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