Download Viral Vaccines

Virology 3rd Year
lecture1
College of Dentistry
Text book: Essenial Microbiology for Dentistry by Samaranayake
Introduction
Early period of identification
Recent identification
What is virus?
Virus" is from the Greek meaning for "poison" and was initially described by
Edward Jenner in 1798.
Obligatory intracellular parasite
Smallest infectious agent
Has simple structure
Has one type of nucleic acid
Not true cell
* lacks ribosome
* mitochondria
* cell wall
* ribosome
Viral structure
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Viral classification
 Old classification
Type of host: human, animal, plant..etc
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Tissue affinity: neurotropic, viscerotropic.etc
Geographical location: Coxsackie, Newcastle
 Recent classification
Nature of N.A: single, double stranded DNA or RNA
Shape : icosahedra, helical, complex
Envelop: enveloped or non-enveloped
Assembly: cytoplasm, nucleus
Physical and chemical nature: size, sensitivity, dimension
Viral replication
 Attachment:
 Penetration
 Uncoating
 Replication
 Assembly and Realase
Pathogenic effect on host cells
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Permissive cells
1.
2.
3.
Destruction (lysis)
Cell fusion (syncytia)
Inclusion bodies
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4.
Transformation
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Non permissive cells
1. Latent
2. Chronic (persistent)
3. Oncogenic
4. Slow
Viral cultivation
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Cell culture
1. Organ culture: slice of organ
2. Tissue culture: fragment of minced organ
3. Cell culture:
Primary CT: variety of cells with limited growth(5-10)
Diploid CT : single type divided up to 100 times derived from
embryo
Continuous CT: single type, indefinite growth, originated from
cancer
Cell culture serves purposes
1. Primary isolation
2. Vaccine production
3. Basic researches
 Embryonated eggs
 Laboratory animals
Route and spread of viral infection
 Vertical (congenital) ……. Rubella
 Viral zoonosis from animal to human, Orf
 Horizontal
1. Skin route ,
warts
2. Oral route
entrovirus
3. Respiratory route
rhinovirus
4. Urogenital route (sexually transmitted) CMV
Viral spread: direct, lymphatic, viraemia, CNS, PNS
Viral Diagnosis
Viral infection diagnosed by clinical criteria??
(By the time virus isolation has been made, patient is either died or recovered)
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Importance of viral diagnosis
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Management of the patient…. Rubella
Management of the patient’s contact.. HBV
Study the effectiveness of immunization HBV, HIV
Epidemiological surveillance
* screening of blood donors
* distribution of particular virus
* investigation of new outbreak
Viral diagnostic techniques
1. Direct
 Electron microscope (stool exam for Rota virus)
 Detection of viral antigen in infected cell by FAT
 Viral isolation in TC or lab. animals
2. Indirect
serological tests to identify unknown virus by known antibodies (ELISA, RIA,
FAT, CFT, etc
Interferons
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Low m.wt proteins confer cell ability to resist viral infection
Host specific
Non specific antiviral activity
Types
Alpha IF
Beta IF
Gamma IF
leukocytes
fibroblast
lymphocytes
Mechanism of interferons
Released IF from infected cell
interact with membrane of surrounding cells resulting in the production of:
 Endonucleases: degrade RNA
Protein kinases: block initiation
of protein synthesis
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Viral Vaccines
•Traditional approach
prevention rather than cure
•great success WHO program
eradication of small pox
Why we use vaccines?
• Cheaper
• Prophylactic
• Prevent congenital abnormalities
• Control disease and eradicate it
Types of Viral Vaccines
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1. Live attenuated vaccine
attenuation for human
 not natural host
 treated in cell culture
e.g. polio virus ;
disadvantage: revertant
s h e lf lif e
2. Killed or inactivated vaccines
safer than live e.g. Rabies
disadvantage:
complete inactivation
s h e lf lif e
3. Subunit vaccine
recombinant DNA technology
production of free N.A vaccine
e.g. HBs Ag
mutant
Viral chemotherapy
Type of viral infections
lytic
persistent
latent
Antiviral are nucleoside analogues
(precursors of DNA or RNA)
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Acyclovir (zovirax): affect on herpes viruses (inhibit DNA synthesis)
Amantadine : treatment of influenza virus (prevent shedding of virus)
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• Ribavirin : treatment of RSV, Lassa fever (inhibit binding of mRNA to ribosome)
•AZT
act on reverse transcriptase of HIV
Viriods
•Smallest agents
•Cause plant disease
•Naked, closed circular ss RNA
•Replicate using host cell enzymes
•Not associated with human disease
Prions
(proteinaceous infectious particles)
•Cause disease of long i.p.
•Neither viruses nor viriods
•Do not have either DNA or RNA
•Ability to self replicate
•Cause scrapie (CNS dis. of sheep)
•Resistant to heat & chemicals
• Transmitted to animals by ingestion
• Neurological transmission has been reported
Prions induced diseases
• K u ru
fatal neurological disease
• Creutzfeldt-jakob
chronic encephalopathy
** prions replicate first in lymph tissue
spongy like appearance
brain
intracellular vacuoles
Prevention & dental implication
• No treatment or vaccines
• Not consuming susceptible food
• Disposable equipments in dental practice should be incinerated
• Autoclave instruments at 131 for 18 min.
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