CSB351Y1 Lecture Notes - Lecture 46: Dependoparvovirus, Helper Virus, Ambidensovirus
26 May 2018
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Lecture 46
Orthopox
• Entomopox (infect insects), chordopox (infect vertebrates) – cowpox, orthopox (vaccinia, variola/smallpox)
• Vaccina virus used in lab (safe) and is used for smallpox (virus no longer found in nature)
Poxivirus structure
• Enveloped, brick-shaped or ovoid (220-450nm long and 140-260nm wide, has surface tubules/filaments
• Intracellular mature virus (IMV/IEV) particle OR extracellular enveloped virus (EEV) which has double membrane
• Linear, dsDNA, 130-375kb (genome flanked by inverted ITR, covalently closed at extremities)
• No introns, no RNA splicing since replication doesn’t happen in the nucleus
• Early, intermediate and late gene expression
• Replication in cytoplasm:
- Early – DNA synthesis, intermediate – direct late gene expression, late – virus structural proteins
- Enter cell, uncoat, make virus and enzymes, genome replication, transcription, assembly,
maturation/golgi wrapping → IMV/IEV → release →EEV (has additional lipid bilayer)
- EEV and IEV uses different attachment proteins and receptors on virus surface
- EEV for efficient cell-to-cell spread of virus
- IEV for stability for person-to-person contact
Parvoviridae
• Parovirus, dependovirus, densovirus
- Dependovirus need help from another co-infecting virus for replication (adenovirus often
helper virus and herpesvirus) – also called AAVs
- Parovirus can replicated independently (autonomous parovirus) and so do densovirus
• 20-26nm, ssDNA, 5kb naked icosahedral
• Human parovirus B19 (rash)
• Smallest DNA viruses infecting eukaryotes (only package –sense DNA except dependovirus
and few autonomous parovirus like human parovorius B19 which packages both strands)
• All members have ssDNA, palindromic sequences at both ends
• Autonomous parovorius – requires healthy dividing cells for replication
- Adenovirus has general regulators of gene expression causing some viral genes (helper or
AVV) to be expressed and others inhibited
• Dependovirus (AAVs) require either coinfection with helper virus or exposure of cells to toxic (metabolic
inhibitors, carcinogens, UV) for replication
• Epidemiology – HPB19 in all human populations, 80% adults have past infection
- Present throughout year, more common in spring and summer, in schools, pupils infected of young
• Transmission – HPB19 respiratory (aerosols) but can be bloodborne
• Pathology – erythematous rash/infectiosum or fifth disease or slapped cheek disease
- Infection of early RBC precursors and is worsened for people with short RBC lifespan
- Illness similar to rubella in that it may cause joint polyarthropathy in women, viral spread to placenta
- No evidence of clinical illness by AAV infections, just paroviruses (AAV appears to reduce tumors)
• Canine parovirus type 2 (CPV2) – highly contagious, young dog to dog but direct/indirect feces
- Cardiac (respiratory/cardiovascular failure) and intestinal (vomiting, dysentery) form
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Document Summary
Orthopox: entomopox (infect insects), chordopox (infect vertebrates) cowpox, orthopox (vaccinia, variola/smallpox, vaccina virus used in lab (safe) and is used for smallpox (virus no longer found in nature) Intracellular mature virus (imv/iev) particle or extracellular enveloped virus (eev) which has double membrane. Early dna synthesis, intermediate direct late gene expression, late virus structural proteins. Enter cell, uncoat, make virus and enzymes, genome replication, transcription, assembly, maturation/golgi wrapping imv/iev release eev (has additional lipid bilayer) Eev and iev uses different attachment proteins and receptors on virus surface. Dependovirus need help from another co-infecting virus for replication (adenovirus often helper virus and herpesvirus) also called aavs. Adenovirus has general regulators of gene expression causing some viral genes (helper or. Present throughout year, more common in spring and summer, in schools, pupils infected of young: transmission hpb19 respiratory (aerosols) but can be bloodborne, pathology erythematous rash/infectiosum or fifth disease or slapped cheek disease.
