Review Class

Question 1

What is the difference between innate and intrinsic immunity?

Answer 1

Innate: Sensors, based on PRRs, initiates signalling cascades
Intrinsic: Restriction factors, constitutive passive immunity in all cells. Innate can amplify intrinsic immunity.

Question 2

Induction of key antiviral genes would include…?

Answer 2

IFNbeta induced from PRR signalling

ISGs - often viral restriction factors

Question 3

What phase of a response is from PRR to activating genes?

Answer 3

First wave

Question 4

What is second wave of anti-viral responses?

Answer 4

IFNbeta signals to IFN receptor ISG stimulation

Question 5

What does PKR do?

Answer 5

Recognizes RNA and inhibits translational machinery. Slows all protein manufacturing, viral and host as well.

Question 6

What does APOBEC do?

Answer 6

Causes mutations in RNA.

Question 7

What does the second wave of an anti-viral response initiate?

Answer 7

Viral restriction factors

Question 8

Name three forms of IRF3 viral evasion strategies.

Answer 8

Degrade/sequester IRF3
Inhibit phosphorylation
Inhibit dimerization
Inhibit nuclear translocation
Inhibit interaction with transcriptional co-activators of target genes.

Question 9

What is an IRES?

Answer 9

Internal ribosomal entry sequence.

Question 10

What does an IRES do?

Answer 10

It is an RNA structure with secondary structure which allows docking of translational machinery within a transcript instead of starting at the 5’ cap. Allows cap independent initiation of translation in the middle of a messenger RNA.

Question 11

Why do viruses use IRES?

Answer 11

Control translation levels of specific viral proteins
Shut off host cell translation while maintaining viral transcript translation
Because they are “tricksy”

Question 12

What are host cell factors that interact with the IRES?

Answer 12

IRES-transacting factors (ITAFs) are cellular RNA binding proteins.

Question 13

What is similar to a virus but doesn’t produce virus proteins? What are they?

Answer 13

Viroids. They are RNA sequences that have no proteins.

Question 14

What are satellite viruses?

Answer 14

viruses that cannot replicate without a helper virus

Question 15

What is a virophage?

Answer 15

a satellite virus that harms helper viruses. Provirophages after integration into the host giant virus genome.

Question 16

What are transpovirons?

Answer 16

Linear plasmids. Like linear episomes not in the genome.

Question 17

What do transponsons include? What does it do?

Answer 17

Transposase. It allows it to cut and paste into new plases.

Question 18

Describe the refolding prion model of proliferation.

Answer 18

When the good prion conformation is converted by the mutated form to create more and more of the mutatnt form.

Question 19

Describe the seeding prion model of proliferation.

Answer 19

At some point there is an equilibrium which is not harmful but if the good form converts to the mutant form then they aggregate and cause disease. Spontaneous conversion.

Question 20

What does CRISPR do?

Answer 20

Recognizes portions of bacterial or archaeal DNA sequences that match previously seen portions and they can then interfere. The cell will make CRISPR RNAs which will bind to the genome and Cas will cut the DNA.

Question 21

Give an example of viral latency and draw a matching viral titre curve.

Answer 21

One big infection with a decrease in viral titre and plateau with potential peaks of reinfection and episodic reactivation.

Question 22

What are the outcomes of viral replication?

Answer 22

Acute infection
Chronic infection
Latent infection
Transformation and cancer

Question 23

What is the difference between latent and chronic infection?

Answer 23

Latent infection is asymptomatic with a half of genome replication.
Chronic is a slow burn of infection with constant replication and damage.

Question 24

Which stage of the herpes life cycle would remain constant if the virus was latent?

Answer 24

Episomal DNA within the nucleus of an infected cell.

Question 25

What do SV40 T antigens do?

Answer 25

Turn off apoptosis by inhibiting p53.

Promote replications

Question 26

How does polyomavirus get their genome integrated into the host cell’s?

Answer 26

We don’t know. But it does.

Question 27

What are the major pathways altered by oncogenic viruses?

Answer 27

Cell cycle
protein synthesis
interferon and inflammatory response
DNA repair
Apoptosis

Question 28

What is a viral escape mutant? Give an example using a specific virus.

Answer 28

Point mutation in epitopes used for recognition by the immune system. HIV.

Question 29

What do multiple point mutations cause?

Answer 29

Antigenic drift is small mutations that drift from the original copy over time.

Question 30

Recombination can occur in which type of viruses?

Answer 30

RNA viruses because RdRps can template switch. DNA can also but it is less likely.

Question 31

What determines cell tropism?

Answer 31

Surface/endosomal receptors on envelopes or capsids. These can be almost anything.
Cells in which the virus can replicate - matching receptors.