Deck 33: Intrinsic Cellular Defenses Against Virus Infection

Question 1

Interferon $\alpha$ is a protein that….

A)binds to a cell surface receptor and induces the expression of new cellular genes.
B)binds to a viral peptide and presents it to the cytotoxic T lymphocytes.
C)degrades viral and cellular mRNAs after it has been activated by dsRNA.
D)binds to the surface of a virion and prevents it from attaching to the host cell.
E)phosphorylates proteins,like eIF2 $\alpha$ ,and inhibits translation of mRNAs.

Answer 1

binds to a cell surface receptor and induces the expression of new cellular genes.

Question 2

Besides their subcellular locations,which of the following distinguishes TLR-2 from TLR-3?

A)Only TLR-2 can recognize viral capsid proteins.
B)Only TLR-2 can recognize viral glycoproteins.
C)Only TLR-2 can recognize viral ssRNA.
D)Only TLR-2 can recognize CpG motifs on viral DNA.
E)Only TLR-2 can recognize viral dsRNA.

Answer 2

B

Question 3

Which of the following is NOT an example of viral gene product used to avoid the antiviral effects of the PKR enzymes?

A)Adenovirus VA I RNAs
B)Vaccinia SK-1 protein
C)Reovirus $\sigma$ 3 capsid protein
D)HIV tat transactivator
E)These are all examples of anti-PKR proteins.

Answer 3

These are all examples of anti-PKR proteins.

Question 4

Which of the following is the best-known substrate of the interferon induced PKR?

A)Jak kinase
B)Ribonuclease L
C)Translation factor eIF2 $\alpha$
D)IRF-3
E)Large ribosomal subunit

Question 5

Which of the following is NOT a transcription factor that regulates cellular antiviral defenses?

A)TBK-1
B)IRF-3
C)IRF-7
D)NF- $\kappa$ B
E)All of the above are transcription factors.

Question 6

Toll-like receptors (TLRs)2 and 4 are found on the surface of host cells while TLR 3 and 9 are found on the endosomal membranes.

Question 7

Which of the following is an accurate description of autophagy?

A)Engulfment of one cell by another cell.
B)Engulfment of an extracellular virus particle.
C)Degradation of cellular components in a phagosome.
D)Degradation of cellular DNA by nucleases.
E)Degradation of cellular proteins by proteases.

Question 8

When interferon $\alpha$ binds to its receptor it stimulates an intracellular signaling pathway.Which of the following proteins is part of this signaling pathway?

A)NF- $\kappa$ B and HMG1 proteins
B)Caspase proteins
C)Jak and Stat proteins
D)IRF-3 and IRF-7 proteins
E)Death inducing signaling complex

Question 9

Both RIG-1 and TLR-7 are membrane bound proteins that can bind to single-stranded viral RNA.

Question 10

Which of the following can induce the extrinsic apoptosis pathway?

A)Direct damage to cellular DNA.
B)Binding of TNF $\alpha$ to the a cell surface receptor.
C)Increased activity of the p53 protein.
D)Release of cytochrome c from the mitochondria.
E)Activation of the cytoplasmic caspase enzymes.

Question 11

Which of the following is NOT a type of antiviral cytokine?

A)Interferon $\alpha$ (alpha)
B)Interferon $\delta$ (delta)
C)Interleukin-6
D)Tumor necrosis factor $\alpha$ (alpha)
E)NF- $\kappa$ B

Question 12

Human herpesvirus 8 produces a viral homologue of the v-IRF protein.Which of the following describes how this viral homologue inhibits the interferon pathway?

A)It binds to the interferon promoter and inhibits transcription.
B)It stimulates the expression of the Mx protein.
C)It blocks the activation of the PKR enzymes by double-stranded RNA.
D)It prevents binding of interferon $\alpha$ to its receptor.
E)It inactivates the caspase enzymes.

Question 13

Which of the following interferon induced proteins has the ability to hydrolyze GTP?

A)2',5'-oligo(A)snythetase
B)Jak-Stat
C)PKR
D)Mx
E)Ribonuclease A

Question 14

What is the role of the enzyme IKK in cellular antiviral defenses?

A)It phosphorylates the Stat protein during interferon signaling.
B)It phosphorylates IRF-3 transcription factor and activates it.
C)It phosphorylates the NF- $\kappa$ B protein and activates it.
D)It phosphorylates the IkB protein and inactivates it.
E)It phosphorylates the IkB protein and activates it.

Question 15

Which of the following is NOT a characteristic of the intrinsic cellular defenses against virus infections?

A)They act rapidly after infection with the virus.
B)They can act locally at the site of the infection.
C)They involve pathogen detection receptors.
D)They involve the release of cytokines and interferon.
E)They are specific for a certain type of virus.

Question 16

When interferon $\alpha$ binds to its receptor,which of the following events does NOT occur?

A)Two interferon receptors associate with each other.
B)One Jak kinase phosphorylates another Jak kinase.
C)Stat1 and Stat2 proteins bind to a phosphorylated receptor.
D)Two Stat proteins bind to each other and form a dimer.
E)The Stat dimer activates the MAP kinase in the cytoplasm.

Question 17

Which of the following molecules is the activator for ribonuclease L,which is part of the interferon induced antiviral pathway?

A)GTP
B)2' 5'-oligo(A)
C)dsRNA
D)ssRNA
E)DNA with unmethylated CpG

Question 18

Which of the following is found on the surface of the host cell or on endosomal membranes and can recognize viral nucleic acids?

A)Toll-like receptor
B)2'-5'-oligo(A)synthetase
C)Jak-Stat receptor
D)RNA-induced silencing complex
E)Interferon receptor

Question 19

The presence of double-stranded DNA in the cytoplasm is recognized by cellular receptors and initiates antiviral defenses.

Question 20

Dicer cleaves double-stranded viral RNA into which of the following?

A)small interfering RNAs
B)micro interfering RNAs
C)RNA induced silencing complex
D)small regulatory RNAs
E)VA RNAs

Question 21

Interferon can only induce an antiviral state in a cell if it enters the nucleus and binds to the promoters of interferon inducible genes.

Question 22

The interferon system induces the expression of two inactive enzymes.Name these two enzymes,explain how are they activated,and describe the advantage of producing them as inactive proteins?

Question 23

Interferon is an excellent treatment for certain viral infections,like those caused by heptatitis B and C,because it has very few side effects.

Question 24

Plants,invertebrates and fungi rely on RNA interference to protect against virus infection since they do not produce interferon.

Question 25

Many of the symptoms that accompany a virus infection,including fever,lethargy and muscle pain,are the result of the pro-inflammatory cytokines produced by infected cells.

Question 26

Why is double-stranded RNA such a potent inducer of a cell's antiviral defenses? Describe one antiviral defense system that requires double-stranded RNA in order to be activated.