Special Lab - Virology

Question 1

virus

Answer 1

• submicroscopic
• requires electron microscopy
• obligate intracellular pathogen
• infect animals, plants, and bacteria

Question 2

virions or virus particles are made up of three parts:

Answer 2

• inner nucleic acid core made up of DNA or RNA
• capsid = protein coat protecting inner nucleic acid
• envelope = lipid-rich outer coating that protects some larger viruses

Question 3

enveloped viruses

Answer 3

tend to be more fragile; die when exposed to environment or dry out
- herpes virus, influenza
- require close contact or moist aerosol droplets for transmission

Question 4

non-enveloped viruses

Answer 4

hardy and able to survive for long periods
- hep B

Question 5

viral replication steps

Answer 5

• adsorption
• penetration
• uncoating = shed its protein coat and genome is released
• synthesis = released genome directs the host cell to ceat viral components
• maturation = viral particles assemble and mature within cell
• release = virus departs host either by lysis or budding (enveloped virus)

Question 6

cardinal rules in specimen collection for virus detection

Answer 6

• obtain specimen early in disease process (blood, body fluids, sputum, stool, urine, etc.)
• appropriate means of transport; cool and moist in high protein media with antibiotics if contaminated with normal flora
• if delayed processing = store at 4C
• proper specimen required from affected site (ex: diarrhea = submit feces)

Question 7

direct detection in clinical material

Answer 7

• not as sensitive as culture but quick
• microscopy looking for CPE
• electron microscopy
• immunofluorescence staining
• EIA

Question 8

CPE

Answer 8

cytopathic effects
some viruses show specific cell changes or cytopathic effects that can be used to ID virus
ex: HSV in cell culture spreads to adjacent cells very quickly forming a cluster or plaque of infected cells and it grows on many diff cell types

Question 9

nucleic acid-based detection

Answer 9

• short TAT
• high sensitivity
• quantitative
• multiplex (multiple viruses at once)
• expensive!!! so only in high vol or centralized labs
• hybridization assay, PCR, branched DNA, flow cytometry, etc.

Question 10

isolation of virus in culture

Answer 10

• specific CPE in cell cultures can be used for presumptive ID
• cell culture (most common), animal inoculation, and embryonated eggs (rare)

Question 11

serological antibody assays

Answer 11

• looks for the host’s response to virus (not specifically looking for virus)
• since host response baries and immunocomp = minimal response … testing may be inaccurate
• used for non-culturable agents = hepatitis, titres (immune status), transplant patient monitoring or epidemiological studies

Question 12

common antivirals

Answer 12

acyclovir
inteferon-alpha
amantadine