Download Chapter 13b

TORTORA • FUNKE
• CASE
Microbiology
AN INTRODUCTION
EIGHTH EDITION
B.E Pruitt & Jane J. Stein
Chapter 13, part B
Viruses, Viroids, and Prions
Attachment, Penetration, and Uncoating
Figure 13.14
Release of an enveloped virus by budding
Note that the envelope is from
the host cell membrane plus any
protein the virus directed the cell
to make (antigens)
Figure 13.20
Multiplication of DNA Virus
Papovavirus
1 Virion attaches to host cell
7 Virions are released
Host cell
DNA
Capsid
DNA
2 Virion penetrates
cell and its DNA is
uncoated
Cytoplasm
6 Virions mature
Capsid proteins
mRNA
5 Late translation;
capsid proteins
are synthesized
4 Late transcription;
DNA is replicated
3 Early transcription and
translation; enzymes are
synthesized
Figure 13.15
Pathways of Multiplication for RNA-Containing Viruses
Compare + strand and strand RNA
•+ strand is like mRNA
• - strand is complementary
to + strand (like a DNA
template)
Figure 13.17
Multiplication of a Retrovirus
Reverse
Transcriptase
copies RNA code
into host DNA
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
Viral RNA
Identical
strands of
RNA
2 Virion penetrates
cell and its DNA is
uncoated
4 Transcription of the
Viral proteins
RNA
provirus may also occur,
producing RNA for new
retrovirus genomes and
RNA that codes for the
retrovirus capsid and
envelope proteins.
Provirus
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.
Figure 13.19
Cancer
• Activated oncogenes transform normal cells into
cancerous cells. Protooncogenes - not activated or just
a normal gene.
• 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.
Oncogenic Viruses
• Oncogenic DNA Viruses
• Adenoviridae
• Oncogenic RNA viruses
• Retroviridae
• Papovaviridae
• Viral RNA is
transcribed to DNA
which can integrate
into host DNA
• Hepadnaviridae
• HTLV 1
• Heresviridae
• Poxviridae
• HTLV 2
Oncogenic Viruses
Latent and “slow” viral infections
• 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)
Prions
• Infectious proteins
• Inherited and transmissible by ingestion,
transplant, & surgical instruments
• Spongiform encephalopathies: Sheep
scrapie, Creutzfeldt-Jakob disease and
mad cow disease
• Kuru (Tribes in New Guinea)
Prions
PrPSc
PrPc
1
2
3
4
Lysosome
Endosome
5
6
7
8
Figure 13.21
• Plant Viruses
• Plant viruses
enter through
wounds or via
insects
• Viroids
• Viroids are
infectious
RNA; potato
spindle tuber
disease
Figure 13.22
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
• Viral conjuncitivitis
Double-stranded DNA, nonenveloped viruses
• Papillomavirus
(human wart virus)
• Polyomavirus
• Cause tumors,
some cause
cancer
Double-stranded DNA, nonenveloped viruses
• Orthopoxvirus (vaccinia and smallpox viruses)
• Molluscipoxvirus
• Smallpox, molluscum contagiosum, cowpox
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
Double-stranded DNA, nonenveloped viruses
• 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
Single-stranded RNA, + strand, nonenveloped
• Hepatitis E virus
• Norovirus (Norwalk
agent) causes
gastroenteritis
Single-stranded RNA, + strand, nonenveloped
• Alphavirus
• Alphaviruses
are transmitted
by arthropods;
include EEE,
WEE
• Rubivirus (rubella
virus)
Single-stranded RNA, + strand, nonenveloped
• Arboviruses can replicate
in arthropods; include
yellow fever, dengue, SLE,
and West Nile viruses
• Hepatitis C virus
Single-stranded RNA, + strand, nonenveloped
• Coronavirus
• Upper respiratory
infections
Single-stranded RNA, – strand, one RNA strand
• Vesiculovirus
• Lyssavirus (rabies
virus)
• Cause numerous
animal diseases
Single-stranded RNA, – strand, one RNA strand
• Filovirus
• Enveloped,
helical viruses
• Ebola and
Marburg viruses
Marburg kills
BBC
Single-stranded RNA, – strand, one RNA strand
• Paramyxovirus
• Morbillivirus
• Paramyxovirus causes
measles
• parainfluenza, mumps
and Newcastle disease
Single-stranded RNA, – strand, one RNA strand
• Hepatitis D virus
• Depends on
coinfection with
Hepadnavirus
Single-stranded RNA, –
strand, multiple RNA strands
• 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
Single-stranded RNA, –
strand, multiple RNA strands
• Arenavirus
• Helical capsids
contain RNAcontaining
granules
• Lymphocytic
choriomeningitis
• VEE and Lassa
Fever
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
Double-stranded RNA, nonenveloped
• Reovirus (Respiratory
Enteric Orphan)
• Rotavirus
• Mild respiratory
infections and
gastroenteritis
• Colorado tick fever