+ssRNA - Picornaviridae (Polio) Flashcards
Do +ssRNA have RdRps in the virion? Why or why not?
No.
Because they are structurally identical to mRNA and are therefore able to be translated immediately in the host.
Are +ssRNAs infectious on their own?
No.
Because they are structurally identical to mRNA and are therefore able to be translated immediately in the host.
Where do RNA viruses multiply?
In the cytoplasm of the host cell
How much more +RNA is there than -RNA?
10-100 fold
What two subsets of picornaviridae did we study? Name the viruses in each class.
Enterovirus: poliovirus, rhinovirus, and coxsackievirus
Hepatovirus: Hep A
What does Coxsackie virus cause?
Myocarditis
Give a brief description of the steps to Picornavirus replication strategy.
Attachment and endocytosis
Capsid releases VP4 to open a pore in the host for RNA to enter cytoplasm
Vpg is removed from viral RNA which is translated to a viral polyprotein
Shutoff of cellular cap-dependent translation through cleavage via viral protease
Reaplication in viral factories from ER vesicles.
dsRNA genome from +ssRNA which makes more +RNA
RNA packaged in preassembled procapsids
Cell lysis and maturation by host protease
What is picornavirus VPg?
Viral protein that caps mRNA and primes RNA synthesis reactions
What is an IRES? What does it do?
Internal Ribosomal Entry Sequence. It allows for translation initiation mid-transcript
What are the host cell factors that interact with the IRES?
What do they do?
IRES transacting factors (ITAFs)
They are cellular RNA binding proteins
What does the cleavage of P1 lead to in picornaviruses?
VP0, 1, and 3 which form protomers
What is a picornavirurus pentamer?
5 protomers
How can you tell that a picornavirus has matured?
Provirion leads to mature virion when VP0 is cleaved into VP2 and VP4
How is Poliovirus transmitted?
Where does it infect (cell/tissue tropism)?
Fecal-oral routes
GI tract is primary infection, epithelial cells via CD155, and can invade CNS in some individuals
Describe polio vaccines.
Inactivated polio vaccine: dead virus by Jonas Salk
Oral polio vaccine: live-attenuated by Sabin
