CB623

Question 1

What are entry points of viral infections in humans?

Answer 1

1. respiratory tract
   eg. influenza
2. oral cavity
   eg. Hep A
3. Genital tract
   eg. Herpes virus, HIV
4. Skin
   eg. rabies, yellow fever

Question 2

What is pathogenesis?

Answer 2

manner of development of diease
virus kills too many cells for host to cope with
ussually occurs by direct pathogenic effects on cell

Question 3

What are the principle routes of viral spread through the body?

Answer 3

circulatory and nervous system

-dissemination as opposed to localised infection

Question 4

What is localised spread of virus?

Answer 4

when the target organ is the same portal of entry
eg. influenza
colds and many alimantory tract infections

Question 5

What is episomal latency?

Answer 5

when viral genes are stabilized floating in the cytoplasm or nucleus as distinct objects

Question 6

What is an example of viral migration from entry portal to target organs?

Answer 6

dissemination in the blood.
eg. small pox or measles
target organs for small pox = respiratory mycosa, spleen, bone marrow or lymph nodes
target organ for measles = lympathic and respiratory system and brain

Question 7

What is the most persistent human virus?

Describe virus persistence?

Answer 7

HIV integrates into host DNA.
wait for suitable time for release based on transcription factors as viruses have lots of tf binding sites.
deep resevoirs so difficult to get rid of virus.

Question 8

What are some mechanisms that viruses use to escape the immune system?

Answer 8

1. avoidance of neutralising antibodies by spreading from cell to cell.
2. budding into cytoplasmic vacuoles.
3. genetic varitation (quaispecies)
4. being latent, inhibition of immune and non specific defences

Question 9

What is EBV?

Answer 9

Epstein Barr Virus
virus maintained in the immune system
latency does not result in production of virions
instead genome circulises to episome and copied by DNAp
only portion of genes expressed can persist in B lymphocyte

Question 10

where is herpes simplex mainted?

Answer 10

in NS can clear and reappear

Question 11

What are the 2 types of host defences?

Answer 11

non specific
- anatomic barriers, skin mucus inhibitors fever, inflammation and phagocytosis
induced
NK and interferon

Question 12

How does a fever help against viral infection?

Answer 12

a fever reduces mortality/replication for many viral infection
even 1 degree change wil affect replicative kinetics of virus
need specific temperature to replicate

Question 13

What is phagocytosis most effective against?

Answer 13

bacteria rather than viruses,

Question 14

How does
1. low virulence herpes simplex and influenza
2. HIV
3. high hirulence hiv and herpes
respond to phagocytosis?

Answer 14

1. disruption, dissolved in phagocyte
2. hiv persists
3. multiplies.

Question 15

What extracellular affects does interferon have?

Answer 15

induction of viral state
increase in MHC1 expression
activation of NK cells

Question 16

How do NK cells work?

Answer 16

by increasing MHC1 on normal cells but not infected cells.
killer receptors kill infected cells but normal cells are safe because they have lots of MHC1 which inihibit K receptors.