1. The Influenza Virus
Hemagglutinin (HA) spikes used for attachment to host cells
Neuraminidase (NA) spikes used to release virus from cell
INFLUENZA ANIMATION
Figure 24.15

2. The Influenza Virus Antigenic shift Antigenic drift
Changes in HA and NA spikes
Probably due to genetic recombination between different strains infecting the same cell
Antigenic drift
Point mutations in genes encoding HA or NA spikes
May involve only 1 amino acid
Allows virus to avoid host cell antibodies
ANTIGENTIC SHIFT ANIMATION

3. Influenza Serotypes Type Antigenic Subtype Year Severity Common Name A
H3N2
H1N1
H2N2
H5N1
1889
1918
1957
1968
2004
2009
Moderate
Severe
Low
Spanish Flu
Asian Flu
Hong Kong Flu
Bird Flu
Swine Flu
Hemagglutinin types = H1 –H17
Neuraminidase types = N1-N9

4. DNA Viruses
Adenovirus – acute respiratory infections like the common cold
Poxvirus - cowpox, smallpox
Herpesvirus – 100 herpesviruses are known! Ex: HHV-1 and HHV-2 Simplexvirus – coldsores, HHV-3 – chickenpox and HHV-4 – mono
Papovavirus – warts. Some of these species are capable of causing cancer.

5. Viruses General Life Cycle:
Virus Replication
Viruses General Life Cycle:
Attachment
Penetration/entry
Biosynthesis
Assembly/Maturation
Release
Bacterial Viruses (phages)
Animal
Viruses
Transduction – when phage packages - it occasionally brings piece of host DNA with it.
Lytic
Lysogenic
Lysogen – a latently infected bacteria cell
Lysogenic Phages – a latent virus
Phage (short for bacteria phage) – virus that infects bacteria.
Plaques
replication
Transduction – when an error is made and package’s host DNA instead! – Usually random event
Non-infectious
Cell metabolism SLOWS OR STOPS
Host Cell Dies
Prophage – virus has incorporated it’s DNA into bacteria’s DNA

6. Multiplication of Animal Viruses
Attachment: Viruses attach to cell membrane
Penetration by endocytosis or fusion
Uncoating by viral or host enzymes
Biosynthesis: Production of nucleic acid and proteins
Maturation: Nucleic acid and capsid proteins assemble
Release by budding (enveloped viruses) or rupture

7. Attachment, Penetration, Uncoating
By pinocytosis
Figure 13.14a

9. Attachment, Penetration, Uncoating
By fusion
Figure 13.14b

11. Multiplication of DNA Virus
Figure 13.15

12. RNA Viruses ssRNA: + strand Picornovirus – polio Smallest viruses
Togavirus – arthropod-borne arboviruses
Enveloped (toga)
ssRNA: - strand
Rhabdovirus – rabies
Bullet shaped
Retrovirus
Lentivirus – HIV which cause AIDS

13. Sense Strand (+ Strand) RNA Virus
Figure 13.17a

14. Antisense Strand (– Strand) RNA Virus
Figure 13.17b

15. Double-Stranded RNA Virus
Figure 13.17c

16. Multiplication of RNA-Containing Viruses
Figure 13.17

17. Multiplication of a Retrovirus
Figure 13.19

19. Viral escape – presence or absence of envelope
Two methods by which mature viruses escape their host cell
1. Host cell lysis - releases naked or non-enveloped viruses
2. Budding – virus passes through cell membrane – takes part of host cell’s membrane – envelope is formed around capsid

20. Budding of an Enveloped Virus
Figure 13.20

21. Budding of an Enveloped Virus
Figure 13.20

22. Growing Animal Viruses
Animal viruses may be grown in living animals or in embryonated eggs
Figure 13.7

23. Bacteriophages

24. Figure 13.6 The complex shape of bacteriophage T4.
Bacteriophages (Phages)
Figure The complex shape of bacteriophage T4.
Head
Tail fibers
Tail
Base plate

25. A Viral One-Step Growth Curve
Figure 13.10

26. The Lytic Cycle Attachment: Phage attaches by tail fibers to host cell
Penetration: Phage lysozyme opens cell wall; tail sheath contracts to force tail core and DNA into cell
Biosynthesis: Production of phage DNA and proteins
Maturation: Assembly of phage particles
Release: Phage lysozyme breaks cell wall

27. Lytic Cycle of a T-Even Bacteriophage1 2 3
Figure 13.11

28. The Lytic Cycle
The lytic cycle is a phage reproductive cycle that culminates in the death of the host cell
The lytic cycle produces new phages and digests the host’s cell wall, releasing the progeny viruses
A phage that reproduces only by the lytic cycle is called a virulent phage
Bacteria have defenses against phages, including restriction enzymes that recognize and cut up certain phage DNA

29. Lytic Cycle of a T-Even Bacteriophage4
Figure 13.11

30. Figure 13.8 The lytic replication cycle in bacteriophages.

31. Figure 13.9 Pattern of virion abundance in lytic cycle.
The Lytic Cycle Progression
Figure Pattern of virion abundance in lytic cycle.

32. Growing Lytic Viruses Viruses must be grown in living cells
Bacteriophages form plaques on a lawn of bacteria
Figure 13.6

33. Results of Multiplication of Bacteriophages
Lytic cycle
Phage causes lysis and death of host cell
Can lead to Generalized transduction
Lysogenic cycle
Prophage DNA incorporated in host DNA
Phage conversion
Can lead to Specialized transduction

34. The Lysogenic Cycle
The lysogenic cycle replicates the phage genome without destroying the host
The viral DNA molecule is incorporated into the host cell’s chromosome
This integrated viral DNA is known as a prophage
Every time the host divides, it copies the phage DNA and passes the copies to daughter cells

35. The Lysogenic Cycle
An environmental signal can trigger the virus genome to exit the bacterial chromosome and switch to the lytic mode
Phages that use both the lytic and lysogenic cycles are called temperate phages

36. The Lysogenic Cycle
Figure 13.12

37. Generalized Transduction2 3 4 5 6
Figure 8.28

38. Generalized Transduction2 3 4 5 6
Figure 8.28

39. Specialized Transduction
Figure 13.13

40. Specialized Transduction
Figure 13.13

41. Viruses General Life Cycle:
Viral Replication
Viruses General Life Cycle:
Attachment
Penetration/entry
Biosynthesis
Maturation
Release
Bacterial Viruses (phages)
Animal
Viruses
Transduction – when phage packages - it occasionally brings piece of host DNA with it.
Lytic
Lysogenic
Lysogen – a latently infected bacteria cell
Lysogenic Phages – a latent virus
Phage (short for bacteria phage) – virus that infects bacteria.
Plaques
replication
Transduction – when an error is made and package’s host DNA instead! – Usually random event
Non-infectious
Cell metabolism SLOWS OR STOPS
Host Cell Dies
Prophage – virus has incorporated it’s DNA into bacteria’s DNA

42. hIV HUMAN IMMUNODEFICIENCY VIRUS

43. AIDS
1981: In United States, cluster of pneumonia and Kaposi's sarcoma (cancer of skin & blood vessels) discovered in young homosexual men
The men showed loss of immune function
1983: Discovery of virus causing loss of immune function – HIV

44. The Origin of AIDS
Crossed the species barrier (from chimps & monkeys) into humans in Africa in the 1930s through animal butchering for food
Patient who died in 1959 in Congo is the oldest known case
Spread in Africa as a result of urbanization
Spread worldwide through modern transportation and unsafe sexual practices

45. HIV Transmission HIV survives 6 hours outside a cell
HIV survives less than 1.5 days inside a cell
Infected body fluids transmit HIV via
Sexual contact
Breast milk
Transplacental infection of fetus
Blood-contaminated needles
Organ transplants
Artificial insemination
Blood transfusion

47. Structure of HIV and Infection of CD4+ Cell
Figure 19.13

48. HIV Attachment
Figure 19.13

49. Fusion of the HIV w/Cell
HIV Entry
Figure 19.13
Figure 19.13

50. HIV Infection
Figure 13.19

51. Active HIV Infection in CD4+ T Cells
Latent virus
Figure 19.14b

52. Active HIV Infection in Macrophages
Figure 19.15b

53. Latent HIV Infection in Macrophages
Figure 19.15a

54. Vaccine Difficulties Why?

55. Vaccine Difficulties
Mutations – retroviruses mutate more often than DNA viruses. Why?
Hint: compare enzymes involved.
Antibody-binding sites “hidden” when viruses are latent

56. The Progression of HIV Infection
Figure 19.16

57. Worldwide Distribution of AIDS and HIV
14,000 new cases worldwide per day!
Figure 19.17

58. Chemotherapy reverse transcriptase inhibitors Protease inhibitors
Fusion inhibitors
HAART – highly active antiretroviral therapy
Combination of drugs to counteract drug mutations
Cannot eliminate latent viruses; goal is to reduce viral load to level that immune system can handle

59. What antivirals did you find???

60. Other Ideas
Lactobacillis in vaginal microbiota that can produce bacteriocins that inhibit HIV
Virus decoys – HIV binds decoy instead of CD4
Boosting immunity – hormone to increase CD4 cells