Host Response to Viral Infection

Question 1

What physical and chemical defenses are part of innate immunity?

Answer 1

1. Skin
2. Mucous membranes
3. GI tract
4. Resp tract

Question 2

___________ cells synthesize and release a variety of cytokines, including type II IFN

Answer 2

NK cells

Question 3

What recognizes PAMPS on viruses?

Answer 3

PRRs on surface of host cells (Ex: TLR)

Question 4

What occurs when PRR on macrophage binds to PAMP on virus cell?

Answer 4

Stimulates

1. Phagocytosis
2. Chemotaxis
3. Inflamm mediators
4. Interferons

Question 5

_________ (DNA/RNA) viruses are stronger inducers of interferon than _______ (DNA/RNA) viruses

Answer 5

RNA is stronger inducer of interferon than DNA viruses

Question 6

Interferons are known to have anti-cancer properties, how should they ideally be administered?

Answer 6

Parenteral route (Injection)

** interferons are orally inactive bc its a glycoprotein

Question 7

True or False: Interferons are virus specific

Answer 7

FALSE - no virus specificity

Question 8

What are examples of Type 1 interferons?

Answer 8

IFN-a

IFN-b

Question 9

How is IFN-a produced and what kind of interferon is it?

Answer 9

Leukocyte interferon - Type 1

Produced in large quantities by plasmacytoid dendritic cells

Question 10

How is IFN-b produced and what kind of interferon is it?

Answer 10

Fibroblast interferon - Type 1

Secreted by virus infected fibroblasts

Question 11

How do type 1 interferons inhibit virus replication?

Answer 11

1. Activates latent RNAase to degrade viral RNA
2. Synthesizes Mx proteins that bind and trap viral nucleocapsid and inhibit virus assembly
3. Synthesizes Protein Kinase R (PKR) which prevents translation of viral RNA

Question 12

What roles do type 1 IFNs have?

Answer 12

1. Inhibits viral rep
2. Activates NK cells
3. Increases Ag presentation and MHC I expression
4. Stimulates differentiation of monocytes into dendritic cells
5. Maturation of DCs
6. Memory T cell proliferation

Question 13

Example of a type II interferon?

Answer 13

IFN-y

Question 14

How is IFN-y produced?

Answer 14

Type II interferon produced by Ag-stimulated T cells and NK cells

Question 15

Examples of Type III interferons?

Answer 15

IFN-λ1

IFN-λ2

IFN-λ3

Question 16

When are Type III interferons expressed?

Answer 16

In response to viral infections and activation of TLRs

Functions as immunoregulator

Question 17

_______ interferons were recently discovered

Answer 17

Type III interferons- IFN-λ1, IFN-λ2, IFN-λ3

Question 18

_________ antigens elicit a protective Cell mediated immune response

Answer 18

Internal viral Ag

Question 19

________ antigens elicit a protective humoral AND CMI response

Answer 19

Surface Ag

Question 20

In humoral immunity, Ab can be directed against ?

Answer 20

Viral proteins on free virions (capsid or nucleocapsid)

OR against viral proteins on surface of infected cells

Question 21

What is virus neutralization?

Answer 21

Ab neutralizes virus by preventing attachment and entry into host cell

Ab binds to viral capsid or host envelope

Question 22

What are antiviral effects of antibodies?

Answer 22

1. Virus Neutralization
2. Opsonization
3. Clumping of viruses (Immunocomplex formation)
4. Complement activation
5. ADCC pathway

Question 23

What is opsonization?

Answer 23

Coating of virions with Ab which is then detected and phagocytosed by macrophages and neutrophils

** Ab puts a sticker on virus infected cell which attracts host cells to come kill

Question 24

What are ways viruses evade the immune system? (9)

Answer 24

1. Ag plasticity
2. Antigenic multiplicity
3. Negative cytokine regulation
4. Down reg of MHC I pathway
5. Inhibition of complement
6. Evasion of neutralizing Ab
7. Latency
8. Cell to cell spread
9. Inhibition of apoptosis

Question 25

What is antigenic plasticity?

Answer 25

- Method viruses use to hide from IR - rapid changes in structure of Viral Ag, may be a result of mutation (Ag drift) , reassortment, or recombination (Ag shift)

Question 26

What is antigenic multiplicity?

Answer 26

- Antigenic variants with little or no cross reactivity - Immune system can't recognize variants

Question 27

How do viruses evade the immune system by negative cytokine regulation?

Answer 27

1. Virokines are made by the virus which mimics host cytokines 2. Viroceptors are made by the virus which mimic host receptors and is able to encode proteins (down reg)

Question 28

True or False: Rapid changes in structure of a viral Ag of a virus over time due to mutations is known as antigenic multiplicity

Answer 28

FALSE - Antigenic plasticity