Other Picornaviridae

Question 1

Parecho classification & structure

Answer 1

Family: Picornaviridae
Genus: Parechovirus (separate from Enteroviruses)

NON enveloped linear (+)ssRNA
Icosahedral capsid from 4 proteins VP1-VP4 (same as entero).

Baltimore - IV

Question 2

Rhinovirus

Answer 2

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

Question 3

Polio structure & classification

Answer 3

Family: Picornaviridae
Species: Enteroviruses C

(+)ss RNA NON Enveloped

Baltimore: IV

Wildtypes 1,2,3

Question 4

Cardiovirus

Answer 4

Family: Picornaviridae
Genus: Cardiovirus

(+)ssRNA NON enveloped

Baltimore: IV

Eg: Saffold virus

Clinical: IFI, AFP, meningitis.

Diagnostics: RT-PCR

Treatment: NO

Vaccine: NO

Question 5

Parecho clinical syndrome

Answer 5

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.

Question 6

OPV related infections

Answer 6

1. 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.
2. 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.

Question 7

Polio pathogenesis

Answer 7

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.

Question 8

Polio clinical syndrome

Answer 8

1. Mild illness with fever and IFI - 98%
2. 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.

Question 9

Polio diagnostics

Answer 9

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.

Question 10

Post polio syndrome

Answer 10

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.

Question 11

Polio therapeutics

Answer 11

Same as EV

No FDA approved antivirals.
1. Pleconaril - capsid inhibitor
2. Pocapavir - capsid inhibitor
3. Remdesivir

IVIG in life threatening infections