Picornaviruses and togaviruses Flashcards
Why did the polio pandemic started
because we started to get more clean and would get sanitation.
-kids before used to get it really fast while they were still drinking their mothers
-now adults got it later
how do you get polio
fecal oral
symptoms
-fever
-heachache
-vomitting
-diarrhea
-neck stiff
-pain
-death
What was the first vaccine for polio
-salks vaccine
-inactivated polio vaccine devceloped in hela cells
-needs to be refregiratred
-delivered by injection
-safe high potency
-lowkey annoying
Oral polio vaccine
-live attenuated virus
-not refrigerated
True or false: polio has no animal reservoir
true
True or false: polio is almost erradicated
true
True or false: polio is a pocornavirus
true
Stats about picornaviruses
- Non-enveloped viruses
- Icosahedral capsid
- 25-30 nm in diameter
- Genome: (+) ssRNA
- Monopartite, linear
- 7 - 8.5 kb in length
What was the first virus discovered?
-Foot and mouth disease: fmdv
-highly infectuous
-for animals that have cloves
True or false: HepA is a pocornavirus
true
Symptoms of HAV+how it is spreaded around
–nausea and vomiting
-Spread by diredt contact, food, beverages and cups and spoons
-from fecal matter
True or false: HAV is an acute infection
true
-most people can actually recover from the infection
True or false: the common cold is a picornavirus
true
do picornaviruses code for a polyprotein
true
how do picornaviruses get in?
integrins
where do viral receptors bind: picornaviruses
canyon
how many VP proteins do picornaviruses have
4
VP1-4
true or false: picornaviruses replicate in nucleus
false they do it in the cytoplasm
Entry and uncoating of picornaviruses
Some picornaviruses use receptor-mediated endocytosis
(rhinovirus, FMDV), while others (poliovirus) inject their viral
RNA directly across the plasma membrane
True or false: picornaviruses have a cap-dependent translation
false: independent
* Does not contain a 5’ cap
structure
* Must initiate translation in
a cap-independent
manner
* Internal Ribosomal Entry
Site (IRES) mechanism
* Allows viral translation
during host protein
synthesis shutoff
What is the dilema of +ssran viruses
they have to turn off translation to start replication
How do +ssran make the shift from translation to replication
they circularize
-which helps recruiting the proteins required like 3cd and PC which binds to the IRES
True or false: Togavirus Replication Occurs
on Virus-induced Cellular Vesicles
false: it is picornaviruses
* Vesicles are induced by the viral proteins 2B, 2C and 3A
* Required for viral RNA synthesis
- nucleation site for replication complex formation
Vesicle formation in virus-infected cell
True or false: picornavirus replication
induces SMVs and DMVs
- Early in infection - single- membrane vesicles (SMVs)
containing dsRNA are derived from the ER and golgi - Later vesicles wrap around themselves to form double-membrane vesicles (DMVs)
How does viral packaging and assembly works? for picornaviruses
YOU BASICALLY HAVE ALL THE SUB UNITS AND THEN YOU EITHER put the virus in or you have the capsid around the rna
What was a system used for production of infectious polio in vitro
cdna that then you make rna and then put in cultured cells
Stats about togaviridae
- Toga (Latin = gown or cloak)
- Two genera: Rubivirus (Rubella virus)
and Alphavirus (27 members) - Enveloped viruses (icosahedral envelope)
- Icosahedral capsid
- 70 nm in diameter
- Genome: (+) ssRNA
- Monopartite, linear
- 9-11 kb in length
Name 2 viruses that are part of the togaviridae fam
rubivirus and alphaviruses like chikunguya
true or false: rubella is an acute ibfection
true
how does rubella spreads
through the air or caughuing
who are the the hosts for rubella
humans
true or false: the us is rubella free
true
True or false: picornaviruses are arthropod borne viruses
false: it is alphaviruses
what are arthropod borne viruses
- Arthropod-borne viruses (Arboviruses)
- Group of viruses transmitted by arthropod (insect) vectors
- Replicate in both cold-blooded arthropods and warm- blooded vertebrate hosts (adaptable)
- Infection in insects is often not cytopathic, but persistent
- Arboviruses were initially classified together; but they have:
- Distinct genome organization and replication strategies
- Reclassified into different families: Togaviridae, Flaviviridae and Bunyaviridae
True or false: we are accidental hosts of alphaviruses
true
Naturally it is between moquitoes and wild birds
how id chikuguya transmitted
Aedes aegypti and Aedes albopictus
what does chikungutya mean
disease that bends uo the joints
symoptoms of chikunguya
Symptoms: abrupt onset of fever, severe joint pain (may persist
for weeks to years), arthritis (with joints exhibiting tenderness and swelling), skin rash, myalgia (esp. in lower back and leg muscles)
- more rare: neurological features and cardiac manifestations, death (neonates, >65 yrs, and immunocompromised)
-highly debitating=economic impacts
Where is chikunguya usually is
south america/asia/africa
true or false: togaviruses encode for polyproteins
true
which virus has extremely uniform particles
togaviruses
40 copies each of E2, E1, and Capsid proteins
All have Icosahedral symmetry
= Extremely uniform particles
where do togaviruses replicate
in the cytoplasm
cellular entry of toga viruses
- Cell receptors are unclear (mutations in E2
accumulate in culture that can alter receptor binding) - E2 can bind Laminin (rodent/primates) and
Heparin Sulfate (upon passage in culture) - Virions enter cells by receptor-mediated endocytosis
- pH drop in endosomes causes a conformational
change in E1/E2 leading to membrane fusion and
release of the nucleocapsid
non structural proteins of togaviruses translation
- Genomic RNA contains a 5’ methylated cap and 3’ poly-A tail
- Nonstructural proteins (NSPs) are translated directly from the
genome - Readthrough of a UGA codon occurs 10-20% of the time the complete P1234 polyprotein
-strand rna synthesis of togaviruses
Partially cleaved NSPs are responsible for negative-strand RNA synthesis aka p123 and nsp4
Temporal Regulation of Negative-
and Positive-strand RNA Synthesis of togaviruses
- Partially (cis-) cleaved NSPs can catalyze negative-strand RNA
synthesis and transcription of subgenomic mRNAs - Subgenomic mRNAs encode the structural proteins
- Proteolytic processing (trans-cleavage) of NSPs results in positive-strand RNA synthesis
which viruses replication takes place on cytopathic vacuoles
togavirus
* dsRNA spherules form at the plasma membrane
* Internalization of these structures by the endo-
lysosomal pathway results in formation of
cytopathic vacuoles (CPVs)
Packaging, and assembly of togaviruses
Structural proteins are cleaved during translation and directed to different cellular locations
- Capsids self cleave and bind to a packaging signal in the genomic RNA to form nucleocapsids
- pE2, 6K and E1 are processed by host signal peptidase and furin protease in the ER
- Further modification of envelope proteins occurs during translocation through the trans-golgi network on their way to the cell surface
true or false: togaviruses capsid proteins interact
with the cytoplasmic tails of envelope proteins on
the cell surface
true
how do togavirus virions exit the cell
by budding
