Viral Rep And Infection Flashcards
What do viruses bind to first on host cells and why (via their surface proteins)
Bind to low affinity receptors (proteoglycans)
This increases likelihood of them binding to primary receptors
What are co receptors
Receptors which in some cases eg hiv are needed to be bound to aswell as primary receptors for fusion of membrane with envelope
Which low affinity proteoglycans does HIV bind to
Heparin sulfate
What is the primary receptors for hiv which glycoprotein 120 binds to
CD4
What does gp120 CD4 binding allow
Conformational changes in virus which unveils chemokine coreceptor binding site it can bind to
What are the 2 coreceptors hiv binds to
Ccr5
Cxr4
What happens when gp41 binds to ccr5 or cxr4 in hiv attachment
Fusion of cell membrane with the envelope causing release of nucleocapsid
Are all receptors protein
No
Some are carb or lipids
What is the process called where non enveloped viruses get internalised (envelope can’t fuse with membrane)
receptor mediated endocytosis
How can non enveloped and enveloped viruses be internalised via receptors endocytosis
attach to the surface via gp/ surface proteins
These then get internalised into a vesicle from the membrane of the cell
Vesicle then fuses with endosome and causes lowered ph
This causes conformational shape in virus and released
What is the difference between enveloped release from vesicle and non enveloped via ph change
Enveloped allows fusion of envelope with vesicle and nucleocapsid released
Non enveloped form in pores in the vesicle and nucleocapsid released
How many classes of virus are there due to Baltimore classification (genome Rep and mrna production)
7
Name the 5 main types of viral genome
Ds dna
Ss dna
Ds rna
Ss rna (+)
Ss rna (-)
What is the difference between ss rna + and -
+ means it uses the sense strand so needs reverse transcriptase
- means it uses anti sense so can use polymerase as normal
Which enzymes do dna viruses use for rep and transcription
Dna and rna polymerase from host
Sometimes own
Which enzyme do viruses need to produce if they have rna (-) antisense
Rna dependant rna polymerase for both rep and transcription
Which enzyme is needed for rna + sense strand viruses
Reverse transcriptase
What are structural proteins translated via virus
Proteins needed to form virion eg capsomeres
Give an example of non structural proteins translated for virus
Proteins for genome replication eg rna dependant rna polymerase
Where do viruses get ribosome needed for translation
Host cell
What do most viruses need in translation similar to eukaryotes and why is it needed
5’ cap
Allows 40s subunit binding and also initiation factors for translation
How is IRES used to allow viruses to translate without 5’ cap
Viral rna will form a secondary structure similar to the 5’ cap which means IF and ribosome can bind
Name some modifications viral proteins can undergo post translation
Glycolysation, acylation
Sometimes viral genomes translate into a large poly protein which is then cleave by which enzyme to form things like structural capsomeres
Proteases
Where are proteins glycosylated to form viral glycoproteins
RER
Where are the new viral glycoproteins transferred to via vesicles after productjon in RER
Membrane of cell
How does budding allow an envelope and also glycoproteins to be found on viruses
The nucleocapsid is wrapped in the cell membrane with the viral glycoproteins and this forms the lipid envelope
Other than the cell membrane , how else is the lipid envelope acquired
RER or nucleus
How do non enveloped viruses get released
Cell lysis
How can viruses spread cell to cell
Through pores or membrane fusion
What is it called when viruses spread to a secondary site in blood
Primary viraemia
What is another word for transmission after release
Shedding eg via lungs respiratory
What is secondary viraemia
When viruses spread to target organs either the ones originally infected or other via the blood form the secondary site
Which site of the body has no Shedding of the body from this target organ
The brain (no transmission)
