Other Picornaviridae Flashcards
Parecho classification & structure
Family: Picornaviridae
Genus: Parechovirus (separate from Enteroviruses)
NON enveloped linear (+)ssRNA
Icosahedral capsid from 4 proteins VP1-VP4 (same as entero).
Baltimore - IV
Rhinovirus
Family: Picornaviridae
Genus: Enterovirus
(+)ss RNA NON enveloped
Baltimore: IV
More than 100 Serotypes
Receptor: intercellular adhesion molecule-1 (ICAM-1). 1). ICAM-1 is usually expressed on nonciliated epithelial cells of the adenoid and nasopharyngeal mucosa (18); in addition, ICAM-1 is present on endothelial cells, in the germinal center, and on the basal surface of the ciliated epithelium.
Clinical: Common cold, CAP, asthma exacerbation.
Diagnostics: RT-PCR
Therapeutics: Supportive
Vaccine: NO
Polio structure & classification
Family: Picornaviridae
Species: Enteroviruses C
(+)ss RNA NON Enveloped
Baltimore: IV
Wildtypes 1,2,3
Cardiovirus
Family: Picornaviridae
Genus: Cardiovirus
(+)ssRNA NON enveloped
Baltimore: IV
Eg: Saffold virus
Clinical: IFI, AFP, meningitis.
Diagnostics: RT-PCR
Treatment: NO
Vaccine: NO
Parecho clinical syndrome
PeV 1 & 3 most associated with disease
Similar to EVs - Febrile syndrome, RTI, exanthema, meningitis, encephalitis, myocarditis, neonatal infections.
Serotype 3 can cause fulminant hepatitis and meningoencephalitis in infants.
OPV related infections
- Vaccine derived polio viruses (VDPV): emerged from Sabin OPV strains. These strains circulate in low population immunity and undergo genetic reversion to similar to wild type - causing poliomyelitis.
- Vaccine associated paralytic poliomyelitis (VAPP): OPV virus strain reverts to neurovirulejce during replication in GI tract in immunosuppressed patients.
Incidence 1 in 2.5 million vaccine doses.
Whereas VAPP is an adverse event following exposure to OPV, VDPVs are polioviruses whose genetic properties indicate prolonged replication or transmission. Three categories of VDPVs are recognized:
(1) circulating VDPVs (cVDPVs) from outbreaks in settings of low OPV coverage,
(2) immunodeficiency-associated VDPVs (iVDPVs) from individuals with primary immunodeficiencies, and
(3) ambiguous VDPVs (aVDPVs), which cannot be definitively assigned to either of the first 2 categories.
Polio pathogenesis
Similar to other Picornaviridae.
Faeco-oral transmission and replication in oropharyngeal and GI lymphatic tissue with transient viraemia.
Receptor: PVR (CD155)
Crosses BBB into CNS/retrograde axonal transport from muscle to nerves to CNS.
Viral replication in spinal motor neurons leading to classic syndrome.
Polio clinical syndrome
- Mild illness with fever and IFI - 98%
- Severe - 2%
A. Non paralytic A severe illness with fever and meningitis.
B. Paralytic - AFP with anterior horn cell injury. Rare: 0.5 to 0.05% of all polio cases.
Polio diagnostics
Stool and throat swab - 2 samples 24 hours apart within 14 days of AFP for RT-PCR and typing.
CSF - pleocytosis - initial neutrophils and then replaced by lymphocytes.
RT-PCR and typing.
MR & EMG.
Post polio syndrome
Progressive muscle weakness after a prolonged period of stability - usually 35 years after (range 8 to 70 years).
Persistent EV/Polio in neurons in latent stage or demyelination - unclear.
Polio therapeutics
Same as EV
No FDA approved antivirals.
1. Pleconaril - capsid inhibitor
2. Pocapavir - capsid inhibitor
3. Remdesivir
IVIG in life threatening infections
Polio vaccine strain
OPV - trivalent Sabin 1,2,3
IPV - Salk 1-3
Polio vaccine schedule
Primary immunisation
<10 - 3 doses 1 month apart of the hexavalent
Reinforcing dose after 3 years from last dose - DTAP/IPV.
> 10 years - TD/IPV 3 does 1 month apart
Reinforcing dose after 5 years.
2nd booster 10 years after 1st booster.
