1 / 56

Viruses

Viruses. Prof. Khaled H. Abu-Elteen Hashemite University. Viruses. smallest infections agents intracellular parasites-can reproduce only in host cells. can not carry on independent metabolism first virus discovered was tobacco mosaic virus [TMV] in 1892.

zubeda
Download Presentation

Viruses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Viruses Prof. Khaled H. Abu-Elteen Hashemite University

  2. Viruses • smallest infections agents • intracellular parasites-can reproduce only in host cells. • can not carry on independent metabolism • first virus discovered was tobacco mosaic virus [TMV] in 1892. • in 1931 virus cultured in the lab using tissue culture. • viruses are not cellular • consist only of a nucleic acid either DNA or RNA, surrounded by a protein coat.

  3. Virus facts • generally more resistant to some disinfectants than most bacteria. • most are susceptible to heat, except hepatitis virus • not affected by antibiotics

  4. VIRUS STRUCTURE • Basic rules of virus architecture, structure, and assembly are the same for all families, some structures are much more complex than others. • The capsid (coat) protein is the basic unit of structure; functions that may be fulfilled by the capsid protein are to: • Protect viral nucleic acid • Interact specifically with the viral nucleic acid for packaging • Interact with vector for specific transmission • Interact with host receptors for entry to cell • Allow for release of nucleic acid upon entry into new cell • Assist in processes of viral and/or host gene regulation

  5. Nucleoprotein has two basic structure types: • HELICAL:Rod shaped, varying widths and specific architectures; no theoretical limit to the amount of nucleic acid that can be packaged • CUBIC (Icosahedral):Spherical, amount of nucleic acid that can be packaged is limited by the of the particle • Virus structure is studied by: • Transmission electron microscopy (EM) • Cryo EM – one of the most powerful methods currently available • X-Ray diffraction

  6. Principles of basic virus structure • Nucleoprotein must be stable but dissociatable • Capsid is held together by non-covalent, reversible bonds: hydrophobic, salt, hydrogen bonds • Capsid is a polymer of identical subunits • Terms: • Capsid = protein coat • Structural unit = protein subunit • Nucleocapsid = nucleic acid + protein • Virion = virus particle • Capsid proteins are compactly folded proteins which: • Fold only one way, and robustly • Vary in size, generally 50-350 aa residues • Have identifiable domains • Can be described topologically; similar topological features do not imply evolutionary relationships

  7. Basic virus structure DNA or RNA Capsid protein Naked capsid virus Nucleocapsid + = Lipid membrane, glycoproteins Enveloped virus Nucleocapsid +

  8. Capsid symmetry Matrix Lipid Glycoprotein Icosahedral Helical Naked capsid Enveloped

  9. Icosahedral naked capsid viruses Adenovirus Electron micrograph Foot and mouth disease virus Crystallographic model

  10. Helical naked capsid viruses RNA Protein Tobacco mosaic virus Electron micrograph Tobacco mosaic virus Model

  11. Icosahedral enveloped viruses Herpes simplex virus Electron micrograph Herpes simplex virus Nucleocapsid cryoEM model

  12. Helical enveloped viruses Influneza A virus Electron micrograph Paramyxovirus Electron micrograph

  13. 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

  14. Properties of naked capsid viruses Capsid is resistant to Drying Heat Detergents Acids Proteases 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

  15. Atomic Resolution Microscope at UC Berkeley The Atomic Resolution Microscope is specifically designed for performance in the high resolution imaging mode with a point-to-point resolution of 1.5Å. Typical modern transmission EM: This JEOLTransmission Electron Microscope, similar to the one we use at Rutgers, is housed at Colorado State University

  16. Classification of viruses • on the basis of: • nucleic acid they contain ( DNA or RNA ) • the size, shape and structure of the virus • the tissue the infect

  17. DNA viruses • i) Poxivirus group (DNA) virus – pathogenic to skin small pox, cow pox • ii) Herpes virus group (DNA) • Latent infection may occur and lasts the life span of the host. • Cold sores • Shingles • Chicken pox • iii) Adenovirus group (DNA) • Catarrhs • Conjunctivitis • iv) Papovirus group (DNA) • Wart virus

  18. Adeno viruses

  19. Adenovirus-Associated Human Disease Pharyngitis    Acute Respiratory Disease    Pneumonia    Pharyngoconjunctival Fever    Epidemic Keratoconjuntivitis    Genitourinary Infections (cervicitis, urethritis )    Gasteroenteritis    Some asymptomatic and persistent infection    Adenovirus oncogenically tranforms rodent cells but not human cells.

  20. AIDS Virus

  21. HIV

  22. HIV

  23. Herpes Simplex Virus I

  24. Human T- cell Lymphotropic Virus (HTLV)

  25. Human T- cell Lymphotropic Virus • HTLV-1 stands for Human T-cell Lymphotropic Virus. • It is a retrovirus, in the same class of virus as the AIDS virus, HIV-1. • HTLV-I is associated with a rare form of blood dsycrasia known as Adult T-cell Leukemia/lymphoma (ATLL) and a myelopathy, tropical spastic paresis. • However, even with infection, fewer than 4% of seropositive persons will experience overt associated disease.

  26. Herpes Simplex Type II Virus

  27. Herpes Simplex Type II Virus

  28. Herpes Simplex Type II Virus

  29. Herpes Simplex Type I Virus

  30. Hepatitis • Hepatitis • a. chemically induced • b. viral infection A, B, C, D, E, F • Viral hepatitis is the most common liver disease found worldwide. • Epstein Barr virus • Herpes virus • Cytomegalovirus

  31. Hepatitis B (HBV) • DNA virus • has an outer surface structure known as hepatitis B surface antigen (HBs Ag) & an inner core component known as hepatitis B core Antigen (HBc Ag) • Long incubation period—up to 6 months. • Transmitted through blood contact. • Some modes of transmission as those for HIV. • HBV is very serious illness. • Series of 3 immunizations are given on day 0, 30, 180.

  32. Hepatitis C • Blood borne pathogen. • Also found in water like HV-A • Many become carriers

  33. Hepatitis D • Super-infects some patients who are already infected with HBV. • HBV is required as a helper to initiate infection. • blood borne.

  34. Hepatitis A Virus

  35. Hepatitis B: Causes

  36. Hepatitis B

  37. Hepatitis C: Getting Tattoos

  38. Infectious mononucleosis

  39. Picorna Virus

  40. Picorna Virus Primary site of infection is lymphoid tissue associated with the oropharynx and gut (GALT).

  41. Polio Virus

  42. Poliomyelitis

  43. Human Papilloma Virus

  44. Genital Warts - HPV • Causes genital warts

  45. Measles

  46. Mumps

  47. German Measles (Rubella)

  48. Chicken pox

  49. Chicken Pox Active lesions

  50. Small pox

More Related