CBG Lecture 22: Virus Cell Interactions Flashcards
(38 cards)
what morphological effects do viruses have on host cell
effects on nucleus (nuclear inclusion)
inclusion bodies: due to virus factories sometimes remain till cell lysis
cytoskeletal effects
syncytia giant cell formation
what are inclusion bodies
viral replicating factories
what cytoskeletal changes do viruses have on cells
RNA virus is associated with microtubules so changes the cytoskeleton and bends cell into new shapes
what are syncytia
giant cell formaiton -giant multinucleate cell caused by fusion of infected and non infected cell due to viral envelope
which viruses use syncytia
measles and retroviruses
outline main effects viruses have on host cells
- morphological
- biochemical
- genetic
what biochemical effects do viruses have on host cell
- activate cellular protein kinases and transcription factors
activates cell oncogenes, cell cycle arrest
inhibit DNA synthesis
what genetic effects do viruses have on host cell
genralised chromosomal damage
transformation
introduction of oncogenes
give example of induced viral defence
interferon stimualtion of cells which acts to induce a viral state
what does interferon effect the activation of
transcription, translation, protein processing and virus maturation inhibitors
how does interferon block viral activation of transcription inhibitor
by blocking mRNA synthesis
how does interferon block viral activation of translation inhibitor
by blocking mRNA cap methylation, viral RNA function and tRNA
how does interferon block viral activation ofprotein processing inhibior
by blocking protein glycosylation
how does interferon block viral activation of virus maturation inhibiot
by blocking glycoprotein maturation and budding
what is the HIV combination theory
combo of different drugs allowing normal lifespan for HIV sufferes :AZT to inhibit RT, then protease -> attack many stages of lifecycle
give an exmaple of induced effect by TIP
activation of TIP = translation inhibitory protein
how does TIP activation work
interferon binds to outside of cell
TIP produces TIP RNA, translated = TIP protein, bunds to ribosome and modifies it slowing its speed but makes ribosome more careful about the RNA it translates therefore more likely to transfer host RNA and not viral
what is a viral counterdefernce to TIP activation
Influenza has a cap snatching mechanism, it original RNA is capless but takes host cap and puts on its virus therefore host cant get its protein
give an example of a non induced effect against retrovirus
APOBEC3G defends against retroviruses (HIV has overcome this defence by acquisition of vif gene -viral infectivity factor gene)
how has HIV overcome APOBEC
acquired vif gene
how does non induced APOBEC effect work
APOBEC is human antiviral defence eenzyme which catalyses the deamination of C to U in ssDNA on noncoding strand (G -> A on coding strand) this is HYPERMUTATION
how does vif work
vif gene disrupts the antiviral activity of APOBEC by targeting it for ubiquitination
what is base change caused by APOBEC
hypermutation of C to U in ssDNA non coding strand which is G to A hypermutation on coding
despite vif, on what % of viruses does APOBEC work
30%
