1. Medical Technology Department, Faculty of Science, Islamic University-Gaza MB M ICRO B IOLOGY Dr. Abdelraouf A. Elmanama Ph. D Microbiology 2008 Chapter 13 Viruses, Viroids, and Prions

2. 2008 Viruses Viruses contain DNA or RNA And a protein coat Some are enclosed by an envelope Some viruses have spikes Most viruses infect only specific types of cells in one host Host range is determined by specific host attachment sites and cellular factors

3. 2008 Viruses Figure 13.1

4. 2008 Helical Viruses Figure 13.4a, b

5. 2008 Polyhedral Viruses Figure 13.2a, b

6. 2008 Complex Viruses Figure 13.5a

7. 2008 Viral Taxonomy Family names end in -viridae Genus names end in -virus Viral species: A group of viruses sharing the same genetic information and ecological niche (host). Common names are used for species Subspecies are designated by a number

8. 2008 Viral Taxonomy Herpesviridae Herpesvirus Human herpes virus 1, HHV 2, HHV 3 Retroviridae Lentivirus Human Immunodeficiency Virus 1, HIV 2

9. 2008 Growing Viruses Viruses must be grown in living cells. Bacteriophage s form plaques on a lawn of bacteria. Figure 13.6

10. 2008 Growing Viruses Animal viruses may be grown in living animals or in embryonated eggs. Figure 13.7

11. 2008 Growing Viruses Animal and plants viruses may be grown in cell culture. Continuous cell lines may be maintained indefinitely. Figure 13.8

12. 2008 Cytopathic effects Serological tests Detect antibodies against viruses in a patient Use antibodies to identify viruses in neutralization tests, viral hemagglutination, and Western blot Nucleic acids RFLPs PCR Virus Identification

13. 2008 Virus Identification Figure 13.9

14. 2008 AttachmentPhage attaches by tail fibers to host cell PenetrationPhage lysozyme opens cell wall, tail sheath contracts to force tail core and DNA into cell BiosynthesisProduction of phage DNA and proteins MaturationAssembly of phage particles ReleasePhage lysozyme breaks cell wall Multiplication of Bacteriophages (Lytic Cycle)

15. 2008 Figure 13.10.1 Attachment: Phage attaches to host cell. Penetration: Phage pnetrates host cell and injects its DNA. Merozoites released into bloodsteam from liver may infect new red blood cells 1 2 3 Bacterial cell wall Bacterial chromosome Capsid DNA Capsid Sheath Tail fiber Base plate Pin Cell wall Tail Plasma membrane Sheath contracted Tail core

16. 2008 Figure 13.10.2 4 Maturation: Viral components are assembled into virions. Tail 5 Release: Host cell lyses and new virions are released. DNA Capsid Tail fibers

17. 2008 One-step Growth Curve Figure 13.11

18. 2008 Lytic cyclePhage causes lysis and death of host cell Lysogenic cycleProphage DNA incorporated in host DNA

19. 2008 The Lysogenic Cycle Figure 13.12

20. 2008 Specialized Transduction Figure 13.13 Prophage exists in galactose-using host (containing the gal gene). Phage genome excises, carrying with it the adjacent gal gene from the host. Phage matures and cell lyses, releasing phage carrying gal gene. 1 2 3 Prophage gal gene Bacterial DNA Galactose-positive donor cell gal gene Phage infects a cell that cannot utilize galactose (lacking gal gene). 4 Galactose-negative recipient cell Along with the prophage, the bacterial gal gene becomes integrated into the new host’s DNA. 5 Lysogenic cell can now metabolize galactose. 6 Galactose-positive recombinant cell

21. 2008 AttachmentViruses attaches to cell membrane PenetrationBy endocytosis or fusion UncoatingBy viral or host enzymes BiosynthesisProduction of nucleic acid and proteins MaturationNucleic acid and capsid proteins assemble ReleaseBy budding (enveloped viruses) or rupture Multiplication of Animal viruses

22. 2008 Attachment, Penetration, and Uncoating Figure 13.14

23. 2008 Release of an enveloped virus by budding Figure 13.20

24. 2008 Multiplication of DNA Virus Figure 13.15 Virion attaches to host cell Virion penetrates cell and its DNA is uncoated Early transcription and translation; enzymes are synthesized 1 2 3 DNA Late transcription; DNA is replicated 4 Late translation; capsid proteins are synthesized 5 Virions mature 6 Capsid Papovavirus Host cell DNA Cytoplasm Virions are released 7 Capsid proteins mRNA

25. 2008 Pathways of Multiplication for RNA-Containing Viruses Figure 13.17

26. 2008 Multiplication of a Retrovirus Figure 13.19 Retrovirus penetrates host cell. Virion penetrates cell and its DNA is uncoated The new viral DNA is tranported into the host cell’s nucleus and integrated as a provirus. The provirus may divide indefinitely with the host cell DNA. 1 2 3 DNA Transcription of the provirus may also occur, producing RNA for new retrovirus genomes and RNA that codes for the retrovirus capsid and envelope proteins. 4 Mature retrovirus leaves host cell, acquiring an envelope as it buds out. 5 Capsid Reverse transcriptase Virus Two identical + stands of RNA DNA of one of the host cell’s chromosomes Provirus Host cell Reverse transcriptase Viral RNA RNA Viral proteins Identical strands of RNA

27. 2008 Activated oncogenes transform normal cells into cancerous cells. Transformed cells have increased growth, loss of contact inhibition, tumor specific transplant and T antigens. The genetic material of oncogenic viruses becomes integrated into the host cell's DNA. Cancer

28. 2008 Oncogenic DNA Viruses Adenoviridae Heresviridae Poxviridae Papovaviridae Hepadnaviridae Oncogenic Viruses Oncogenic RNA viruses Retroviridae Viral RNA is transcribed to DNA which can integrate into host DNA HTLV 1 HTLV 2

29. 2008 Latent Viral Infections Virus remains in asymptomatic host cell for long periods Cold sores, shingles Persistent Viral Infections Disease processes occurs over a long period, generally fatal Subacute sclerosing panencephalitis (measles virus)

30. 2008 Infectious proteins Inherited and transmissible by ingestion, transplant, & surgical instruments Spongiform encephalopathies: Sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Sträussler- Scheinker syndrome, fatal familial insomnia, mad cow disease PrP C, normal cellular prion protein, on cell surface PrP Sc, scrapie protein, accumulate in brain cells forming plaques Prions

31. 2008 Prions Figure 13.21 PrP c PrP Sc 1 2 34 5 678 Endosome Lysosome

32. 2008 Figure 13.22 Plant Viruses Plant viruses enter through wounds or via insects Viroids Viroids are infectious RNA; potato spindle tuber disease

33. 2008 Some Plant Viruses Table 13.6

34. 2008 Virus Families Single-stranded DNA, nonenveloped viruses Parvoviridae Human parvovirus Fifth disease Anemia in immunocompromised patients

35. 2008 Double-stranded DNA, nonenveloped viruses Mastadenovirus Respiratory infections in humans Tumors in animals

36. 2008 Double-stranded DNA, nonenveloped viruses Papillomavirus (human wart virus) Polyomavirus Cause tumors, some cause cancer

37. 2008 Double-stranded DNA, nonenveloped viruses Orthopoxvirus (vaccinia and smallpox viruses) Molluscipoxvirus Smallpox, molluscum contagiosum, cowpox

38. 2008 Simplexvirus (HHV1 and HHV 2) Varicellavirus (HHV 3) Lymphocryptovirus (HHV 4) Cytomegalovirus (HHV 5) Roseolovirus (HHV 6) HHV 7 Kaposi's sarcoma (HHV 8) Some herpesviruses can remain latent in host cells Double-stranded DNA, nonenveloped viruses

39. 2008 Double-stranded DNA, nonenveloped viruses Hepadnavirus (Hepatitis B virus) Use reverse transcriptase to produce DNA from mRNA

40. 2008 Single-stranded RNA, + strand, nonenveloped Enterovirus Enteroviruses include poliovirus and coxsackievirus Rhinovirus Hepatitis A virus

41. 2008 Single-stranded RNA, + strand, nonenveloped Hepatitis E virus Norovirus (Norwalk agent) causes gastroenteritis

42. 2008 Single-stranded RNA, + strand, nonenveloped Alphavirus Alphaviruses are transmitted by arthropods; include EEE, WEE Rubivirus (rubella virus)

43. 2008 Single-stranded RNA, + strand, nonenveloped Arboviruses can replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses Hepatitis C virus

44. 2008 Single-stranded RNA, + strand, nonenveloped Coronavirus Upper respiratory infections

45. 2008 Single-stranded RNA, – strand, one RNA strand Vesiculovirus Lyssavirus (rabies virus) Cause numerous animal diseases

46. 2008 Single-stranded RNA, – strand, one RNA strand Filovirus Enveloped, helical viruses Ebola and Marburg viruses

47. 2008 Single-stranded RNA, – strand, one RNA strand Paramyxovirus Morbillivirus Paramyxovirus causes parainfluenza, mumps and Newcastle disease

48. 2008 Single-stranded RNA, – strand, one RNA strand Hepatitis D virus Depends on coinfection with Hepadnavirus

49. 2008 Influenzavirus (Influenza viruses A and B) Influenza C virus Envelope spikes can agglutinate RBCs Single-stranded RNA, – strand, multiple RNA strands

50. 2008 Bunyavirus (CE virus) Hantavirus Single-stranded RNA, – strand, multiple RNA strands

51. 2008 Arenavirus Helical capsids contain RNA- containing granules Lymphocytic choriomeningitis VEE and Lassa Fever Single-stranded RNA, – strand, multiple RNA strands

52. 2008 Lentivirus (HIV) Oncogenic viruses Use reverse transcriptase to produce DNA from viral genome Includes all RNA tumor viruses Single-stranded RNA, two RNA strands, produce DNA

53. 2008 Double-stranded RNA, nonenveloped Reovirus (Respiratory Enteric Orphan) Rotavirus Mild respiratory infections and gastroenteritis Colorado tick fever