Picornoviruses

Question 1

what are the picornoviruses?

Answer 1

polio
echo
rhino (only non fecal oral)
coxsackie
Hep A

Question 2

Major features of Picornaviruses

Answer 2

• icosehedral capsid
• naked
• linear, (+)ssRNA
• acid stable and fecal oral (mostly)
• replicate in cytoplasm
• proteases cleave one LARGEEEEE polypeptide into multiple fx proteins

Question 3

immune response to picornoviruses

Answer 3

• IgG, IgM protection against viremia, but not infection
• IgA crucial at mucosal surfaces to protect against infection
• maternal antibodies
• epitopes on capsid define host serotypes –> recognized by broadly neutralizing antibodies
• IFN will initally limit tropism/replication

Question 4

whats the big disease these viruses cause? are there seasonal patterns?

Answer 4

1 cause of aseptic meningitis

peak between June-Nov
peak megningitis= aug

Question 5

most polio infections are asymptomatic, but what disease are seen with poliovirus?

Answer 5

1) paralytic poliomyelitis (acute flaccid)–> destroys neurons in anterior horn –> LMN signs
2) non paralytic poliomyelitis –> asepctic meningitis
3) abortive poliomyelitis –> sore throat, minor URI
4) asymptomatic (90-95%!!!!!!!!!!!!!!!)

can circulate unnoticed!

Question 6

describe infection timeline of poliovirus?

Answer 6

day 0: ingest fecal stuff –> replicates in pharynx, small I, peyers patches

day 1-2: low level viremia –> infx of non neural tissue, adipose, skeletal m

day 2-7: amplified viremia

day 7-14: cross BBB –> kills MOTOR NEURONS (0.5-2%)

Question 7

vaccines for polio?

Answer 7

IPV (salk) KILLED –> IgG/IgM only, limited mucosal
-used in USA exclusively now

OPV (sabin) LIVE ATTEN –> orally to induce IgA!!! Also does IgG, IgM
-developing countries
-vaccine assoc paralytic poliomyelitis
SO be careful of giving someone B cell dysfunction

Question 8

echoviruses

Answer 8

aseptci meningitis and URIs

Question 9

similarities and differences in presentations of Coxsackie A vs B?

Answer 9

BOTH: aseptic meningitis, paralysis, URIs

A: herpangina (mouth blisters), acute hemorrhagic conjunctivitis, hand foot and mouth disease

B: dilated cardiomyopathy, pericarditis, bornholm, hepatitis

Question 10

Rhinovirus

Answer 10

transmitted by fomites!

• acid labile
• likes warmer temps –> 33 degrees –> upper resp tract

Question 11

hepatitus A

Answer 11

causes acute viral hepatitis
gx with IgM ab
-killed vaxine
-contaminated water sources –> in developing countries

Question 12

what age group do enteroviruses cause meningitis in?

Answer 12

6mos- 60 years

Question 13

CSF findings that can distinguish aseptic from septic meningitis?

Answer 13

septic has LOW glucose/ high protein

aseptic has normal protein and normal sugars

Question 14

PV genome in a nutshell?

Answer 14

mRNA orgs that replicate via RNA mechanisms in your cytoplasm

contains: 5’ terminal protein, APg, 5’ NTR, long ORF, poly A tail

Question 15

PV replication in a nut shell

Answer 15

• ORF gets translated by HOST ribosomes, tRNAs
• long viral polyprotein cleaved into MANY viral particles by VIRAL proteases

(+)RNA –> (-)RNA –> (+)RNA
RF (replicative form RNA): -RNA template on which to make multiple +RNA strands
IF (intermediate form RNA): partially ss/dsRNAs being produced

Question 16

3 functions that PV virion RNA serves?

Answer 16

genome
Viral mRNA –> for tranlsation
template RNA –> for replication

Question 17

who gets VAPP? how?

Answer 17

first dose babes
people exposed to these babes with no vaccine
immunocompromised

mech: reverts to wildtype form in the gut

Question 18

why do babies get so sick from these?

Answer 18

b cell immunity and IFN response don’t align and show up at the right time