Picornaviruses Flashcards
Which virus families are classified as picornaviruses?
Enteroviruses Rhinoviruses Hepatitis A Virus Polioviruses Coxsackieviruses Echoviruses
What is the genome, shape, envelop, serotype ID method, common site of infection, and recombination ability of picornaviruses?
Naked icosahedral ss(+)RNA
Epitopes on capsid proteins recognized by antibodies that neutralize infectivity → Abs are serotype specific
Serotypes are defined by the neutralizing Abs in humans
Picornaviruses are common in respiratory infections
Viruses within same species can recombine if they infect same cell (i.e. polio can recombine with another Group C viruses in human cell like coxsackie)
Are picornaviruses acid stable or labile?
Most are acid stable (entero, polio, hepatitis A, Coxsackie, echo)
Rhinoviruses are not stable and are degraded in the GI tract
What diseases can enteroviruses cause?
• Fever/Rash (exanthems) esp in kids in summer/fall
• Aseptic meningitis
• Neonatal infections → can be fatal
• Cause 1/3 of acute myocarditis usu in younger pts
• Enterovirus 71 can cause Hand-Foot and Mouth Disease
acute flaccid paralysis
• Enterovirus 70 can cause hemorrhagic conjunctivitis
What diseases can rhinoviruses cause?
Upper respiratory infections
Most common cause of common cold
Self-limiting
What is the pathogenesis of poliovirus?
• Day 0: ingest fecal material (shed virus for 2-6 wks)
• Day 1-2: low level viremia (infection of nonneural tissues)
• Day 2-7: amplified viremia
• Day 7-14: CNS infection (in 0.5-2% of infection)
o Get across BBB (retrograde axonal infection or provocation poliomyelitis i.e. from trauma=unilateral OR “Trojan horse” vs leukocyte=bilateral)
o Motor neurons (NOT sensory) destroyed
What is the IPV, what immune response does it trigger, and what is its downside?
IPV: Inactivated Polio Vaccine
o Killed, injected, no vaccine-assoicated disease
o Protective IgG
o Limited mucosal immunity, more expensive that OPV
o As of 2000, CDC recommends exclusive use of IPV
What is the OPV, what immune response does it trigger, and what is its downside?
OPV=live attenuated
o Live attenuated; oral, inexpensive
o Systemic AND mucosal immunity
o Vaccine-associated poliomyelitis (VAPP)→ 1/500,000
• Who gets VAPP?: Most recent OPV recipients or contacts of OPV recipients, community acquired, immunologically abnormal
• How? Live attenuated types 1, 2, 3 → have attenuating mutations in each type in vaccine to make in non-infectious → can have a mutation to revert back to WT strain that is infectious → cause disease
o Contraindicated in immunocompromised
o Can recombine with another Group C viruses in human cell (i.e. coxsackie)
What diseases can coxsackieviruses cause?
- Coxsackievirus A can cause Hand-Foot and Mouth Disease → highly infectious, usually resolves in 1 wk
- Coxsackievirus A24 can cause hemorrhagic conjunctivitis
- Coxsackievirus B in acute myocarditis and pericarditis
What does ECHOvirus mean, and what diseases does it cause?
• Enteric, Cytopathic, Human, Orphan virus = ECHO (orphan=no disease association)
What do picornaviruses contain?
Virion: 60 copies each of four viral capsid proteins (VP1-VP4) and one viral RNA – do NOT contain replication proteins
How do picornaviruses attach to cells?
Attachment: specific cellular receptor reaches into canyon of virion particle → virus receptor interaction primary determinant of host range and tissue tropism
• CD155 for polioviruses
• ICAM-1 or LDLR for rhinoviruses
Where do protein and RNA synthesis occur for picornaviruses? Assembly and release of virion?
Protein synthesis and RNA replication (viral RNA-dependent RNA polymerase has high error rate) occur in cytoplasm → do NOT have replicase proteins
o Assembly of capsid protein and viral RNA in cytoplasm
o Release via cell lysis and/or exocytic processes release the new virus particles
