CBG22 Flashcards
What are cells that support viral infection?
permissive
What does a productive infection often lead to?
cytopathic effects
changes in cell
What does infection of a non permissive cell lead to?
abortive or restrictive infection
What is a persistent infection?
dont produce much
What is a chronic infection?
low level over a long period of time
What does a cytodical productive infection lead to?
death, releasese of infectious virus, morphological biochemical and physiological change and DNA degradation.
What does a cytodical abortive infection lead to?
variable cell survival
no relase of virus
barable morphological, biochemical and physiological changes
maybe dna mutation
What does a laten infection lead to?
survival, no changes
perhaps dna mutation
What does chronic infectoiin lead to?
variablle affects release of virus variable morphological effects dont strongly effect biochemistry or physiology may cause mutations
What do morphological effects include?
changes to nucleus (nuclear inclusion)
cytoskeleton
giant cell fromation
How can a virus be diagnosed by looking at cytoskeleton?
example
by looking at affects on cytoskeleton
seen via light microscope
eg. nucelear and cytoplasmic inclusion in cell infected by cytomegalovirus
What affect do measles and retroviruses have on cells that can be seen under the light microscope?
syncita produced by fusion of viral envelope with uninfected cells.
- virion entering cell causes production of viral fusion proteins
- causes cell to fuse more than one nucleus
- syncitial cell
What are the effects of viruses on cell biochemistry and physiology?
- activation of cellular proteins and kinases and transcription factors.
- activation of cellular oncogenes, cell cycle arrest
- inhibition of DNA synthesis
What genetic effects can viruses have on host cells?
transformation , generalised chromosome damage.
What happened to the viral syncitin gene?
stolen from viruses and domesticated in mammals
twice in primates
involved in placental formation
What is the modern HIV medicine?
a combination of inhibitors
- as in interferon
What is an example of an induced defence?
via interferon
-alpha and beta are the main antiviral defences in the body
interferon acts to induce viral state in cells ‘siege state’
from point of infection
stimulated by viral RNA
What does interferon do?
as it is easy for virus to develop a mutation interferon activates a variety of inhibitors at the same time to target differetn stages of life cycle.
- Transcription inhibitors. - block mrna synthesis
- Translation inhibitors - block mrna, via cap and methylation- methylase, protein kinase, phosphodiesterase
- protein processing inhibitor - blocks protein glycosylation
- virus maturation inhibitors - blocks budding and glycoprotein maturation
What can host defences to viruses be?
induced or non induced.
viral signals induce antibody defences to ready for infection
- not on all the time as slow down transcription/lation so inefficient
What is TIP?
translation inhibitory protein anti viral defence protein activated by interferon once translated binds to ribosomes making it more particular about mRNA it transaltes only translates mrna with cap
What mechanism does influenza have to overcome TIP?
cap snatching mechanism
not only increases viral translation but decreases host
What is an example of a non induced defence?
APOBEC3G which defends against retroviruses.
enters viron and causes C->U G->A on coding strand- destroys virus
via hypermutation
- hits 30% of viruses that infect cells
How does TRIM5 work?
act against uncoatinf of virus by binding to capsid protein- chimp
-TRIM5 blocks HIV in chimps
our TRIM5 blocks chimp RV
What is RSV?
Rous Sarcoma Virus
Retrovirus
causes sarcoma in chickens
+ sense
src was taken up by RSV and incorperated into genome
src gene is an oncogene- stimualtes uncontrolled mitosis
src is non essential but increases its virulance
