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G eneral characteristics of Viruses

G eneral characteristics of Viruses. Introduction. I. I. Conception 1. Virus: Viruses are obligate intracellular parasites at the genetic level. 2. Virion: The entire infectious unit or the complete virus particles 3. Atypical virus like agents (subvirus)

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G eneral characteristics of Viruses

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  1. General characteristics of Viruses

  2. Introduction I. I. Conception 1. Virus: Viruses are obligate intracellular parasites at the genetic level. 2. Virion: The entire infectious unit or the complete virus particles 3. Atypical virus like agents (subvirus) 1)Viroid:Viroids consist solely of a single molecule of circular RNA without a protein coat or envelope.

  3. Introduction I. Conception 2)Prion (unconventional virus)Prion are infectious protein particle that are composed solely of protein, i.e. they contain no detectable nucleic acid. CJD Kuru Fatal Familial Insomnia Scrapie of sheep and goat Bovine spongiform Encephalopathy (BSE) 3)Satellites: virusoid

  4. Satellites

  5. Introduction II. Developing history III. Medical Virology

  6. Basic properties of viruses • . Structure and Chemical composition of viruses • 1.Size and shape • Measuring the size of viruses. • A . Direct observation in the electron microscope • B . Filtration through membranes of graded • C . Sedimentation in the ultracentrifuge • D . Comparative measurements

  7. 1. Size and shape

  8. Basic properties of viruses 2.Basic structure 1)Nonenveloped virion

  9. Nonenveloped virion

  10. Basic properties of viruses 2)Enveloped virion

  11. Enveloped virion

  12. Basic properties of viruses 3)Types of symmetry A . Cubic symmetry B . Helical symmetry C . Complex structure

  13. Types of symmetry

  14. Basic properties of viruses 3.Chemical composition 1)Nucleic acid DNA: dsDNA; ssDNA RNA:+ssRNA; -ssRNA; dsRNA; +ssRNA Retroviridae

  15. Nucleic acid 3-1

  16. Nucleic acid 3-2

  17. Nucleic acid 3-3

  18. Basic properties of viruses 2)proteins 3)lipids 4)carbohydrates

  19. Basic properties of viruses II.Viral Replication 1. Replication 2. Steps in Viral replication 1)Recognition and attachment to the target cell 2)Penetration 3)Uncoating 4)Gene expression & genome replication 5)Assembly & release

  20. Steps in Viral replication

  21. Replication: example 1

  22. Replication: example 2

  23. Replication: example 3

  24. Basic properties of viruses Abnormal multiplication A.Defective virus: A virus particle that is functionally deficient in some aspect of replication. B.Abortive infection: Infection in which some or all virus components are synthezised but no infective virus is produced.

  25. Viral pathogenicity and Immunity In this section, you will learn: $ Viral Pathogenicity $Immunity for viral infection

  26. Viral pathogenicity and Immunity I.Viral Pathogenicity

  27. Viral Pathogenicity

  28. Viral pathogenicity and Immunity 1.modes of transmissions 1)Horizontal transmission: Transmission between person of any age after birth, usually excluding via the maternal milk.

  29. modes of transmissions 1)   Horizontal transmission 2-1

  30. modes of transmissions 1)   Horizontal transmission

  31. Viral pathogenicity and Immunity 2)Vertical transmission: Spread of infection parent to the young via the placenta or genital tract. Transmission via the maternal milk is sometime included.

  32. Vertical transmission

  33. Viral pathogenicity and Immunity 2.Types of viral infections 1)inapparent infections 2)apparent infections A.Acute infection B.Persistent infection a)chronical infection: HBV b)latent infection: HSV Varicella--zoster virus

  34. latent infection: HSV

  35. Viral pathogenicity and Immunity C) slow virus infection （HIV. kuru) D) delayed complication after acute viral infection. SSPE

  36. Viral pathogenicity and Immunity 3.Viruses-host interaction 1)cell level A.lytic infection (Cytocidal infection) : cytopathic effect ( CPE ) Alternation in the Microscopic apperance of cell in culture following infection with a virus. B.steady state infection : fusion of cells, new antigen. C.integration D.apoptosis E.inclusion body: An area of abnormal staining in a virus- infected cell. F.Cell transformation : alternation in cell morphology and / or behaviour, …….

  37. Viral pathogenicity and Immunity 3.Viruses-host interaction 2)Host immune response A.   inflammatory reaction Bacteria : inflitration of polymophonuclear leukocyte Viruses : inflitration of mononuclear cell and lymphocytes. B. Immune pathology a. Cell-mediated immunity : measles virus , HIV b. Antibody-mediated immunity : dengue virus : ab+RBC+C----hemolysis, HBV

  38. Viral pathogenicity and Immunity II.Immunity for viral infection 1.non-specific immune NK , IFN 1)Interference phenomenon A.Definition : prevention of the replication of one virus by another. B.Types of interference C.Mechanisms of interference

  39. Viral pathogenicity and Immunity 2)Interferon (IFN) A.   Definition: Interferons(IFNs) are host-coded proteins of the large cytokine family that inhibit viral replication; they are produced by intact animals or cultured cells in response to viral infection or other inducers. B.   types of IFN C.   antiviral activity

  40. Antiviral activity

  41. Viral pathogenicity and Immunity 2.Specific immune 1)humoral immune A.Neutralization antibodies B.Hemagglutination antibodies C.CF antibodies 2)Cellular immunity

  42. Laboratory Diagnosis of Viral Disease In this section, you will learn: $ Introduction $Procedure

  43. Laboratory Diagnosis of Viral Disease Introduction Object Procedure I.Specimens 1.Kinds of specimen 2.Time

  44. Laboratory Diagnosis of Viral Disease II.Methods 1.Cytology 2.Electron microscopy 3.Viral isolation 1)animals 2)chicken embryo 3)Tissue culture A.Definition: The growth or maintenance of living tissue in a liquid or soft gel medium in vitro.

  45. Laboratory Diagnosis of Viral Disease B.Types of cell culture a. Primary cell culture b. Cell line C.   Detection of virus-infected cells a. CPE b. Adsorption of RBC c. Interference d. PCR

  46. Detection of virus-infected cells: CPE

  47. Detection of virus-infected cells: CPE

  48. Laboratory Diagnosis of Viral Disease D.Quantitation of viruses a. TCID50(50% Tissue culture infected dose ): Infections dose of 50% CPE of tissue cultures caused by viral minimum infected dose is called TCID50 b. PFU : under controlled condition,single plague can arise from a single infection virus particle, termed a plague-forming unit.

  49. Laboratory Diagnosis of Viral Disease 4.Serologic methods 1)   complement fixation 2)   Hemagglutination inhibition 3)   Neutralization 4)   Fluorescent antibody 5)   Radioimmunoassay 6)   Enzyme-linked Immunosorbent Assay (ELISA)

  50. Laboratory Diagnosis of Viral Disease 5.Detection of viral genetic material 1)   nucleic acid hybridization technique : a. Southern blot b. Northern blot 2)   polymerase chain reaction (PCR), RT-PCR 6.   Western blot 7.   Biochip/DNA microarray/gene chip

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