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Flashcards in Intro to Virology Deck (20)
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Compare the attachment sites of enveloped vs. non-enveloped viruses.

Attachment sites in non-enveloped viruses have a 3D structure; while glycoprotein spikes in enveloped viruses serve that purpose.


Describe the significance of the negative (-) ss RNA strands and how they differ from the (+).

(-) ss RNA strands must be TRANSCRIBED first into message before being translated.


Define tissue tropism in regards to viral entry.

Tissue tropism refers to a specific cell that a virus will attach to due to its receptor.


Compare/contrast the mode of entry between enveloped and non-enveloped viruses into host tissues.

Non-enveloped viruses use 3D proteins to enable their endocytosis into the host cell. Enveloped viruses (2 mechs) can fuse with host membrane via glycoprotein-receptor interaction (uncoated).


Distinguish the way in which RNA and DNA viruses replicate in the host cell. What are the exceptions of each.

RNA viruses replicate in the cytoplasm (exc. influenza). DNA viruses replicate in the nucleus (exc. POX virus).


Briefly describe viral replication in 6 steps.

1. enters via receptors
2. Makes enzymes
3. makes more genome
4. makes structural proteins
5. packages new viral particles; assembly
6. envelope buds out of host cell for release


Describe the 2 ways in which new viral progeny can be released from host cell.

1.) Lysis
2.) Budding off - where virus acquires glycoproteins and envelope on the way out


Briefly describe the 4 effects that viruses have on host cells.

1. No apparent effect
2. Kill host cells (LYSIS)
3. Fuse infected cells (multi-nucleated GIANT cells)
4. Transform cells (MALIGNANT)


Describe what enables the fusion of virally-infected cells.

Glycoprotein spikes that were activated by the viral progeny facilitates fusion of infected cells.


Briefly describe the protocol for viral plaque assay in 3 steps.

1. Dilute a viral stock
2. infect a monolayer of cells
3. Each area of clearing represents a functional, LIVE PARTICLE


Define Hem-agglutination and how it can be used to detect a virus.

the ability to agglutinate RBCs (i.e. measles or influenza) will be shown as a pale sheen of RBCs in test tubes; negative result will show as a pellet at the bottom.


Define hemagglutination inhibition and the significance of a (+) result.

If the patient has antibodies against the virus, they will be neutralized and no hemagglutination will result. This is shown as a red pellet at the bottom of the tube.


Distinguish a virion from a virus.

A virion is a viral particle; whereas each virus has a specific morphology to its virion. For example, the polio virus has an "icosahedral virion"


What viral component do neutralizing antibodies bind to in the case of Polio virus?

Nucleocapsid protein


Define the limitation of serologic diagnosis of viral infections.

Presence of antibody in a single sample may not be sufficient for a diagnosis of current infection.


Which of the following assays will detect only infectious virions: ELISA, PCR, Hemagglutination, Plaque assay, Western Blot? Define it.

Plaque assay - a method to count the number of LIVE VIRAL particles that may be infectious


What is the function of nucleocapsid in all viruses?

Protect the genome from nuc leases


Where does the variation which creates multiple serotypes occur in viruses?

Structural variation of proteins at the virus surface


Differentiate the early phase from the late phase of the viral replication cycle.

Early phase = production of viral enzymes;
Late phase = production of structural proteins and assembly of new virions


What mode of immune defense does a virus escape by spreading from one cell to another by induction of uninfected cells with infected cells?

Neutralization of virions by antibody. This is possible since the virus doesn’t need to go into circulation to spread from one cell to the next.