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VIROLOGY

VIROLOGY. Margaret.Hunt@uscmed.sc.edu 733-3293 Building 2, B-4 (office), B16(lab). OUTLINE. introduction to viruses structure and classification basic virology clinical virology. VIROLOGY. different structure different method of replication implications for diagnosis treatment

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VIROLOGY

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  1. VIROLOGY Margaret.Hunt@uscmed.sc.edu 733-3293 Building 2, B-4 (office), B16(lab)

  2. OUTLINE • introduction to viruses • structure and classification • basic virology • clinical virology

  3. VIROLOGY • different structure • different method of replication • implications for • diagnosis • treatment • prevention

  4. CONTROL METHODS • INVOLVE KNOWLEDGE OF: • RESERVOIRS • MODE OF TRANSMISSION • METHODS TO INACTIVATE VIRUS OF INTEREST • VACCINES • ANTI-VIRAL DRUGS • DEVELOPMENT OF DRUG RESISTANCE

  5. EMERGING VIRAL DISEASES • Some North American examples: • HIV/AIDS • Hantavirus pulmonary syndrome (HPS) • West Nile encephalitis (WNV) • Severe acute respiratory syndrome (SARS) • Monkey pox • Human metapneumovirus • 2009 H1N1 pandemic influenza

  6. Consequences of viral infections • 50% of all absenteeism • Children: • 7 or more viral infections per year that involve a visit to a physician

  7. Consequences of viral infections • Suffering, followed by recovery • Persistent disease • Fatal disease • Congenital disease • Contributory factor in cancer • Contributory factor in other diseases

  8. SOME ARE ASYMPTOMATIC!

  9. VIRUSES CAN BE USEFUL • VACCINE DEVELOPMENT • GENE THERAPY • TOOLS TO INVESTIGATE HOST CELLS

  10. WHAT ARE VIRUSES? “A PIECE OF BAD NEWS WRAPPED UP IN A PROTEIN”

  11. WHAT ARE VIRUSES? • NUCLEIC ACID GENOME: • DNA OR RNA • PROTEIN COAT • PROTECTION, ENTRY • LIPID ENVELOPE IN SOME VIRUSES • SMALL • (20-400nm) • OBLIGATE INTRACELLULAR PARASITES

  12. Virus particle = virion White, DO and Fenner, FJ. Medical Virology, 4th Ed. 1994

  13. Koneman et al. Color Atlas and Textbook of Microbiology 5th Ed. 1997

  14. Growth on artificial media Division by binary fission Contain DNA and RNA Contain protein synthesis machinery Contain muramic acid Sensitive to antibiotics Bacteria often yes yes yes often yes Viruses never no Either DNA or RNA no* no no * The arenavirus family appears to ‘accidentally’ package ribosomes, but these appear to play no role in protein synthesis.

  15. CONSEQUENCES • HEAVILY PARASITIC ON HOST CELL • NO BROAD RANGE ANTIBIOTICS • NEED TO LOOK FOR WEAK LINK

  16. HOST RANGE • MAY BE WIDE OR NARROW • MAY BE INSECT/ANIMAL, INSECT/PLANT • DO NOT CROSS EUCARYOTE / PROCARYOTE BOUNDARY

  17. FACTORS AFFECTING HOST RANGE - CELL SURFACE RECEPTORS CYTOPLASM

  18. FACTORS AFFECTING HOST RANGE • CELL SURFACE RECEPTORS • AVAILABILITY OF REPLICATION MACHINERY • ABILITY TO GET OUT OF CELL AND SPREAD • HOST ANTI-VIRAL RESPONSE

  19. VIRAL STRUCTURE – SOME TERMINOLOGY • virus particle = virion • protein which coats the genome = capsid • capsid usually symmetrical • capsid + genome = nucleocapsid • may have an envelope

  20. ICOSAHEDRAL SYMMETRY • 20 faces • 12 vertices http://www.tulane.edu/~dmsander/WWW/Video/Video.html

  21. 5-FOLD 3-FOLD 2-FOLD ICOSAHEDRAL SYMMETRY

  22. ICOSAHEDRAL SYMMETRY NUCLEIC ACID IS INSIDE

  23. ICOSAHEDRAL SYMMETRY

  24. CAPSOMER ICOSAHEDRAL SYMMETRY = PENTON (pentamer)

  25. CAPSOMER CAPSOMER = HEXON ICOSAHEDRAL SYMMETRY = PENTON

  26. Adenovirus

  27. 12 PENTONS 240 HEXONS Adenovirus

  28. herpesvirus capsid (membrane removed) http://www.bocklabs.wisc.edu/Herpesvirus.html

  29. 12 vertices 5 neighbors 12 PENTONS HEXONS 6 neighbors 20 faces polypeptides capsomers

  30. ICOSAHEDRAL SYMMETRY

  31. rhinovirus Jean-Yves Sgrohttp://www.bocklabs.wisc.edu/multimedia.html

  32. SYMMETRY OF NUCLEOCAPSID • ICOSAHEDRAL • HELICAL

  33. TOBACCO MOSAIC VIRUS nucleic acid protein adapted from: Klug and Caspar Adv. Virus Res. 7:225

  34. Helical symmetry • Length controlled by nucleic acid • Helix may be stiff or flexible

  35. COMPLEX SYMMETRY surface view cross section POXVIRUS FAMILY White, DO and Fenner, FJ. Medical Virology, 4th Ed. 1994

  36. ENVELOPE • OBTAINED BY BUDDING THROUGH A CELLULAR MEMBRANE (except poxviruses) • POSSIBILITY OF EXITING CELL WITHOUT KILLING IT • CONTAINS AT LEAST ONE VIRALLY CODED PROTEIN

  37. CYTOPLASM

  38. ENVELOPE • OBTAINED BY BUDDING THROUGH A CELLULAR MEMBRANE (except poxviruses) • POSSIBILITY OF EXITING CELL WITHOUT KILLING IT • CONTAINS AT LEAST ONE VIRALLY CODED PROTEIN • ATTACHMENT PROTEIN • LOSS OF ENVELOPE RESULTS IN LOSS OF INFECTIVITY

  39. ENVELOPE

  40. 5 BASIC TYPES OF VIRAL STRUCTURE nucleocapsid icosahedralnucleocapsid lipid bilayer ICOSAHEDRAL ENVELOPED ICOSAHEDRAL helicalnucleocapsid COMPLEX nucleocapsid lipid bilayer glycoprotein spikes = peplomers HELICAL ENVELOPED HELICAL Adaptedfrom Schaechter et al., Mechanisms of Microbial Disease

  41. UNCONVENTIONAL AGENTS • VIROIDS • RNA only • Small genome • Do not code for protein • So far, only known viroids are in plants • hepatitis delta virus (agent) • - some viroid, some virus features

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