PART III: The Virus - PowerPoint PPT Presentation

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PART III: The Virus

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  1. PART III: The Virus

  2. 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

  3. 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.

  4. 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).

  5. Coronaviruses • Survival • 229 E • 6 days in suspension • 3 hours after drying on surface • OC43 • <1 hr after drying on surfaces

  6. 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

  7. Coronavirus-infected Vero E6 cells (isolate from SARS patient) by thin section EM

  8. 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

  9. 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

  10. Coronavirus particle by negative stain EM (isolate from patient with SARS)

  11. Coronavirus-infected cell in BAL of SARS patient

  12. Lung of patient with fatal SARS showing diffuse alveolar damage and syncytial giant cells

  13. Multinucleated syncytial giant cellsin lung of SARS patient

  14. 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