Virology (BIOL 312) Module 6 Pt. 1

Gastrointestinal viruses

Rotavirus family

Reoviridae

What tissue does rotavirus have tropism for?

Jejunum and duodenum epithelial cells

Rotavirus genome

• dsRNA

• Linear, 11 segments

Rotavirus route of transmission

Fecal-oral (shocker)

Rotavirus capsid (and envelope?) structure

• Icosahedral (double shell capsid)

• Naked

Rotavirus receptor

Sialic acid

What age group does rotavirus affect most?

<2 yo

What group of rotavirus infects humans, and how many antigenic types are there? Which proteins determine these types?

• Group A

• 5

• Determined by VP4 (spikes) and VP7 (outer capsid layer), since they’re the only ones on the outside of the capsid

Rotavirus location of replication

Cytoplasm

Rotavirus mechanism of immunity

IgA, secreted in the intestinal mucous

Where does rotavirus virion assembly occur?

In the endoplasmic reticulum

How do rotavirus virions exit the host cell?

Cell lysis

What is diarrhea caused by in rotavirus infection?

• Inability of the small intestine to absorb water

• Excess secretion of water

• Increased movement in GI tract, signalled by seratonin

What causes nausea and vomiting in rotavirus infection?

The two vomiting centres in the brain are activated when the vagus nerve is stimulated. The proximity of the duodenum to the stomach may also play a role

Rotavirus incubation period

1-3 days

Rotavirus clinical manifestation

• Acute vomiting

• Hella watery diarrhea

• Dehydration and hypernatremia caused by the diarrhea can be deadly

Rotavirus treatment

• Fluid and electrolyte replacement (oral is ideal, but IV will do when vomiting prevents that from working)

Rotavirus diagnosis

• Sample from stool

• RT-PCR or EIA to detect antigen

Rotavirus proteins

• Structural: VP1-VP7

• Nonstructural: NSP1-NSP6

Rotavirus seasonality

Winter

Poliovirus and Coxsackie virus family

Picornaviridae

Poliovirus and Coxsackie virus genus

Enterovirus

Members of the enterovirus genus, such as poliovirus and coxsackie virus, are _____ to ___ pH

resistant, low

Enterovirus genus genome

(+)ssRNA

Enterovirus genus capsid (and envelope?) structure

• Icoashedral

• Naked

Enterovirus climate preference

Warmer climates

Enterovirus transmission

• Fecal-oral (espeially in children)

• Resp. secretions, saliva, blister fluid

What is required for mRNA in the host cell to bind ribosomes?

eIF4G and a 5’ cap

Enterovirus protease 2A function

Cuts eIF4G, preventing host mRNA for antiviral proteins from being able to bind to ribosomes and be translated

Enterovirus site(s) of replication

• Epithelial cells and lymphoid tissue in the GI tract and URT

• Tropism for basically everything

What age group does polio most commonly affect?

Children <5 yo

Poliovirus receptors

• PVR (poliovirus receptor)

• CD155 (an Ig-like receptor)

Poliovirus incubation period

7-14 days

What percent of people infected with poliovirus are asymptomatic?

Roughly 80%

Clinical manifestations of symptomatic poliomyelitis

Flu-like syndrome (sore throat, fever, tiredness, nausea, headache, stomach pain)

Abortive poliomyelitis

The poliomyelitis clears after initial symptoms; does not spread to CNS. This is the most common outcome

What happens when poliomyelitis spreads to the CNS?

• Aseptic meningitis (stiff neck and/or back, pain, non-paralytic)

• Paralytic poliomyelitis (<2%)

Paralytic poliomyelitis

• Asymmetric flaccid paralysis

• Do NOT lose sensation

• Typically impacts legs, though can move further up (hence the necessity of iron lungs)

• Caused by degeneration of motor neurons

Can patients with Paralytic poliomyelitis recover?

• Could potentially recover when the infection clears

• If symptoms persist once the infection has cleared and the inflammation is gone, they will not recover

Risk of paralysis due to poliomyelitis increases with ___

age

Bulbar polio

• A severe form of poliomyelitis affecting the brainstem

• Paralyzes muscles controlled by cranial nerves

• Life-threatening

What antibodies does the Inactivated or killed polio vaccine (IPV) elicit?

IgG

What antibodies does Sabin (oral poliovirus vaccine) elicit?

IgA

Poliomyelitis diagnosis

• Sample from saliva or stool

• RT-PCR

Poliomyelitis treatment

• No antivirals

• Supportive care

What could you find on a spinal cord biopsy from a patient with poliomyelitis that has spread to the CNS (not in abortive or subclinical cases)?

Mononuclear cells

Coxsackie virus incubation period

2-10 days

Coxsackie virus clinical manifestation

• Usually asymptomatic

• Cold symptoms, muscle aches, rash around mouth, feet, hands (can also involve arms, legs, and buttocks)

• HFMD especcially in kids

Herpangina

• Sores in the mouth (mainly soft palate)/throat caused by coxsackie virus

• May or may not be accompanied by other symptoms