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Transcript
CHAPTER-II
Introduction to viruses
R.KAVITHA, M.PHARM,
LECTURER, DEPARTMENT OF PHARMACEUTICS,
SRM COLLEGE OF PHARMACY,
SRM UNIVERSITY, KATTANKULATHUR
.
Definition of a Virus
Sub microscopic entity consisting
of a single nucleic acid surrounded
by a protein coat and capable of
replication only within the living
cells of bacteria, animals or
plants.
Definition of a Virus
Obligate
Intracellular
Parasite
Virion Structure
Lipid Envelope
Nucleic Acid
Protein
Capsid
Virion
Associated
Polymerase
Spike
Projections
Virion Morphology
•
Simple Structure
•
Repetitive Structure
•
High Level of Redundancy
Virus Morphology
Helical
Icosahedral
Virus Replication
1 Virus attachment
2
3
1
5
4
5
6
4
2
3
7
8
7
6
8
and entry
Uncoating of virion
Migration of
genome nucleic
acid to nucleus
Transcription
Genome replication
Translation of virus
mRNAs
Virion assembly
Release of new
virus particles
Cytopathic Effect (cpe)
Adenovirus
Herpes virus
Transmission of Viruses
•
•
•
•
•
Respiratory transmission
9 Influenza A virus
Faecal-oral transmission
9 Enterovirus
Blood-borne transmission
9 Hepatitis B virus
Sexual Transmission
9 HIV
Animal or insect vectors
9 Rabies virus
Virus Tissue Tropism
•
Targeting of the virus to specific tissue
and cell types
•
Receptor Recognition
9 CD4+ cells infected by HIV
9 CD155 acts as the receptor for
poliovirus
In vivo Disease Processes
• Cell destruction
• Virus-induced changes to gene
expression
• Immunopathogenic disease
Acute Virus Infection
Amount of virus
Symptoms
Virus
Time
Generation of Novel Influenza A Viruses
Human H2N2
ANTIGENIC SHIFT
Genetic Reassortment
Avian H3N8
Point mutation of HA and NA
genes
ANTIGENIC DRIFT
Human H3N2
Viruses and Human Tumours
•
Epstein Barr Virus
9 Burkitt’s Lymphoma
•
Human papillomavirus
9 Benign warts
9 Cervical Carcinoma
•
Human T-cell Leukaemia Virus (HTLV-1)
9 Leukaemia
•
Hepatitis C virus
9 Liver carcinoma
Virus-induced tumours
Virus
Infection
[ ]
Uninfected
Cell
?
Uncontrolled cell
growth and tumour
formation
Virus-induced transformation
Normal cells
Transformed cells
Virus-Induced Tumours
•
•
•
•
Virus infects cell.
Virus nucleic acid, as DNA,
integrates into cellular genome.
Virus causes changes in cellular gene
expression.
Uncontrolled cell multiplication and
tumour formation.
Treatment and Prevention
of Virus Infections
•
Antivirals
•
Vaccines and immunisation
Antiviral Targets
•
Attachment/Entry
•
Nucleic acid replication
•
Virus protein processing
•
Virus maturation
Problems with Antivirals
• Identification of virus-specific
target.
• Generation of resistant variants.