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31 Cards in this Set
- Front
- Back
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what is the eclipse period in the life cycle of a virus?
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the time period during which there is no detectable virus in the blood
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what is the cytopathic effect? Can noninfectious viruses contribute to this?
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when virus infection in a tissue culture expands and many cells in the culture become infected or have already died; no
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what is the only way to directly count infectious units or live infectious virions in a clinical specimen?
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plaques due to Cytopathic effect
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what are plaque forming units?
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individual infectious virus from original sample
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do tumor cells cause CPE? Why/why not? How are these viruses detected?
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no; they do not cause lysis or death of cells; with abnormal proliferation
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what are inclusion bodies? What is their use clinically?
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nuclear or cytoplasmic aggregates of protein that are indicative of cells infected with viruses; they can be used to identify a specific virus
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what is the most specific way to identify a virus? How does this work? What is the limitation as to which types of virus this can ID?
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neutralization using specific Ab; virus that would normally cause plaques do not; only infectious viruses detected
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how can pairing amt of Ab in acute and convalescent sera from a patient be used to diagnose a viral disease?
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titrated against known viruses that are compatible with the clinical presentation.
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what is the term for a switch in antibody status from none against a virus to some against a virus?
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seroconversion
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which two types of test can be run in the lab for rapid viral diagnosis?
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PCR and fluorescent Ab
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what is the name of the identical building blocks of a virus' protein coat? What 2 types of symmetry are usually found in these?
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capsomers; helical or icosahedral
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in an unenveloped virus, what is the antigen?
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capsomer proteins
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how does an unenveloped virus normally enter a cell?
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by injecting the genome from the cell surface -- the capsid remains outside
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when is the eclipse period of a viral infection over?
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when new virions have been assembled and are then detectable in the serum of the patient
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do lattices normally form between viruses and Antibodies? Why or why not?
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no bc both Fab fragments bind to Ag on the same virus
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when is Ab not effective at neutralizing a virus?
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when the virus is replicating intracellularly and when infected cells are in close contact
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what is the nature of the protein coat for all RNA viruses that are simple nucleocapsids? DNA viruses?
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they are icosahedral; same
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in general, how stable are simple nucleocapsid viruses?
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very -- direct person to person contact is not required for transmission
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what is the host range of a virus? The tissue tropism?
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the species of animal that can be infected by a given virus; specific tissues that can be infected by a virus
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what happens when phenol is added to polio virus? Is the virus still infectious at this point?
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the RNA is isolated from the protein capsule; yes
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what type of polymerase enzyme does polio virus use?
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RNA-dependent RNA polymerase
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where is viral RNA made in polio virus?
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in the cytoplasm
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what is the effect of polio virus on host cell macromolecule synthesis?
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DNA, RNA, protein synthesis inhibited
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which, + or - ssRNA can act as mRNA?
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positive RNA
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once the polio virus genome is translated into a long protein, what occurs?
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protein chopped up into 8 functional proteins
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once proteins have been translated, what does the polio virus do? What is the replicative intermediate in these cells?
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uses RNA-dependent RNA pol to transcribe - RNA from the + ssRNA genome; the - RNA strand
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what is a viremia?
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infectious virions in the blood
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what is an incubation period for a viral infection?
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length of time between infection and the onset of specific symptoms
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if a virus' growth in cells causes no significant illness but produces a viremia that allows infection of other tissues, how long is the incubation period normally? How long will immunity last?
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weeks to months; decades or life
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if a virus' growth at the site of entry into the body (mucosal surfaces) causes illness, how long will the incubation period be? On which Ig is immunity dependent? How long does immunity last?
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days; IgA; 3-10 years
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if a virus causes no specific illness and spreads to other tissues via the neural pathway, how long will the incubation period be?
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long
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