O slideshow foi denunciado.
Seu SlideShare está sendo baixado. ×

Intro to Virology.pptx

Carregando em…3

Confira estes a seguir

1 de 37 Anúncio

Mais Conteúdo rRelacionado

Semelhante a Intro to Virology.pptx (20)

Mais recentes (20)


Intro to Virology.pptx

  1. 1. Sahibzada Tasleem Rasool
  2. 2. Sahibzada Tasleem Rasool The students will be able to a. Define basic structures of viruses. b. Describe properties of naked and enveloped viruses c. Discuss the nomenclature and classification of viruses d. Identify various groups of viruses e. Describe viral pathogenesis and steps involved in that. f. Discuss mechanisms of genetic material exchange among viruses. g. Describe outcomes of genetic variation. h. Timelines and disease patterns
  3. 3. Sahibzada Tasleem Rasool Introduction to Viruses A virus is an obligate intracellular parasite and it is minimally constructed f two elements • A Genome …… DNA or RNA • Protein content…..which makes the capsid and some necessary proteins including enzymes Viruses could be • Non-enveloped • Enveloped
  4. 4. Sahibzada Tasleem Rasool Basic virus structure Capsid protein Nucleocapsid Naked capsid virus DNA RNA or = + Nucleocapsid Lipid membrane, glycoproteins Enveloped virus +
  5. 5. Sahibzada Tasleem Rasool Capsid symmetry Icosahedral Helical Naked capsid Enveloped Lipid Glycoprotein Matrix
  6. 6. Sahibzada Tasleem Rasool Icosahedral naked capsid viruses Adenovirus Electron micrograph Foot and mouth disease virus Crystallographic model http://www.ncbi.nlm.nih.gov/ICTVdb/Images/Ackerman/Animalvi/Adenovir/799-16.htm http://virology.wisc.edu/virusworld/ICTV8/fmd-foot-and-mouth-ictv8.jpg
  7. 7. Sahibzada Tasleem Rasool Helical naked capsid viruses Tobacco mosaic virus Electron micrograph Tobacco mosaic virus Model RNA Protein http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/em_tmv.gif Caspar and Klug, Adv Virus Res. 1960;7:225-325
  8. 8. Sahibzada Tasleem Rasool Icosahedral enveloped viruses Herpes simplex virus Electron micrograph Herpes simplex virus Nucleocapsid cryoEM model http://web.uct.ac.za/depts/mmi/stannard/emimages.html http://virology.wisc.edu/virusworld/images/herpescapsid.GIF
  9. 9. Sahibzada Tasleem Rasool Helical enveloped viruses Influneza A virus Electron micrograph Paramyxovirus Electron micrograph http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html http://web.uct.ac.za/depts/mmi/stannard/paramyx.html
  10. 10. Sahibzada Tasleem Rasool Properties of enveloped viruses  Envelope is sensitive to  Drying  Heat  Detergents  Acid  Consequences  Must stay wet during transmission  Transmission in large droplets and secretions  Cannot survive in the gastrointestinal tract  Do not need to kill cells in order to spread  May require both a humoral and a cellular immune response Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5th edition, Elsevier Mosby, Philadelphia, PA Box 6-5
  11. 11. Sahibzada Tasleem Rasool Properties of naked capsid viruses  Capsid is resistant to  Drying  Heat  Detergents  Acids  Consequences  Can survive in the gastrointestinal tract  Retain infectivity on drying  Survive well on environmental surfaces  Spread easily via fomites  Must kill host cells for release of mature virus particles  Humoral antibody response may be sufficient to neutralize infection Adapted from Murray, P.R. Rosenthal K.S., Pfaller, M.A. (2005) Medical Microbiology, 5th edition, Elsevier Mosby, Philadelphia, PA , Box 6-4
  12. 12. Sahibzada Tasleem Rasool VIRUSES DNA RNA Single Stranded Double Stranded Double Stranded Single Stranded
  13. 13. Sahibzada Tasleem Rasool David Baltimore places viruses in to one of the seven groups depending on a combination of their nucleic acid (DNA or RNA), strandedness (single-stranded or double-stranded), and method of replication. DNA viruses Group I ……………dsDNA Viruses Group II ………….. ssDNA Viruses RNA viruses Group III …………. dsRNA Viruses Group IV …………. ssRNA Viruses +ive sense Group V ……………ssRNA Viruses -ive sense Reverse transcribing viruses Group VI…………RNA Reverse Transcribing Viruses Group VII……….. DNA Reverse Transcribing Viruses
  14. 14. Sahibzada Tasleem Rasool Classification of Human Viruses "Group" Family Genome Genome size (kb) Capsid Envelope dsDNA Poxviridae dsDNA, linear 130 to 375 Ovoid Yes Herpesviridae dsDNA, linear 125 to 240 Icosahedral Yes Adenoviridae dsDNA, linear 26 to 45 Icosahedral No Polyomaviridae dsDNA, circular 5 Icosahedral No Papillomaviridae dsDNA, circular 7 to 8 Icosahedral No ssDNA Anellovirus ssDNA circular 3 to 4 Isometric No Parvoviradae ssDNA, linear, (- or +/-) 5 Icosahedral No Retro Hepadnaviridae dsDNA (partial), circular 3 to 4 Icosahedral Yes Retroviridae ssRNA (+), diploid 7 to 13 Spherical, rod or cone shaped Yes dsRNA Reoviridae dsRNA, segmented 19 to 32 Icosahedral No ssRNA (-) Rhabdoviridae ssRNA (-) 11 to 15 Helical Yes Filoviridae ssRNA (-) 19 Helical Yes Paramyxoviridae ssRNA (-) 10 to 15 Helical Yes Orthomyxoviridae ssRNA (-), segmented 10 to 13.6 Helical Yes Bunyaviridae ssRNA (-, ambi), segmented 11 to 19 Helical Yes Arenaviridae ssRNA (-, ambi), segmented 11 Circular, nucleosomal Yes Deltavirus ssRNA (-) circular 2 Spherical Yes ssRNA (+) Picornaviridae ssRNA (+) 7 to 9 Icosahedral No Calciviridae ssRNA (+) 7 to 8 Icosahedral No Hepevirus ssRNA (+) 7 Icosahedral No Astroviridae ssRNA (+) 6 to 7 Isometric No Coronaviridae ssRNA (+) 28 to 31 Helical Yes Flaviviridae ssRNA (+) 10 to 12 Spherical Yes Togaviridae ssRNA (+) 11 to 12 Icosahedral Yes
  15. 15. Sahibzada Tasleem Rasool Virus replication: general
  16. 16. Sahibzada Tasleem Rasool Group I: Viruses possess double-stranded DNA and include such virus families as Herpes viridae (examples like • HSV1 (oral herpes), • HSV2 (genital herpes), • Vericilla Zoster Virus (chickenpox), • EBV (Epstein-Barr virus), • CMV (Cytomegalovirus)), • Poxviridae (smallpox)
  17. 17. Sahibzada Tasleem Rasool Group II: Viruses possess single-stranded DNA and include such virus families as Parvo-viridae (Parvo virus) and the important bacteriophage M13.
  18. 18. Sahibzada Tasleem Rasool RNA viruses Group III: Viruses possess double-stranded RNA genomes, e.g. rotavirus. These genomes are always segmented.
  19. 19. Sahibzada Tasleem Rasool Group IV: Viruses possess positive-sense single-stranded RNA genomes. Many well known viruses are found in this group, including the picorna viruses (which is a family of viruses that includes well-known viruses like •Hepatitis A virus, •enteroviruses, •rhinoviruses, •poliovirus, •foot-and-mouth virus), •SARS virus, • hepatitis C virus, •rubella virus.
  20. 20. Sahibzada Tasleem Rasool Group V: Viruses possess negative-sense single-stranded RNA genomes. The deadly Ebola and Marburg viruses are well known members of this group, along with • influenza virus, • measles, • mumps • rabies.
  21. 21. Sahibzada Tasleem Rasool Reverse transcribing viruses Group VI: Viruses possess single-stranded RNA genomes and replicate using reverse transcriptase. The retroviruses are included in this group, of which HIV is a member.
  22. 22. Sahibzada Tasleem Rasool Reverse transcribing viruses . Group VII: Viruses possess double-stranded DNA genomes and replicate using reverse transcriptase. The hepatitis B virus can be found in this group. See diagram next slide The replication of the viruses can be better understood once their classification and nomenclature is clear. The viruses are classified according to the type of genetic material they contain.
  23. 23. Sahibzada Tasleem Rasool
  24. 24. Sahibzada Tasleem Rasool Viral pathogenesis  Cycle of infection  Entry  Primary site replication  Spread within the host  Shedding  Transmission  Effects on cells  Effects on organism
  25. 25. Sahibzada Tasleem Rasool Cycle of infection Secondary sites Spread Entry Shedding Shedding Local Lymphatic Neuronal Blood (viremia) Primary site
  26. 26. Sahibzada Tasleem Rasool Entry  Mucous membranes or skin  Respiratory  Oral  Sexual  Ocular  Percutaneous  needles, wounds, bites
  27. 27. Sahibzada Tasleem Rasool Shedding, transmission  Routes  Respiratory  Gastrointestinal (oral-fecal)  Urogenital  Skin  Mechanisms  Indirect contact  Aerosols  Fomites  Direct contact  Lesions  Saliva  Sex  Animal or insect bites  Maternal-neonatal
  28. 28. Sahibzada Tasleem Rasool Portals of entry of viruses into the host, and sites of shedding from the host. (From Fields Virology, 4th ed, Knipe & Howley, eds, Lippincott Williams & Wilkins, 2001, Figure 9-2) Routes of entry and shedding
  29. 29. Sahibzada Tasleem Rasool Exchange of genetic information between two genomes. "Classic" recombination This involves breaking of covalent bonds within the nucleic acid, exchange of genetic information, and reforming of covalent bonds. This kind of break/join recombination is common in DNA viruses or those RNA viruses which have a DNA phase (retroviruses). The host cell has recombination systems for DNA. Recombination enables a virus to pick up genetic information from viruses of the same type and occasionally from unrelated viruses or even the host genome
  30. 30. Sahibzada Tasleem Rasool DNA virus recombination
  31. 31. Sahibzada Tasleem Rasool If a virus has a segmented genome and if two variants of that virus infect a single cell, progeny virions can result with some segments from one parent, some from the other. This is an efficient process - but is limited to viruses with segmented genomes. Reassortment is a non- classical kind of recombination Reassortment may play an important role in nature in generating novel reassortants.
  32. 32. Sahibzada Tasleem Rasool RNA virus reassortment
  33. 33. Sahibzada Tasleem Rasool Clinical significance of genetic variation  Antigenic variation…..Body can not coup with the virus  Drug resistance……..Difficulty in designing and making new vaccines
  34. 34. Sahibzada Tasleem Rasool Time course of infection; host response prodrome symptoms at secondary sites pro- drome symptoms at primary site healing innate immunity: interferon adaptive immunity: cellular, antibody inflammatory; immunopathogenesis 0 2 4 6 8 10 12 time (days) Infection without spread: Infection with spread: Host Response:
  35. 35. Sahibzada Tasleem Rasool Patterns of disease From Schaechter’s Mechanisms of Microbial Disease; 4th ed.; Engleberg, DiRita & Dermody; Lippincott, Williams & Wilkins; 2007; Fig. 31-9
  36. 36. Sahibzada Tasleem Rasool
  37. 37. Sahibzada Tasleem Rasool Major diseases caused by human viruses "Group" Family Human pathogens (disease) dsDNA Poxviridae Variola (smallpox); Orf (pustular dermatitis); Molluscum contagiosum (pustular dermatitis) Herpesviridae Herpes simplex 1,2 (oral, genital herpes); Varicella-zoster (chickenpox); Epstein-Barr (mononucleosis); Cytomegalovirus (neonatal abnormalities); HHV6 (roseola); HHV8 (Kaposi's sarcoma) Adenoviridae Adenovirus (respiratory infection, conjunctivitis) Polyomaviridae Polyomavirus (benign kidney infection, respiratory disease, leukoencephalopathy) Papillomaviridae Papillomavirus (warts, genital carcinoma) ssDNA Anellovirus Unknown Parvoviradae B-19 (fifth disease, fetal death) Retro Hepadnaviridae Hepatitis B ("serum" hepatitis) Retroviridae HIV (aids); HTLV (leukemia) dsRNA Reoviridae Rotavirus (infantile gastroenteritis) ssRNA (-) Rhabdoviridae Rabies virus (rabies) Filoviridae Ebola virus (ebola) Paramyxoviridae Parainfluenza virus (respiratory infection); Mumps virus (mumps); Respiratory syncytial virus (respiratory infection); Measles virus (measles) Orthomyxoviridae Influenza virus (influenza) Bunyaviridae Hantaan virus (hemorrhagic fever with renal syndrome) Arenaviridae Lassa fever virus (hemorrhagic fever) Deltavirus Hepatitis D (fulminant acute hepatitis) ssRNA (+) Picornaviridae Poliovirus (polio), rhinovirus (URI), Hepatitis A ("infectious" hepatitis) Calciviridae Norwalk (gastroenteritis) Hepevirus Hepatitis E (acute hepatitis) Astroviridae Astrovirus (gastroenteritis) Coronaviridae Coronavirus (respiratory infection) Flaviviridae Yellow fever virus (yellow fever); Hepatitis C (hepatitis) Togaviridae Eastern Equine encephalitis virus (encephalitis); Rubella virus (rubella)