Immunity to Viruses

Question 1

Horizontal transmission

Answer 1

Direct person-to-person spread

Question 2

Vertical transmission

Answer 2

Transfer of infection from parents to offspring

Question 3

Viruses are dependent upon what to replicate?

Answer 3

Host cell

Question 4

Tropism

Answer 4

Ability of virus to replicate in particular cells or tissues

Question 5

Typical viral life cycle

Answer 5

1. Enter through cell surface receptor
2. Use cell biosynthetic machinery to replicate
3. Error prone replication generates mutations
4. Particles are assembled together to form new virus

Question 6

Difference between cytolytic and non-cytolytic viruses

Answer 6

Cytolytic viruses cause destruction of host cell: host cell membrane is ruptured to release viral particles
Non-cytolytic viruses leave host cell alive: use host cell membrane as coat for viral particles

Question 7

Innate immune mediators of viral response

Answer 7

Complement: prevent spread of virus
Toll-like receptors
Interferons

Question 8

Toll-like receptors: role in viral response

Answer 8

Recognize virus, triggering activation of immune response

Question 9

Type 1 interferons

Answer 9

Interferon alpha and beta
Anti-viral
Produced by innate immune cells and local cells

Question 10

Type 2 interferons

Answer 10

Interferon gamma
Produced by T cells to amplify immune response
Involved in viral immune response

Question 11

Benefit of interferon response

Answer 11

Interferon responses are fast

Question 12

Complement activation in viral response

Answer 12

Classical pathway: antibody recognizes viral antigens and binds to them

Question 13

Antibody role in viral response

Answer 13

Neutralize extracellular virus
Opsonization of virus for phagocytosis
Complement activation
Prevent spread of virus

Question 14

Antibody classes involved in viral response

Answer 14

IgM: indicator of recent or current infection
IgG: more effective than IgM
IgA: protection of mucosal surfaces

Question 15

CD4 T cell role in viral response

Answer 15

Synthesize cytokines that trigger immune response

Question 16

CD8 T cell and NK cell role in viral reponse

Answer 16

Induction of infected cell death through apoptosis or perforin/granzyme pathway

Question 17

Host evasion: interferon

Answer 17

Block synthesis of interferons

Question 18

Host evasion: antigen presentation

Answer 18

Block antigen delivery to MHC I
Reduce surface expression of MHC I
Reduce MHC II level on APC

Question 19

Host evasion: C3b

Answer 19

Bind C3b, inhibiting complement activation

Question 20

Host evasion: changing surface antigen

Answer 20

Inability to produce effective immune response

Question 21

Host evasion: immunosuppression

Answer 21

Direct infection of immune cells, cause cytokine imbalance

Question 22

How INF alpha and beta work

Answer 22

Induce resistance to viral replication
Increase MHC class I expression and antigen presentation
Activate NK cells to kill virus-infected cells