Download 2.Virus

Virus
Transmission
History
„
Iwanowski (1892)
„
„
Discovered viruses
Beijerinck (1898)
„
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Demonstrated potency of
viruses
Walter Reed (1901)
„
„
Twort & d’Herrelle
(1915)
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Frosh & Loefller (1898)
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Foot & mouth disease
Yellow fever
Discovered
bacteriophage
Viral Size
„
10 nm - 500 nm
Viral Structure
Capsids
„
Composed of protein
subunits called
capsomeres.
„
Functions
„
Protective
„
Recognition/attachment
to host cells
„
Introduction of nucleic
acid into host cell
Envelopes
„
Composition
„
„
„
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Lipids from host cell
membrane
Proteins
Glycoproteins
Function
„
„
Camouflage?
Recognition/attachment
to host cell
Genome
„
RNA or DNA
„
Double or singlestranded
„
Segmented or
nonsegmented
ds DNA
ss RNA
nonsegmented
ss DNA
ds RNA
segmented
Viral Shape
Helical
Isometric
(cubic)
Viral Shape
Complex
Classification of Viruses
„
Host range
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Very specific
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Enveloped or nonenveloped
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Type of nucleic acid
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Shape
Bacteriophage
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Viruses that infect bacteria.
Types of Bacteriophage
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Virulent
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Lytic multiplication cycle
Temperate
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Lysogenic multiplication cycle
E. coli host bacillus
Bacteriophage
Adsorption
Lytic Cycle
E. coli host bacillus
Bacteriophage
Bacterial Viral
DNA
DNA
Penetration
Adsorption
Lytic Cycle
E. coli host bacillus
Bacteriophage
Bacterial Viral
DNA
DNA
Penetration
Lytic
phase
Duplication of phage components;
replication of virus
genetic material
Adsorption
Lytic Cycle
E. coli host bacillus
Bacteriophage
Bacterial Viral
DNA
DNA
Adsorption
Penetration
Lytic
phase
Ec
lip
se
ph
as
e
Duplication of phage components;
replication of virus
genetic material
Assembly of
new virions
Lytic Cycle
E. coli host bacillus
Bacteriophage
Bacterial Viral
DNA
DNA
Lytic Cycle
Adsorption
Penetration
Lytic
phase
Ec
lip
se
ph
as
e
Duplication of phage components;
Maturation
replication of virus
genetic material
Assembly of
new virions
Lytic Cycle
E. coli host bacillus
Bacteriophage
Release of viruses
Bacterial Viral
DNA
DNA
Adsorption
Vi
rio
n
ph
as
e
Lysis of weakened cell
Penetration
Lytic
phase
Ec
lip
se
ph
as
e
Duplication of phage components;
Maturation
replication of virus
genetic material
Assembly of
new virions
Lysis
Burst size
http://www.oranim.ac.il/courses/microbiology/phagelab.htm
Lytic Multiplication Cycle
Lysogenic Cycle
lysogen
Lysogenic State
Prophage
Lysogenic Conversion
Bacterium
Disease
Phage encoded
property
Corynebacterium
diphtheriae
Diphtheria
Diphtheria toxin
Clostridium
botulinum
Botulism
Botulinum toxin
Streptococcus
pyogenes
Scarlet fever
Erythrogenic toxin
Propagation of Bacteriophage
Infect bacteria
Mix with molten
soft agar
plaque
Plate
Determining φ Titer
http://www.slic2.wsu.edu:82/hurlbert/micro101/pages/Chap9.html
Animal Viruses
Orfvirus
Ebola virus
Vaccinia virus
Animal Viruses
3 orders (-virales)
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21 families (-viridae)
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14 RNA virus families
7 DNA virus families
Families divided into genera (-virus)
Multiplication Cycle of An
Animal Virus
1. Attachment
Glycoprotein spikes
bind to receptors on
host cell surface
Attachment
QuickTime™ and a
Sorenson Video decompressor
are needed to see this picture.
Multiplication Cycle: Entry I
2. Entry (Endocytosis)
Multiplication Cycle: Entry II
2. Entry
(Fusion of cell membrane with viral envelope)
Multiplication Cycle
3. Uncoating
Nucleic acid is released
from nucleocapsid
Multiplication Cycle
4. Replication of Nucleic Acids & Proteins
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Viral proteins
A. DNA enters nucleus.
Cytoplasm
Viral DNA
A
B. DNA is transcribed.
C
Nuclear pore
B
C. RNA is exported to
cytoplasm & translated.
Viral mRNA
D
Nucleus
D. DNA is replicated in
nucleus.
Replicated
viral DNA
E. Viral DNA inserted into
host genome.
E
Mature
virus
Host DNA
Multiplication Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Viral proteins
Cytoplasm
Viral DNA
Nuclear pore
5. Maturation/Assembly
„ New nucleocapsids
self-assemble
Viral mRNA
Nucleus
5
Replicated
viral DNA
Mature
virus
Host DNA
Multiplication Cycle
6. Release of virus
Life Cycle of Retrovirus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Virus
A. Penetration & uncoating of
viral RNA.
A
(+)
Viral
RNA
(+) B
(+)
B. Translation of + RNA.
C. Synthesis of - RNA to
serve as template for
synthesis of new + RNA.
D. Synthesis of + RNA.
E. Assembly of new virus
particles.
(–)
C
Viral
proteins
D
(+)
(+)
(+)
(+)
E
Capsid
Cytoplasm
Nucleus
Damage to Host
„
Cytopathic effects
„
„
Syncytia
Inclusion bodies
Outcomes of
Animal Virus Infections
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Acute Infection
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Persistent Infection
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„
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Late complications following an acute infection
Latent infection
Chronic infection
Slow infection
Cell Transformation
Acute Infections
„
„
Short duration
Host normally develops long-lasting immunity
Nester et al (2007) Microbiology: A Human Perspective, 5th ed.,
McGraw-Hill, New York, NY, p. 342
Persistent Infections
Nester et al (2007) Microbiology: A Human Perspective, 5th ed.,
McGraw-Hill, New York, NY, p. 348
Persistent Infections
Nester et al (2007) Microbiology: A Human Perspective, 5th ed.,
McGraw-Hill, New York, NY, p. 348
Transformation of Host Cells
Viral Host Range
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Usually very narrow
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Can be broadened
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Phenotypic mixing
Genetic Reassortment
Phenotypic Mixing
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Viruses switch
protein coats.
Genetic Reassortment
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Occurs in viruses with segmented genomes.
Leads to antigenic shift.
Propagation of Animal Viruses
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Must have living cells
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Cell/tissue culture
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Embryonated chicken
eggs
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Live animals
Cell/Tissue Culture
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Primary culture
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Tissue prepared
directly from animal.
“normal” cells
Tumor cell lines
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Immortal cell lines
Embryonated Chicken Eggs
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Signs of viral propagation
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Death of embryo
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Pocks on membranes
Quantitation of Animal Viruses
Nester et al (2007) Microbiology: A Human Perspective, 5th ed., McGraw-Hill, New York, NY, p. 357
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Plaque assay
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Microscopic assay
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ID50 or LD50 assay
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Dilution at which 50% of
inoculated host cells are
infected or killed.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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Hemagglutination assay
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http://homepage.usask.ca/~vim458/virology/stud2006/k9flu/
hemagglutination_assay.jpg
+ hemagglutination
- hemagglutination
Useful for titering flu virus
Plant Viruses
Wheat mosaic virus
Tobacco mosaic virus
Spread of Plant Viruses
„
Enter via wound or
insect bite.
„
Spread from cell to
cell through
plasmodesmata.
Copyright © Mayang Murni Adnin, 2001-2005.
Prions
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Discovered by Stanly
Prusiner in 1982
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1997 Nobel Prize in Medicine
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Infectious proteins that attack
animals.
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Causes transmissible
spongiform encephalopathies
(TSE).
Spongiform Encephalopathies
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Humans
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Sheep
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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Scrapie
Cows
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Kuru
Creutzfeldt-Jakob
Gerstmann-Sträussler
Mad cow disease
Deer and Elk
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Chronic wasting disease
http://pathy.fujita-hu.ac.jp/~tsutsumi/photo/photo112-3.htm
Viroids
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Infectious RNA that
attacks plants.
http://www.dpvweb.net/dpv/showfig.php?dpvno=362&figno=02
„
Catalyze hydrolysis
of RNA.
http://www.kcom.edu/faculty/chamberlain/Website/Lects/Prions.htm