8 - VIRUSES General Characteristics Require LIVING cells...

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VIRUSES
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General Characteristics • Require LIVING cells for growth and replication (cell cultures, embryonated eggs, living animals/plants) • Have DNA or RNA… NEVER both! • Multiply by separate synthesis of nucleic acid and protein, combine to form virus particles • Size varies from 10 nm-300 nm
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?? What are viruses made of ??
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Basic Components Nucleic Acid -infectious genetic material Protein Coat Surface Antigens -protein or carbohydrate -highly variable -protective
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REPLICATION 1. Adsorption 2. Penetration and uncoating 3. Nucleic acid and protein synthesis 4. Assembly 5. Release
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REPLICATION West Nile Virus Replication 1. Adsorption 2. Penetration and Uncoating 3. Nucleic acid and protein synthesis 4. Assembly 5. Release
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How do we detect viral infections? 1.Detect the virus itself! 2.Detect the immune response…antibodies against the virus!
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Viral Diagnosis A. Detection in clinical specimens 1. Visualisation by Electron microscopy EM Coronaviridae EM Picornaviridae EM Poxviridae
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Viral Diagnosis A. Detection in clinical specimens 2. Cell culture (cytopathic effects, hemagglutination, immunofluorescence) Immunofluorescence of hepatitis C in cell culture Adenovirus induces hemagglutination Cytopathic effect of herpes simplex virus
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Viral Diagnosis A. Detection in clinical specimens 3. Detection of viral antigens (ELISA) Direct ELISA Viral antigen Antibody Fluorescent tag Indirect ELISA Viral antigen Antibody Fluorescent tag
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Viral Diagnosis B. Detection of patient’s immune responses • Antibody detection, presence or absence (ELISA) – IMMUNITY TEST • Rise in antibody titre or high antibody titre – DIAGNOSTIC TEST Viral antigen Antibody Fluorescent tag Determine titre
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What types of viruses will we learn about? 1. Viruses of the breathing 2. Enteric viruses 3. Viruses of diarrhea 4. Viruses of the rashes 1. Viruses of the glands 2. Viruses of the liver 3. Viruses of the brain 4. Viruses of the immune system…aka…HIV
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Respiratory Viruses Respiratory disease Different families 1. Influenza viruses 2. Parainfluenza viruses 3. Respiratory syncytial viruses 4. Rhinoviruses 5. Adenoviruses 6. Echoviruses, coxsackie viruses, herpes viruses (occasional respiratory tract infection)
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Influenza Viruses • Influenza virus type A: major epidemics • Influenza virus type B: milder disease • Produce haemagglutinin (diagnostic) • Frequent recombination = High antigenic variability = Pandemics
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Influenza Viruses • Clinical: – fever, variable respiratory symptoms – Infants and elderly more susceptible • Diagnosis: – Throat washings, naso-pharyngeal aspirate inoculated into cell culture • Serum: – Paired sera (acute and convalescent stage) • Prevention: – Annual vaccination especially for high risk groups
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25 April 2009 : Pandemic phase 3. Surveillance for flu should be intensified 27 April 2009 : Pandemic phase 4. The likelihood of a pandemic has increased 29 April 2009 : Pandemic phase 5. Countries activate pandemic plans
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8 - VIRUSES General Characteristics Require LIVING cells...

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