Lecture 21 - Poliovirus Flashcards
What genome type do Polioviruses have?
(+) ssRNA
What effect does Polio generally cause people?
paralysis
Has Polio been eradicated?
no
What disease does Poliovirus cause?
Poliomyelitis
What type of virus is Poliovirus? What does that mean?
enterovirus = intestines = where the virus likes to infect
What can be done with a (+)ssRNA? What is it’s template? How can it be translated into protein?
(+)ssRNA –> (-)ssRNA = template to make more (+)ssRNA | can be directly translated into protein
Where do enteroviruses multiply?
mucosa of the gut
How serious are most of the diseases due to enteroviruses?
usually mild and result in full recovery of the patients
What viral family are Polioviruses part of?
Picornaviridae
What does it tell us about Polioviruses due to the fact that they are very resistant to most of the antimicrobials used to target viruses?
can stick around for a long time and hard to eliminate it
Where is VP4 found?
inside of capsid
Where is the VPg protein found? At end of the genome?
found on the RNA (+ss) genome | 5’ end
What is VPg used for?
replication, serves as a protein primer
What significant structure is at the 5’ end? What purpose does it serve?
clover-leaf tRNA-like structure = serves as an internal ribosomal entry site (IRES)
What does the internal ribosomal entry site (IRES) mean?
ribosomes can enter with that and do not need to rely on a 5’ cap
Why does the Polioviral genome don’t need to acquire a 5’ cap?
it has an IRES that the ribosome can bind to and start translation
For a monocistronic genome, how does the Poliovirus carry out translation for the different proteins it needs?
encodes a POLYPROTEIN precursor = gets cleaved and cut up to different proteins
What is the receptor for Poliovirus?
CD155 (poliovirus receptor PVR)
What are the 2 lymphoid tissues that poliovirus infects?
Peyer’s patches and tonsils
Which viral proteins form a pore on the host cell membrane?
VP1 and VP4
Where are Peyer’s patches found?
along the intestines
Where does the injection of the Poliovirus genome occur?
at the cell membrane or in early endosomes after being endocytosed
After the Poliovirus genome enters the cytoplasm, what immediately occurs?
VPg is removed = translation can happen efficiently
After translation of the Poliovirus genome, what happens next?
polyprotein = processed via protease
In terms of the replication process, what happens first?
protein products for viral RNA replication transported to membrane-bound vesicles
During genome replication, what happens after the proteins are transported to membrane-bound vesicles?
VPg acts as a protein primer = make (-)ssRNA –> dsRNA –> (+)ssRNA
Why must genome replication occur within membrane-bound vesicles?
due to dsRNA intermediate
How does Poliovirus exit the cell?
via lysis
What is the portal of entry of Poliovirus?
mouth
What is the transmission of Poliovirus?
fecal-oral or oral-oral
What percent of poliovirus infections causes mild symptoms? What are these mild symptoms?
4-8% = malaise, fever, flu-like, GI disturbances
What percent of poliovirus infections cause paralysis? What are characteristics of this paralysis?
1-2% = flaccid paralysis leading to inflammation and destruction of neurons; paralysis can be asymmetric
What is the defining symptom of Poliomyelitis?
flaccid paralysis
What is flaccid paralysis?
can’t move but limbs are limpy
What are the 3 forms of paralytic poliomyelitis?
spinal, bulbar, bulbospinal
What is the spinal paralytic form of poliomyelitis?
when the virus infects lower spinal cord = asymmetric/symmetric paralysis due to spinal cord
What is the bulbar paralytic form of poliomyelitis?
muscle weakness; cannot talk or swallow, hard time breathing = lung muscle impacted | iron-lung
What is the bulbospinal paralytic form of poliomyelitis?
combination of the bulbar and spinal paralytic forms of poliomyelitis
What is the transient viremia stage and when during the Poliovirus pathogenesis does it occur?
virus is in the blood for a short time | after infects and replicates initial sites of infection
How does the virus get into the central nervous system?
through the blood
Where and when did polio epidemics occur?
intermittently, seasonally, and more often in industrialised countries
Why was Polio a mass public concern?
disease appearance was mysterious (its all of the sudden and didn’t know the cause of symptoms) and seasonal | paralyze respiratory muscles | disfiguring, crippling, and sometimes fatal
What is the percentage of Polio infected individuals are asymptomatic?
95%
