Virus quantitation Flashcards
virus quantification
counts number of viruses in a specific volume to determine the virus concentration
virus titer
lowest concentration of virus that still infects cells - can be number of infectious units/mL of sample
2 types of viral quantification test
biological and physical
biological test
depends on virus particle initiating a successful replication cycle
EX: plaque assay, pock assay, endpoint titration methods
physical test
does not depend on any biological activity of the virus
EX: EM counts, hemagglutination, immunological assays (ELISA), PCR and flow cytometry
direct counting of viral particles in solution (2)
- Transmission electron microscopy - most direct method
- Virus counter 2100
viral quantification based on AG concentration (2)
- hemagglutination assay
- Single radial immunodiffusion (SRID)
viral quantification based on gene expression (1)
quantitative polymerase chain reaction (qPCR)
Biological assay
monolayer plaque assay
plaque definition
unit of
plaque: circular zone of necrotic cells surrounded by viable cells in a monolayer
unit: plaque-forming units/mL (PFU) = minimum # virus in sample to form X amount of plaques
EX: if a solution has PFU of 1000 pfu/mL then every mL has enough virus to form 1000 plaques.
biological assay
pock assay
pock definition
unit
pock: necrotic area on chorioallantoic membrane of embryonated egg
unit: pock forming units/mL = min # virus present in sample to produce x pock forming units
biological assay
Transformation assay definition
unit
quantitative determination of titers of oncogenic viruses —-cancerous cells pile up on each other
unit: focus-forming units/mL
biological assay
Quantal assays endpoint
virus dilution that affects 50% of the test subject
TCID50 =
tissue culture infectivity dose50, infectious dose which will infect 50% of the cell monolayers challeneged with the defined inoculum
