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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Microbiology
B.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
Chapter 13, part BViruses, Viroids, and Prions
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Attachment, Penetration, and Uncoating
Figure 13.14
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Release of an enveloped virus by budding
Figure 13.20
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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 mature6
Capsid
Papovavirus
Host cell
DNA
Cytoplasm
Virions are released7
Capsid proteins
mRNA
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Pathways of Multiplication for RNA-Containing Viruses
Figure 13.17
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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
CapsidReverse 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
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• 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
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• 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
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• 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)
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• 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
Prions
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Prions
Figure 13.21
PrPc
PrPSc
1 2 3 4
5 6 7 8
Endosome
Lysosome
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• Plant Viruses
• Plant viruses enter through wounds or via insects
• Viroids
• Viroids are infectious RNA; potato spindle tuber disease
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Some Plant Viruses
Table 13.6
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Virus Families
• Single-stranded DNA, nonenveloped viruses
• Parvoviridae
• Human parvovirus
• Fifth disease
• Anemia in immunocompromised patients
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Double-stranded DNA, nonenveloped viruses
• Mastadenovirus
• Respiratory infections in humans
• Tumors in animals
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Double-stranded DNA, nonenveloped viruses
• Papillomavirus (human wart virus)
• Polyomavirus
• Cause tumors, some cause cancer
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Double-stranded DNA, nonenveloped viruses
• Orthopoxvirus (vaccinia and smallpox viruses)
• Molluscipoxvirus
• Smallpox, molluscum contagiosum, cowpox
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• 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
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Double-stranded DNA, nonenveloped viruses
• Hepadnavirus (Hepatitis B virus)
• Use reverse transcriptase to produce DNA from mRNA
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Single-stranded RNA, + strand, nonenveloped
• Enterovirus
• Enteroviruses include poliovirus and coxsackievirus
• Rhinovirus
• Hepatitis A virus
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Single-stranded RNA, + strand, nonenveloped
• Hepatitis E virus
• Norovirus (Norwalk agent) causes gastroenteritis
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Single-stranded RNA, + strand, nonenveloped
• Alphavirus
• Alphaviruses are transmitted by arthropods; include EEE, WEE
• Rubivirus (rubella virus)
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Single-stranded RNA, + strand, nonenveloped
• Arboviruses can replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses
• Hepatitis C virus
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Single-stranded RNA, + strand, nonenveloped
• Coronavirus
• Upper respiratory infections
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Single-stranded RNA, – strand, one RNA strand
• Vesiculovirus
• Lyssavirus (rabies virus)
• Cause numerous animal diseases
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Single-stranded RNA, – strand, one RNA strand
• Filovirus
• Enveloped, helical viruses
• Ebola and Marburg viruses
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Single-stranded RNA, – strand, one RNA strand
• Paramyxovirus
• Morbillivirus
• Paramyxovirus causes parainfluenza, mumps and Newcastle disease
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Single-stranded RNA, – strand, one RNA strand
• Hepatitis D virus
• Depends on coinfection with Hepadnavirus
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• Influenzavirus (Influenza viruses A and B)
• Influenza C virus
• Envelope spikes can agglutinate RBCs
Single-stranded RNA, – strand, multiple RNA strands
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• Bunyavirus (CE virus)
• Hantavirus
Single-stranded RNA, – strand, multiple RNA strands
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• Arenavirus
• Helical capsids contain RNA-containing granules
• Lymphocytic choriomeningitis
• VEE and Lassa Fever
Single-stranded RNA, – strand, multiple RNA strands
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• 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