07a: Picornaviruses Flashcards
Picornavirus: (enveloped/non-enveloped) with (ss/ds) (RNA/DNA). Also (helical/icosahedral/complex) capsid.
Non-enveloped;
ssRNA (pos-sense strand)
Icosahedral (and v. stable)
Picornavirus family contains which medically significant genera?
- Enterovirus
- Rhinovirus
- Heparnavirus (not important for this class)
T/F: Entero- and rhino-viruses are both resistant to inactivation by heat and low pH.
False - both resistant to heat inactivation, but only enterovirus resistant to low pH
T/F: Entero- and rhino-viruses are both resistant to inactivation by detergent.
True
T/F: Enteroviruses are stable in presence of proteases and bile.
True
Binding site of (X) virus is a canyon-like structure at the vertices of the (capsid/envelope). This prevents (Y) from accessing the binding site.
X = picornavirus
Capsid (icosahedron)
Y = Ab (too big)
(X) virus family enters host via viropexis. What occurs immediately after entry into cell?
X = picornavirus
Genome uncoated and plus-sense RNA translated immediately
Following translation of picornavirus mRNA in (nucleus/cytoplasm), (X) event takes place. The (host/viral) (Y) Polymerase then synthesizes (plus/neg)-sense RNA template.
Cytoplasm;
X = polyprotein cleavage (by viral proteases)
Viral; X = RNA-dep-RNA
Neg-sense
T/F: Replication and assembly of picornaviruses take place in cytoplasm.
True
T/F: Picornavirus virions released either by budding or lysis.
False - lysis
Enteroviruses usually transmitted via (X) route. Outbreaks typically occur in which settings/seasons?
X = fecal-oral
Crowded conditions (schools/daycares) and in the summer
Enterovirus infection is often presented with (X) symptoms.
X = no
But viral shedding can occur for up to a month
T/F: Enteroviruses are human pathogens that typically cause enteric (GI) disease.
False
Poliovirus, part of the (X) virus genera, infection in (early/late) life causes more severe disease.
X = enterovirus (in picornavirus family)
Late
Coxsackievirus, part of the (X) virus genera, infection in (early/late) life causes more severe disease.
X = enterovirus (in picornavirus family)
Late
(Newborns/adults/elderly) are at the highest risk of serious enterovirus infection.
Newborns and neonates
Poliovirus has (broad/narrow) tissue tropism. This is because it:
Narrow;
Recognizes receptor found on only few/certain cell types
T/F: All enteroviruses has narrow tissue tropism.
False - poliovirus does; others are relatively broad
Enterovirus: primary replication occurs in (X). Later, replication occurs in (Y) of intestinal tract.
X = lymphoid tissues/mucosa of pharynx/tonsils
Y = lymphoid tissue of Peyer’s patches
T/F: Enterovirus infection pathogenesis, if symptoms present, typically due to immunopathogenesis (not viral cytopathic effects).
False
Enterovirus infection: viral shedding may occur for (X) days. This (can/can’t) be reduced if viral-specific Ab are present.
X = 30
Can’t (shedding occurs despite Ab presence)
T/F: Enterovirus infection provides life-long immunity.
True - but type-specific
Enterovirus: (X) protective response plays major role in preventing initial establishment of
infection in the oropharynx and GI tract.
X = Intestinal IgA
Enterovirus: (X) protective response plays major role in preventing viremic spread.
X = Serum IgG
T/F: Poliovirus causes asymptomatic illness 90% of the time in unvaccinated people.
True!
Most severe outcome of poliovirus infection is:
Paralytic poliomyelitis (0.2% in unvacc people)
Aside from asymptomatic illness, list the three illnesses that can be caused by poliovirus in unvaccinated people.
- Abortive poliomyelitis (5%)
- Nonparalytic poliomyelitis (aseptic meningitis; 2%)
- Paralytic poliomyelitis (0.2%)
Poliovirus transmitted via (X) route. There are (Y) number of serotypes and vaccines to how many of those?
X = fecal-oral Y = 3
2 vaccines that contain all 3 serotypes
Paralytic poliomyelitis: generally characterized by an (symmetrical/asymmetrical) (X) with (ipsi/bi/contra)-lateral sensory loss.
Asymmetrical
X = flaccid paralysis
NO sensory loss
Which critical cells are dying in paralytic polio to produce the characteristic symptoms?
Anterior horn neurons in SC
T/F: Paralytic polio always results in death within the next few weeks.
False - paralysis progression can be followed by complete recovery, residual paralysis, or death
Bulbar polio results when the virus affects (X), resulting in which symptom?
X = brain stem
Respiratory paralysis
T/F: When CNS invasion occurs in polio, the virus can be found in stool.
True
When prodrome/minor illness is taking place in poliovirus infection, can the organism be detected in stool?
No, not yet
Treatment for polio primarily involves (X).
X = symptomatic relief, resp support, physiotherapy
T/F: There’s no standard antiviral therapy for polio.
True - but pleconaril available on limited basis
Sabin vaccine for (X) infection is (live/dead). List some advantages.
X = poliovirus
Live, attenuated
- Replicates in GI (IgA produced)
- Easy to administer (oral)
- Longer immunity
Sabin vaccine: list some disadvantages.
- Can revert to virulent strain (cause polio)
- Other enteroviruses interfere with replication
- Must keep cold
Salk vaccine for (X) infection is (live/dead). How many doses are given?
X = poliovirus
Dead
4 doses (in early life, done by age 6 or so)
T/F: Salk vaccine is preferred over Sabin vaccine. It’s the only one available in the US.
True
T/F: One advantage of Salk vaccine is secondary protection by spread to others.
False - true of Sabin vaccine
T/F: Neonates should be vaccinated for polio a day or two after birth since they are most susceptible to infection.
False - first dose at 2 months; maternal Ab protect for about 6 mo.
T/F: In case of polio outbreak, quarantine would help control/prevent spread.
False - proven ineffective
Most common diseases caused by Groups A and B Coxsackievirus:
- Aseptic meningitis!!
- Non-specific URT disease (flu-like)
- Rashes
- Polio-like paralytic disease (transient)
Most common route of transmission of Coxsackievirus is (X). Can also be transmitted via (Y).
X = fecal-oral route Y = aerosolized droplets
Group A Coxsackievirus targets (X) body sites. List the two group-specific diseases it causes.
X = skin/mucous membranes
- Herpangina
- Hand-foot-and-mouth disease
T/F: Both group-specific diseases caused by Group A Coxsackievirus are self-limiting.
True
Herpangina symptoms:
Fever, sore throat, tender vesicles in oropharnyx, anorexia, vomiting
(Due to group A Coxsackievirus infection)
(X) disease caused by (Y) microorganism: small, tender cutaneous vesicles on palms/soles
and buttocks; ulcers in oral mucosa, mild fever.
X = Hand-foot-and-mouth disease Y = group A Coxsackievirus
List the two group-specific diseases caused by group B Coxsackievirus
- Pleurodynia
2. Pericarditis/myocarditis
T/F: Both group-specific diseases caused by Group B Coxsackievirus are self-limiting.
False - can lead to more serious heart damage/failure
Most frequent cause of common cold is (X). Infection occurs via which routes/mechanisms?
X = rhinovirus
Direct: resp droplets
Indirect: contaminated fomites
T/F: Child is more likely to suffer from common cold than adult.
True
T/F: Rhinovirus replicates best at body T (37oC) in LRT than in cooler T in URT.
False - vice versa
T/F: Rhinovirus not extremely infectious (requires about 500 virions to initiate serious infection).
False! Just 1 virion to initiate infection!
T/F: Cell-mediated immunity plays largest role in battling rhinovirus infection
False - plays no role..
T/F: Nasal IgA and serum IgG are induced by rhinovirus infection.
True - but transient and relatively ineffective
