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POM (Principles of Medicine) > Viral immune evasion > Flashcards

Viral immune evasion Flashcards

1
Q

What are the main functions of antibodies?

A

Antibody neutralizes extracellular virus blocks viral attachment proteins (Glycoproteins, capsid proteins); destablises viral structure
Antibodies opsonize virus for identification for phagocytosis; promotes lysis and destruction of the target cell through the complement cascade, and antibody-dependent cellular cytotoxicity; resolves lytic viral infections; blocks the viraemic spread of target tissue.

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2
Q

What is the function of IgM in terms of viral infections?

A

IgM indicator of recent/current infections

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3
Q

Which Ig type is the most effective antiviral?

A

IgG

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4
Q

Which Ig is cardinal for the protection of mucosal surfaces?

A

IgA

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5
Q

How is a viral infection resolved?

A

Resolution of infection requires elimination of free virus (antibody agglutination), and the virus-producing cell (immune-cell mediated lysis)

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6
Q

How do rhinoviruses evade antibodies?

A

Rhinoviruses display antigenically distinct serotypes; multivalent required

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7
Q

How does HIV evade antibodies?

A

Exist as multiple clades/quasispecies

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8
Q

How does Hepatitis B virus (HBV) and Ebola evade antibodies?

A

`Encode secreted surface antigens, that remove associated antibody, preventing it from reaching viral particles/infected cells

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9
Q

How many serotypes are present for the Dengue virus?

A

4

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10
Q

How does serotyping cause antibody evasion for Dengue virus?

A

1) Previous infection with one serotype followed by infection with different serotype results in antibody-dependent enhancement of disease
2) Virus enters immune cells via antibody & Fc-receptor.
3) Triggers Dengue hemorrhagic fever. Antibodies present from primary DENV infection bind to infecting DENV particle - primary antibodies cannot neutralize the virus
AB-Virus complex attaches tp Fcy receptors on monocytes, assisting in infection mechanism

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11
Q

How do DENV particles enter into immune cells?

A

Antibody via Fc receptor

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12
Q

Which type of fever is triggered by DENV?

A

Hemorrhagic fever

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13
Q

How does the influenza virus evade antibodies?

A

Influenza viruses mutate frequency evolving, attributing to antigenic drift
Influenza viruses acquire new antigens by reassortment with animal viruses (Antigenic shift) - leads to pandemics,
Alters neuraminidase and haemaglglutinin structure

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14
Q

What is antigenic drift?

A

Mutations causes changes in antigenic viral structure

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15
Q

What is the antigenic shift?

A

Influenza viruses acquire new antigens by reassortment with animal viruses.

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16
Q

Which antiviral agents are produced from virally infected cells?

A

Interferons (IFN)

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17
Q

Which viral molecules induces the synthesis of interferons?

A

Double-stranded RNA
RNA that lacks a 5’ cap
Cytoplasmic DNA

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18
Q

Which receptors to interferons bind to?

A

Interferon receptors

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19
Q

What response is initiated upon interferon binding on surrounding cells?

A

Induces antiviral state

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20
Q

Which cell cannot induce an antiviral state?

A

The infected host cell secreting interferons

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21
Q

Which genes are activated and transcribed upon activation of antiviral state?

A

Genes that are transcribed inhibit viral replication (2’5’ oligoadenylate synthetase and protein kinase R - this degrades viral & host RNA

22
Q

What function is performed by 2’5’oligoadenylate synthetase?

A

Degrades viral and host RNA

23
Q

Which immune cell is mainly activated by interferons?

A

Natural killer cells

24
Q

What are the three types 1 IFNs?

A

IFN-alpha
betab
Beta

25
Q

Which cells secreted type 1 IFNs?

A

All cells

26
Q

Which IFN receptor is present on all tissues?

A

IFN-alpha Receptor

27
Q

Which cells are specialized IFN-alpha secreting?

A

Plasmacytoid dendritic cells

28
Q

How many genes exist for IFN-B?

A

1

29
Q

How many isotypes exist for IFN-a?

A

13/14 isotypes

30
Q

Which IFN type is IFN-y?

A

Type II

31
Q

Which cells secrete IFN-y?

A

NK cells and activated T cells

32
Q

Which receptor is activated by IFN-y?

A

IFN-yR

33
Q

Which type of interferon is IFN-lambda?

A

Type III

34
Q

Which receptors are IFN-Lambda signaled through?

A

IL28R
IL10-B
These are known as IFN-delta receptors, mainly present on epithelial surfaces

35
Q

How do HBV and influence develop resistance to interferon action?

A

Blocks the production of interferon by inhibition of IFN transcription
Produce protein NS1 that counters RNA sensing and prevents polyA processing

36
Q

How are NK cells activated in terms of an antiviral response?

A

IFN-alpha

Interleukin-12

37
Q

How are macrophages activated in terms of an antiviral response?

A

Activated NK cells secrete IFN-y binds to macrophage IFNyRs

38
Q

What is the function performed by activated NK cells during an antiviral response?

A

NK cells target and kill virus-infected cells (enveloped viruses)
Secrete IFN-y to activate macrophages

39
Q

A reduction in which cell surface molecules results in NK cytotoxic response?

A

Reduction in the number of functional MHC-iu molecules

40
Q

Which viruses are responsible for reducing MHC-I surface molecules in infected cells?

A

Cytomegalovirus

Herpes Simplex Virus

41
Q

Which type of lymphocytes are NK cells classified as?

A

Group 1 innate lymphocytes (ILCs)

42
Q

Which type of NK receptors regulate cytotoxicity?

A

Inhibitory receptors

43
Q

What is the function performed by inhibitory receptors?

A

Recognizing cognate MHC-I, and inactivates NK cells- preventing cell lysis

44
Q

What happens to cells which lose MHC-I?

A

Vulnerable to cytotoxic granules containing perforin and granzymes being secreted- lysis of target cell

45
Q

What is the function performed by macrophages during an anti-viral response?

A

Macrophages filter viral particles from blood; inactivate opsonized virus particles

46
Q

What is the function performed by dendritic cells during an anti-viral response?

A

Plasmocytoid dendritic cells produce IFN-alpha and other cytokines
Initiate and determine nature of CD4 and CD8 T-cell response
Dendritic cells undergo antigen presentation - presents antigen to CD4 T cells

47
Q

Which type of viral infections are controlled by T-cells?

A

Controls enveloped and noncytolytic viral infections, recognize viral peptides presented by MHC molecules associated on cell surface membrane

48
Q

What are linear epitopes?

A

Antigenic viral peptides derive from viral proteins (Glycoproteins and nucleoproteins)

49
Q

What T cells are cytotoxic?

A

CD8, responds to MHC1 protein complexes on infected cells

50
Q

What are Th2 responses?

A

Required for humoral immunity- can be detrimental if they prematurely limit the Th1 inflammatory and cytolytic response

51
Q

How do viruses evade T cells?

A

Herpes Simplex HSV, and cytomegalovirus CMV encode proteins that interfere with MHC antigen processing pathway
Viruses impair lymphocyte function: HIV kills CD4 T cells, and alters macrophage function
HSV prevents CD8 T cell lysis

POM (Principles of Medicine) (34 decks)

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