PART III: The Virus

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PART III The Virus
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Coronavirus

• Single-strand RNA, nonsegmented, enveloped,
  31,000 NTs
• 2 serogroups (229E and OC43) in humans
• 1/3 of common colds
• Reinfections common
• Envelope
• S - spike protein
• M - matrix protein
• HE - hemagglutinin

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Coronavirus Family

• Cause mild to moderate respiratory illnesses such
  as common cold.
• Able to survive in dry air for up to 3 hours.
• Can be killed by exposure to ultra-violet light,
  so they will not survive under sunlight.
• Mutate easily, and each mutation triggers off an
  epidemic of respiratory disease.

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Coronavirus Family

• A new mutation, which arose in Guangdong is
  suspected of causing SARS
• The name coronavirus refers to the protein
  molecules surrounding the virus, making it look
  like a crown (n.corona lat crown).

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Coronaviruses

• Survival
• 229 E
• 6 days in suspension
• 3 hours after drying on surface
• OC43
• lt1 hr after drying on surfaces

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Laboratory Evidence as of 4/03/2003
No. pos. patients
Assay
Findings
Culture (Vero E6 cells) EM (cell culture,
BAL) PCR (tissue, swabs) Serology (IFA,
EIA) Histopathology
Viral growth Virus-like particles,
Coronavirus Coronaviral nucleic acid Antibody DAD
(ARDS)
4 2 11 5 4
Results not mutually exclusive Source CDC
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Coronavirus-infected Vero E6 cells (isolate from
SARS patient) by thin section EM
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Vero E6 cells inoculated with Oropharyngeal
Specimns from Patients with SARS. The typical
early cytopathic effect seen with coronavirus
isolates from patients with SARS is shown in
Panel A (x40). Infected Vero cells are shown
reacting with the serum of a convalescent patient
in an indirect fluorescence antibody assay in
Panel B (x400).
Ksiazek et al. A novel Coronavirus associated
with SARS. NEJM April 10, 2003
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Ultrastructural characteristics of
SARS-Associated Coronavirus Growth in Vero E6
cells. Panel A shows a thin-section
electorn-microscopical view of viral
nucleocapsids aligned along the membrane of the
rough endoplasmic reticulum (arrow) as particles
bud into the cisternea. Enveloped virions have
surface projections (arrowhead) and an
electron-lucent center. Directly under the viral
envelope lies a characteristic ring formed by the
helical nucleocapsid, often seen in
cross-section. Negative stain electron microscopy
(Panel B) shows a stain-penetrated coronavirus
particle with an internal helical
nucleocapsid-like structure and club-shaped
surface projections surrounding the periphery of
the particle, a finding typical of coronaviruses
(methylamine tungstate stain). The bars represent
100 nm.
Ksiazek et al. A novel Coronavirus associated
with SARS. NEJM April 10, 2003
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Coronavirus particle by negative stain
EM (isolate from patient with SARS)
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Coronavirus-infected cell in BAL of SARS patient
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Lung of patient with fatal SARS showing diffuse
alveolar damage and syncytial giant cells
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Multinucleated syncytial giant cellsin lung of
SARS patient
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Histopathological Evaluation of Lung Tissue from
Patients with SARS. Tissue shows diffuses
alveolar damage, abundant foamy macrophages, and
multinucleated syncytial cells (Panel A). Higher
magnification of syncytial cells show no
conspicuous viral inclusions (Panel B). Panel C
shows immunohistochemical staining of
SARS-associated coronavirus infected
cells Name Proposed Urbani Coronavirus
Ksiazek et al. A novel Coronavirus associated
with SARS. NEJM April 10, 2003