Micro J210 Virology 1

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Micro J210 Virology 1
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Micro J210 Virology 1
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  1. What is a virus?
    • -discovered in 1898
    • -Visualized only after discover of electron microscope in 1930
    • -A virus particle is also called a virion
    • -smaller than bacteria
  2. How are viruses unique?
    • -Their simple, very small, acellular
    • -The presence of either DNA or RNA, not both, in the same viral particle
    • -Their inability to reproduce independently of living, 2-50 genes.
  3. What is a virus composed of?
    • -DNA or RNA and protein capsid which surrounds the nucleic acid
    • -Combo of nucleic acid and capsid is called a nucleocapsid
  4. What is a naked virus?
    • -If it only has a protein capsid, it is naked
    • -The subunits are call capsomeres and the entire protein coat is called the capsid
  5. What is an envelope virus?
    • -Membrane derived from host cell
    • -in the envelope are viral proteins.
    • -Enveloped viruses are not very stable since envelope is it is a membrane.
    • -The envelope has protein and carbs, some from the host.
  6. What are the parts of a naked viruses?
    • -Capsid
    • -Nucleic acid
    • -Capsomere
    • -Nucleocapsid
    • -Virion
  7. What are the parts of an envelope virus?
    • -Capsid
    • -Nucleic acid
    • -Capsomere
    • -Nucleocapsid
    • -Virion
    • -Envelope
    • -Spike (envelope glycoproteins)
  8. What is the genetic makeup of a virus?
    • -DNA or RNA
    • -Single or Double stranded
  9. What are of the shapes of a viral capsid?
    • -Icosahedral (hexagonal, most common)
    • -Helical (spiral staircase-shaped)
  10. What is the viral growth rate?
    • -Viruses make separate parts within the host cell they are infecting and then assemble into many viral particles
    • -1 Human virus (12-72) = 100,00 virions
  11. What can a virus infect?
    • -Animal: Influenze
    • -Plant: Tobacco mosaic virus
    • -Bacteria viruses: Bacteriophage
  12. Why study viruses?
    • -Viral diseases have been some of the major concern for epidemics in humans. (Polio, rabies, smallpox, yellow fever)
    • -Leading cause of all human disease (Common acute respiratory, GI, Ebola, AIDS, Hepatitis C, Hantaviruses, SARS)
    • -Can be useful for gene therapy
  13. What are some viral diseases?
    -Measles, Mumps, Chicken pox (shingles, reactivation of diseases), small pox.
  14. What is the effect of viral infections on cells?
    • - Visible effects on the patient
    • 1. Direct damage of virus to cells, make cells different
    • 2. Host defense mechanisms (immunocytopathology) Sickness caused by immune system working
  15. What are the visible effects of viral pathology at the cellular level?
    • -Cell death
    • -Giant Cell formation, Syncytia
    • -Rounding up of cells
    • -Pilling up of cells
    • -Inclusion boides inside the cells
  16. What is cell death?
    • -CPE, cytopathic effect
    • -Lysis of host cell, viral plaques, bacteriophage
    • -Plaque assay of bacteriophage
  17. What is giant cell formation?
    • -CPE, cytopathic effect
    • -Syncytia, when cells fuse together to form large cells with many nuclei
    • -Sticks to the T cells so they cannot kill anymore
  18. What is round up of cells?
    • -III of viral CPE.
    • -Rounded up as result of infection
  19. What is pilling up of cells?
    • -CPE IV, Transformation, focus formation, wart
    • -Warts are small, painless growth
    • -Raised round or oval growth on the skin
    • -No discomfort unless in a bad area, goes away on their own within two years
    • -Venereal warts can cause cancer
  20. What is inclusion bodies?
    • -CPE V
    • -Visible by EM
    • -Lesion inside the cell
  21. What is the life cycle of a virus?
    • 1. Attachment
    • 2. Penetration
    • 3. Uncoating
    • 4. Replication of Nucleic acids
    • 5. Protein synthesis
    • 6. Assembly
    • 7. Release
  22. What is attachment?
    • -1 step in life cycle
    • -Lock and key, matching part
    • -Attachment proteins, specific surface proteins for each virus
    • -Cell specific-receptors
  23. What is penetration?
    • -Life cycle step 2, follows attachment
    • -Same step in bacteriophage with uncoating
    • 1. Endocytosis-Whole virus goes in and then the capsule is released
    • 2. Membrane fusion- just capsule is released
  24. What is uncoating?
    • Step 3 of life cycle
    • -Removal of membrane and capsid proteins, usually carried out by cellular enzymes that chew off the viral coat by lysosome function
  25. What is replication of nucleic acids?
    • -Step 4 of the life cycle
    • -DNA virus: nucleus, 1-2 viral and many cellular enzymes
    • -RNA virus: cytoplasm, always uses viral coded enzymes
  26. What is protein synthesis?
    • -Step 5 of life cycle
    • -Cytoplasm, both viruses use cellular ribosomes and the rest of the host cell protein synthetic machinery
  27. What is assembly?
    • -Step 6 of life cycle
    • -Nucleic acid and capsid proteins come together and undergo self assembly which is a spontaneous process
  28. What is release?
    • -Final step of life cycle
    • -Lysis of cell, naked virus
    • -Budding: enveloped virus: reverse process of membrane fusion. The virus acquires the membrane from the host cell but the membrane always contains viral protein that are required for specific attachment.
  29. What are the portals of viruses into the body?
    • -Skin: HPV, Warts
    • -Respiratory tract: Rhinovirus, common cold
    • -GI tract: Rotavirus, diarrhea
    • -Eye: Adenovirus, conjunctivitis
    • -Genitourinary tract: Herpes virus, genital herpes
    • -Direct entry: West nile, Hep B, Rubella, HIV
  30. What is the host-virus interaction?
    • -Spread of virus throughout the body-viremia-target organ
    • 1. Local replication at the site of entry, grow into large number
    • 2. Spread into blood, viremia
    • 3. Dissemination throughout the body-now any susceptible organ may be infected, can go in the lymphatic system to spread
    • 4. Disease: Symptoms are usually seen in cells of only the target organ. Observable clinical symptoms
  31. When are we asymptomatic?
    -After exposure to the virus, asymptomatic until the virus reaches the target organ and cause symptoms, and this is called the incubation time (period) of the virus.
  32. What is the incubation period?
    -The amount of time between infection with a virus or bacteria to beginnings of the symptoms
  33. What does the incubation period depend on?
    • -Distance between the site of infection and target organ. Short: 2 days for Flu, respiratory tract is both. Long: Weeks to months for rabies virus.
    • -Growth rate of the virus. Fast: 1 to 2 for flu. Slow: weeks to months for papillomavirus for warts
  34. What is an interferon?
    • -Host defense
    • -Innate
    • -Alpha: PMNS and macrophages
    • -Beta: produced by Fibroblasts
    • -Gama: produced by CD4 T cells
    • -Cellular protein
    • -Can work by warning neighboring cells
    • -Antiviral states in the neighboring cells: Degrades RNA, inhibit protein synthesis
  35. What is humoral response to viruses?
    • -Host defense
    • -Neutralizing antibodies
    • -Opsonization
    • -Complement fixation
  36. What is neutralizing antibodies?
    • -Host defense
    • -render virus harmless, coats virus particle, inhibit attachment, if partial binding-no penetration, attachment. Aggregation-reduction in virus infectivity
  37. What is opsonization?
    • -Host defense
    • -Enhancement of phagocytosis
    • -Antibodies with virus attach to PMNs which kill the virus
    • -Nk cells kill antibody coated viral particles by process of antibody dependent cellular cytotoxicity (ADCC)
  38. What is complement fixation?
    • -Host defense
    • -Activation of complement cascade
    • -Component of complement C3 is an opsonin
    • -Viral proteins present in infected cell membrane or viral envelope can by lysed by C6, 7, 8, which form the MAC attack
    • -ONLY enveloped viruses
  39. What is the role of CD4 (helper) and CD8 (T killer cell)?
    • -Cellular response, these cells act on virus infected cells, not directly on virus.
    • -CD4 T cell: They recognize the new viral antigens, proliferate and produce cytokines that activate B cells to release neutralizing antiviral antibodies
    • -Activate T killer cells.
  40. What is the importance of smallpox?
    • -WHO started in 1967 to eradicate smallpox from the earth, gone by 1977.
    • -Last naturally occurring in 1977, somalia.
    • -National stockpile of vaccine in case of bioterrorism.
  41. What is a DNA vaccine?
    • -Being tested
    • -Get into patient cells and express the gene produce
  42. What are other viral vaccines?
    • -Live attenuated, vaccinia
    • -Killed- Flu
    • -Sub- viral component: Hep B, Recombinant
  43. What are specific examples of human DNA viruses?
    • 1. Herpes Viruses
    • 2. Adenovirus: Conjunctivitis, diarrhea
    • 3. Paravovirus: Pox virus
    • 4. HPV, warts

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