Viruses
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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

VIRUSES

CHAPTER 10


What are viruses

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


Viruses

  • 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


  • Viral shapes and sizes

    Viral Shapes and Sizes

    • Helical: Tobaco mosaic virus (TMV),

    • Polyhedral : picornavirus,adenovirus

    • Icosahedral:

    • Complex :

    • pox virus,

    • bacteriophage


    Host range and specificity infectious properties

    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


    Rna viruses

    RNA Viruses

    • Chromosomal Arrangements

      • + strand

      • – strand

      • Double strand


    Rna virus families table 10 1 page 277

    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


    Rna virus families cont

    RNA Virus Families (cont.)

    • B. (-) Sense RNA viruses

    • Paramyxoviridae

    • Measles

    • Rhabdoviridae

    • Rabies


    Rna virus families cont1

    RNA Virus Families (cont.)

    • Orthomyxoviridae

    • Influenza A and B

    • Filoviridae

    • Marburg, Ebola

    • Bunyaviridae

    • Respiratory distress

    • hemorrhagic fevers

    • Arenaviridae

    • Lassa fever


    Rna virus families cont2

    RNA Virus Families (cont.)

    • C. Double-Stranded RNA Viruses

    • Reoviridae

    • Respiratory and

    • GI. infections


    Dna virus families

    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


    Dna virus families cont

    DNA Virus Families (cont.)

    • Papovaviridae

    • Warts, cervical

    • and penile cancers

    • Hepadnaviridae

    • Hepatitis B viruses


    Dna virus families cont1

    DNA Virus Families (cont.)

    • B. Single-Stranded DNA Viruses

    • Parvoviridae Fifth disease

    • (erythema infection) in children


    Emerging viruses

    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


    Viral replication general characteristics of replication

    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


    Bacteriophages discovered in 1915 frederic twort in england 1917 by felix d herelle in france

    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


    Bacteriophages replication of t even phages

    BacteriophagesReplication of T-even Phages


    Phage growth and the estimation of phage numbers

    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


    Bacteriophages

    Bacteriophages

    • Plaque counts


    Bacteriophages1

    Bacteriophages

    • Lysogeny (prophage, lysogenic conversion)

      lysogen (Bacterium and a temperate phage)


    Animal viruses

    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)


    Animal viruses1

    Animal Viruses

    • RNA viruses

    • Occur in the cytoplasm

    • Latent viruses

    • Herpesvirues (dsDNA viruses)

    • chickenpox, shingles


    Culturing animal viruses

    Culturing Animal Viruses

    • Live animals

    • Eggs

    • Embryonated

    • herpes, pox, influenza

    • viruses


    Culturing animal viruses1

    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


    Viral cytopathic effects cpe

    Viral Cytopathic Effects (CPE)

    • Cytopathy

    • Syncytia

    • Transformation

    • Negri body

    • Teratogenic effects


    Viruses and teratogenesis

    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.


    Viruslike agents

    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.


    Viroids

    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.


    Viroids1

    Viroids


    Viruses

    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)


    Viruses and cancer viral oncology f peyton rous 1911 rous sarcoma virus

    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


    Human cancer viruses

    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


    How cancer viruses cause cancer

    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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