Viral Pathogenesis: Host responses to viral infections

Question 1

True or False: Innate defenses are immediate and non-specific.

Answer 1

True

Question 2

What are the three general outcomes of viral infections of a cell?

Answer 2

1. Abortive infection
2. Lytic Infection
3. Persistent Infection

Question 3

What are the three categories persistent infections?

Answer 3

1. Chronic
2. Latent
3. Transforming

Question 4

What are the two types of cytopathic effects on virus infection?

Answer 4

1. Direct cell damage

2. Indirect cell damage

Question 5

Define permissive.

Answer 5

A cell that provides the machinery and components required for completion of viral replication. May result in latent or transforming infection.

Question 6

Define non-permissive

Answer 6

A cell that does not provide the machinery and components required for completion of viral replication.

Question 7

Name three types of innate defenses.

Answer 7

1. Natural barriers (skin, mucus, etc.)
2. Cells (macrophages, neutrophils, etc.)
3. Soluble Factors (interferons, cytokines, etc.)

Question 8

What are host restriction factors?

Answer 8

Intracellular blocks to viral replication that are part of the innate immune response.

Question 9

True or False: Modern-day vertebrate innate immune system is optimized to defend against modern viral threats.

Answer 9

False. they are optimized to defend against ancient, extinct viruses.

Question 10

Are toll-like receptors (TLRs) part of the innate immune or adaptive immune system?

Answer 10

Innate.

Question 11

TLR3 recognize..

Answer 11

Double-stranded RNA

Question 12

TLR4 recognize…

Answer 12

Fusion proteins and envelope protein

Question 13

TLR7 and TLR8 recognize…

Answer 13

Imidazoquinoline and single-stranded RNA

Question 14

TLR 9 recognize…

Answer 14

CpG-conting DNA

Question 15

What does retinoic acid-inducible gene I (RIG-I)-like helicase recognize?

Answer 15

Viral nucleic acid

Question 16

What is the role of type I interferons?

Answer 16

Antiviral cytokines secreted by most infected cells. Control genes whose transcription is regulated by ISREs.

Question 17

What is the role of type II interferons?

Answer 17

Produced by T cells and NK cells. Controls genes whose transcription is regulated by GAS(gamma activated site)

Question 18

What symptoms are likely to manifest upon sufficient release of IFN?

Answer 18

Fever, chills, nausea, and malaise

Question 19

What is the role of PKR in IFN-induced anti-viral state?

Answer 19

Phosphorylates and therefore inactivates a cellular translation initiation factor to decrease protein synthesis.

Question 20

What is the role of OAS in IFN-induced anti-viral state?

Answer 20

Degrades mRNA

Question 21

Name five types of cells in the innate defense

Answer 21

1. Mononuclear phagocytosis
2. Dendritic Cells
3. NK cells (contain virus)
4. Granulocytes

Question 22

True or False: Antibodies produced during primary virus infections are usually of lower affinity and often of the IgM isotype.

Answer 22

True

Question 23

What type of antibody inhibits virion/host attachment and neutralizes toxins and enzymes?

Answer 23

IgA

Question 24

What three functions does IgG play to prevent viral infection?

Answer 24

1. Inhibits fusion of enveloped viruses with host membrane
2. Opsonize virions to enhance phagocytosis (with IgM)
3. can facilitate complement lysis of enveloped viruses (with IgM)

Question 25

What three functions does IgM play to prevent viral infection?

Answer 25

1. Can coat and agglutinate some virions 2. Opsonize virions to enhance phagocytosis (with IgG) 3. can facilitate complement lysis of enveloped viruses (with IgG)

Question 26

What is APOBEC3G?

Answer 26

A human protein that interferes with the replication of HIV by incorporating itself into virus particles and damaging the genetic material of the virus.

Question 27

What is Vif?

Answer 27

The HIV protein that blocks APOBEC activity can function in two ways: (1) by binding to APOBEC3G and preventing incorporation into virus particles; and (2) by targeting APOBEC3G for destruction and elmination.

Question 28

What two interferons are considered type I interferons?

Answer 28

INF-alpha and INF-beta

Question 29

What interferon is considered a type II interferon?

Answer 29

INF-gamma

Question 30

Cells respond to IFN through receptors through which signalling pathways?

Answer 30

Jak/Stat

Question 31

Name nine strategies to evade host defenses.

Answer 31

1. Antigenic variation 2. Inhibition of the INF pathway 3. Inhibition of apoptosis and cell cycle control 4. Immune tolerance 5. Immunoprivilaged sites 6. Infection of the immune system 7. Restricted expression of viral genome (hide) 8. Viral molecules that act as inhibitors or decoys 9. Down regulation of host proteins