Adenovirus, parvovirus, polyomavirus Polyomavirus genome

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Adenovirus, parvovirus, polyomavirus
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Adenovirus
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Case presentation
A 68 year old African American male status post
a heart and kidney transplant on immunosuppresive
therapy presents with altered mental status,
fever, diarrhea, productive cough was found on
exam to have decreased breath sounds with
bilateral harsh breath sounds, bilateral eye
injection and redness. Lab work revealed
leukocytosis of 14,000 on initial exam, cultures
negative and CT chest revealing patchy
consolidation right upper lobe, left lower lobe.
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Adenovirus classification

• Infect numerous vertebrate species (fish to
  human)
• Only vertebrates (so far)
• 51 human serotypes

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Adenovirus structure, genome

• Icosahedral, non enveloped, 90 nM diameter
• 36 kb (medium sized) linear dsDNA

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Adenovirus Genome

• 36 kb (medium sized) linear dsDNA
• Early genes for host and viral transcription
  control, viral DNA replication
• Late genes for virion structure

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Adenovirus replication

• Replicates and assembles in nucleus via DNA
  intermediate
• Uses host transcription apparatus, but modifies
  it to facilitate virus gene expression
• Uses oncogenes (E1) in a fashion similar to
  papillomaviruses
• Transcription cascade (early and late genes)
• Encodes virus specific DNA replication apparatus,
  including viral DNA polymerase

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Adenovirus replication cycle
(From Fields Virology, 4th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2001, Fig.
67-5.)
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Adenovirus pathogenesis

• Only one third of serotypes cause most clinical
  disease
• Widespread
• Respiratory or fecal-oral tramsmission
• May establish viremia
• Replication in respiratory tract, eye,
  gastrointestinal tract, urinary bladder
• Persistence for months
• Responsible for 5 of acute respiratory disease
  (ARD) in children under 5
• ARD in military recruits
• Conjunctivitis
• Hemorrhagic cystitis
• Gastroenteritis and diarrhea
• Some serotype specificity in pathogenesis

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Adenovirus disease
(From Fields Virology, 5th ed, Knipe Howley,
eds, Lippincott Williams Wilkins, 2007, Table
64.1.)
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Adenovirus pathogenesis
From Medical Microbiology, 5th ed., Murray,
Rosenthal Pfaller, Mosby Inc., 2005,, Fig. 50-4.
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Adenovirus diagnosis

• Cell culture
• Viral antigen detection (ELISA,
  immunofluorescence)

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Adenovirus vaccine

• Live, wild type enteric coated vaccine for
  military recruits
• Asymptomatic infection of gut raises protective
  immune response for respiratory infection

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Summary adenovirus

• Structure
• Medium sized (36 kb) dsDNA genome, naked capsid
• Pathogenesis
• respiratory or fecal oral transmission
• replication in nucleus moderately host dependent
• local spread viremia
• cellular and humoral immunity important virus
  encodes countermeasures against MHC I expression
  and apoptosis
• direct cell damage from replication respiratory
  illness, conjunctivitis, gastroenteritis,
  cystitis
• Diagnosis
• culture, viral antigen detection
• Treatment/prevention
• live military vaccine
• Gene therapy vector

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Parvovirus
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Case presentation

• The patient was a 19-year-old pregnant female
  who presented at 22 weeks gestation with signs
  and symptoms of preeclampsia.
• An ultrasonogram revealed intrauterine fetal
  demise. Hydrops (abnormal accumulation of fluid
  in tissues) was present. Labor was induced, and
  a stillborn fetus was delivered. An autopsy was
  performed on the fetus. Severe autolysis was
  evident, which is consistent with intrauterine
  demise. On histopathologic examination of the
  fetus, characteristic intranuclear viral
  inclusions were seen in erythroid precursor cells
  in the bone marrow and liver. Serologic evidence
  of acute infection due to maternal exposure to
  parvovirus B19 supported the diagnosis in this
  case.

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Classification

• Parvoviruses affect many animal species
• Vertebrates and invertebrates
• Limited but noteworthy interspecies transmission
• Human, cat, dog and pig parvoviruses economically
  and socially important
• Two human viruses
• B19
• Adeno associated virus (AAV)

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Parvovirus structure

• Icosahedral, non enveloped, 18-26 nM diameter
  (reeeeally small)
• 5 kb, linear, single stranded DNA genome
  (reeeeally small)
• Depending on virus, only one of both DNA strands
  may be encapsidated, but if both, they are
  encapsidated separately.

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Canine parvovirus
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Parvovirus Genome

• 5 kb, linear, single stranded DNA
• Inverted terminal repeats essential for
  replication and integration (dependoviruses)
• Two genes
• Rep is required for DNA replication
• Cap encodes capsid proteins

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Parvovirus replication

• Replicates and assembles in nucleus via DNA
  intermediate
• Uses host transcription apparatus
• Encodes control protein (Rep) for DNA and RNA
  synthesis
• Two replication styles
• Autonomous
• Helper dependent

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Autonomous parvovirus replication

• Includes the human pathogen B19
• Must replicate in mitotically active cells
  (S-phase)
• Preference for erythroid lineage

Postulated replication of parvovirus (B19) based
on information from related viruses (minute virus
of mice). The internalized parvovirus delivers
its genome to the nucleus, where the
single-stranded (plus or minus) DNA is converted
to double-stranded DNA by host factors and DNA
polymerases present only in growing cells.
Transcription, replication, and assembly occur in
the nucleus. Virus is released by cell
lysis.(From Medical Microbiology, 5th ed.,
Murray, Rosenthal, Kobayashi Pfaller, Mosby
Inc., 2002, Fig. 56-2.)
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Helper dependent parvovirus (AAV) replication

• Includes human non-pathogenic adeno associated
  virus (AAV)
• Absolutely dependent on adenovirus as helper
• Several adenovirus genes are involved in helper
  function
• Efficient, site specific integration during
  replication
• Integration not required for replication
• Integrated provirus may be activated to replicate
  by infection with helper

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Parvovirus pathogenesis

• Human parvovirus B19
• Widespread (50 - 90 of population depending on
  age), mostly asymptomatic infections
• Respiratory transmission
• Viremia
• Infects erythroid precursor cells in bone marrow
• Disease
• Erythema infectiosum (fifth disease) in children
• Acute polyarthritis in adults
• Transient aplastic crisis in anemic individuals
• Hydrops fetalis in seronegative pregnant women
• Results from anemia in fetus
• Adeno associated virus (AAV)
• No known human disease

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Erythema infectiosum (fifth disease)

• Facial erythema (slapped cheek)
• Lacy, reticular evanescent maculopapular eruption
  on trunk and extremities
• Rash represents immune response

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Parvovirus pathogenesis
From Medical Microbiology, 5th ed., Murray,
Rosenthal Pfaller, Mosby Inc., 2005, Fig. 56-3.
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(No Transcript)
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Parvovirus diagnosis

• Serology
• Viral nucleic acid

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Parvovirus

• Structure
• Small (5 kb) linear ssDNA genome, naked capsid
• Pathogenesis
• respiratory transmission
• replication in nucleus, very host dependent,
  needs S phase cells or helper virus
• viremia
• antibody important in immunity
• targets erythroid lineage cells fifth disease
  (symptoms immunological) transient aplastic
  crisis hydrops fetalis
• Diagnosis
• serology, viral nucleic acid
• Treatment/prevention
• None
• Gene therapy vector

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Polyomavirus
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Case presentation
21 year old white female status post B cell
acute lymphocytic leukemia. Treated with bone
marrow transplant. Developed graft vs host
disease, HSV I, cystitis, hematuria and passage
of blood clots. Continuous bladder irrigation,
cystoscopy, clot evacuation, bilateral urethral
catheter placement/occluding nephrostomy tubes to
hopefully prevent cystectomy.
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Polyomavirus classification

• Infect a variety of vertebrates, birds to humans

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Polyoma virus structure

• Icosahedral, non enveloped capsid, 40-45 nM
  diameter
• 36 kb (medium sized) linear dsDNA

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Polyomavirus genome

• Early genes for host and viral transcription
  control, viral DNA replication
• Late genes for virion structure

Genome of the SV40 virus. The genome is a
prototype of other polyomaviruses and contains
early, late, and noncoding regions. The noncoding
region contains the start sequence for the early
and late genes and for DNA replication (ori). The
individual early and late messenger RNAs are
processed from the larger nested
transcripts.(From Medical Microbiology, 5th ed.,
Murray, Rosenthal Pfaller, Mosby Inc., 2005,
Fig. 52-7.)
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Polyomavirus replication

• Replicates and assembles in nucleus via DNA
  intermediate
• Uses host transcription apparatus
• Transcription cascade (early and late genes)
• Encodes a single virus specific DNA replication
  initiation protein, T antigen.
• T antigen is also an oncoprotein stimulates
  cellular DNA replication strategy analagous to
  papillomaviruses.

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Polyomavirus replication
Replication cycle of polyomaviruses. Steps in the
replication cycle are indicated by numbers as
follows 1, adsorption of virions to the cell
surface 2, entry by endocytosis 3, transport to
the cell nucleus (route and mechanism not yet
known) 4, uncoating 5, transcription to produce
early region mRNAs 6, translation to produce
early proteins (T antigens) 7, viral DNA
replication 8, transcription to produce late
region mRNAs 9, translation to produce late
proteins (capsid proteins) 10, assembly of
progeny virions in the nucleus 11, entry of
virions into cytoplasmic vesicles (mechanism
unknown) 12, release of virions from the cell by
fusion of membrane vesicles with the plasma
membrane 13, released virion. (From Fields
Virology, 4th ed, Knipe Howley, eds, Lippincott
Williams Wilkins, 2001, Fig. 63-4.)
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Polyomavirus pathogenesis

• Two widespread human polyomaviruses, JC and BK
• Respiratory infection, usually asymptomatic
• Persistent infection in kidneys
• Clinical disease results from immunosuppression
  (persistence is important!)
• AIDS gives rise to JC induced progressive
  multifocal leukoencephalopathy (PML)
• Lytic infection of myelin producing
  oligodendrocytes apparent lesions by MRI or CT
  neurologic symptoms (muscle weakness, cognitive
  abnormalities, sensory visual deficits)
• Bone marrow transplant gives rise to hemorrhagic
  cystitis (BK virus)
• Recent association (80) of polyomavirus with
  Merkel cell carcinoma, a neuroendocrine carcinoma
  of the skin
• Virus genome usually present integrated into host
  genome
• T antigen expression

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Polyomavirus pathogenesis
From Medical Microbiology, 5th ed., Murray,
Rosenthal Pfaller, Mosby Inc., 2005, Fig.52-8.
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Polyomavirus

• Structure
• Small (5 kb) circular dsDNA genome, naked capsid
• Pathogenesis
• respiratory transmission
• replication in nucleus very host dependent
• viremia
• persistence in kidneys reactivation with immune
  compromise
• inapparent infection hemorrhagic cystitis PML
• Diagnosis
• viral nucleic acid
• Treatment/prevention
• cidofovir ?