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POM 4 Immunology > 4.7 Viral Immune Evasion > Flashcards

4.7 Viral Immune Evasion Flashcards

1
Q

What is the ultimate goal of the immune response to a viral infection?

A

Eliminate both the virus and the host cells harbouring or replicating the virus

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2
Q

What are the five functions of antibody in the anti-viral response? BRONK

A

Block viremic spread to target tissue
Resolve lytic viral infections
Opsonise virus for phagocytosis
Neutralise virus
Kill virus via complement cascade and antibody-mediated cytotoxicity

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3
Q

Describe how antibody neutralises extracellular virus?

A

Blocks viral attachment proteins (glycoproteins, capsid proteins)

Destabilises viral structure

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4
Q

Which Ig class is an indicator of recent infection?

A

IgM

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5
Q

Which Ig class is a more effective anti-viral than IgM?

A

IgG

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6
Q

Which Ig class is important for pretecting mucosal surfaces?

A

IgA

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7
Q

What does HIV exist as?

A

Quasi-species/multiple clades

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8
Q

How does HIV escape antibody recognition?

A

Exists as multiple quasi-species

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9
Q

How does HBV and Ebola virus evade antibody recognition?

A

Encode secreted surface antigens that mop up antibody, stopping it from reaching virus particles or infected cells

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10
Q

How many serotypes does Dengue Virus exist as?

A

4

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11
Q

What triggers Dengue Haemorrhagic fever?

A

Previous infection with 1 dengue virus serotype followed by infection with another serotype

This causes the virus to enter immune cells via antibodies or Fc receptors, causing antibody-dependent enhancement of disease

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12
Q

Which virus shows antigenic drift?

A

Influenza virus

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13
Q

What is antigenic drift?

A

When viruses mutate and evolve each year

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14
Q

Describe how influenza undergoes antigenic shift?

A

Influenza viruses can also acquire completely new antigens by reassortment with animal viruses

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15
Q

Why is finding a cold vaccine difficult?

A

Rhinovirus is the most common cold causing pathogen and has too many serotypes

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16
Q

What is the name of the small proteins released by virally infected cells that play a role in immune protection against viruses?

A

Interferons

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17
Q

How is interferon production induced?

A

The presence of molecules made by viruses that are sensed by the cell as foreign or in the wrong cellular location

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18
Q

What might trigger the production of interferon from a virally infected cell?

A

Double-stranded RNA
RNA that lacks a 5’ cap
DNA in the cytoplasm

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19
Q

What does interferon do once secreted from the cell?

A

Binds to interferon recptors and activates the anti-viral state of the cell and surrounding cells

20
Q

What does the antiviral state involve?

A

Gene transcription to block viral replication

21
Q

What is synthesized in the anti-viral state through the transcription of anti-viral genes?

A

2’5’ oligoadenylate synthetase and protein kinase R

22
Q

What are the two type 1 IFNs?

A

IFN-α and IFN-β

23
Q

Which cells secrete IFN-β?

A

All cells

24
Q

Which cells secrete IFN-α?

A

Plasmacytoid dendritic cells (PDCs)

25
Q

Where is the IFN-α receptor found?

A

On all tissues

26
Q

How many genes are there for IFN-β and IFN-α?

A

There is one gene for IFN-β, but 13/14 isotypes of IFN-α

27
Q

What is type 2 IFN?

A

IFN-γ

28
Q

Which cells produce IFN-γ?

A

Activated T Cells and NK Cells

29
Q

Which receptor does IFN-γ signal through?

A

IFN-γR

30
Q

What is type 3 IFN?

A

IFN-λ

31
Q

What are the main IFN-λ receptors?

A

IL28R and IL10-β

32
Q

Where are IL28R and IL10-β found?

A

On epithelial surfaces

33
Q

How does hepatitis B block the production of Interferon?

A

Through the inhibition of IFN transcription

34
Q

How does influenza block the production of interferon?

A

Produces a protein (NS1) that counters RNA sensing and prevents polyA processing

35
Q

What 2 cytokines are NK Cells activated by?

A

IFN-α and interleukin-12

36
Q

What do activated NK cells release and what does this do?

A

IFN-γ which activates macrophages

37
Q

What do NK cells do?

A

NK cells target and kill virus-infected cells (especially enveloped viruses)

38
Q

Which types of viruses do NK cells specifically target?

A

Enveloped viruses

39
Q

When does an NK cell release toxic substances?

A

When the NK cell finds a cell displaying fewer than normal MHC molecules

40
Q

Which viruses might infect a cell and trigger NK cells to release toxic substances?

A

Cytomegalovirus or Herpes Simplex Virus infected cells with fewer MHC molecules

41
Q

What do macrophages do in the viral response?

A

Filter viral particles from the blood and inactivate opsonised virus particles

42
Q

What is a function which macrophages and DCs share?

A

Present antigen to CD4 T cells

43
Q

What is the viral peptide that cytotoxic CD8 T cells respond to?

A

Class I MHC protein complexes on the infected cell surface carrying viral proteins

44
Q

How do viruses like HSV and cytomegalovirus counter the T cell response?

A

Encode proteins that interfere with the MHC antigen processing pathway

45
Q

How does HIV evade the immune response?

A

Kills CD4 T cells and alters macrophage function

46
Q

How does HSV evade the immune response?

A

Prevents CD8 T cell killing by encoding proteins which interfere with the MHC antigen processing pathway

POM 4 Immunology (14 decks)

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