Introduction To Virology

INTRODUCTION to
Dr Retno Budiarti, dr, M.Kes

Microbiology Department
Medical Faculty Hang Tuah
University
CHARACTERISTICS
 Smallest infectious agent

 about 20 – 300 nm in diameter
 Totally depend upon a living cell, either
eukaryotic or prokaryotic, for replication and
existence
 Some viruses possess complex enzyme of
their own : RNA or DNA polymerases but they
cannot amplify & reproduce the information in
their own genomes without assistance
CHARACTERISTICS
 Contain only one kind of nucleic acid, RNA or

DNA
 Have a component a receptor-binding protein for
attaching to cells
 To see the virus electron microscope
 Growth need living cells/ tissues
 Only have certain enzyme for metabolism and
energy
 Easy mutated changes antigenic
property
 Multiplication different from bacteria
Terminology
 Virion : The complete virus particle, identic

with nucleocapsid or the nucleocapsid plus
a surrounding envelope
 Capsid : the protein shell that encloses the
nucleic acid genome
 Capsomer : morphologic unit on the
surface of icosahedral virus particles,
represent clusters of polypeptides
Terminology
 Nucleocapsid : the protein-nucleic acid

complex representing the packaged form
of the viral genome.
 Envelope : a lipid containing membrane
that surrounds some virus particles.
Virus Structure
Capsids, Nucleic Acid, Envelope
DNA VIRUSES
ENVELOPED NAKED
Double – stranded Double – stranded Single

stranded
Icosahedral Complex Icosahedral Icosahedral

HERPES POX PAPOVA PARVO
HEPADNA ADENO
RNA VIRUSES
Single – stranded Double – stranded
Positive – stranded (+) Negative – stranded (-)
Naked Enveloped Enveloped Naked
*PICORNA *TOGA BUNYA *REO

*CALICI *FLAVI ORTHOMYXO
CORONA PARAMYXO
RETRO RHABDO
ARENA
FILO
VIRAL REPLICATION
STRUCTURAL
PROTEINS
POSITIVE (+) RNA
TRANSLATION
ENZYMES
STRUCTURAL
PROTEINS
NEGATIVE (-) RNA POSITIVE (+)
TRANSCRIPTION RNA (mRNA) TRANSLATION
with virus RNA dependent
RNA polymerase ENZYMES
STRUCTURAL
PROTEINS
RNA DNA mRNA
REVERSE TRANSCRIPTION TRANSLATION
TRANSCRIPTION ENZYMES
STRUCTURAL
PROTEINS
DNA mRNA
TRANSCRIPTION TRANSLATION
ENZYMES
DETECTION OF VIRUS-INFECTED CELLS
1. Development of cytopathic effect (CPE) :
Morphologic changes in the cells : cell lysis, necrosis,
inclusion formation, giant cell formation, cytoplasmic
vacuolization
2. Appearance of a virus-encoded proteins :
Hemagglutinin of influenza viruses
3. Adsorpsion of erythrocytes to infected cells :
hemadsorption due to the presence of virus encoded
hemagglutinin (parainfluenza,influenza) in cellular
membranes
4. Detection of virus specific nucleic acid : PCR
5. Viral growth in an embryonated egg may result in
death of the embryo
INCLUSION BODY FORMATION
In the course of virus multiplication within cells
virus-specific structure : inclusion bodies
they are become larger than the
individual virus particle & often have an
affinity for acid dyes (eosin)
can be situated in the :
 nucleus
 cytoplasm
 both
CYTOPATHIC EFFECT OF VIRAL INFECTION
TRANSMISSION OF VIRAL INFECTION
 DIRECT CONTACT
droplet/aerosol
influenza virus
morbilli virus
smallpox virus
 GASTROINTESTINAL TRACT (ORALLY)
enterovirus
Hepatitis A, E virus
poliomyelitis virus
 ANIMAL BITE : rabies virus
 VECTOR : dengue virus
 PARENTERAL : Hepatitis B, C virus, HIV
PATHOGENESIS OF VIRAL DISEASES
Viral pathogenesis :
interaction of viral and host factors
leads to disease production
Virus pathogenic if : can infect and cause signs
of disease of the host
Virus virulent : produce more severe disease
Steps in viral pathogenesis :
Viral entry & primary replication

Viral spread and cell tropism
Cell injury & clinical illness
Recovery from infection
Virus shedding
Viral entry & primary
replication
 A virus must first attach to and enter cells
of one of the body surface
 Virus replicate at the primary site of entry
Viral spread and cell tropism
 Viruses produces disease at sites distant
from their point of entry
 The most common route Mechanisms of
viral spread is via the bloodstream of
lymphatics (viremia), in some case,
neuronal spread is involved.
Cell injury & clinical illness
 Destruction of virus infected cells in the
target tissues and physiologic alterations
produced in the host by the tissue injury
are partly responsible for the developnent
of disease
Recovery from infection
 Recovery mechanisms involve humoral
and CMI, inerferon and other cytokines
and othr host defense factors
 Recovery associated with viral clearence
Virus shedding
 Shedding occurs at different stages of
disease depending on the particular agent
involved.
 This is a necessary step to maintain a viral
infection in populations of hosts
IMMUNE RESPONSE OF VIRAL INFECTION
1. NONSPESIFC IMMUNE RESPONSE
- skin
- cillia/ mucose layer of respiratory tract
- gastrointestinal tract : gastric acid, bile,
peristaltic movement, limphoid tissue
- urinary tract urine stream
- conjunctiva of the eye tears
- phagocytosis PMN neutrophil
macrophages
reticuloendothelial
system
2. SPECIFIC IMMUNE RESPONSE
 HUMORAL RESPONE
* Neutralization Ab
immunity
- neutralize infectivity
- latent state
- prevent reinfection
 CELLULAR RESPONSE
Most important in viral infection
involve : T-helper, T- suppressor, T-
cytotoxic cells
DIAGNOSTIC METHODS OF VIRAL INFECTION
1. Clinical symptoms
2. Laboratory diagnosis
Typical clinical symptoms

 Polyomyelitis
 Chicken Pox
 Measles
 Mumps
Laboratory diagnosis
1. Electron microscope morphology
2. Light microscope special staining
~ type of virus
 Variola virus inclusion bodies
Gispen staining : PASCHEN BODIES
 Rabies virus specimen : brain
Sellers staining : inclusion bodies in nerve
cells NEGRI BODIES
 Molluscum contagiosum virus skin nodule
Lugol staining : inclusion bodies in
cytoplasm of epithel cell
MOLLUSCUM BODIES
Laboratory diagnosis :
3. Culture
specimen : depend on the disease
in vitro, in ovo, or in vivo
4. Serology
 Raise of antibody titer
 Antigen detection from the specimen
 Viral type identification :
agglutination, precipitation,
complement fixation test, neutralization,
inhibition haemagglutination, FIA, ELISA, RIA
PREVENTION AND TREATMENT OF VIRAL
INFECTIONS
1. VIRAL VACCINES
 Killed-virus vaccines
 Attenuated live-virus vaccines
 Future prospect :
- attenuation of viruses by genetic
mapping
- DNA vaccines
2. INTERFERONS
IFNs :
host-coded proteins of large cytokine
family
inhibit viral replication
produced by intact animal or cell
culture in response to viral infection
or other inducers
first line of defense against viral
infection
Thank you....

Introduction To Virology

Uploaded by

Copyright:

Available Formats

Introduction To Virology

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Introduction To Virology

Uploaded by

Copyright:

Available Formats

INTRODUCTION to

Dr Retno Budiarti, dr, M.Kes

 Smallest infectious agent

 Contain only one kind of nucleic acid, RNA or

 Virion : The complete virus particle, identic

 Nucleocapsid : the protein-nucleic acid

Double – stranded Double – stranded Single

Icosahedral Complex Icosahedral Icosahedral

Positive – stranded (+) Negative – stranded (-)

Naked Enveloped Enveloped Naked

PICORNA TOGA BUNYA *REO

Viral entry & primary replication

Typical clinical symptoms

You might also like