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Viruses

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Viruses

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    1. Viruses

    2. What are viruses? Very small Obligatory intracellular parasites Difficult to isolate, detect, cultivate Somewhat like Rickettsia…

    3. What are viruses? Contain genetic material DNA or RNA Protein coat Sometimes encased in lipids, carbs and proteins Reproduction inside living cells No metabolic enzymes Use host enzyme Problem for drug creators!

    4. What is a host range? Host cells a virus can infect Very narrow Useful for treating diseases? Viral therapy Oncolytic viruses Range determined by cell receptor sites

    5. What is a virion? One, complete, infectious viral particle Contains Nucleic acid DNA or RNA Both can be double- or single-stranded Protein coat (capsid) Classification based on type of capsid Capsomeres: protein subunits

    6. What is a virion? Contains envelope (not all) Covers capsid Lipids, carbs, proteins Used to fuse with host PM May have spikes

    7. What types of viruses are there? Helical Rabies, ebola

    8. What types of viruses are there? Polyhedral Animal, plant, phages

    9. What types of viruses are there? Enveloped Influenzavirus

    10. What types of viruses are there? Complex Many phages Additional structures

    11. What are some viruses I should know? No specific epithet DNA viruses Adenoviridae Poxviridae Herpesviridae Human herpes virus 1, HHV 2, HHV 3 Papovaviridae Hepadnaviridae

    12. What are some viruses I should know? RNA viruses Picornaviridae Retroviridae Lentivirus Human Immunodeficiency Virus 1, HIV 2

    13. Viral Replication

    14. How do viruses multiply? Virus only has a few genes and proteins All other proteins come from host cell E.g. ribosomes, tRNA, etc. Must take over host metabolism

    15. How do phages multiply? Two possibilities Lytic cycle Lysogenic cycle T-4 About 100 genes Multiplication in 5 stages Attachment Penetration Biosynthesis Maturation Release animation

    16. What’s the difference between lytic and lysogenic cycles?

    17. What else should I know about the lysogenic phase? When latent (temperate phase) Can’t be infected with the same virus again Phage conversion can happen C. diptheriae: produces toxin only in latent phase C. botulinum, C. cholerae and some streptococci also Specialized transduction is possible

    18. How do viruses multiply in animals like us? Different mechanism of entry Assembly of parts and synthesis also differs Different maturation and release

    19. What’s different about entry? Attachment first Sites vary from person to person Penetration Q: how does it happen in phages? Endocytosis OR Fusion (animation) HIV

    20. What happens next? Uncoating by viral or host enzymes Biosynthesis nucleic acids DNA RNA proteins

    21. Is RNA biosynthesis the same? Mostly… Animation HIV—retrovirus animation

    22. What are the final stages for multiplication in animal viruses? Maturation Nucleic acid Capsid proteins Release budding (enveloped viruses) or animation Rupture

    23. Viruses and disease

    24. Is there a connection between viruses and cancer? Yes! Oncogenic viruses 10% of all cancers DNA integrates into host cell Tumor-specific transplantation antigen (TSTA) Cytopathic changes

    25. Can you give me some examples? HPV—cervical cancer Adenoviridae—adenocarcinoma Herpesviridae Epstein-Barr (EB) virus—Burkitt’s lymphoma HHV-8—Kaposi’s sarcoma Hep-B—liver cancer

    26. Do all viral infections causes symptoms immediately? No Latent period for many EB may be latently carried in 9 out 10 people Herpesviruses can stay for lifetime Cold sores Chickenpox—shingles (zoster) Persistent infections for some Usually fatal Gradual appearance and worsening of symptoms Subacute sclerosing panecephalitis (from measles)

    27. What are prions? Not viruses Infectious proteins Inherited and transmissible by Ingestion Transplant surgical instruments Mad Cow Disease Creutzfeldt-Jacob disease

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