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Chapter 13, part B

Chapter 13, part B. Viruses, Viroids, and Prions. Attachment, Penetration, and Uncoating. Figure 13.14. Release of an enveloped virus by budding. Figure 13.20. Multiplication of DNA Virus. Papovavirus. 1. Virion attaches to host cell. 7. Virions are released. Host cell. DNA. Capsid.

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Chapter 13, part B

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  1. Chapter 13, part B Viruses, Viroids, and Prions

  2. Attachment, Penetration, and Uncoating Figure 13.14

  3. Release of an enveloped virus by budding Figure 13.20

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

  5. Pathways of Multiplication for RNA-Containing Viruses Figure 13.17

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

  7. Cancer • 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.

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

  9. 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)

  10. Prions • 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 • PrPC, normal cellular prion protein, on cell surface • PrPSc, scrapie protein, accumulate in brain cells forming plaques

  11. Prions PrPSc PrPc 2 3 4 1 Lysosome Endosome 5 6 7 8 Figure 13.21

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

  13. Some Plant Viruses Table 13.6

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

  15. Double-stranded DNA, nonenveloped viruses • Mastadenovirus • Respiratory infections in humans • Tumors in animals

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

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

  18. Double-stranded DNA, nonenveloped viruses • 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

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

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

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

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

  23. Single-stranded RNA, + strand, nonenveloped • Arbovirusescan replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses • Hepatitis C virus

  24. Single-stranded RNA, + strand, nonenveloped • Coronavirus • Upper respiratory infections

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

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

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

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

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

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

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

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

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

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