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VIRUSES

VIRUSES. CHAPTER 10. What are Viruses?. Obligate intracellular parasites Virion : A complete virus particle, including its envelop, if it has one, is called virion . Viral components Nucleic acids: Genome Capsid: capsomers nucleocapsid. Envelope ( Contain lipid )

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VIRUSES

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  1. VIRUSES CHAPTER 10

  2. What are Viruses? • Obligate intracellular parasites • Virion: A complete virus particle, including its envelop, • if it has one, is called virion. • Viral components • Nucleic acids: • Genome • Capsid: • capsomers nucleocapsid

  3. Envelope (Contain lipid) • Nonenvelope-naked virus, nonenveloped viruses. spikes: causes various types of red blood cells to clump---hemagglutination Glycoprotein • similar to cellular membrane • i. protection ii. infect by fusion

  4. Viral Shapes and Sizes • Helical: Tobaco mosaic virus (TMV), • Polyhedral : picornavirus,adenovirus • Icosahedral: • Complex : • pox virus, • bacteriophage

  5. Host Range and Specificity : Infectious Properties • Viral Host range • Viral specificity • pappillomaviruses: only skin cell • Cytomegaroviruses: salivary gland, G.I. • liver, lungs, placenta, fetus CNS, etc. • Viral Origins: • living or nonliving • viruses, • viroids, • plasmids

  6. RNA Viruses • Chromosomal Arrangements • + strand • – strand • Double strand

  7. RNA Virus Families (Table 10. 1, page 277) • 11 RNA virus families • A. (+) Sense RNA Viruses Picornaviridae • Polio, Common cold, Hepatitis A Togaviridae • Rubella (German measle) • Equine encephalitis Flaviviridae • Yellow fever • Retroviridae • HTLV-L, HIV, adult leukemia, AID, tumors

  8. RNA Virus Families (cont.) • B. (-) Sense RNA viruses • Paramyxoviridae • Measles • Rhabdoviridae • Rabies

  9. RNA Virus Families (cont.) • Orthomyxoviridae • Influenza A and B • Filoviridae • Marburg, Ebola • Bunyaviridae • Respiratory distress • hemorrhagic fevers • Arenaviridae • Lassa fever

  10. RNA Virus Families (cont.) • C. Double-Stranded RNA Viruses • Reoviridae • Respiratory and • GI. infections

  11. DNA Virus Families • A. Double-Stranded DNA viruses • Adenoviridae • Respiratory infections • Herpesviridae • Oral and genital herpes • Chickpox, shingles • Table 10. 3, page 283. • Poxviridae • Smallpox, • Cowpox

  12. DNA Virus Families (cont.) • Papovaviridae • Warts, cervical • and penile cancers • Hepadnaviridae • Hepatitis B viruses

  13. DNA Virus Families (cont.) • B. Single-Stranded DNA Viruses • Parvoviridae Fifth disease • (erythema infection) in children

  14. Emerging Viruses • Previously endemic • Crossed species barriers • 1900 pandemic poliovirus • 1950 vaccines • Sabin • Salk • Measles, • Yellow fever • Vectors (carriers), Mosquitoes. 20 including Dengue fever arboviruses are emerging viruses. • Hanta viruses: Huntavirus pulmonary syndrome (HHS) • Swine flu pandemic in 1918, killed 20-40 millions. • Pig flu viruses-human flu viruses--- bird flu (avian flu) (1997- • 2003). • Travel

  15. Viral Replication: General characteristics of replication • Activities • Adsorption • Penetration (virus or chromosome): the entry of virions into host cells. • Synthesis • Maturation: assembly of the newly synthesized viral components into complete virions. • Release

  16. Bacteriophagesdiscovered in 1915, Frederic Twort in England; 1917 by Felix d’Herelle in France. • Replication of Bacteriophages: phage therapy, page 286-287 • T-even phages for Escherichia coli • Delbrück

  17. BacteriophagesReplication of T-even Phages

  18. Phage Growth and the estimation of Phage Numbers • Growth curve for a bacteriophages • Figure 10.12, page 289. • Eclipse period: penetration to biosynthesis • Latent period: penetration to release • Total virus, viral yield Plaque Assay Bacterial lawn

  19. Bacteriophages • Plaque counts

  20. Bacteriophages • Lysogeny (prophage, lysogenic conversion) lysogen (Bacterium and a temperate phage)

  21. Animal Viruses • DNA viruses • Penetration by endocytosis or fusion. • DNA replication in the nucleus • release by budding • Latency, chronic infection, cancer • (Table 10. 6, 292)

  22. Animal Viruses • RNA viruses • Occur in the cytoplasm • Latent viruses • Herpesvirues (dsDNA viruses) • chickenpox, shingles

  23. Culturing Animal Viruses • Live animals • Eggs • Embryonated • herpes, pox, influenza • viruses

  24. Culturing Animal Viruses • Cell Culture (Monolayers, Subculturing) • Primary cell cultures • A strain of primary culture transferred: Diploid fibroblast strain (immature cells that produce collagen as well as the substance of connective tissues) (from fetal tissues) • Continuous cell line

  25. Viral Cytopathic Effects (CPE) • Cytopathy • Syncytia • Transformation • Negri body • Teratogenic effects

  26. Viruses and Teratogenesis • Induction of defects during embryonic development • Teratogens: chemical, or drug, or other agent that induce teratogenic effects. • Teratogenic virues: Cytomegalovirus (CMV), herpes simplex virus( HSV) types 1 and 2, and rubella virus. • TORCH series (blood test): detect anti bodies against Toxoplasma, other disease-causing viruses, (hepatitis B and the varicella , or chicken pox viruses), rubella virus, CMV, and HSV.

  27. Viruslike Agents • Satellites • Small, single-stranded RNA molecules (500-2,000) nucleotides, lack gene for replication. In the presence of helper virus, they can replicate. • Satellite viruses • Satellite nucleic acids (virusoids) • DELTA HEPATITIS VIRUS(HDV) • Thought to be Hepatitis Delta Virus (HDV) (1,679—1683 nucleotide). • Similar to viroid and to virusoid. RNAs that infect plants. • Require coinfection with hepatitis B (HBV) in order to replicate. Enhance the virulence of HBV. • Especially frequent (over 60%) infection rate in parts of Amazan, Central Africa, and the Middle East.

  28. VIROIDS • 1971 T. O. Diener discovered in potato tumor spindle disease.. An infectious particle smaller than a virus. • Differ from viruses • 1. single circular RNA, MW 246-399 nucleotides. • 2. Exist inside of cell nucleoli, as particle without capsid or • envelopes. • 3. does not require a helper virus. • 4. does not produce proteins • 5. Is always copied in the host nucleus • 6. not apparent in infected tissues.

  29. Viroids

  30. PRIONSHans Gerhard Creuzfeldt and Alfons Maria Jakob.Stanely Prusiner 1982. coined the term Prion (Proteinaceous infectious particle) • Prions Creutzfeldt-Jakob Diseases (CJD) Kuru Scrapie Bovine spongiform encephalopathy (BSE) (Mad Cow Disease)

  31. Viruses and Cancer:Viral oncology, F. Peyton Rous, 1911.Rous sarcoma virus • Mechanism of cancer causation • Neoplasm: localized accumulation of cells known as tumor: • Begnin • Malignant • metastasize

  32. Human Cancer Viruses DNA viruses 1.Epstein-Barr virus (EBV) : a herpesvirus cause Burkitt Lymphoma. 2. Human papilomaviruses (HPV-8, HPV-16)) cause uterine cerevix cancer, a sexually transmitted disease. 3. Hepatitis B virus (HBV): (DNA) : liver cancer. 4. Herpesvirus 8: Kaposi sarcoma: cancer of the endothelial cancer of the blood vessels or lymphatic system RNA viruses 5. HTLV-1: adult T cell leukemia/lymphoma Retroviruses 6. HIV virus: AIDS

  33. How Cancer Viruses Cause Cancer • Neoplastic transformation • Viral genes: • Suppressor genes; • Oncogenes: produce proteins cause uncontrollable host cell division • Protooncogenes: normal gene , when under the control of virus, can cause uncontrolled cell division. --- become oncogenes.

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