Review Class Flashcards
What is the difference between innate and intrinsic immunity?
Innate: Sensors, based on PRRs, initiates signalling cascades
Intrinsic: Restriction factors, constitutive passive immunity in all cells. Innate can amplify intrinsic immunity.
Induction of key antiviral genes would include…?
IFNbeta induced from PRR signalling
ISGs - often viral restriction factors
What phase of a response is from PRR to activating genes?
First wave
What is second wave of anti-viral responses?
IFNbeta signals to IFN receptor ISG stimulation
What does PKR do?
Recognizes RNA and inhibits translational machinery. Slows all protein manufacturing, viral and host as well.
What does APOBEC do?
Causes mutations in RNA.
What does the second wave of an anti-viral response initiate?
Viral restriction factors
Name three forms of IRF3 viral evasion strategies.
Degrade/sequester IRF3 Inhibit phosphorylation Inhibit dimerization Inhibit nuclear translocation Inhibit interaction with transcriptional co-activators of target genes.
What is an IRES?
Internal ribosomal entry sequence.
What does an IRES do?
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.
Why do viruses use IRES?
Control translation levels of specific viral proteins
Shut off host cell translation while maintaining viral transcript translation
Because they are “tricksy”
What are host cell factors that interact with the IRES?
IRES-transacting factors (ITAFs) are cellular RNA binding proteins.
What is similar to a virus but doesn’t produce virus proteins? What are they?
Viroids. They are RNA sequences that have no proteins.
What are satellite viruses?
viruses that cannot replicate without a helper virus
What is a virophage?
a satellite virus that harms helper viruses. Provirophages after integration into the host giant virus genome.
What are transpovirons?
Linear plasmids. Like linear episomes not in the genome.
What do transponsons include? What does it do?
Transposase. It allows it to cut and paste into new plases.
Describe the refolding prion model of proliferation.
When the good prion conformation is converted by the mutated form to create more and more of the mutatnt form.
Describe the seeding prion model of proliferation.
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.
What does CRISPR do?
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.
Give an example of viral latency and draw a matching viral titre curve.
One big infection with a decrease in viral titre and plateau with potential peaks of reinfection and episodic reactivation.
What are the outcomes of viral replication?
Acute infection
Chronic infection
Latent infection
Transformation and cancer
What is the difference between latent and chronic infection?
Latent infection is asymptomatic with a half of genome replication.
Chronic is a slow burn of infection with constant replication and damage.
Which stage of the herpes life cycle would remain constant if the virus was latent?
Episomal DNA within the nucleus of an infected cell.
What do SV40 T antigens do?
Turn off apoptosis by inhibiting p53.
Promote replications
How does polyomavirus get their genome integrated into the host cell’s?
We don’t know. But it does.
What are the major pathways altered by oncogenic viruses?
Cell cycle protein synthesis interferon and inflammatory response DNA repair Apoptosis
What is a viral escape mutant? Give an example using a specific virus.
Point mutation in epitopes used for recognition by the immune system. HIV.
What do multiple point mutations cause?
Antigenic drift is small mutations that drift from the original copy over time.
Recombination can occur in which type of viruses?
RNA viruses because RdRps can template switch. DNA can also but it is less likely.
What determines cell tropism?
Surface/endosomal receptors on envelopes or capsids. These can be almost anything.
Cells in which the virus can replicate - matching receptors.
