Viral mechanisms

Question 1

Give 4 examples of viruses that evade the innate immune response

Answer 1

Hep C: protease cleaves Mavs
Influenza: Binds Rig-I/RNA complex, inhibits translation
Ebola: Inhibits Rig-I, Stop IFN signalling in neighbour cells
Pox: Soluble cytokine receptor

Question 2

Give 5 viruses and how they avoid the cellular adaptive immune response

Answer 2

EBV: produces peptide that CAN’T be processed by proteasome

HSV: Blocks access to TAP on ER

CMV:

• Stops ATP binding to TAP, preventing translocation of peptide
• Binds to tapasin, prevents loading of peptide onto MHC

Adenovirus:

• Prevents recruitment of TAP to tapasin (thus preventing loading)
• Holds MHC in ER

KSHV: Polyubiquitinilylation, internalisation + lysis of MHC

HPV: Holds MHC in ER

Question 3

What is the missing-self mechanism?

Answer 3

NK cells detect viruses that don’t present any MHC and kill them

Question 4

How do viruses evade missing-self response by NK cells?

Answer 4

By making MHC analogues

Question 5

Genetic drift vs shift?

Answer 5

Drift = Continued rapid evolution due to antigenic pressure from host (influenza H3N2 + HIV)

Shift = Introduction of new subtypes from animals (influenza)

Question 6

How many serotypes do rhinovirus, measles, polio, and dengue have?

Answer 6

Rhinovirus - Hundreds
Measles - 1
Polio - 3
Dengue - 4

Question 7

How many updates have there been for H3N2?

Answer 7

6 in last 10 years

28 since 1968

Question 8

How does HIV evade the humoral adaptive immune response?

Answer 8

Spike gp120

1. Large space between spikes prevents Ab crosslinking
2. Masks epitopes via glycosylation
3. Functionally important parts of molecule are poorly accessible

Question 9

What is the mechanism of Dengue Haemorrhagic Fever?

Answer 9

Antibody-dependent Enhancement of Dengue:

Antibodies made against previous infection can bind, but have no effect.
Antibody-virus complex detected by macrophages
Virus can then invade macrophages, causing cytokine storm
Leaky endothelium -> haemorrhagic fever

Question 10

What is humoral immunity?

Answer 10

Part of adaptive immune system

B-cells produce antibodies, specific ones bind to viral antigens and kill them

Question 11

How do viruses evade humoral immunity?

Answer 11

1. Antigenic shift + drift

2. Having multiple serotypes