Viral immunity

Question 1

Do viruses cause diseases in all their hosts?

Answer 1

Not primary hosts

Only in secondary hosts (e.g. rabies in bats cf to humans, dogs)

Question 2

Do viral vaccinations target primary hosts or secondary hosts?

Answer 2

Secondary

Question 3

Why don’t viruses cause disease in their primary host?

Answer 3

Have ability to co-exist

Question 4

Why are well adapted viruses not successfully prevented via vaccination?

Answer 4

Antigenic variation

Question 5

Describe basic viral reproduction

Answer 5

Viruses invade host cell
Synthesis viral nucleic acids and proteins
Self-assembly of new viral macromolecules into virus particles
Virus particles release from host cell

Question 6

What is a singular virus particular called?

Answer 6

Virion

Question 7

What are the 3 possible outcomes of viral infections in cells?

Answer 7

Lytic infection - death of cell to release viral particles
Persistent infection - release of viral particles from cell without death
Latent infection - virus resent but doesn’t harm cell, later becomes lytic infection

Question 8

What is transformation by viruses?

Answer 8

Viruses change a normal cell into a tumour cell

Question 9

What immune component makes up innate viral immunity?

Answer 9

Interferons - type 1 and type 2

Question 10

How can interferons act as antivirals?

Answer 10

Protect neighbouring cells by blocking viral receptors

Question 11

What are the 2 types of interferons and where are they found?

Answer 11

Type 1 - IFN alpha and beta - fibroblasts (tissue cells)

Type 2 - IFN gamma - activated T and NK cells

Question 12

What do type 1 interferons do? (Found in fibroblasts in cell tissue)

Answer 12

Stimulate NK activity

Secrete type 2 interferons

Question 13

What do type 2 interferons do (found in activated T and NK cells)?

Answer 13

Prevent viral growth by secreting nitric oxide

Activate macrophages

Question 14

What is first produced in response to viral infection? What cells originally mediated viral killing of cells? Which cells take over?

Answer 14

Production of interferons and interleukin 12
NK cells mediate killing of infected cells
Then T cells takeover when virus titre has decreased
After T cells - antibodies

Question 15

What is the key protective process the immune system causes during viral infections?

Answer 15

Killing of infected host cells (by NK cells, then T cells)

Question 16

What does antibody-mediated (humoral) immunity of viral infections involve? (role of antibodies)

Answer 16

Block adsorption of visions into target cells
Stimulates phagocytosis of viruses
Triggers complement to cause lysis
Causes viral agglutination

Question 17

Which antibodies are most important in viral immunity? How can antibodies sometimes enhance viral disease?

Answer 17

IgG

Mediate attachment of virus to cells, cause hypersensitivity reactions

Question 18

What can the antibodies produced in response to a virus bind to?

Answer 18

Antigens on infected cells

Antigens of virus itself

Question 19

What is the last part of the immune response activated by viruses?

Answer 19

Antibodies

Question 20

What do NK cells do? Are they innate or adaptive immunity?

Answer 20

Bridge between innate and adaptive immunity

Kill virus infected cells and tumour cells

Question 21

NK cells kill (lyse) virally infected cells and tumour cells. How do they know which cells to kill?

Answer 21

Kill host cells lacking MHC I expression

Kill cells with stress induced proteins

Question 22

What induces NK activity?

Answer 22

Interferon

Question 23

What is the most-important anti-viral mechanism? What 3 parts does this involve?

Answer 23

Cell-mediated immunity:
NK activity
Macrophage activation
Tc response to infected host cells

Question 24

What are the 2 major problems with protective immunity to viruses?

Answer 24

Viruses good at evading immune response

Prolonged immune response leads to detrimental pathological changes in hsst

Question 25

How do viruses stay alive in the immune system?

Answer 25

Intefer with interferons 
Survive phagocytosis
Evade antibody responses 
Inhibit infected cell death 
Induce immunosuppression

Question 26

What can activate latent viral infections?

Answer 26

Stress - reduces immunity