Picornivirus Diseases

Question 1

Give a rundown on Picrornaviruses.

Answer 1

• Small (they are pico)
• Positive-sense, ssRNA
• Naked
• Icosahedral

Question 2

How do Picornaviruses infect humans?

Answer 2

Fecal-oral transmission (except Rhinovirus, which is acid-labile)

Question 3

Enteroviruses are broken down into subtypes not mentioned by Sketchy. Give the categories and examples of each.

Answer 3

• Enterovirus A: Coxsackie A
• Enterovirus B: Coxsackie B
• Enterovirus C: Polio

Question 4

What is the utility of the subcategorization of the enteroviruses?

Answer 4

The viruses in each category can recombine and make chimeric genomes.

Question 5

Antibodies to what portion of the Picornavirus virion confers host immunity?

Answer 5

Capsid proteins

Question 6

Enterovirus D68 caused a fleeting outbreak of _____________ in 2014 and then quickly waned.

Answer 6

flaccid encephalitis

Question 7

Sketchy does not have a separate video for which Enterovirus?

Answer 7

Echovirus (remember the echoing birds in the top of the aviary)

Question 8

In general, Enterovirus typically causes disease in which season?

Answer 8

Late summer and early fall

Question 9

The Picornaviruses can infect ______________.

Answer 9

any tissue of the body

Question 10

Why is it that the encapsulated bacteria and Enterovirus become the most common causes of meningitis in children 6 months to 6 years?

Answer 10

Maternal antibodies persist for the first six months of life and prevent infection with these organisms.

Question 11

How do Picornaviruses replicate?

Answer 11

They are positive-sense, ssRNA that directly encodes a polyprotein that contains the capsid protein and replicase proteins.

Question 12

Which protein makes positive-sense RNA from negative-sense RNA?

Answer 12

RNA-dependent RNA polymerase (RDRP)

Question 13

Describe the overall pathogenesis of Picornaviruses.

Answer 13

1) Typically, the primary infection is the GI or respiratory mucosa.
2) Viremia leads to the infection of target organs.
3) IgG will lead to future immunity, but IgA is needed to prevent future infection.

Question 14

Almost all Poliovirus infections are _________________.

Answer 14

asymptomatic (95%)

Question 15

People infected with Polio become infectious _________________ after being infected themselves.

Answer 15

almost immediately

Question 16

How does Polio infect the CNS?

Answer 16

It can infect lymphocytes which can cross the BBB (which produces bilateral paralysis), or it can infect motor neurons at the NMJ (asymmetric paralysis).

Question 17

What are the benefits of Sabin’s attenuated vaccine?

Answer 17

It is inexpensive and induces both IgA and IgG immunity.

Question 18

Why did the oral polio vaccine regimen lead to infections in the community?

Answer 18

The live virus had attenuating mutations. In the body, mutations occurred that reverted the attenuated virus to live virus in two days.

Question 19

What Enterovirus was discovered in 2014 at Children’s Hospital Colorado?

Answer 19

Enterovirus 68 (which causes acute flaccid paralysis)

Question 20

Introduction of a vaccine in 2000 led to a drop from 100,000 cases per year to 10,000 cases per year in _____.

Answer 20

HAV

Question 21

Polio binds to which receptor?

Answer 21

CD155

Question 22

Picornavirus virions do not have ___________ proteins.

Answer 22

replicase (thus, RDRP is the first protein that Picornaviruses translate)

Question 23

Briefly explain how Picornaviruses replicate.

Answer 23

They use ribosomes to make RNA-dependent RNA polymerase. Then, the RDRP makes (-) RNA which is used as a template to make more (+) RNA –also done by RDRP.

Question 24

Explain why paralytic polio emerged relatively recently.

Answer 24

Polio usually causes paralysis only in adults. Prior to a couple hundred years ago, poor sanitation standards led to widespread polio infection of young children. Because young children are less likely to get paralytic polio, paralytic polio was uncommon until better sanitation practices meant that

Question 25

_______________ can cause hemorrhagic gastroenteritisi in newborns.

Answer 25

Echovirus

Question 26

From the time of ingestion onward, how quickly does polio infect the CNS?

Answer 26

Two weeks