Poliovirus Infection
Poliovirus is a member of the picornavirus family, which also includes rhinoviruses, coxsackieviruses, echoviruses, enteroviruses, and hepatitis A virus.
Picornaviruses
are small, about 300 angstroms in diameter, and are comprised of an icosahedral
protein coat and a single-stranded positive sense RNA genome.
Poliovirus
infection occurs by the fecal-oral route, when the host ingests the virus,
which replicates in the alimentary tract. The virus is then shed in the feces.
Most polio infections are asymptomatic. In about 5 percent of cases, the virus
replicates in other tissues. Paralytic poliomyelitis occurs in less than 1
percent of cases.
Viral
entry
Poliovirus
infection begins with the virus binds to the receptor CD155 on the host cell
surface. CD155 is an immunoglobulin-like receptor also known as poliovirus
receptor. Upon binding, an irreversible conformational change occurs to the
viral particle. The mechanism by which the virus enters the cell is believed to
be receptor-mediated endocytosis, after which the viral RNA is released into
the cellular cytoplasm.
Polio has
a positive sense RNA viral genome. That means it can be directly translated
into protein by the host cell. The viral proteins of poliovirus are:
- 3D(pol)--an
RNA dependent RNA polymerase
- 2A(pro)
3C(pro)/3CD(pro)--proteases that cleave the viral polypeptide
- VPg
(3B)--binds viral RNA and is required for synthesis of RNA
- 2BC,
2B,2C, 3AB, 3A, 3B--protein complex needed for viral replication
- VP0--cleaved
into VP1 and VP3, and VP2 and VP4, the proteins of the viral capsid
Viral
production
Upon
release into the cytoplasm, the viral RNA is translated by the host cell
machinery into a single polyprotein. The 5’ end of poliovirus is long compared
to the host cell’s mRNA, about 700 nucleotides, and highly structured. That
region directs translation of the viral RNA, and is known as the internal
ribosome entry site.
To learn more about the related topics being discussed at the Vaccine Congress 2024, you can join the conference.
For info: https://vaccines.annualcongress.com/
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