Viral diagnostics eac for finals

4,931 views

Published on

Published in: Health & Medicine, Technology
0 Comments
4 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
4,931
On SlideShare
0
From Embeds
0
Number of Embeds
9
Actions
Shares
0
Downloads
585
Comments
0
Likes
4
Embeds 0
No embeds

No notes for slide

Viral diagnostics eac for finals

  1. 1. VIRAL DIAGNOSTICS February 2012Friday, March 2, 2012
  2. 2. REMINDER: REMAINING SCHEDULE Modifications: PH Viruses merged with Emerging and Re-emerging Viruses (March 2)Friday, March 2, 2012
  3. 3. PLENARY GROUPS: Advances in Laboratory Diagnostics (Then and Now) • INFLUENZA (AH1N1 • HIV by Lao to Manahan and SEASONAL FLU) by Group Advincula to Bundang Group • HEPATITIS A/B/C by Pedregosa to Santos, Dana • INFLUENZA (AVIAN Group FLU) by Cailao to Emerciana Group • SARS by Santos, Fatima to Velasco Group • DENGUE by Faderog to Jamias GroupFriday, March 2, 2012
  4. 4. LABORATORY DIAGNOSIS OF VIRAL INFECTIONSFriday, March 2, 2012
  5. 5. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTINGFriday, March 2, 2012
  6. 6. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are collected to diagnose?Friday, March 2, 2012
  7. 7. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are collected to diagnose? • Respiratory tract infections: Nasal and bronchial washings, throat and nasal swabs, sputumFriday, March 2, 2012
  8. 8. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are collected to diagnose? • Respiratory tract infections: Nasal and bronchial washings, throat and nasal swabs, sputum • Eye infections: throat and conjunctival swab/scrapingFriday, March 2, 2012
  9. 9. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are collected to diagnose? • Respiratory tract infections: Nasal and bronchial washings, throat and nasal swabs, sputum • Eye infections: throat and conjunctival swab/scraping • Gastrointestinal tract infections: stool and rectal swabsFriday, March 2, 2012
  10. 10. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are collected to diagnose? • Respiratory tract infections: Nasal and bronchial washings, throat and nasal swabs, sputum • Eye infections: throat and conjunctival swab/scraping • Gastrointestinal tract infections: stool and rectal swabs • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  11. 11. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are • Maculopapular rash: throat, stool, collected to diagnose? and rectal swabs • Respiratory tract infections: Nasal and bronchial washings, throat and nasal swabs, sputum • Eye infections: throat and conjunctival swab/scraping • Gastrointestinal tract infections: stool and rectal swabs • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  12. 12. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are • Maculopapular rash: throat, stool, collected to diagnose? and rectal swabs • Respiratory tract infections: Nasal • CNS (encephalitis and meningitis and bronchial washings, throat cases): stool, tissue, saliva, brain and nasal swabs, sputum biopsy, cerebrospinal fluid • Eye infections: throat and conjunctival swab/scraping • Gastrointestinal tract infections: stool and rectal swabs • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  13. 13. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are • Maculopapular rash: throat, stool, collected to diagnose? and rectal swabs • Respiratory tract infections: Nasal • CNS (encephalitis and meningitis and bronchial washings, throat cases): stool, tissue, saliva, brain and nasal swabs, sputum biopsy, cerebrospinal fluid • Eye infections: throat and • Genital infections: vesicle fluid or conjunctival swab/scraping swab • Gastrointestinal tract infections: stool and rectal swabs • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  14. 14. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are • Maculopapular rash: throat, stool, collected to diagnose? and rectal swabs • Respiratory tract infections: Nasal • CNS (encephalitis and meningitis and bronchial washings, throat cases): stool, tissue, saliva, brain and nasal swabs, sputum biopsy, cerebrospinal fluid • Eye infections: throat and • Genital infections: vesicle fluid or conjunctival swab/scraping swab • Gastrointestinal tract infections: • Urinary tract infections: urine stool and rectal swabs • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  15. 15. STORAGE AND COLLECTION OF BIOLOGICAL SPECIMENS FOR VIRAL TESTING • What types of specimens are • Maculopapular rash: throat, stool, collected to diagnose? and rectal swabs • Respiratory tract infections: Nasal • CNS (encephalitis and meningitis and bronchial washings, throat cases): stool, tissue, saliva, brain and nasal swabs, sputum biopsy, cerebrospinal fluid • Eye infections: throat and • Genital infections: vesicle fluid or conjunctival swab/scraping swab • Gastrointestinal tract infections: • Urinary tract infections: urine stool and rectal swabs • Bloodborne infections: blood • Vesicular rash: vesicle fluid, skin scrapingsFriday, March 2, 2012
  16. 16. General Categories • Direct Examination • Indirect Examination (Virus Isolation) • SerologyFriday, March 2, 2012
  17. 17. DIRECT EXAMINATIONFriday, March 2, 2012
  18. 18. DIRECT: clinical specimen is examined directly for the presence of virus particles, virus antigen or viral nucleic acids • Electron Microscopy morphology / immunoelectron microscopy • Light microscopy histological appearance - e.g. inclusion bodies • Antigen detection immunofluorescence, ELISA etc. • Molecular techniques for the direct detection of viral genomesFriday, March 2, 2012
  19. 19. ELECTRON MICROSCOPY • BASIS: morphology • MAGNIFICATION: 50,000 • USE: • diagnosis of viral gastroenteritis by detecting viruses in faeces e.g. rotavirus, adenovirus, astrovirus, calicivirus and Norwalk- like viruses • detection of viruses in vesicles and other skin lesions, such as herpesviruses and papillomaviruses • NOTE: With the availability of reliable antigen detection and molecular methods for the detection of viruses associated with viral gastroenteritis, EM is becoming less and less widely usedFriday, March 2, 2012
  20. 20. ELECTRON MICROSCOPY • SENSITIVITY & SPECIFICITY ISSUES: • sensitivity and specificity of EM may be enhanced by immune electron microscopy • virus specific antibody is used to agglutinate virus particles together and thus making them easier to recognize, or to capture virus particles onto the EM grid • DISADVANTAGE: • expense involved in purchasing and maintaining the facility • poor sensitivity (at least 10 to 10 virus particles per ml in 5 6 the sample required for visualization) • observer must be highly skilledFriday, March 2, 2012
  21. 21. Electronmicrographs of viruses commonly found in stool specimens from patients suffering from gastroenteritis. From left to right: rotavirus, adenovirus, astroviruses, Norwalk-like viruses.  (Courtesy of Linda M. Stannard, University of Cape Town, http://www.uct.ac.za/depts/mmi/stannard/emimages.html) Influenza Virus Ebola VirusFriday, March 2, 2012
  22. 22. Friday, March 2, 2012
  23. 23. Friday, March 2, 2012
  24. 24. IMMUNOELECTRON MICROSCOPY PARAMYXOVIRUSES Int. J. Morphol., 28(2):627-636, 2010 COXSACKIE B4 VIRUS (http://www.rightdiagnosis.com) NEW CASTLE DISEASE (Veits J et al. PNAS 2006;103:8197-8202)Friday, March 2, 2012
  25. 25. LIGHT MICROSCOPY • ASSUMPTION: Replicating virus often produce histological changes in infected cells. • Viral inclusion bodies: collections of replicating virus particles either in the nucleus or cytoplasm • EXAMPLES: negri bodies (RABIES) and cytomegalic inclusion bodies (CYTOMEGALOVIRUS / CMV) • Not sensitive or specific; BUT useful adjunct in the diagnosis of certain viral infectionsFriday, March 2, 2012
  26. 26. LIGHT MICROSCOPY RABIES http://infectionnet.org’; http://virology-online.com CYTOMEGALOVIRUS http://www.meddean.luc.edu http://en.citizendium.orgFriday, March 2, 2012
  27. 27. ANTIGEN DETECTION Immunofluorescence (IF) • specimen: nasopharyngeal aspirates for respiratory viruses (e.g.. RSV, flu A, flu B, and adenoviruses) • specimen: stool (rotavirus) • specimen: skin scrapings (HSV) • specimen: serum (HepB)* • Advantage: rapid to perform; result being available within a few hours • Disadvantage: technique is often tedious and time consuming; result difficult to read and interpret; sensitivity and specificity poor • NOTE: quality of the specimen obtained is of utmost importance in order for the test to work properly • * also categorized as serological assayFriday, March 2, 2012
  28. 28. ANTIGEN DETECTION Immunofluorescence (IF) CYTOMEGALOVIRUS http://www.med.upenn.eduFriday, March 2, 2012
  29. 29. ANTIGEN DETECTION Immunofluorescence (IF) VARICELLA ZOSTER VIRUS BMJ Case Reports 2009; doi:10.1136/bcr.07.2008.0461 AFRICAN SWINE FEVER Journal of General Virology March 2005; 86 (3)Friday, March 2, 2012
  30. 30. ANTIGEN DETECTION Molecular Probes • Dot-blot and Southern-blot: use of specific DNA/RNA probes for hybridization • Specificity: depends on the conditions used for hybridization • Allow for the quantification of DNA/RNA present in the specimen • Sensitivity: not better than conventional viral diagnostic methods.Friday, March 2, 2012
  31. 31. ANTIGEN DETECTION Molecular Probes CYTOMEGALOVIRUS EPSTEIN-BARR VIRUS http://www.fgsc.net Mol Path 2000;53:255-261 doi:10.1136/mp.53.5.255Friday, March 2, 2012
  32. 32. ANTIGEN DETECTION Molecular Probes (PCR) • extremely sensitive technique (1 DNA molecule in a clinical specimen) • ISSUES: contamination (danger of false + result); + result may not necessarily indicate the INFLUENZA presence of disease http://www.nanohelix.netFriday, March 2, 2012
  33. 33. ANTIGEN DETECTION Molecular Probes (PCR)Friday, March 2, 2012
  34. 34. INDIRECT EXAMINATIONFriday, March 2, 2012
  35. 35. INDIRECT: the specimen into cell culture, eggs or animals in an attempt to grow the virus (virus isolation) • Cell Culture - cytopathic effect, haemadsorption, confirmation by neutralization, interference,  immunofluorescence etc. • Eggs pocks on CAM - haemagglutination, inclusion bodies • Animals disease or death confirmation by neutralizationFriday, March 2, 2012
  36. 36. RECALL: Koch’s PostulatesFriday, March 2, 2012
  37. 37. RECALL: 1. Organism present only in Koch’s Postulates diseased individualsFriday, March 2, 2012
  38. 38. RECALL: 1. Organism present only in Koch’s Postulates diseased individuals 2. Organism cultivated in pure culture from diseased individualFriday, March 2, 2012
  39. 39. RECALL: Koch’s PostulatesFriday, March 2, 2012
  40. 40. 3. Organism causes disease RECALL: when injected into Koch’s Postulates healthy individualsFriday, March 2, 2012
  41. 41. 3. Organism causes disease RECALL: when injected into Koch’s Postulates healthy individuals 4. Organism re-isolated from infected individual from point 3.Friday, March 2, 2012
  42. 42. MODIFICATION TO THE KOCH’S POSTULATE (T.M. River, 1937) • Isolate virus from diseased hosts • Cultivation of virus in host cells • Proof of filterability • Production of a comparable disease when the cultivated virus is used to infect experimental animals • Re-isolation of the same virus from the infected experimental animal • Detection of a specific immune response to the virusFriday, March 2, 2012
  43. 43. TYPES OF CELL CULTURE • Primary cells - e.g. Monkey Kidney • essentially normal cells obtained from freshly killed adult animals; can only be passaged once or twice • Semi-continuous cells - e.g. Human embryonic kidney and skin fibroblasts • taken from embryonic tissue; may be passaged up to 50 times • Continuous cells - e.g. HeLa,Vero, Hep2, LLC-MK2, BGM • immortalized cells i.e. tumour cell lines; may be passaged indefinitely NOTE: Primary cell culture are widely acknowledged as the best cell culture systems available since they support the widest range of viruses BUT are very expensive and it is often difficult to obtain a reliable supply. Continuous cells are the most easy to handle BUT range of viruses supported is often limitedFriday, March 2, 2012
  44. 44. PRESENCE OF GROWING VIRUS IS USUALLY DETECTED BY: • Cytopathic Effect (CPE) - may be specific or non-specific e.g. HSV and CMV produces a specific CPE, whereas enteroviruses do not • Haemadsorption - cells acquire the ability to stick to mammalian red blood cells • mainly used for the detection of influenza and parainfluenzaviruses. NOTE: Confirmation of the identity of the virus may be carried out using neutralization, haemadsorption-inhibition, immunofluorescence, or molecular testsFriday, March 2, 2012
  45. 45. Detection of Herpes Virus Simplex 1 using the shell vial technique and immunofluorescence Tissue culture cells are grown on coverslips on the bottom of shell vialsFriday, March 2, 2012
  46. 46. Quantitative Assays Quantitative Plaque AssaysFriday, March 2, 2012
  47. 47. CYTOPATHIC EFFECTSFriday, March 2, 2012
  48. 48. CYTOPATHIC EFFECTS • Visible results of viral infection • Cell death by • Multiplying viruses • Inhibition of DNA, RNA or protein synthesis • Effects on permeability of membraneFriday, March 2, 2012
  49. 49. CYTOPATHIC EFFECTS • Cytopathic effects (CPEs) of infected cells can be observed with inverted light microscopes • Rounding/detachment from plastic flask • Syncytia/fusion (Fusion of cells) • Shrinkage • Increased refractility • Aggregation • Loss of adherence Cytopathic effect of HSV, enterovirus 71, and RSV in cell culture. Note the ballooning of cells in the cases of HSV and enterovirus 71. Note syncytia formation in the case of RSV. (Linda Stannard. University of Cape Town, • Cell lysis/deathFriday, March 2, 2012 Virology Laboratory,Yale-New Haven Hospital)
  50. 50. Quantitative Assays  Tissue Culture Infectious Dose: TCID50  Measure cytopathic effects other than lysis  Concentration of virus it takes to produce cytopathic effect (CPE) in 50% of the dishes of cells infected with virusFriday, March 2, 2012
  51. 51. Quantitative Assays TCID50 AssaysFriday, March 2, 2012
  52. 52. PROBLEMS WITH CELL CULTURE • Long period (up to 4 weeks) required for a result to be available • Sensitivity is often poor and depends on many factors, such as the condition of the specimen, and the condition of the cell sheet • Very susceptible to bacterial contamination and toxic substances in the specimen • Many viruses will not grow in cell culture at all e.g. Hepatitis B and C, Diarrhoeal viruses, parvovirus etc.Friday, March 2, 2012
  53. 53. SEROLOGYFriday, March 2, 2012
  54. 54. SEROLOGICAL TESTS • ASSUMPTION: • Primary Exposure: first antibody to appear is IgM, which is followed by a much higher titre of IgG • Secondary exposure or Re-infection: level of specific IgM either remain the same or rises slightly But IgG shoots up rapidly and far more earlier than in a primary infection. • ASSAYS AVAILABLE: • EIA and RIA, one can look specifically for IgM or IgG (most sensitive) • CFT and HAI, one can only detect total antibody, which comprises mainly IgG (not so sensitive) • The sensitivity and specificity of the assays depend greatly on the antigen used • Assays that use recombinant protein or synthetic peptide antigens tend to be more specific than those using whole or disrupted virus particlesFriday, March 2, 2012
  55. 55. SEROLOGY: detection of rising titres of antibody between acute and convalescent stages of infectionFriday, March 2, 2012
  56. 56. NOTE: CRITERIA FOR PRIMARY INFECTION • A significant rise in titre of IgG/total antibody between acute and convalescent sera • however, a significant rise is very difficult to define and depends greatly on the assay used • CFT and HAI: normally taken as a four-fold or greater increase in titre • The main problem is that diagnosis is usually retrospective because by the time the convalescent serum is taken, the patient had probably recoveredFriday, March 2, 2012
  57. 57. NOTE: CRITERIA FOR PRIMARY INFECTION • Presence of IgM • EIA, RIA, and IF may be used for the detection of IgM • offers a rapid means of diagnosis • PROBLEMS: interference by rheumatoid factor, re- infection by the virus, and unexplained persistence of IgM years after the primary infectionFriday, March 2, 2012
  58. 58. NOTE: CRITERIA FOR PRIMARY INFECTION • Seroconversion • changing from a previously antibody negative state to a positive state e.g. seroconversion against HIV following a needle-stick injury, or against rubella following contact with a known case • A single high titre of IgG (or total antibody) • very unreliable means of serological diagnosis since the cut-off is very difficult to defineFriday, March 2, 2012
  59. 59. SEROLOGY: detection of rising titres of antibody between acute and convalescent stages of infection • Classical Techniques • Newer Techniques • Complement Fixation Test • Radioimmunoassay (RIA) • Hemagglutination Inhibition • Enzyme Immunoassay (EIA) Test • Particle Agglutination Tests • Immunofluorescence Technique (IF • Western Blot (WB) • Neutralization Tests • Recombinant Immunoblot assay (RIBA) • Single Radial HemolysisFriday, March 2, 2012
  60. 60. LIMITATIONS OF SEROLOGY • For viruses such as rubella and hepatitis A, the onset of clinical symptoms coincide with the development of antibodies (detection of IgM or rising titres of IgG in the serum of the patient would indicate active disease) • Many viruses often produce clinical disease before the appearance of antibodies such as respiratory and diarrheal viruses (any serological diagnosis would be retrospective and therefore will not be that useful) • There are also viruses which produce clinical disease months or years after seroconversion e.g. HIV and rabies (mere presence of antibody is sufficient to make a definitive diagnosis)Friday, March 2, 2012
  61. 61. DISADVANTAGES OF SEROLOGYFriday, March 2, 2012
  62. 62. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent seraFriday, March 2, 2012
  63. 63. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent sera • Mild local infections may not produce a detectable humoral immune response (e.g. HSV genitalis)Friday, March 2, 2012
  64. 64. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent sera • Mild local infections may not produce a detectable humoral immune response (e.g. HSV genitalis) • Extensive antigenic cross-reactivity between related viruses may lead to false positive results (e.g. Japanese B encephalitis and Dengue)Friday, March 2, 2012
  65. 65. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent sera • Mild local infections may not produce a detectable humoral immune response (e.g. HSV genitalis) • Extensive antigenic cross-reactivity between related viruses may lead to false positive results (e.g. Japanese B encephalitis and Dengue) • Immunocompromised patients often give a reduced or absent humoral immune responseFriday, March 2, 2012
  66. 66. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent sera • Mild local infections may not produce a detectable humoral immune response (e.g. HSV genitalis) • Extensive antigenic cross-reactivity between related viruses may lead to false positive results (e.g. Japanese B encephalitis and Dengue) • Immunocompromised patients often give a reduced or absent humoral immune response • Patients with infectious mononucleosis and those with connective tissue diseases such as SLE may react non-specifically giving a false positive resultFriday, March 2, 2012
  67. 67. DISADVANTAGES OF SEROLOGY • Long length of time required for diagnosis for paired acute and convalescent sera • Mild local infections may not produce a detectable humoral immune response (e.g. HSV genitalis) • Extensive antigenic cross-reactivity between related viruses may lead to false positive results (e.g. Japanese B encephalitis and Dengue) • Immunocompromised patients often give a reduced or absent humoral immune response • Patients with infectious mononucleosis and those with connective tissue diseases such as SLE may react non-specifically giving a false positive result • Patients given blood or blood products may give a false positive result due to the transfer of antibodyFriday, March 2, 2012
  68. 68. HEMAGGLUTINATION/ HEMAGGLUTINATION-INHIBITION/ COMPLEMENT FIXATION TESTFriday, March 2, 2012
  69. 69. • Some viruses agglutinate RBCs • Mumps, measles, influenza • Hemagglutination • Clumps RBCsFriday, March 2, 2012
  70. 70. HEMADSORPTION TEST Hemadsorption of red blood cells onto the surface of a cell sheet infected by mumps virus (Courtesy of Linda Stannard, University of Cape Town).Friday, March 2, 2012
  71. 71. ENZYME -LINKED IMMUNOSORBENT ASSAY (ELISA)Friday, March 2, 2012
  72. 72. HIV & ELISAFriday, March 2, 2012
  73. 73. WESTERN BLOT TO CONFIRM HIVFriday, March 2, 2012
  74. 74. (b) (c) Image courtesy of Bio-Rad Laboratories Figure 5.21c: The typical results of a Western blot Figure 5.21b: The structure of HIV-1. testing patient serum for HIV-1 antibodies.Friday, March 2, 2012
  75. 75. WESTERN BLOT TO CONFIRM HIVFriday, March 2, 2012
  76. 76. SEROLOGY AND HEPATITISFriday, March 2, 2012
  77. 77. SEROLOGY AND HEPATITISFriday, March 2, 2012
  78. 78. SEROLOGY AND HEPATITISFriday, March 2, 2012
  79. 79. SEROLOGY AND HEPATITISFriday, March 2, 2012
  80. 80. SEROLOGY AND HEPATITISFriday, March 2, 2012
  81. 81. SEROLOGY AND HEPATITISFriday, March 2, 2012
  82. 82. USUALLY DIAGNOSED BY SEROLOGY • Hepatitis Viruses - hepatitis A, B and C infections are usually diagnosed by serology as these viruses cannot be routinely cultured • including the test for HBsAg • HIV - HIV infection is normally diagnosed by serology • The only instance when serology cannot be relied on is in diagnosing HIV infection in the newbornFriday, March 2, 2012
  83. 83. USUALLY DIAGNOSED BY SEROLOGY • Rubella and parvovirus - rubella and parvovirus infections are usually diagnosed by serology • difficult to isolate and parvovirus cannot be isolated by routine cell culture • onset of clinical symptoms for these infections coincide with the appearance of antibodies and thus there is little need for other means of diagnosis • EBV - although EBV serology is reliable, the heterophile antibody test is usually used for diagnosing cases of infectious mononucleosisFriday, March 2, 2012
  84. 84. MAY BE DIAGNOSED BY SEROLOGY BUT NOT METHOD OF CHOICE • HSV - although CFT and other serological tests are available for HSV, HSV infections are usually diagnosed by cell culture • Electron microscopy, immunofluorescence and PCR are available as rapid diagnostic methods • Serology is not that reliable in the case of HSV infections, in particular reactivations • CMV - although serology is available for diagnosing CMV infections, it is not reliable as most cases of CMV infections are a result of reactivation/reinfection • Cell culture (including the DEAFF test) and rapid methods such as the CMV antigenaemia test and PCR are preferred means of diagnosisFriday, March 2, 2012
  85. 85. MAY BE DIAGNOSED BY SEROLOGY BUT NOT METHOD OF CHOICE • Respiratory viruses - diagnosis of respiratory virus infections is more commonly made by cell culture or more rapidly by immunofluorescence of the clinical material • CFT and HAI techniques are usually used for serology and any diagnosis is going to be retrospective • Enteroviruses - enterovirus infections are usually diagnosed by cell culture • Serology has a very limited role to play as available tests such as neutralization, are cumbersome to perform and in any case, the diagnosis would be retrospectiveFriday, March 2, 2012
  86. 86. MAY BE DIAGNOSED BY SEROLOGY BUT NOT METHOD OF CHOICE • Rabies - serology is used along with other direct detection methods in diagnosing rabies and it may be used to check for immunity after vaccination • Arboviruses - arbovirus infections may be diagnosed by serology or virus isolation • Arboviruses will not usually grow in routine cell cultures and may require mosquito cell lines or animal inoculation.Friday, March 2, 2012
  87. 87. NOT NORMALLY DIAGNOSED BY SEROLOGY • Diarrhoeal viruses - diagnosis is going to be retrospective • normally diagnosed by electron microscopy and the detection of viral antigens by ELISA or particle agglutination • Papovavirus - serology is of virtually no value in diagnosing papovavirus infections • Poxviruses - serology is of little value in diagnosing poxvirus infectionsFriday, March 2, 2012
  88. 88. SAFETY FIRST! Figure 5.25b: A CDC researcher working on a BSL-4 infectious agent. Figure 5.25c: A CDC scientist showers in a protective suit before leaving a BSL-4 laboratory.Friday, March 2, 2012
  89. 89. Friday, March 2, 2012 QUIZ TIME!
  90. 90. • Draw the general serologic course of a viral disease/infection and label properly (6 points) • Give one direct examination to diagnose a given viral pathogen and cite one virus that can use this method for diagnosis (8 points) • Give one indirect examination to diagnose a given viral pathogen cite one virus that can use this method for diagnosis (8 points) • Give one serological examination to diagnose a given viral pathogen cite one virus that can use this method for diagnosis (8 points)Friday, March 2, 2012

×