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23 Cards in this Set
- Front
- Back
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Where do most all RNA viruses replicate and what are the major exceptions to this?
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Most replicate in the cytoplasm except for retroviruses and orthomyxoviruses
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How is RNA synthesized in RNA viruses?
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By viral RNA dependent RNA polymerases with 5' capping and 3' polyadenylation
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How do +ssRNA virions replicate their genomes?
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They use "multi-stranded replicative intermediates"; +ssRNA synthesize huge numbers of -ssRNA which is used to generate more +ssRNA via non-structural RNA dependent RNA polymerase
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How do -ssRNA virions replicate their genomes and form proteins?
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They use "multi-stranded replicative intermediates"; structural RNA polymerases convert the -ssRNA into +ssRNA which is used as mRNA and as a template for the production of more -ssRNA (replication)
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When do ssRNA genomes translate mRNA into proteins?
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As a very early step in replication
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How are the mRNA's translated in ssRNA virions?
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THey are translated into viral polyproteins which require protease activity to generate individual proteins
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What is a good target for anti-viral therapy for +ssRNA virions?
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A good target is the proteases that cleave the polyprotein generated by mRNA translation; occurs by protease inhibits specific for these proteases
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How is the genome of +ssRNA virions replicated?
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Via RNA polymerases that are newly synthesized from the translation of the genome
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How are -ssRNA virions replicated?
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Transcription of the negative strand by structural RNA dependent RNA polymerases with subsequent translation of the monocistronic mRNA; generated +ssRNA strands are used for replication of -ssRNA genome strands which are incorporated into the new virions
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What is the first step of retrovirus replication and what enzyme is used?
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The +ssRNA is transcribed into dsDNA via viral RNA dependent RNA polymerase which is incorporated into the cellular genome
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What makes retroviruses unique?
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They generate a provirus
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What happens after the retroviral provirus is generated?
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Transcription by the host using it's own DNA dependent RNA polymerase along with translation of the mRNA transcript, polyprotein cleavage and assembly in the cytoplasm
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What is genetic reassortment and what type of viruses are capable of this?
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It is the mixing of genome segments in RNA virions with segmented genomes; occurs when a cell is infected with two different virions
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What is polyploidy/heteroploidy?
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When more than one -ssRNA genome is packaged into a virion; possible with lipid-envelope RNA viruses
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What are pseudotype viruses?
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This is the phenotypic mixing of lipid-envelope viruses or capsid proteins of different serotypes of nake icosohedral virions; the phenotype and genotype are not the same
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What are defective interfering particles?
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Virions with mutated genomes that require the wild-type virus to help the mutated virus in infection; they decrease the number of wild-type virions generated and become enriched themselves
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What is a syncytia and in what virus is it typically seen?
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Multi-nucleated cells formed by membrane fusion of virus-infected cells withe adjacent uninfected cells; characteristic of all paramyxoviruses
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What are the cytopathic effects of viral replication?
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Cell destruction, syncytia, cell aggregation
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What method is used if there is minimal cytopathic effects?
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Immunofluorescense using anti-viral antibodies
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What is the hemagglutination inhibition assay?
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This assay uses RBCs to bind to surface proteins of viruses initiating agglutination and titering of specific anti-viral IgG in the sera
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In an ELISA assay of viral proteins, what is the difference between detection of IgM vs. IgG?
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IgM indicates current or recent infection whereas IgG is usally indicative of a past infection or immunization
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For what is the Western Blot assay used?
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The confirmatory test for patient sera which is HIV-antibody positive in an intial IgG capsture ELISA
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What methods are used to calculate the "viral load" of genome RNA or DNA particles from plasma/serum of HIV or Hep B/C infection?
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RNA viral load can be calculated with RT-PCR and DNA viral load with PCR or branched DNA assays
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