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Viruses

Viruses. http://www.bing.com/images/search?q=virus&view=detail&id=5AD62840C81847683B7591AEC1F651E75C9E986E&first=1. What is a virus?. Characteristics Infectious agent Contains nucleic acids within a protein capsid

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Viruses

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  1. Viruses http://www.bing.com/images/search?q=virus&view=detail&id=5AD62840C81847683B7591AEC1F651E75C9E986E&first=1

  2. What is a virus? • Characteristics • Infectious agent • Contains nucleic acids within a protein capsid • May or may not be enveloped in lipid bilayer envelope (mostly animal viruses) • Requires host cell to reproduce! http://www.chm.bris.ac.uk/webprojects2006/Kelly/influenzafigure1.jpg

  3. Is it alive? • Viruses do not quite fit the all of the definitions of life ? http://3.bp.blogspot.com/_j-GXGQi_LBM/Sq5j9-GjgkI/AAAAAAAAACI/aUOfmBDZdr0/s320/RIP+Tomb+Stone.jpg http://travelerfolio.com/tf2/photos/2010/03/funny-frankenstein-monster.jpg http://affordablehousinginstitute.org/blogs/us/wp-content/uploads/borat_thumbs_up.jpg

  4. Definitions of Life Homeostasis Organization Metabolism Growth Adaptation Response to Stimuli Reproduction

  5. Viral Structure • 3 components • 1. Nucleic Acids (DNA or RNA) • 2. Capsid made from protein, • May be helical or icosohedral (20 triangular sides) • 3. Envelope • Made from lipids when virus exits cell • No envelope  naked http://www.proprofs.com/flashcards/upload/a3545428.jpg

  6. Viral Genomes • DNA or RNA • Both can be single stranded (ss) or double stranded (ds) • DNA or RNA affects where the protein replicates in the cell • May be segmented  genes on separate pieces on nucleic acid http://www.mcb.uct.ac.za/tutorial/genomes.gif

  7. Capsids • Capsomers encoded by 1 or 2 genes • Multiple protein protomers (capsomer) form the capsid via self assembly • Protect genetic material http://www.youtube.com/watch?v=X-8MP7g8XOE&feature=related http://www.nicerweb.com/bio1151/Locked/media/ch19/19_03-ViralStructure-L.jpg

  8. Capsids and Symmetry • Primarily made of symmetric capsomers forming hexamers • Requires a certain number of asymmetric capsomers • Some use a triangular capsomer system http://en.wikipedia.org/wiki/Icosahedral_capsid

  9. Capsids and Symmetry • Symmetric capsomers make up helical capsids forming a helix. http://o.quizlet.com/i/aD6L0oSIeUjYrwx3qRka0w_m.jpg

  10. The Envelope • Derived from cell membrane of host cell • Aids in entry into the host cell • Contains glycoproteins http://education.expasy.org/images/Fusion_plasmamb.jpg

  11. Well, what is a glycoprotein? • Lock and Key mechanism  viral glycoproteins interact with cell surface receptors to gain entry into host cells • Called peplomers on the virus • http://www.youtube.com/watch?v=yEAf8gF9wTU&feature=fvwrel http://withfriendship.com/images/e/21947/Glycoprotein-picture.gif

  12. Lock and key means susceptibility • Cells must have a glycoprotein that corresponds to the peplomer in order to be susceptible. Ex. CD4 cells and HIV http://www.elmhurst.edu/~chm/vchembook/images/571lockkey.gif

  13. Susceptibility vs. Permissiveness • Susceptibility: ability to be infected • Permissive: ability for virus to replicate and bud off virions in an infected cell. • Vectors  may be infected but not permissive • Nonpermissiveness due to antiviral response

  14. Antiviral Response • Infected cell presents antigens  • primes humoral immune response • Puts the cell and surrounding cells into a static state • Signals for NK cells to kill the infected cell http://images.tutorvista.com/content/immune-system/interferons-action.jpeg

  15. Resealing the envelope • Enveloped viruses get a new envelope by budding from the host cell • Virus contains peplomers and glycoproteins from the cell!! http://www.lolpix.com/_pics/Funny_Pictures_340/Funny_Pictures_3403.jpg http://www.prism.gatech.edu/~gh19/b1510/repcycvi.gif

  16. Lytic vs. Lysogenic Cycle http://diverge.hunter.cuny.edu/~weigang/Images/13-12_lysogeniccycle_1.jpg

  17. + vs – Stranded Viruses

  18. Steps of Viral Replication Attachment/Adsorption (2) Penetration -Receptor-Mediated Endocytosis -Fusion Proteins -Translocation (3) Uncoating (4) Transcription of Early mRNA (5) Translation of Early Proteins

  19. Replication (cont.) (6) Replication of Viral Nucleic Acid (7) Transcription of Late mRNA from Progeny Genomic Nucleic Acid (8) Translation of Late Proteins (9) Assembly (10) Release of Viral Progeny -Host Cell Lysis -Budding

  20. * Link

  21. Influenza: AKA the Flu • Key virulence factors: • Neuraminidase- enables virus to be released from host cell • Hemagluttinin- binds virus to cell to enter and exit • H#N# signifies variations of these proteins http://publications.nigms.nih.gov/findings/mar06/agbandje-mckenna_files/images/image3.png

  22. Herpes Simplex (HSV-1)

  23. Herpes Simplex (HSV-2)

  24. Varicella Zoster (VSV)

  25. Ebstein-Barr (EBV)

  26. Human Papilloma Virus (HPV)

  27. Coronavirus

  28. Orthomyxovirus

  29. Rhinovirus

  30. Ebola

  31. “In biology, nothing is clear, everything is too complicated, everything is a mess, and just when you think you understand something, you peel off a layer and find deeper complications beneath. Nature is anything but simple.” “When people asked him why he didn’t work with those viruses, he replied, ‘I don’t particularly feel like dying.’” “It showed a kind of obscenity you see only in nature, an obscenity so extreme that it dissolves imperceptibly into beauty.” “Humans in space suits make monkeys nervous.”

  32. Human Immunodeficiency Virus (HIV) -RNA Retrovirus -Transmission: (1) Anal, Oral, Vaginal Intercourse (2) In Utero

  33. Deaths attributed to HIV/AIDS: 1.8 Million (approx. 6.7 Billion worldwide)

  34. Thanks!

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