Hepatitis_111008

Hepatitis_111008 - Hepatitis Biology 301 Fall 2008 Overview...

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Hepatitis Biology 301 Fall 2008
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Overview What is hepatitis? Subtypes Focus on Hepatitis A, B, and C Biological Mechanisms Transmission/Infection Diagnosis Prevention Treatment Case Studies
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What is Hepatitis? It is condition of the INFLAMMATION OF THE LIVER. Can be caused by toxins, excessive alcohol, certain drugs, and some viral or bacterial infections. Can lead to LIVER DYSFUNCTION and CIRRHOSIS. Most commonly, it is caused by a family of VIRUSES: Most Common: Hepatitis A Virus (HAV) Hepatitis B Virus (HBV) Hepatitis C Virus (HCV) Others, less common: Hepatitis D Virus (HDV) Hepatitis E Virus (HEV) HFV and HGV
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Hepatitis A: Biology Picornavirus—very SMALL (“pico” RNA) 28 nm in diameter Single stranded positive sense RNA genome Genome surrounded by a naked (unenveloped) icosahedral capsid. Replication: Binds to surface of HEPATOCYTE (liver cell) The RNA genome enters and remains in the CYTOPLASM, does NOT enter host nucleus. Acts like mRNA and immediately is used for VIRAL PROTEIN SYNTHESIS. RNA genome REPLICATES, and assembly into NEW VIRAL PROGENY occurs.
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Hepatitis B: Biology Hepa dna virus 40 nm in diameter Relaxed circular partly double- stranded DNA genome. Becomes Covalently Closed Circular ( cccDNA ) when it enters host cell nucleus. Host Cell = hepatocyte (liver cell) Viral envelope is host-derived Virus particles are also present in bloodstream. Very Stable virus: pH- and heat-resistant Can survive for 7 days outside of body Structures: DNA = partly double-stranded DNA Polymerase = for genome replication Core Angtigens: HB c Ag and
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Hepatitis B: Biology (Life Cycle) 1. Virus attaches and binds to HEPATOCYTE (by unknown receptor). 2. Core (with viral DNA) ENTERS cytoplasm and is UNCOATED. 3. Viral DNA enters host NUCLEUS 4. Forms cccDNA—used as a TEMPLATE to transcribe new VIRAL RNA. Does NOT integrate into host chromosome 5. In Cytoplasm, the viral RNA is translated into new VIRAL PROTEINS (antigens). 6. New VIRAL PROGENY are assembled and new viral DNA genome is made from the RNA intermediate. 7. New viral progeny bud off of host cell. Drugs Target the last steps Dienstag NEJM 2008 CYT NUC
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Hepatitis C: Biology Flavivirus Positive strand RNA virus with host-derived envelope. 30-60 nm in diameter. Less stable than HBV Stable for 16 hours to 4 days HCV binds to heptaocyte by either: the CD81 antigen low density lipoprotein (LDL) receptor Via its envelope glycoproteins Structural proteins Core proteins (on nucleocapsid) Envelope proteins
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Hepatitis C: Biology (Life Cycle) 1. HCV ATTACHES and ENTERS hepatocyte
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Hepatitis_111008 - Hepatitis Biology 301 Fall 2008 Overview...

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