REOVIRIDAE: Respiratory-Enteric-Orphan viruses.

on 29.1.09 with 0 comments

  • STRUCTURE: Non-enveloped, double-stranded segmented (-) RNA, in 10-12 segments. Contains concentric inner and outer capsids.
    • VP4: Viral glycoprotein neutralization antigen.
    • VP7: Viral glycoprotein neutralization antigen, derived from host-cell ER.
    • RNA-dependent RNA-Polymerase can make messenger RNA's out of the double-stranded viral genome.
    • Rigid capsule makes fecal-oral transmission possible.
  • REPLICATION: The inner capsid always remains intact.
    • The outer capsid is removed upon entry into the cell.
    • Inside the capsid, the RNA-dependent RNA-polymerase makes subgenomic (+) mRNA's. These mRNA's are transported into host-cell cytoplasm and translated into proteins.
    • Inside the capsid, the (-) RNA's are used as templates to make new ds-RNA genomes, which are then released outside the capsid.
    • The new genomes are assembled along with the viral proteins to make new infectious particles.
  • EPIDEMIOLOGY: Fecal-oral transmission.
    • Infection occurs in 6 months to 2 years old. Neonates, older children, and adults are usually asymptomatic. Breast-milk IgA probably provides protection for neonates.
    • Prevalent in winter, but throughout year in tropical climates. Unexplained west-to-east trend in seen in its incidence: Nov ------> Feb as you go from West ------> East in United States.
    • STRUCTURE: 3 serotypes.
    • MANIFESTATIONS: Commonly infects, but asymptomatic, hence they are orphan viruses.
  • ROTAVIRUS: Group-A Rotavirus has 4 serotypes, based on the VP7 antigen.
    • MANIFESTATIONS: Gastroenteritis, which can be life threatening. It is the major cause worldwide, in infants and young children.
      • MECH is believed to be decreased absorption at brush border, but not sure.
    • IMMUNITY: Serotype-specific, and incomplete.
    • DIAGNOSIS: ELISA of stool samples
    • TREATMENT: IV-fluid replacement. Oral rehydration therapy.
    • VACCINE: In clinical trials are re-assortment-viruses containing genomes that encode VP4 or VP7. These are human viruses that infect the cell and reassort with the segmented genome of the rotavirus, rendering it non-pathogenic.
  • ORBIVIRUS: All are arboviruses. Most are asymptomatic. 10 segments.
      • MANIFESTATIONS: Standard common viremia symptoms: fever, myalgia, rash, vomiting. May see maculopapular rash.
      • STRUCTURE: Has 12 segments, not 10.

Category: Microbiology Notes



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