Chapter 13, part B

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