/Immune Evasion Flashcards

1
Q

what kinds of host defenses are there against virus infec?

A

type I interferon
innate immune
adaptive immune
apoptotic

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2
Q

What controls the number of viruses in an viral infection?

A

innate immune response (IFN alpha, IFN beta, TNF alpha, IL12 release and NK cell mediated killing of infected cells)

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3
Q

What reduces the virus titer after a stable viral count in an viral infection?

A

T cell mediated killing of infected cells

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4
Q

problems with giving IFNs as antivirals?

A

flu-like symptoms, but interferon alpha is used in treatment of chronic hepatitis C

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5
Q

How are IFN alpha and beta made in the context of a viral infection?

A

viral products (genomes) are sensed by pattern recognition receptors—>signaling—>transcription factor (interferon response factors) activation, IRFs bind to ISRE response element–>IFN alpha and beta expressed

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6
Q

What does IFN alpha and beta do?

A

bind to neighboring cells’ receptors and induce an antiviral state

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7
Q

What pathway does the IFN alpha and beta use in a nearby cell?

A

JAK STAT

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8
Q

What do type I IFNs activate in a neighboring cell?

A

Protein Kinase R

2’-5’ oligoadenylate synthase

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9
Q

What does Protein kinase R do?

A

PKR is a pattern recognition receptor that binds dsRNA
It phosphorylates eIF-2alpha, which normally carries MET tRNA to the 40S ribosome to start protein synthesis

With phosphorylation of eIF-2alpha, translation is inhibited

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10
Q

What does OAS (2’-5-oligoadenylate synthase) do?

A

binds to and is activated by dsRNA
once activated, catalyzes production of oligo adenylate from ATP
Oligo adenylate activates RNAse L—mRNA degradation

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11
Q

What are components of the anti-viral state

A

increased MHC I expression
increased mRNA degradation
decreased viral protein synthesis
increased activation of NK cells

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12
Q

What is TNF made by?

A

macrophages
CD4 T cells
NK cells

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13
Q

What cytokine promotes death signaling?

A

TNF

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14
Q

What is IL1 beta made by?

A

activated macrophages

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15
Q

What are the major pro inflammatory cytokines

A

TNF
IL1beta
IL6

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16
Q

What cells are cytotoxic?

A

CD8 t cells

NK cells

17
Q

What kinds of signals do NK cells get from a target cell?

A 
inhibitory signals from class I molecules
activating signals from NK activating ligands
18
Q

What do infected cells upregulate on their surfaces?

A

Nk activating ligands

19
Q

What kinds of adaptive immune responses are there?

A

cytokine responses (IFNgamma, IL12, IL2)
T cell responses
B cell responses

20
Q

Name 2 methods in which apoptosis occurs

A

TNFalpha binds TNF receptor on cell, activates caspase 8, produces caspase 3, which causes DNA fragmentation

p53–Bax/Bak pores in mitochondria–cytochrome C leaks out–cytochr c binds APAF–caspase 9 is made–caspase 3 is made, which causes DNA fragmentation

21
Q

How do viruses prevent IFN signaling?

A

extracellular: they make proteins that act as IFN receptors that prevent the IFNs from binding natural receptor
intracellular: dephosphorylate EIF-2alpha, decoy RNA that binds PKR, sequester dsRNA, EIF-2alpha decoys that bind activated PKR, etc.

22
Q

What do viruses do to prevent innate cytokine responses?

A

IL-1beta binding protein–prevents pyrogenic activity

23
Q

what do viruses do to prevent complement?

A

make complement control proteins that prevent MAC assembly on the virus itself

24
Q

How do viruses evade the host immune response through MHC?

A

degrade TAP transporter
block TAP transporter
degrade class I MHC
keep class I MHC in ER/Golgi
make class I MHC go to lysosomes for degradation
decrease transcription of components of MHC molecule

25
Q

What do viruses do to evade NK cell activity?

A

modulate MHC I on infected cell surface (remove HLA-A and B, leave HLA-C)

make decoy mHC I like molecules to inhibit NK cells

prevent activating NK cell receptor ligands from getting to cell surface

26
Q

What can viruses modulate in the immunological synapse of TCR and class I MHC?

A

can downregulate adhesion molecules and costimulatory molecules

27
Q

How do viruses inhibit apoptosis of infected cells?

A

soak up TNFs with viral TNF receptors
inhibit caspase
inhibit p53
make homologs of anti-apoptotic proteins like Bcl2

28
Q

Do large or small viruses mutate faster?

A

small

Virology (15 decks)

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