chapter 13, part b
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
MicrobiologyB.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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Release of an enveloped virus by budding
Figure 13.20
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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
DNACytoplasm
Virions are released7
Capsid proteins
mRNA
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Pathways of Multiplication for RNA-Containing Viruses
Figure 13.17
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Prions
Figure 13.21
PrPc
PrPSc
1 2 3 4
5 6 7 8
Endosome
Lysosome
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.22
• Plant Viruses• Plant viruses
enter through wounds or via insects
• Viroids• Viroids are
infectious RNA; potato spindle tuber disease
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Some Plant Viruses
Table 13.6
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Virus Families
• Single-stranded DNA, nonenveloped viruses• Parvoviridae
• Human parvovirus• Fifth disease
• Anemia in immunocompromised patients
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Mastadenovirus• Respiratory
infections in humans
• Tumors in animals
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Papillomavirus (human wart virus)
• Polyomavirus• Cause tumors,
some cause cancer
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Orthopoxvirus (vaccinia and smallpox viruses)
• Molluscipoxvirus• Smallpox,
molluscum contagiosum, cowpox
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded DNA, nonenveloped viruses
• Hepadnavirus (Hepatitis B virus)• Use reverse
transcriptase to produce DNA from mRNA
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Enterovirus• Enteroviruses
include poliovirus and coxsackievirus
• Rhinovirus• Hepatitis A virus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Hepatitis E virus
• Norovirus (Norwalk agent) causes gastroenteritis
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Alphavirus• Alphaviruses are
transmitted by arthropods; include EEE, WEE
• Rubivirus (rubella virus)
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Arboviruses can replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses
• Hepatitis C virus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, + strand, nonenveloped
• Coronavirus• Upper respiratory
infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Vesiculovirus • Lyssavirus (rabies
virus)• Cause numerous
animal diseases
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Filovirus• Enveloped,
helical viruses• Ebola and
Marburg viruses
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Paramyxovirus• Morbillivirus
• Paramyxovirus causes parainfluenza, mumps and Newcastle disease
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Single-stranded RNA, – strand, one RNA strand
• Hepatitis D virus• Depends on
coinfection with Hepadnavirus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Influenzavirus (Influenza viruses A and B)
• Influenza C virus• Envelope spikes
can agglutinate RBCs
Single-stranded RNA, – strand, multiple RNA strands
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Bunyavirus (CE virus)• Hantavirus
Single-stranded RNA, – strand, multiple RNA strands
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Arenavirus• Helical capsids
contain RNA-containing granules
• Lymphocytic choriomeningitis
• VEE and Lassa Fever
Single-stranded RNA, – strand, multiple RNA strands
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• 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
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Double-stranded RNA, nonenveloped
• Reovirus (Respiratory Enteric Orphan)
• Rotavirus• Mild respiratory
infections and gastroenteritis
• Colorado tick fever