Pathogenesis 2

Question 1

What is endocytosis and what do viruses exploit this for?

Answer 1

• endocytosis is [part of the cell machinery for moving large sized materials into cell through engulfing
• viruses exploit this to gain entry

Question 2

What are some of the different mechanism for endocytosis?

Answer 2

• vesicles
• pits

Question 3

What may enveloped viruses do to gain entry?

Answer 3

• may fuse with endosomal membrane

Question 4

What can lead to the release of the virus from the endosome?

Answer 4

• pH change

Question 5

What viruses use the endocytic route and where are they released?

Answer 5

• non-enveloped viruses
• viruses released directly into cytoplasm

Question 6

What are the different methods of viral release?

Answer 6

• budding from plasma membrane = enveloped viruses acquire envelope
• exocytosis = opposite to endocytosis
• lysis = cell rupture

Question 7

What do viruses want to do to the host?

Answer 7

• they have adapted to infect, spread and shed with minimal adverse impact on the host

Question 8

If there is tissue injury - what may this assist?

Answer 8

• may assist viral propagation but not compromise the ability of virus to replicate and shed

Question 9

What are two forms of shedding that assists viral transmission?

Answer 9

• coughing
• sneezing

Question 10

What does a cellular tropism require?

Answer 10

• requires cellular receptors and environment conducive to virus gene expression and replication

Question 11

What do cytopathic infections cause?
What is the final outcome?

Answer 11

• loss of functions that are essential for cell survival
• final outcome = cell degeneration/necrosis or apoptosis

Question 12

What processes are essential for non-enveloped viruses to be released?

Answer 12

• cytocidal (cell death)
• cytolytic (cell lysis/rupture)

Question 13

What do noncytopathic viruses do?

Answer 13

• may cause persistent infection
• cell survives but cannot eliminate virus

Question 14

What happens if there is persistence production and persistence non-productive?

Answer 14

• persistence productive = viral progeny = carrier state
• persistence non-productive = no progeny

Question 15

What is latency a type of?

Answer 15

• a type of persistence

Question 16

What happens when the viral gene is not transcribed?

Answer 16

• there are no progeny

Question 17

How does a virus maintain its genome during latency?

Answer 17

• it integrates viral nucleic acid in the cells DNA

Question 18

What viruses can generate DNA copy?

Answer 18

• DNA or RNA viruses

Question 19

What is the genome expression like in a latent infection?

Answer 19

• periodically reactivated progeny

Question 20

What ways can a cytopathic infection ultimately kill the host cells?

Answer 20

• preventing host synthesis of macromolecules
• producing degradative enzymes or toxic products
• inducing apoptosis

Question 21

What are cytopathic effects?
How can these be seen?

Answer 21

• biochemical and or structural changes in infected cells
• some can be seen under a light microscope and may assist in identification of virus/viral group

Question 22

What are inclusion bodies?
How can you see them?

Answer 22

• sites if viral transcription and genome replication
• can be seen under a microscope

Question 23

What viruses can inclusion bodies be seen in?

Answer 23

• intranuclear = DNA viruses which disrupt nuclear matrix
• cytoplasmic = viruses with high replication in cytoplasm

Question 24

Negri bodies are pathognomonic - what are they?

Answer 24

• they are cytoplasmic inclusions in neurons that are composed or rabies virus proteins and RNA

Question 25

Where are Negri bodies found?

Answer 25

- pyramidal cells of Ammons horn - cerebellum - medulla - other ganglia

Question 26

How do proteins produce viral proteins? What does this look like?

Answer 26

- by inhibiting host cell production - may be rapid and profound - may be pronounced - or later in infection/gradual

Question 27

What are the effects of viral protein synthesis?

Answer 27

- loss of homeostasis - degeneration and necrosis

Question 28

What can viruses do the cell membranes?

Answer 28

- later plasma membrane permeability - affect ion exchange - change membrane potential - induce new intracellular membranes

Question 29

What do enveloped viruses do to the cell membrane?

Answer 29

- insert surface glycoproteins into host cell membranes as part of budding - leads to membrane fusion of uninfected and infected cells which creates multinucleated syncytium

Question 30

What do virus proteins in the membrane do?

Answer 30

- target for immune responses - may lead to cell lysis

Question 31

What us the cytoskeleton of the cell responsible for? what does it comprise of?

Answer 31

- responsible for structural integrity of cell, organelle transport and cell motility - comprises filament systems - microfilaments, intermediate filaments and microtubules

Question 32

How can viruses use the cells cytoskeleton? How do they damage it and what does this lead to?

Answer 32

- use elements in replication and assembly - damage specific filaments (canine distemper), damage microfilaments leading to cytopathic effects

Question 33

How is apoptosis useful in viral infection?

Answer 33

- eliminates viral factories before progeny produced