Picornaviruses Flashcards
Pico rna virus
Small RNA virus
Poliovirus, Insensitivity to ether, Coxsackievirus, Orphanvirus
Genome
(+)ssRNA
Structure?
Naked icosahedral capsid
VAP
The Canyon
Capsid
Made up of VP1-4 with VP4 being internal
VPg
Binds to 5’ end of the genome and acts as a primer for transcription
Why is expression of the genome infectious?
No viral enzymes are packaged, (+)ssRNA so host can translate itself
Attachment receptor
CD155
Lifecycle
- Attachment - the Canyon binds CD155
- Penetration - Endocytosis which triggers conformational change of capsid
- Uncoating/entry - RNA extruded into cytoplasm
- Gene expression - primary translation followed by proteolytic processing of polyprotein
- Genome replication - (+)ssRNA and replication proteins form double membrane replication organelle. dsRNA intermediate is formed which acts as a template for (+)ssRNA
- Assembly
- Maturation
- Release - lytic or nonlytic
Gene expression
Single large polyprotein
VPg is 5’ primer for RNAP (3D)
5’ UTR contains a RNA structure (IRES) for initiation of translation
3’ UTR translation terminated with polyA tail
IRES
5’ UTR RNA structure used for initiation of translation by recruiting translation initiation factors
Polyprotein protease processing
Viral proteases cleave at recognition sites to produce multiple replication and capsid proteins
Transmission
Oral fecal
Primary site of replication
Intestinal epithelial cells
Secondary replication site
CNS or PNS
Polio Pathogenesis
Polio walks its endocytic vesicle along microtubules using host dynein to get close to nerve cell body
Uncoats near nerve cell body
Replication causes functional cell death by protein synthesis shut down or lysis
Inactivated Polio Virus (IPV) (Salk)
Formalin-inactivated virus
No risk of polio
Protects CNS cells NOT intestinal epithelium
DOES NOT STOP SPREAD
Oral Polio Vaccine (OPV) (Sabin)
3 attenuated serotypes BUT 2 mutations are sufficient for reversion to WT and polio
Cheap
Mucosal immunity
STOPS SPREAD and even spreads contact immunity by she’d of attenuated virus
Pros of Sabin OPV
Cheap
Mucosal immunity
Stops spread
Contact immunity (also sorta con if immunicompromised)
Cons of Sabin OPV
Contact immunity could cause polio if immunicompromised
Reversion to WT sometimes
