Viruses ch 19 – lecture monday 12 2-13


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Viruses ch 19 – lecture monday 12 2-13

  1. 1. Viruses Ch 19 – Lecture Monday 12/2/13 Tuesday: Lab Quiz: Protists and Fungi Wednesday: Lecture Quiz on Fungi Thursday: LAB Exam * Bring book and notes
  2. 2. Importance of Viruses 1. Agent of diseases 2. Vector of gene in biotechnology – 30% of human DNA is viral 3. Agent of evolution or mutation
  3. 3. Smallpox viral disease • Infectious variola virus cause maculopapular rash • Transmission via respiratory droplets • Cause macropuplar rash (not itchy) with permanent scarring • Transmission via respiratory droplets • Humans are the only known host • Eradicated 1979 • Russia and US have smallpox samples • Can be used as a bioweapon • Death occurs in 30% of cases due to respiratory complications
  4. 4. Chicken pox and shingles • Varicella zoster virus • Virus dwell in sensory nerves • Symptoms include rashes, fever, and general malaise • Adult form: shingles
  5. 5. Rabies (hydrophia) • Viral need treatment in 3 days • Zoonotic disease (spread by animals) that cause encephalitis resulting in violence, madness, and hydrophobia • Virus causes nervous damage • Delirium, coma, death • Bats are likely rabies vectors
  6. 6. Herpes I • Herpes I cause sores and blisters
  7. 7. Herpes II • Cause genital blisters • Mild and asymptomic in healthy adults • Can be transmitted to newborn
  8. 8. AIDS • HIV targets specific cells. HIV kills white blood cells with CD4 antigen, primarily T helper cells • T-helper cells are crucial in the activation of other white blood cells • T helper cells are generals. They organize immune strategy. • Death from AIDS is due to opportunistic infections – TB, PDP, Kaposi Sarcoma, toxoplasmosis
  9. 9. AIDS v HIV • HIV positive: • AIDS: T cell count is below 200 micro-liter
  10. 10. Common cold, influenza, SARS, Hanta virus • Cause respiratory problems
  11. 11. Hepatitis A • Liver inflammation • Transmitted primarily contaminated water or food • Infection occurs during childhood • Cause liver damage • Vaccine available 
  12. 12. Hepatitis B • Blood transfusion/exchange • Vaccine vacation  • Can lead to liver cirrhosis (hardening) and caner
  13. 13. Hepatitis C • Transmitted via blood exchange • Most cases are asymptomatic • Can progress to liver cirrhosis and cancer req requiring liver transplant • No effective vaccine available
  14. 14. Warts and cervical cancer • Caused HPV • Can lead to cervical, ovarian, genital, and anal cancers • We all have had it • Can transmit by casual contact  • Vaccine available for 70% of cases called Gardasil. You have to get it before you get sexually active.
  15. 15. Ebola & Marbug • Mortality is as high as 90% • Cause shock due to loss of vascular integrity and loss of coagulation • Endemic and sporadic 
  16. 16. Structure of Viruses • Viruses are NOT cells. • Viruses are obligate intracellular parasites. They are active or reproduce only when inside host cells • Viruses consist of nucleic acid enclosed in capsid (protein coat) and membranous envelope. • Each virus has a host range, a limit number of host cells that it can inflect. – Herpes will attack only nerve cells, not muscle cells – H1N1 can go from one species to another • Viruses are smaller and simpler than bacteria,.
  17. 17. All viruses • 1. Have RNA or DNA • All viruses have protein shells or capsids.
  18. 18. Viral genomes • All viruses have double or single RNA or DNA. It can’t be both DNA and RNA. It is one or the other.
  19. 19. capsid • Protein shell that encloses the viral genome • Functions: attachment to host cell protection of genome • Capsid of some virus is used as a vaccine to induce immunity – BHV, HPV, and polio vaccines
  20. 20. Membranes (some viruses) • Some viruses have membranous envelopes that surround the capsid which helped them infect host cells • Viruses acquire membranes from host cells. • Host cell membranes allow viruses to escape detection by host white blood cells. • exocytosis
  21. 21. spikes • Some viruses have spikes protruding from their envelope (glycoprotein) • Spikes help viruses attach to host cells • H (hemagluttin) N (neuranidase) H1N1: spikes are made of proteins H and N.
  22. 22. Bacteriophages: viruses that infect bacteria • Two types: lytic and lysogenic
  23. 23. Lytic (virulent phage) • Upon entrance, virus directs host cell to synthesize more virus copies. • Capsid stays out. Only DNA or RNA goes inside the host. • Lytic cycle terminates in death of host cell. • Virulent phage: a phase that reproduces only by lytic cycle • Virus only injects the genome into host cells, not capsid
  24. 24. Lysogenic • • • • Viral DNA is incorporated into the host DNA Virus knows when host cell will die Prophage: integrated viral DNA Every time host divides, virus genome also gets copied and viral genome is passed on to daughter cells. • Temperate phage: uses both lytic and lysogenic cycles. HIV is temperate • Does NOT kill host cell immediately