Viral Evasion Flashcards
5 viruses that evade RNA detection?
Influenza - NS1 Lassa - nucleoprotein HepB - X protein HCV - NS5A HIV - cellular inhibitor
How does influenza evade RNA detection?
Binds vRNA
How does Lassa virus evade detection?
Nucleoprotein digests free dsRNA
What does HepB X protein do?
Degrades MAVs to evade RNA induced responses from RIGI-I
How does HIV evade RNA signalling inducing immune responses?
Induces expression of cellular RNaseL inhibitor
How does 2,5 oligoadenylate synthetase induce antiviral responses?
Activates RNaseL dimerisation in response to RNA detection
How does HCV act in 2,5OAS?
NS5A binds so it can’t activate RNaseL
3 viruses that evade DNA induced responses?
HIV-1
Dengue
HCMV
How does HIV degrade excess DNA?
Hijacking cellular 3-5 exonuclease
How does dengue virus evade DNA responses?
NS2B-3 protease degrades STING so no cGAS/IFI16 responses
And no signalling to neighbouring cells
How does HCMV evade DNA detection?
Targets IFI16 to either mislocalise to ER (not nucleus) or prevent oligomerisatiom
How does HCV evade TLR?
NS5A binds TLR7/9 MyD88
NS3/4A protease cleaves TLR3 TRIF
How can viruses prevent responses to IFN?
Polio activates PKR degradation
Vaccinia K3L pseudosubstrate blocks PKR autophos
How can viruses evade detection?
DNA
RNA
TLR signalling
Preventing signalling in response to IFN
How can HCMV evade activation of adaptive immunity?
miRNA inhibits ERAP protease transcription
US6 inhibits TAP ATP binding
US2 & 11 target MHC1 to ERAD
How can adenovirus strain 12 evade immune responses?
E1A inhibits TAP and MHC1 transcription as NFKB isn’t phosphorylated by PKA
Does Adenovirus strain 12 have E3/19K?
No
How does KSHV evade MHC activation?
K3 and K5 ubiquitinate surface MHC1 for endocytosis and degradation
How does EBV evade MHC presentation?
Resistant to proteolysis so no peptides to present during latency
How does HSV evade antigen presentation?
ICP47 inhibits peptide binding by TAP
How can antigenic variation reduce antiviral responses?
Mutations,
Recombination
Reassortment of segmented genomes
Why does antigenic variation reduce CTL activation?
No consistent recognition of peptides for clonal expansion
How does HIV induce antigenic variation?
Low fidelity replication introduces mutations
Which virus can evade “loss of MHC” responses?
HCMV
4 proteins that HCMV uses to evade NK killing due to loss of MHC?
UL18 homolog of MHC
UL40 has TAP independent presentation to maintain HLA-E
UL16 blocks expression of ligands induced by stress of viral infection
miR-UL112 blocks MICB translation
