Poliovirus Flashcards
What is the R0 of poliovirus?
3.5
Why doesn’t poliovirus need to package polymerase with the RNA?
The (+) strand can synthesize their own polymerase
What is the template strand in poliovirus replication?
The (-) strand
What is the poliovirus capsid made up of?
60 copies of 4 proteins
What is the reproductive life cycle of poliovirus like?
Virus binds to PVR and RNA associates with the ribosomes where translation can occur
A polyprotein is made and is cleaved
RNA synthesis occurs on the vesicle membrane: (+) strand moves to the vesicle and (-) and (+) strand copies are made, (+) strand copies are translated
Then the capsid precursors are cleaved and the virion exits via lysis
What is poliovirus RNA translated as and what is it cleaved by?
A single polypeptide
It is cleaved by two virally encode proteases (2Apro and 3Cpro)
What is the first RNA polypeptide cleavage responsible for?
Polypeptide folding and cleavage
What type of polymerase does poliovirus make?
RNA dependent RNAP
What are the characteristics of poliovirus RNA-dependent RNAP?
Copies viral RNA, not host RNA
no proofreading activity which limits the size of the virus
How does 3Dpol pol tell which is viral and host RNA?
ssRNA will hairpin on itself - polymerase has specificity for this structure
What does poliovirus replication use as a primer?
Protein - VPg = viral protein genome
What is 3AB in poliovirus replication?
VPg precursor
What does the cleavage of 3AB to 3C form?
VPg-RNA
How are RNA strands and 3AB linked?
Via a tyrosine
What is the poliovirus genome attached to?
The VPg protein
What is the first step of poliovirus translation?
removal of the VPg protein
When does RNA recombination occur?
When synthesizing (-) strands, 10-20% of viral templates recombine
What do inactivated vaccines induce?
Ab response, they rarely induce cellular immunity
Often need a booster
Why don’t inactivated vaccines induce cellular immunity?
No protein synthesis means that there is no presentation which means that there is no T-cell response
How are attenuated vaccines made?
A virus for humans may be attenuated by passage in non-human cell lines
When do you switch from an attenuated vaccine to an inactivated one?
Once it is eradicated using attenuated
