07a: Picornaviruses Flashcards by Nuna H

Picornavirus: (enveloped/non-enveloped) with (ss/ds) (RNA/DNA). Also (helical/icosahedral/complex) capsid.

Non-enveloped;
ssRNA (pos-sense strand)

Icosahedral (and v. stable)

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Picornavirus family contains which medically significant genera?

Enterovirus
Rhinovirus
Heparnavirus (not important for this class)

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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

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T/F: Entero- and rhino-viruses are both resistant to inactivation by detergent.

True

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T/F: Enteroviruses are stable in presence of proteases and bile.

True

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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)

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(X) virus family enters host via viropexis. What occurs immediately after entry into cell?

X = picornavirus

Genome uncoated and plus-sense RNA translated immediately

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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

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T/F: Replication and assembly of picornaviruses take place in cytoplasm.

True

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T/F: Picornavirus virions released either by budding or lysis.

False - lysis

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Enteroviruses usually transmitted via (X) route. Outbreaks typically occur in which settings/seasons?

X = fecal-oral

Crowded conditions (schools/daycares) and in the summer

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Enterovirus infection is often presented with (X) symptoms.

X = no

But viral shedding can occur for up to a month

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T/F: Enteroviruses are human pathogens that typically cause enteric (GI) disease.

False

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Poliovirus, part of the (X) virus genera, infection in (early/late) life causes more severe disease.

X = enterovirus (in picornavirus family)

Late

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Coxsackievirus, part of the (X) virus genera, infection in (early/late) life causes more severe disease.

X = enterovirus (in picornavirus family)

Late

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(Newborns/adults/elderly) are at the highest risk of serious enterovirus infection.

Newborns and neonates

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Poliovirus has (broad/narrow) tissue tropism. This is because it:

Narrow;

Recognizes receptor found on only few/certain cell types

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T/F: All enteroviruses has narrow tissue tropism.

False - poliovirus does; others are relatively broad

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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

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T/F: Enterovirus infection pathogenesis, if symptoms present, typically due to immunopathogenesis (not viral cytopathic effects).

False

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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)

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T/F: Enterovirus infection provides life-long immunity.

True - but type-specific

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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.

1. Abortive poliomyelitis (5%) 2. Nonparalytic poliomyelitis (aseptic meningitis; 2%) 3. 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 1. Replicates in GI (IgA produced) 2. Easy to administer (oral) 3. Longer immunity

Sabin vaccine: list some disadvantages.

1. Can revert to virulent strain (cause polio) 2. Other enteroviruses interfere with replication 3. 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:

1. Aseptic meningitis!! 2. Non-specific URT disease (flu-like) 3. Rashes 4. 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 1. Herpangina 2. 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

1. 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