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M 124: Virology > Enteroviruses > Flashcards

Enteroviruses Flashcards

1
Q

What are the most common enteroviruses?

A

Poliovirus and Rhinovirus

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2
Q

What are picornaviruses?

A

Family: Picornavirdae
Order: Picornavirales
Realm: Riboviria
Examples genera Enterovirus

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3
Q

Rhinoviruses: VIrus

A

> A, B, and C
(more than 150 genotypes)

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4
Q

Rhinoviruses: Disease

A

Respiratory infections, common cold
Dangerous in young and old patients and asthmatic patients.
No vaccine against them!

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5
Q

Rhinoviruses: Epidemiology

A

Transmission:
> Aerosols and droplet
> Contact with contaminated hands
Distribution:
> Worldwide
> Disease most common in early autumn, late spring
At risk or risk factors:
> Pre-existing respiratory conditions
> No vaccines available
> No licensed antiviral drugs

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6
Q

What are enteroviruses with few or no gut disease manifestations?

A

Examples: picornaviruses
(poliovirus, coxsackievirus, enterovirus 71, enterovirus D68, hepatitis A virus)

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7
Q

Enteroviruses associated with gastroenteritis

A

Examples: rotaviruses, caliciviruses, noroviruses, (Norwalk virus) Often cause disease on cruise ships

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8
Q

Non-polio enteroviruses cause ___ ____ infections and tens of thousands of hospitalizations in the US each year

A

10-15 million

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9
Q

What are enteroviruses?

A

+ single-stranded RNA viruses associated with several human and mammalian diseases.
Named by transmission route through the intestine
Members of the picornavirus family a large and diverse group of small RNA viruses characterized by a single positive strand genomic RNA.
All enteroviruses contain a genome of about 7,500 bases and are known to have a high mutation rate due to low-fidelity replication and frequent recombination.

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10
Q

Enterovirus vs. Coronavirus?

A

Enterovirus:
Viron Size = small 30 nm
Genome size = 7-7.5 kB
Structure = non-enveloped
Infection route = fecal oral and respiratory route
Coronaviruses
Viron Size = large, 120-160 nm
Genome Size = 30 kB
Structure = enveloped
Infection Route = Respiratory route

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11
Q

What is the incubation period of poliomyelitis?

A

5-20 days (hard to track down exposure site).

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12
Q

Describe the effects of poliomyelitis

A

1/200 are paralyzed
Death of anterior horn cell can kill muscles of limbs and torso (can kill right leg).
1) Humoral Antibodies (In bloodstream)
2) Produce mucosal antibodies.
Not stopping infection = paralysis because it reaches the nervous system

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13
Q

What can cause polio?

A

3 strains of polio virus
Consuming contaminated water.
Passed through orally through respiratory droplets as well but feco-oral route is more common.

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14
Q

What are two things that can happen with a natural infection?

A

1) Develop Humoral Antibodies that float in the bloodstream. If the virus gets in the bloodstream, these antibodies can attack and eject the virus.
2) Producing mucosal antibodies that are secreted in the gut to make sure it doesn’t; reproduce.

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15
Q

How does paralysis occur?

A

This is because the polio virus enters the anterior horn cell and kills it leading to the connection between the brain and muscles (limbs, torso, and ribs) etc)

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16
Q

How long does paralysis take?

A

It can occur within a day!

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17
Q

What was the most feared disease of the 40s and 50s?

A

Polio

18
Q

Describe the Salk Polio Virus Vaccine

A

Uses a killed strain of the virus.
Produces humoral antibodies that lower the chance of the virus entering the spine and thus help prevent paralysis.

19
Q

Why isn’t IPV not as effective n tropical countries?

A

Due to poor sanitation.
Also IPV does not produce mucosal antibodies so the virus can reproduce in the gut and thus enter the sewage systems again leading to further infection

20
Q

What is the Sabin vaccine?

A

Oral vaccine
Uses a live-attenuated strain
Produces both humoral and mucosal antibodies which reduce the amount of viruses passed down from feces.

21
Q

Describe impact of OPVs

A

They were used to wipe away polio in the Americas, Europe, and Eastern Asia

22
Q

What are the 3 countries that still deal with poliovirus?

A

Afghanistan,Pakistan, Nigeria

23
Q

Polio Natural Modes of Infection

A

Humans are the only known reservoir of poliovirus which is transmitted most frequently by persons with inapparent infections.

24
Q

Occupational Polio Infections

A

In April 2017, a spill of WPV2 in a production facility in the Netherlands infected 1 operator whose stool tested positive for polio. This highlights the risk of containment breach and emphasizes the need for the appropriate incident response planning and government oversight.

25
Q

What is positive sense and negative sense DNA/RNA?

A

mRNA is the + sense configuration
Complement is the negative sense.

26
Q

Where can the Poliovirus Receptor (PVR) or CD155 be found?

A

Soluble and transmembrane isoforms of PVR can be found in tissues that are susceptible to polio infections such as organs of gastrointestinal tract and nervous tissue.
Also in tissues not associated with polio such as kidney, lungs, liver, and testes.

27
Q

What is the poliovirus life cycle?

A

1) Poliovirus binds to PVR at the cell surface which may be facilitated by LPS to enter the target cell.
2) The poliovirus positive single stranded RNA genome is translated by host cellular machinery to produce a large poly protein.
3) The poly protein is then autoclaved into distinct viral proteins that
4) induce cytoplasmic delocalization of nuclear proteins and the formation of membraneous structures with distinct lipid and protein compositions.
6) These events then allow the viral RNA dependent RNA polymerase to replicate its genome and progeny virions to form.

28
Q

What is the pathogenesis of poliovirus?

A

99% of poliovirus infections are mild or asymptomatic.
Only 1% of poliovirus infections are associated with paralysis.
Reversion of attenuated vaccine may lead to vaccine associated paralysis.

29
Q

Describe human infections of poliovirus

A

Polio continues to be endemic in Pakistan, Afghanistan, and Nigeria
Only 74 reported cases of paralytic polio in 2015.

30
Q

How many cases of Hepatitis A annually in the US?

A

1.4 million cases

31
Q

What are symptoms of poliovirus paralytic disease?

A

5-8 days: fever, vomiting, headache, sore throat
sometimes a fine tremor
Muscle pain (usually 10-29 days); flaccid paralysis (selected muscle groups)
Disease can take up to 5 weeks to manifest paralysis
99% of cases never get to paralysis stage (some may be completely inapparent)
2-5% children die
10-30% of adults die

32
Q

Describe how the polio vaccine is used eradicate polio

A

Live vaccine is more effective but has a small chance of developing polio.
B/c polio incidence is so low in the US we now use the dead Salk vaccine.
Oral vaccines are still used in developing countries.

33
Q

What are key facts about poliomyelitis?

A

Polio mainly affects children under 5.
1 in 200 infections lead to irreversible paralysis.
Among those paralyzed 5% to 10% to die when their breathing muscles become immobilized.
Cases due to wild poliovirus have decreased by over 99% since 1988 from around 350,000 cases to 33 in 2018.
As long as a single child remains infected, children in all countries are at risk of contracting polio.
Failure to eradicate polio from these last remaining strongholds could result in as many as 2000,000 new cases every year within 10 years all over the world.
In most countries, the global effort has expanded capacities to tackle other infectious diseases by building effective surveillance and immune systems.

34
Q

Compare Live vs Dead Vaccine

A

Live:
Dose = low
Booster = no
Duration = many years
Antibody = yes
T-Cell Response = Good
Reversion to Virulence = Possible
Dead
Dose = High
Booster = Yes
Duration = Less
Antibody = yes
T-cell response = poor
Reversion to violence = no

35
Q

What is the primary antibody response?

A

Via disease or vaccination
Antibodies appear in serum after several days
B cells that bind antigen make antibodies
Some B cells become memory cells.

36
Q

What is the secondary antibody response?

A

Via a second exposure to pathogen or booster dose
Antibodies appear in blood within hours
A much bigger response

37
Q

What is the result of a reinfection or a second booster dose of a vaccine?

A

Results in a more rapid antibody response consisting mainly of IgG due to memory B cells formed during the primary response.

38
Q

Explain Baltimore Virus Classification?

A

In 1871, David Baltimore proposed that classes of viruses can be distinguished by two main criteria:
Genome composition (RNA or DNA)
The route used toe express messenger RNA (mRNA).

39
Q

Viral genomes can be:

A

DNA or RNA
Single or double stranded
linear or circular
whole or segmented

40
Q

What is the Baltimore classification based on?

A

genome composition and means of mRNA production.

41
Q

What is the purpose of a genome?

A

1) Inheritance = making more genomes
2) Encode proteins (capsid, replication, etc)

M 124: Virology (22 decks)

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