Download - Virology Far
-
8/2/2019 Virology Far
1/28
VIROLOGY
Ridha Wahyutomo, MD
Dept. Clinical Microbiology andInfectious Disease
-
8/2/2019 Virology Far
2/28
Viruses are the smallest infectiousagents (20-300 nanometers)
Possess only one kind of nucleic acid,either DNA or RNA as their genome
Capable of replication only within
living cells (genetic parasites)
-
8/2/2019 Virology Far
3/28
3
-
8/2/2019 Virology Far
4/28
Viral Structure
VirusParticle
Covering
Capsid
Envelope
CentralCore
Nucleic
Acid
Others
-
8/2/2019 Virology Far
5/28
5
General Structure of
Viruses Size range
most
-
8/2/2019 Virology Far
6/28
Prions - misfolded proteins, contain no nucleic acid cause transmissible spongiform encephalopathies fatal
neurodegenerative diseases
common in animals: scrapie in sheep & goats
bovine spongiform encephalopathies (BSE), aka mad cowdisease
wasting disease
humans Creutzfeldt-Jakob Syndrome (CJS)
Extremely resistant to usual sterilization techniques
-
8/2/2019 Virology Far
7/28
7
Other noncellular infectiousagents
Satellite viruses dependent on otherviruses for replication
adeno-associated virus replicate only incells infected with adenovirus
delta agent naked strand of RNA expressedonly in the presence of hepatitis B virus
Viroids - short pieces of RNA, no proteincoat; only been identified in plants, so far
-
8/2/2019 Virology Far
8/28
Viral Structure: Covering
FUNCTIONS: Protects the nuclear material
Responsible for introduction of viral nucleicacid into a suitable host cell
Stimulates the immune system
-
8/2/2019 Virology Far
9/28
Viral Structure: Covering
- CAPSID CAPSID: The outer protective shell
The most prominent geometric feature
Composed of identical protein subunitsCAPSOMERS
Formed by spontaneous self-assembly ofcapsomers
-
8/2/2019 Virology Far
10/28
Viral Structure: Naked
Viruses
-
8/2/2019 Virology Far
11/28
Viral Structure: Covering -
ENVELOPE Formed when the viral particle carries
off a part of the host cells membrane
(any part of the endomembranesystem may be used)
SPIKES or PEPLOMERS
Protein spikes protruding through theenvelope from the capsid
Essential for attachment to the next host
-
8/2/2019 Virology Far
12/28
Viral Structure:
Enveloped Viruses
-
8/2/2019 Virology Far
13/28
Viral Structure: Central Core
Nucleic Acids Genetic materialof the particle
Viruses maycontain eitherDNA or RNABUTNOT BOTH
DNA or RNA mayexist as single ordouble-stranded
-
8/2/2019 Virology Far
14/28
Viral Morphology
Helical Icosahedral
-
8/2/2019 Virology Far
15/28
Viral Morphology
Enveloped Complex
-
8/2/2019 Virology Far
16/28
Modes of Viral Multiplication
Adsorption - binding of virus to specificmolecule on host cell
Penetration - genome enters host cell
Uncoating the viral nucleic acid is releasedfrom the capsid
Synthesis viral components are produced
Assembly new viral particles are constructed
Release assembled viruses are released bybudding (exocytosis) or cell lysis
-
8/2/2019 Virology Far
17/28
17
Release
budding exocytosis; nucleocapsid bindsto membrane which pinches off and shedsthe viruses gradually; cell is notimmediately destroyed
lysis nonenveloped and complex virusesreleased when cell dies and ruptures
Number of viruses released is variable
3,000-4,000 released by poxvirus >100,000 released by poliovirus
-
8/2/2019 Virology Far
18/28
Cytopathic effects - virus-induceddamage to cells
Changes in size & shape
Cytoplasmic inclusion bodies
Nuclear inclusion bodies Cells fuse to form multinucleated cells.
Cell lysis
Alter DNA Transform cells into cancerous cells
-
8/2/2019 Virology Far
19/28
19
Persistent Infections Persistent infections - cell harbors the
virus and is not immediately lysed
Can last weeks or hosts lifetime; several
can periodically reactivatechronic latentstate
measles virus may remain hidden in brain cellsfor many years
herpes simplex virus cold sores and genitalherpes
herpes zoster virus chickenpox and shingles
-
8/2/2019 Virology Far
20/28
20 Some animal viruses enter host cell and permanently alter
its genetic material resulting in cancertransformationof the cell.
Transformed cells have increased rate of growth,alterations in chromosomes, and capacity to divide for
indefinite time periods resulting in tumors. Mammalian viruses capable of initiating tumors are called
oncoviruses.
Papillomavirus cervical cancer
Epstein-Barr virusBurkitts lymphoma
-
8/2/2019 Virology Far
21/28
-
8/2/2019 Virology Far
22/28
22
Lysogeny Lysogeny results in the spread of the virus
without killing the host cell.
Phage genes in the bacterial chromosome
can cause the production of toxins orenzymes that cause pathologylysogenic conversion. Corynebacterium diphtheriae
Vibrio cholerae Clostridium botulinum
-
8/2/2019 Virology Far
23/28
Lysogeny
-
8/2/2019 Virology Far
24/28
Modes of entry
Respiratory tract though inhalation
Gastrointestinal tract
Skin
Sexual
Direct contact
Transfusion of blood
-
8/2/2019 Virology Far
25/28
Effects of virus on the
host cell CPE or cellular effect
Transformation of normal cell to
malignant cell
Latent infection
Clumping of RBC
-
8/2/2019 Virology Far
26/28
Some of the MedicallyImportant Viruses
Family Genus Common Nameof GenusMembers
Disease
DNA VirusesHerpesviridae Simplexvirus Herpes simplex
1&2 virusCold sores, genitalherpes
Varicella zostervirus
Chicken pox
Adenoviridae Mastadenovirus Human adenovirus Colds, URIPapovaviridae Papillomavirus Human
papillomavirus(HPV)
Warts
Hepadnaviridae Hepadnavirus Hepatits B virus Serum hepatitis
-
8/2/2019 Virology Far
27/28
Some of the Medically Important Viruses
Family Genus Common Name
of GenusMembers
Disease
RNA Viruses
Picornaviridae Enterovirus Poliovirus Poliomyelitis
Hepatovirus Hepatitis A virus Short-term
hepatitisRhinovirus Human rhinovirus Common colds
Togaviridae Alphavirus Rubella virus German measles
Flaviviridae Flavivirus Dengue fever virus Dengue fever
Filoviridae Filovirus Ebola virus Ebola feverOrthomyxoviridae Influenza virus Influenza virus Influenza
Paramyxoviridae Paramyxovirus Measles virus Measles
Rhabdoviridae Lyssavirus Rabies virus Rabies
Retroviridae Lentivirus HIV AIDS
Coronaviridae Coronavirus SARS virus SARS
-
8/2/2019 Virology Far
28/28