Virology- Basics 2
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- Can non-infectious virions in a virus sample contribute to CPE in tissue culture?
- No
- What is the advantage of using CPE?
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CPE is the only method to directly count infectious units, or live infectious virions in a clinical/ laboratory specimen.
BUT IT IS NOT SPECIFIC-ONLY TELL YOU OF THE VIRAL PRESENCE IN THE CULTURE - What are plaques forming units (PFU)?
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PFU are isolated zones of infection in the tissue culture.
These zones represent the cell-to-cell spread of virus from the originally infected cell at the heart of the plaque. - What does the agar medium do in the tissue culture forming PFU?
- It prevents virions from moving around in the tissue culture by diffusion, but will allow the cell-to-cell spread of the virus infection.
- How does tumor virus infection manifest in a tissue culture?
- Abnormal proliferation of cells will result in vast piles or mountains of cells.
- What is an inclusion body?
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When virus infected cells are stained histologically the sites of viral replication or assembly can show up as an inclusion body.
The cellular location (nucleus or cytoplasm) may be characteristic of a particular virus. - What are some detection/ identification methods of viruses?
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Virus cultures
Immunological methods (antibody against virion; may attach fluorescent abs)
PCR (identify viral nucleic acid)
Antibody tests (detect ab against a certain virus) - What are the most common ways of detecting the reaction of virons using specific antibody?
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Neutralization
Complement fixation
Hemagglutination inhibition
Fluorescent ab
Radioimmunoassay, ELISA, etc. - Neutralization
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The most specific way of conclusively identifying a virus along with PCR.
Specific ab is used to identify the virion.
Virions complexed with ab neutralized in their infectivity --> can't induce any PFU or CPE in tissue clutlre. - What is seroconversion?
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The change in ab status from having no ab against a certain virus to having this ab.
Seropositive vs. seronegative - Paired acute vs. Convalescence
- Before immune response vs. after immune response
- Window period
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Between paired acute and convalescent periods.
i.e. infected but not yet detectible ab against the specific ag. - What are some rapid diagnosis methods?
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1) Viral protein atigen can be detected using fluorescent ab.
2) Viral nucleic acid can be identified by the PCR.