chapter 13, part b

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


Attachment, Penetration, and Uncoating

Figure 13.14


Release of an enveloped virus by budding

Figure 13.20


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


Pathways of Multiplication for RNA-Containing Viruses

Figure 13.17


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


• 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


• 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


• 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)


• 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


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


Some Plant Viruses

Table 13.6


Virus Families

• Single-stranded DNA, nonenveloped viruses• Parvoviridae

• Human parvovirus• Fifth disease

• Anemia in immunocompromised patients


Double-stranded DNA, nonenveloped viruses

• Mastadenovirus• Respiratory

infections in humans

• Tumors in animals



• Papillomavirus (human wart virus)

• Polyomavirus• Cause tumors,

some cause cancer



• Orthopoxvirus (vaccinia and smallpox viruses)

• Molluscipoxvirus• Smallpox,

molluscum contagiosum, cowpox


• 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




• Hepadnavirus (Hepatitis B virus)• Use reverse

transcriptase to produce DNA from mRNA


Single-stranded RNA, + strand, nonenveloped

• Enterovirus• Enteroviruses

include poliovirus and coxsackievirus

• Rhinovirus• Hepatitis A virus



• Hepatitis E virus

• Norovirus (Norwalk agent) causes gastroenteritis



• Alphavirus• Alphaviruses are

transmitted by arthropods; include EEE, WEE

• Rubivirus (rubella virus)



• Arboviruses can replicate in arthropods; include yellow fever, dengue, SLE, and West Nile viruses

• Hepatitis C virus



• Coronavirus• Upper respiratory

infections


Single-stranded RNA, – strand, one RNA strand

• Vesiculovirus • Lyssavirus (rabies

virus)• Cause numerous

animal diseases



• Filovirus• Enveloped,

helical viruses• Ebola and

Marburg viruses



• Paramyxovirus• Morbillivirus

• Paramyxovirus causes parainfluenza, mumps and Newcastle disease



• Hepatitis D virus• Depends on

coinfection with Hepadnavirus


• Influenzavirus (Influenza viruses A and B)

• Influenza C virus• Envelope spikes

can agglutinate RBCs

Single-stranded RNA, – strand, multiple RNA strands


• Bunyavirus (CE virus)• Hantavirus



• Arenavirus• Helical capsids

contain RNA-containing granules

• Lymphocytic choriomeningitis

• VEE and Lassa Fever



• 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


Double-stranded RNA, nonenveloped

• Reovirus (Respiratory Enteric Orphan)

• Rotavirus• Mild respiratory

infections and gastroenteritis

• Colorado tick fever

chapter 13, part b

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