LIFE CYCLES OF VIRUSES
• VIRUSES CAN EXHIBIT TWO TYPES OF
LIFE CYCLES.
1. THE LYTIC CYCLE
2. THE LYSOGENIC CYCLE
• SOME VIRUSES EXHIBIT ONLY THE LYTIC
CYLE.
• SOME VIRUSES CAN EXHIBIT BOTH LYTIC
AND LYSOGENIC CYCLES.
The Lysogenic Cycle
• VARIETY OF ANIMAL VIRAL INFECTIONS LYTIC OR LYSOGENIC VIRUSES?
TRANSDUCTION
HOW ANIMAL VIRUSES
ENTER ANIMAL CELLS
HOW ARE ANIMAL VIRUSES
CULTURED IN THE LABORATORY
• CLASSIFICATION OF MEDIA
• LIVING MEDIA AND NON-LIVING MEDIA
CELL CULTURE
HOW ARE CELL CULTURES
GROWN?
• CYTOPATHIC EFFECT - CPE
• SOME VIRUSES, WHEN THEY INFECT A
CELL, CHANGE THE MORPHOLOGY OF THE
CELL IN VERY SPECIFIC WAYS.
ANTIVIRAL AGENTS
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•
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•
GENERALIZATIONS
AMANTADINE
TAMIFLU (RELENZA)
A VARIETY OF NUCLEOSIDE ANALOGS
– ACYCLOVIR, AZT, 3TC, DDI, DDC
• PROTEASE INHIBITORS
• INTERFERONS
AMANTADINE
AVARIETY OF NUCLEOSIDE
ANALOGS
PROTEASE INHIBITORS AND INTERFERONS
HEPATITIS VIRUSES
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•
•
•
•
HAV – 50%
HBV – 30%
HCV – 20%
MODE OF TRANSMISSION
CHRONICITY - CHRONIC OR ACUTE
INFECTION
• TREATMENT/VACCINE
UNCONVENTIONAL
INFECTIVE AGENTS
• VIROIDS - 1967
• SMALL CIRCULAR MOLECULES OF SINGLE
STRANDED RNA
• COMPOSED OF 359 NUCLEOTIDES
• BEST STUDIED VIROID CAUSES DISEASE
IN POTATOES
• 10X SMALLER THAN SMALLEST KNOWN
VIRUS
PRIONS
• INFECTIOUS SELF REPLICATING PROTEINS
• COMPOSED OF ABOUT 250 AMINO ACIDS
• 100X SMALLER THAN THE SMALLEST
KNOWN VIRUS
• CAUSATIVE AGENT OF MAD COW DISEASE
(BOVINE SPONGIFORM
ENCEPHALOPATHY) AND TWO HUMAN
DISEASES
– CREUTZFELDT - JAKOB DISEASE (CJD)
– KURU