(Final) Host response to Viral Infection

Question 1

What 3 host immune responses can your body have to a viral infection?

Answer 1

Innate immunity
adaptive immunity
passive immunity

Question 2

What is the first line of defense against infections?

Answer 2

Innate immunity

Question 3

Does the innate immunity exhibit memory or specificity?

Answer 3

NO

Question 4

What are the only immune defense available after the first few days after viral infection?

Answer 4

Innate immunity

Provides primary physical and chemical defenses

Question 5

Where are defensins located in the body and what is their function?

Answer 5

Defensins = host defense peptides with antiviral activity. They are located in the GI tract and modulate the host immune response

Question 6

What are the primary defense mechanisms of the respiratory tract?

Answer 6

Mucociliary blanket and temperature gradient (nasal passages = 33C - alveoli = 37C)

Question 7

By which mechanism do natural killer cells mediate cell death?

Answer 7

Inducing apoptosis via perforin and granzymes

Question 8

What receptors recognize pathogen associated molecular patterns (PAMPs)?

Answer 8

PRR - pattern recognition receptors

One class of PRRs are the Toll Like Receptors (TLRs)

Question 9

Where are TLRs present? (on what cells)

Answer 9

Macrophages, neutrophils, endothelial cells etc

Question 10

What are the results of TLR stimulation?

Answer 10

Phagocytosis
Chemotaxis
Inflammatory mediators
Inferferons

Question 11

T/F: If TLRs are being chronically/constantly stimulated, there may be an auto immune response

Answer 11

TRUE

Question 12

What are interferons?

Answer 12

IFN = a group of cyotokines that are secreted by somatic cells in response to viral infections and other stimuli

Question 13

T/F: IFN posses potent antiviral, immunomodulating, and anti cancer properties

Answer 13

TRUE

Question 14

T/F: DNA viruses are stronger inducers of interferon that RNA viruses

Answer 14

FALSE

RNA viruses are stronger inducers of IFN than DNA viruses

Question 15

What are the 3 major classes of interferon based on antigenic and chemical difference?

Answer 15

Type I = IFN alpha and IFN beta

Type II = IFN gamma

Type III = IFN lambda1, IFN lambda2, IFN lambda 3

Question 16

What kind of interferons are IFN alph and IFN beta?

Answer 16

IFN alpha = leukocyte interferon. Produces large quanities of plasmacytoid dendritic cells

IFN beta: fibroblast interferon. Secreted by virus infected fibroblasts

Question 17

What is the function of Type 1 interferons?

Answer 17

Inhibit virus replication in host cells
Activate NK cells to kill infected cells
Increase the expression of MHC-1 molecules and antigen presentation
Stimulate differentiation of monocytes into dendritic cells
Maturation of dendritic cells
Stimulates memory T cell proliferation

Question 18

What are the 2 primary functions of Interferon alpha and beta?

Answer 18

Apoptosis via autocrine signaling

Inhibition of virus replication via paracrine signaling

Question 19

What is the function of type II interferons?

Answer 19

Type II = Infereron gamma

Mostly immunoregulatory - produced by antigen stimulated T cells and NK cells

Question 20

What is the primary function of Type III interferons? (Lambda)

Answer 20

Immunoregulation

These are expressed in response to viral infections and activation of TLRs

Question 21

T/F: Interferons aare virus specific (for each virus there will be a specific interferon)

Answer 21

FALSE

THEY ARE NON SPECIFIC

Question 22

What gene is responsible for gene silencing?

Answer 22

SIRNA = Short interfering RNA

Question 23

What are the components of adaptive immune system?

Answer 23

Humoral and cellular

Question 24

Humoral immunity is mediated by _________ that are released from B lymphocytes

Answer 24

Antibodies

Question 25

Cellular immunity is mediated by what cells?

Answer 25

T lymphocytes

Question 26

What immune response will stimulate long term memory after an infection?

Answer 26

Adaptive immunity

Question 27

What does the adaptive immunity produce antibodies against during a viral infection?

Answer 27

Against viral proteins on free virions (capsid or envelope)

OR

Against viral proteins expressed on surface of infected cells

Question 28

What can antibodies do to defend against a viral infection?

Answer 28

Virus neutralization
Opsonization
Immunocomplex formation (clumping of viruses)
Complement system activation
Stimulate antibody dependent cell mediated cytotoxicty

Question 29

What cells partake in the cell mediated immunity?

Answer 29

CD4 helper T cells and CD8 cytotoxic T cells

Question 30

What is antigenic plasticity?

Answer 30

Rapid changes in the structure of the viral antigen

Can be due to a mutation, reassortment, or recombination

Question 31

What is antigenic multiplicity?

Answer 31

Antigenic variants with little or no cross-reactivity

can have many viral serotypes

Question 32

What is the process of negative cytokine regulation?

Answer 32

Blocking of the interferon receptor signal.

Virokines: some viruses synthesize proteins which are homologs of cytokines/interferons

Viroreceptors: Some viruses encode proteins that are homologous to the receptors of cytokines. (serve as a competitive antagonist)

Question 33

T/F: Down regulation of MHC class I pathways and Inhibition of complement activation are examples of viral evasion of the immune system

Answer 33

TRUE

Question 34

What are some ways viruses can evade the immune system?

Answer 34

Evasion of neutralizing ABs, Latency, Cell to cell spread, inhibition of apoptosis, inhibition of complement, down regulation of MHC-I, negative cytokine regulation

Question 35

T/F: Rapid changes in the structure of viral antigen of a virus over time due to mutations is also known as Antigenic Multiplicity

Answer 35

FALSE

this is describing antigenic plasticity