MHMP 2012 Unit 3 Introduction to Virology.pptx

Introduce basic virology subject including the morphology, criteria and the diseases related to the virus

1. Basic Medical Microbiology And Parasitology MHMP 2012 UNIT 3; VIROLOGY

2. Content Structure and classification of viruses Viral replication and life cycle Medical and industrial applications of viruses

3. Carta . . .

4. Viruses

5. Viruses, Viroids and Prions

6. Study of Viruses - Virology 5 Kingdoms Plantae Animalia Fungi Protista Monera

7. 5 Characteristics of Life Cells Grow and maintain their structure by taking up chemicals and energy from the environment Respond to their external environment Reproduce and pass on their organization to their offspring Evolve and Adapt to their environment

8. Viruses are: Acellular Obligate intracellular parasites No ATP generating system No Ribosomes or means of Protein Synthesis

9. Typical Virus 1. Nucleic Acid DNA or RNA (But never both) 2. Capsid (Coat Protein) Some Viruses: A. Envelope B. Enzymes

10. Host range Spectrum of host cells that a virus can infect Some viruses only infect: plants invertebrates protists fungi bacteria (Bacteriophages)

11. Host range Most viruses have a narrow host range Polio virus - nerve cells Adenovirus - cells in upper Respiratory Tract

12. Host range is determined by Viruses ability to interact with its host cell Binding Sites match Receptor Sites Binding Sites - on viral capsid or envelope Receptor Sites - on host cell membrane

13. Viral Size Virus size : 20 nm to 1,000 nm (0.02u-1u)

14. Viral Structure 1. Nucleic Acid 2. Capsid (Coat Protein) Nucleic Acid DNA or RNA (But never both) ssDNA, ds DNA ss RNA, ds RNA

15. Viral Structure ( cont ) Capsid (Coat Protein) protects viral genome from host endonucleases capsomeres Binding Sites Envelope derived from the host cell Binding Sites

16. Viral Morphology 1. Helical

17. Viral Morphology 2. Polyhedral

18. Viral Morphology 3. Enveloped Enveloped Helical Enveloped Polyhedral

19. Viral Morphology 4. Complex

20. Viral Classification Nucleic Acid Morphology Strategy for replication

21. Growing Viruses Bacteriophages Lawn of Bacteria on a Spread Plate Add Bacteriophages Infection will result in “Plaques” Clear zones on plate

22. Growing Viruses Animal Viruses A. Living Animals mice, rabbits, guinea pigs B. Chicken Embryos (Eggs) used to be most common method to grow viruses Still used to produce many vaccines (Flu Vaccine) C. Cell Cultures Most common method to grow viruses today

23. Cell Cultures 1. Primary Cell Lines die out after a few generations B. Diploid Cell Lines derived from human embryos maintained for up to 100 generations C. Continuous Cell Lines Transformed Cells (Cancerous Cells) may be maintained indefinitly HeLa Cells Henrietta Lax 1951 (Cervical Cancer)

24. Viroids and Prions Viroids Naked RNA (no capsid) 300 – 400 nucleotides long Closed, folded, 3-dimensional shape (protect against endonucleases ?) Plant pathogens Base sequence similar to introns

25. Prions Pro teinaceous in fectious particle 1982 Diseases Scrapie (sheep) Creutzfeldt-Jacob disease (CJD) Kuru (Tribes in New Guinea) Bovine Spongiform Encephalopathy (BSE) Mad Cow Disease

26. Viral Replication Bacteriophage 1. Lytic Cycle 2. Lysogenic Cycle

27. Lytic Cycle 1. Attachment- binding sites must match receptor sites on host cell 2. Penetration - viral DNA is injected into bacterial cell 3. Biosynthesis Genome replication Transcription Translation *Virus uses Host Cells enzymes and machinery

28. Lytic Cycle 4. Assembly (Maturation) viral particles are assembled 5. Release Lysis

29. Lysogenic Cycle 1. Attachment 2. Penetration 3. Integration Viral Genome is integrated into Host Cell Genome Virus is “Latent” Prophage

30. Lysogenic Cycle 4. Biosynthesis - Viral Genome is Turned On Genome replication Transcription Translation 5. Assembly 6. Release Lysis

31. Lysogenic Convergence Corynebacterium diphtheriae Streptococcus pyogenes Scarlet Fever Clostridium botulinum

32. Animal Virus Replication (non-enveloped virus) Attachment Binding Sites must match receptor sites on host cell Penetration Endocytosis (phagocytosis) Uncoating separation of the Viral Genome from the capsid

33. Animal Virus Replication (non-enveloped virus) Biosynthesis Genome Replication Transcription Translation Assembly Virus particles are assembled Release Lysis

34. Enveloped Virus Replication Biosynthesis Assembly Release Budding Attachment Penetration Uncoating

35. Retro Viruses (1975) DNA ---------> mRNA ------------> Protein Central Dogma of Molecular Genetics RNA -------> DNA --------> mRNA -------> Protein Normal Virus Retro Virus

36. Re verse Tr anscriptase (Retro) S ynthesis of DNA from an RNA template. RNA-dependent DNA polymerases, also known as reverse transcriptases , drive this process. O ccur naturally in both prokaryotic and eukaryotic organisms, as well as in retroviruses.

37. Retro Viruses 1. Many Cancer causing viruses 2. HIV Human Immunodeficiency Virus AIDS Acquired Immunodeficiency Syndrome

38. HIV VIRUS – VIRUS BERSAMPUL

39. HIV (Human Immunodeficiency Virus) AIDS Acquired Immune Deficiency Syndrome results in failure of the immune system Death usually results from an Opportunistic Infection HIV discovered in 1984 By who ? Luc Montagneir - Pasteur Institute

40. HIV Structure Retro Virus Nucleic acid - RNA (2 strands) envelope ( gp 120 binding sites) Reverse Transcriptase

41. HIV Infection (Cellular Level) 1. Attachment HIV gp 120 binding sites must match CD4 receptor sites CD4 Receptor Sites 1. Macrophages 2. Some cells of CNS 3. T4 Helper Cells (CD4 Cells)

42. Penetration Viral membrane and host cell membrane merge (fusion) Uncoating Capsid is removed and Viral Genome is exposed HIV Infection ( cont )

43. Integration Once viral genome is integrated - 2 possibilities: Nothing (virus is ‘latent’), Virus may be latent for days, weeks, months or years. Median latency time = 10 years HIV Infection ( cont )

44. Latent HIV provirus

45. 2. HIV Genome can be “expressed” or “Turned On” - Once HIV Genome is “turned on” death usually results within 2 years - What causes the HIV Genome to be “turned on”? - Other infections - Stress or shock to the system - Drug abuse - Alcohol abuse - Nutrition - Exercise (Lack of or too much?) - Sunburn ? - (Herpes Simplex 1) HIV Infection ( cont )

46. Once HIV Genome is “turned on” 5. Biosynthesis Genome replication Transcription Translation 6. Assembly Virus particles are put together 7. Release Budding

47. Modes of HIV Transmission HIV is transmitted by exposure to infected body fluids 4 Body Fluids Blood Semen Vaginal Secretions Breast Milk

48. How are these fluids transferred from one person to another? 1. High Risk Sexual Contact unprotected vaginal sex unprotected oral sex unprotected anal sex 2. Needles Intravenous Drug Abuse (sharing dirty needles) Accidental needle sticks

49. How are these fluids transferred from one person to another? 3. Blood to Blood Contact open sores or wounds Transfusions Organ Transplants Artificial Insemination 4. Mother to Child placenta as baby passes thru the birth canal breast milk

50. HIV and the Immune System 1. Cellular Immune System cells phagocytize microbes 2. Humoral Immune System antibodies to destroy or inactivate microbes

51. Clinical Stages of an HIV Infection 1. Acute Infection Initial infection of HIV (exposure to infected body fluids) Viremia Fever Headaches Weakness Muscle and joint aches May last for a couple of weeks Normal CD4 cell count 1200mm 3

52. 2. Asymptomatic disease CD4 cell count < 1000mm 3 Virus is “latent” inside CD4 cells Median latency period - 10 yrs. No signs or symptoms of illness (asymptomatic) HIV Positive - antibodies can be detected in the blood Seroconversion 6 to 8 weeks Clinical Stages of an HIV Infection ( cont )

53. 3. Symtomatic disease CD4 cell count < 600mm 3 Viral Genome is “turned on”, Symptoms begin to appear What causes HIV Genome to be turned on? - Other infections - drug abuse - Stress - nutrition - shock to the system - exercise - alcohol Clinical Stages of an HIV Infection ( cont )

54. Symptoms - chronic fatigue - diarrhea - ow-grade fever - weight loss - night sweats Susceptible to Infections bacterial pneumonia oral and vaginal yeast infections Meningitis tuberculosis Clinical Stages of an HIV Infection ( cont )

55. 4. Advanced disease (AIDS) CD4 cell count < 200mm 3 Severe Opportunistic Infections Pneumocysitis carinii pneumonia (PCP) Fungi Kaposi’s Sarcoma ( Cancer - Skin and Blood vessels) Toxoplasmosis (Brain) Protozoan Cryptosporidiosis (G.I. Tract) Protozoan Other Bacterial, Fungal and Viral Infections Clinical Stages of an HIV Infection ( cont )

56. Blood Test - ELISA E nzyme L inked I mmuno s orbant A ssay tests for HIV Antibodies If ELISA is positive, same sample is tested again If ELISA is positive again, then a Western Blot Test is done. Western Blot - test for Viral antigens

57. Treatment for HIV Infection No Cure AZT ( Azidothymidine) Thymine analog lacks a 3’ OH Chain Terminator Inhibits Reverse Transcriptase

58. Vaccine for HIV ? HIV mutates too rapidly Reverse Transcriptase causes at least 1 mutation each time it is used 1 million variants during Asymptomatic Disease 100 million variants during Advanced Disease (AIDS)

59. The end