Host Response to Viral Infections

Question 1

What are the 3 types of host immune response to viruses?

Answer 1

Innate
Adaptive
Passive

Question 2

What kind of immune response is constantly present and active immediately upon infection?

Answer 2

Innate

Question 3

What systems features defensins as part of its innate protection?

Answer 3

Gastrointestinal tract

Question 4

The mucociliary blanket and a temperature gradient are parts of the innate immunity in what body system?

Answer 4

Respiratory

Question 5

Why can rhinoviruses infect the upper respiratory tract but not the lower, and why can the influenza infect the lower resp tract but not the upper?

Answer 5

Temperature gradient between the upper (33 C) and lower (37 C) respiratory tract helps localize infection.

Question 6

Receptors at the portal of virus entry that recognize PAMPS

Answer 6

Pattern Recognition Receptors (PRR)

Toll-Like Receptors (TLR)

Question 7

When a TLR recognizes a pathogen, it can initiate what immune processes?

Answer 7

Phagocytosis
Chemotaxis
Inflammatory mediators
Interferons

Question 8

T/F: Interferons are cytokines that are secreted by somatic cells in response to viral infections and other stimuli.

Answer 8

TRUE

Question 9

T/F: IFNs are antiviral and anticancer, but are not able to modulate the immune response.

Answer 9

FALSE - they are also immunomodulating

Question 10

Are RNA or DNA viruses stronger inducers of IFNs?

Answer 10

RNA viruses

Question 11

T/F: IFNs can be administered orally for adequate immune protection.

Answer 11

FALSE - must be administered by injection

Question 12

I am:
A leukocyte interferon,
Produced by dendritic cells,
Type 1.

Who am I?

Answer 12

IFN alpha

Question 13

I am a Type 1 fibroblast interferon secreted by virus-infected fibroblasts. Who am I?

Answer 13

IFN beta

Question 14

Roles of Type 1 IFNs

Answer 14

Inhibit virus replication
Activate NK cells
Increase expression of MHC and Ag presentation
Differentiation of monocytes into DCs
Maturation of DCs
Stimulates memory T cell proliferation

Question 15

I am a Type 2 IFN who is mostly immunoregulatory and is produced by Ag stimulated T cells and NK cells. Who am I?

Answer 15

IFN gamma

Question 16

We are Type 3 IFNs who are expressed in response to viral infections and activation of TLRs, and primarily function as immunoregulators. Who are we?

Answer 16

IFN-delta 1, 2, and 3

Question 17

Cellular adaptive immunity is mediated by __________.

Answer 17

T Lymphocytes

Question 18

Humoral adaptive immunity is mediated by ______ released from _________.

Answer 18

Antibodies; B Lymphocytes

Question 19

Internal viral Ag elicit _____ ______ adaptive response.

Answer 19

Cell mediated

Question 20

Surface Ag elicit _______ and ______ adaptive response.

Answer 20

Humoral and Cell mediated

Question 21

T/F: Ab can only be directed against viral proteins on the surface of infected cells.

Answer 21

FALSE - they can also be directed against viral proteins on free virions.

Question 22

In what ways can Ab prevent viral infection?

Answer 22

Virus neutralization: virus can’t attach to cell

Opsonization

Immunocomplex formation (clumping): reduces number of virus particles availble for cell invasion

Activation of Complement

Ab-dependent cell-mediated cytotoxicity

Question 23

Rapid changes in the structure of a virus as a result of mutation, reassortment, or recombination, that may allow the virus to resist immunity generated from a previous infection.

Answer 23

Antigenic plasticity

Question 24

Antigenic variants with little or no cross-reactivity (ex: there are more than 100 types of rhinoviruses).

Answer 24

Antigenic multiplicity

Question 25

What are the 3 ways viruses can evade the immune system?

Answer 25

Negative Cytokine Regulation - generation of virokines and viroceptors.

Down-regulation of MHC class 1 pathway

Inhibition of complement activation

Evasion of neutralizing antibodies

Latency

Cell-to-cell spread

Inhibition of apoptosis (production of caspase inhibitors)