Host response to viral infections -2

Question 1

Innate immunity

Answer 1

• inhibition of virus infection by type 1 interferons

- NK cell-mediated killing of infected cells

Question 2

Interferons

Answer 2

are cytokines produced and secreted by somatic cells in response to a variety of stimuli, including virus infection

Question 3

what are the 3 classes of interferons

Answer 3

• IFN- alpha
• IFN-beta
• IFN-gamma

Question 4

What are the type one IFNs and what do they do?

Answer 4

• alpha and beta
• cause an antiviral state in uninfected cells
• induce apoptosis in infected cells
• stimulate production of MHC class 1 proteins and proteasome proteins

Question 5

IFN-alpha

Answer 5

• leukocyte interferon
• secreted by virus infected macrophages and other leukocytes
• not host specific

Question 6

IFN-beta

Answer 6

• fibroblast interferon
• secreted by virus infected fibroblasts and epithelial cells
• host species specific

Question 7

protein kinase

Answer 7

phosphorylates and inactivates a viral initation protein thereby preventing translation of viral mRNA

Question 8

2-5 A synthesis

Answer 8

activates a ribonuclease that degrades viral mRNA

Question 9

what are your type 2 IFNs

Answer 9

IFN-gamma; immune interferon

Question 10

IFN-gamma

Answer 10

• secreted by: mitogens, antigens, or cytokine stimulate T cells and NK cells
• host specific
• no antiviral activity

Question 11

Adaptive immune responses are directed against _____

Answer 11

viral capsid and envelope antigens

Question 12

Internal viral antigens usually elicit ____

Answer 12

protective CMI responses

Question 13

Surface antigens elicit___

Answer 13

protective humoral and CMI responses

Question 14

Antibodies are effective against viruses only during the ________ stage of virus infection

Answer 14

extracellular

Question 15

Virus neutralization

Answer 15

Neutralizing antibodies prevent virus attachment and entry into host cells

Question 16

opsonization

Answer 16

coating of virons by IgG may facilitate pinocytosis and intracellular killing by macrophages and to limited extent neutrophils

Question 17

clumping of viruses

Answer 17

reduces the number of infectious units available for cell invasion

Question 18

complement activation

Answer 18

opsonization (C3b, iC3b, C4b) and possible direct lysis of enveloped viruses

Question 19

lysis of virus-infects cells

Answer 19

cells expressing viral antigens on their surfaces are susceptible to antibody-mediated destruction via ADCC and complement-mediated cytolysis

Question 20

CMI

Answer 20

• the intracellular replicative steps of viruses and virus-infected cells are major targets for CMI
• responses are more important in recovery from infections with non cytolytic viruses

Question 21

Plasticity

Answer 21

rapidly changing surface antigenic structure by mutation, genetic reassortment or recombination

Question 22

multiplicity

Answer 22

• antigenic variants with little or no cross- reactivity

- specific immunization against the common cold may not be feasible preventive strategy

Question 23

immunosuppression

Answer 23

immunocompetent cells are either lysed or inactivated

Question 24

virokines

Answer 24

-Epstein-Barr virus synthesizes a protein that is a homolog for IL-10, suppresses cytokine production by Th1 CD4 cells

Question 25

viroceptors

Answer 25

the secreted cytokine receptor homologues may bind cytokines and function as competitive antagonists of the cytokine