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8 Cards in this Set

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Picornaviruses should immediately make you think of what structure, genetics, and diseases?
Picornaviruses are (+), non-enveloped = NAKED, and are icosohedral (along with calici, flavivirus, togavirus, and reovirus).

diseases include: Polio, HepA, Rhinovirus, Coxackie,
give some more detail about the genetics of poliovirus: replication/entrance/transcription happens how?
know there are viral proteins 1 through 4 (VP1, VP2, VP3, VP4), and that only 1, 2, and 3 are expressed on the surface (VP4 is inside with the RNA).

VP1 interacts with PVR (polio virus receptor).

there's ONE BIG ORF - so get one big polyprotein that has to be cleaved:

1ABCD makes our VP1 through VP4. Vp1 comes off first. The rest of the genome codes for polymerases.

It's a positive strand virus, so it doesn't carry any RNA-dependent-RNA polymerase!

(+) right to ribosome to get translated.

HOST and VIRAL proteases needed.
what receptor does it use and how does poliovirus get in? receptor? Where is it?
uses the POLIO VIRUS RECEPTOR (PVR), not sure what it is exactly. Note that PV1 interacts with PVR.

receptor is on Neurons/Gastrointestinal Tract.

uses a clathrine coated pit, through which RNA escapes and goes to the ribosome to start everything off.

lots of receptors in the brain - brain stem (so get facial paralysis) - extent of paralysis is related to HOW MUCH BRAIN INVOLVEMENT.
talk about poliovirus's effects on cells, and how this happens
poliovirus is CYTOPATHIC, no question.

polio works by SHUTS OFF HOST CELL SYNTHESIS by messing with a HOST INITIATION FACTOR involved in 5'cap recognition.

Picornaviruses have NO 5' CAP, so they continue to get translated/transcribed even though the cell is shutting down.
talk about polio disease progression, epidemieology, symptoms - who gets sick? life long symptoms?
FECAL/ORAL transmission, like a lot of naked viruses (especially picornaviruses).

replication in GI tract and nerves. Destroys motor neurons in the anterior horn.

MOST INFECTIONS ASYMPTOMATIC, 1/100 to 1/1000 get symptoms (headache/meningitis)

paralysis far more frequent in adults.

so for every paralysis case, there are probably thousands more infected, so one case = likely epidemic.

don't forget POST POLIO SYNDROME - likely not caused by virus (not detected) - decades after surviving polio, get progressive atrophy and DEATH probably. 25% incidence.

in endemic areas, mostly kids get infected and don't get bad disease, so protected when older and less paralysis.

used to be in US, it was rare enough that most kids didn't get infected, but when infected as adults, devistating paralysis resulted = iron lungs, etc.
lab tests/diagnosis of polio?
virus shed in stool for weeks. remember that it's cytopathic, so recover virus from poop and see if it's cytopathic.
talk about different polio vaccines:
first was IPV - whole, KILLED virus, first used. Several round injection. No herd effects.

OPV = later used, oral, attenuated - it's shed in poop for weeks after and can revert to live and cause infection in old people around the innoculated person. NO LONGER USED IN US. requires cold chain, used overseas. Allows for "HERD EFFECTS" - shed attenuated virus can innoculate those around and protect from infection. Or give you polio. Only polio in US caused by OPV.
is it possible to erradicate polio?
yes - there are NO ANIMAL HOSTS - but still crops up in nigeria, afghanistan, pakistan, and india.