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
• 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
• 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