2. Virusus Non-living infectious agents Require host (parasites) Found everywhere. Infect organisms in every kingdom Edward Jenner-first vaccine for smallpox 1796

3. Viral Diseases Viral diseases: – Smallpox, Polio, Measles, Influenza, AIDS, Common Cold

4. Viruses are Infectious Agents But are Host Specific and tissue specific For Example: Cold Virus only infects the cells of the human upper respiratory tract.

5. Virus Structure All contain these 2 structures : – 1. Nucleic Acid (either RNA or DNA) – 2. Protein Coat (capsid)- Made of protein Encloses Genetic material

6. Viral Body Plans Complex virus (bacteriophage) Poylhedral virus Helical virus

8. Some are Enveloped: have an added phospholipid membrane on outside. Examples: HIV, Rhinoviruses, Coronovirus Influenza

9. HIV is an Enveloped Retrovirus Has RNA Retrovirus=RNA—to DNA--- To RNA---To protein Mutates quickly.

10. HIV replication. 1.

11. HIV Replication 1. Binds to specific cell-Helper T cell (white blood cell). 2. Virus attaches, & viral RNA enters. 3. Production -uses host materials to make DNA 4. DNA enters nucleus; RNA made via transcription. 5. RNA leaves nucleus, translation occurs. 6. Assembly of new viruses. 7. Exits by budding and/or lysis of cell.

12. Fig. 20.11, p. 317 viral RNA protein subunits of coat 18 nm diameter, 250 nm length 80-nm diameter lipid envelope; proteins span the envelope, line its inner surface, spike out above it viral RNA reverse transcriptase viral coat (proteins) 100-120 nm diameter DNA protein coat sheath base plate tail fiber 65-nm diameter head, 225-nm total length

13. Virus Reproduction- Takes ~20 min to make hundreds- to-thousands of new viruses Various methods--- but 5 basic steps—as follows :

14. Virus Reproduction-5 basic steps. Lytic Cycle 1. Attach to host cell surface. 2. Entry: whole virus OR just DNA 3.Replication-takes over & direct replication of viral DNA & Proteins 4. Assembly-new viruses 5. Release. By either Budding or Lysis which results in cell death.

15. Defense Against Viruses 1. ??Antibiotics—INEFFECTIVE— because they target cellular processes (viruses are not alive—no cell/processes) 2. Vaccinations—Made of viruses which have been treated so they are harmless Create our own self-defense-build internal antibodies against specific viruses.

16. 2.

17. Defense Against Viruses 3. Virus-Destroying Drugs. They destroy the virus BUT ALSO DESTROY HOST CELL – Example: AZT-slows down AID’s; it’s toxic therefore side effects

18. Why Don’t Vaccines Always Protect? Mutations –  Become Unrecognizable ЖФξ  HIV, Cold Virus, Influenza change often  Viral surface proteins mutate; some VERY OFTEN  Of all the changeable viruses, HIV changes the most!

19. Emerging Viral Diseases Filovirus: A virus harbored in animals without harming them; then passed on to another animal who is harmed FOR EXAMPLE: Ebola :30-90% mortality hemorrhagic fever.

20. Fig. 20.6, p. 314PrionDisease

21. Other Infectious Agent--Prions Small abnormal forms of proteins necessary for operation of neuronsproteins Proteins coagulate as large deposits in brain- Linked to human diseases – Kuru – Creutzfeldt-Jakob disease (CJD) Animal diseases – Scrapie in sheep – Bovine spongiform encephalopathy(mad cow disease)

22. Fig. 20.6, p. 314PrionDisease