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POM Week 3 > Immune evasion by microbes > Flashcards

Immune evasion by microbes 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 may failure to resolve infection lead to?

A

Persistent/ Chronic infection or Death

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3
Q

How do antibodies respond to viral infections?

A

Blocks viral attachment proteins

Destabilises viral structure

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4
Q

What do antibodies do specifically to respond to viral infections?

A
  • Opsonises virus for phagocytosis
  • Promotes killing of target cell by the complement cascade and antibody-dependent cellular cytotoxicity
  • Resolves lytic viral infections.
  • Blocks viremic spread to target tissue
  • IgM is an indicator of recent or current infection
  • IgG is a more effective antiviral than IgM
  • Secretory IgA is important for protecting mucosal surfaces
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5
Q

How do human rhinoviruses escape antibody recognition?

A

Exist as hundreds of antigenically distinct serotypes

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6
Q

How does HIV escape antibody recognition?

A

Exists as multiple clades or quasi-species

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7
Q

How do Hep B and Ebola escape antibody recognition?

A

Encode secreted surface antigens that mop up antibody

Stopping it reaching virus particles or infected cells

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8
Q

How does Dengue virus escape antibody recognition?

A

Exists as 4 serotypes
Previous infection with one serotype followed by infection with a different serotype can lead to antibody dependent enhancement of disease
As virus enters immune cells via antibody and the Fc-Receptor
This triggers Dengue Haemorrhagic Fever

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9
Q

How do influenza viruses escape antibody recognition?

A

Mutate and evolve to change year on year a.k.a antigenic drift
Influenza viruses can acquire new antigens by reassortment with animal viruses a.k.a antigen shift
Can lead to pandemics

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10
Q

How does antibody evasion cause problems for vaccination?

A

Too many rhinovirus serotypes make finding a cold vaccine difficult
A new influenza vaccine is required each year to reflect the circulating virus types

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11
Q

What are interferons?

A

Small proteins play a role in immune protection against viruses

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12
Q

Where do interferons come from?

A

Induced by molecules made by viruses

Secreted from the infected cell and binds to interferon receptors

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13
Q

What do interferons do?

A

Initiates the antiviral state in the infected cells and in surrounding cells.

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14
Q

What is the antiviral state?

A

Transcription of hundreds of genes that block viral replication

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15
Q

What are the different types of interferons?

A

Type I
Type II
Type III

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16
Q

What are the type I interferons?

A

IFN-alpha

IFN-beta

17
Q

What’s the deal with type I interferons?

A

IFN-beta secreted by all cells
IFNR-alpha receptor is present on all tissues
Plasmacytoid dendritic cells are specialist IFN-alpha secreting cells
There is one gene for IFN-beta
13/14 isotopes IFN-alpha

18
Q

What is type II interferon?

A

IFN-gamma

19
Q

What’s the deal with type II interferons?

A

Produced by activated T-cells and NK cells

Signals through a different receptor: IFN-gammaR

20
Q

What is type III interferon?

A

IFN-lamda

21
Q

What’s the deal with type III interferons?

A

Signals through IFN-lamda receptors that are present on epithelial surfaces

22
Q

Summarise the actions of interferons?

A

Binds to cell surface reception

Induces production of anti-viral enzymes

23
Q

How are NK cell activated in response to a viral infection?

A

Activated by IFN-alpha and Interleukin-12

These activate macrophages with IFN-gamma

24
Q

What do NK cells do in response to a viral infection?

A

Target and kill virus-infected cells
When they find cells displaying fewer than normal MHC molecules they release toxic substances
These kill virally infected cells

25
Q

What do macrophages do in response to viral infection?

A

Filter viral particles from blood

Inactivate opsonised virus particles

26
Q

What do dendritic cells do in response to viral infection?

A

Immature and plasmacytoid DCs produce IFN-alpha and other cytokines
Initiate and determine nature of CD4 and CD8 T-cell response

27
Q

What do both macrophages and dendritic cells do in response to viral infection?

A

Present antigen to CD4 T cells

28
Q

What types of viral infections are T-cells essential for?

A

Enveloped and nonocytolytic

29
Q

What do T-cells recognise?

A

Viral peptides presented by MHC molecules on cell surfaces

30
Q

What do CD8 cytotoxic T cells respond to?

A

Class I MHC protein complexes on the infected cell surface

31
Q

Why can CD4 TH2 responses be detrimental?

A

If they prematurely limit the TH1 inflammatory and cytolytic responses

32
Q

Give examples of how viruses can impair lymphocyte function?

A

HIV kills CD4 T cells and alters macrophage function

Herpes simplex virus can prevent CD8 T-cell killing

POM Week 3 (11 decks)

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