Quantification

Question 1

Virus quantification

Answer 1

counts the number of viruses in a specific volume to determine the virus concentration

Question 2

Virus titer

Answer 2

lowest concentration of virus that still infects cells. Also defined as the number of infectious units per ml of the sample

Question 3

Biological viral quantification tests

Answer 3

Depend on a virus particle initiating a successful replication cycle
Plaque assay
Pock assay
Various endpoint titration methods

Question 4

Physical viral quantification tests

Answer 4

Do  not depend on any biological activity of virus particle
electron microscopic particle counts
hemagglutination
immunological assays- ELISA
QPCR
flow cytometry

Question 5

Direct counting of virus particles in solution

Answer 5

Physical test
Direct particle count by transmission electron microscopy
The most direct method to determine the concentration of virus particles in a sample

Virus counter 2100

Question 6

Assessment based on antigen concentration

Answer 6

Physical test
Hemagglutination assay- forms MAT

Single radial immunodiffusion

Question 7

Assessment based on gene exprestion

Answer 7

Quantitative polymerase chain reaction (qPCR)

Physical test

Question 8

Traditional assays/biological assays

Answer 8

Monolayer plaque assay
Plaques formed
Unit: plaque forming units/ml

Question 9

Plaque

Answer 9

circular zone of necrotic cells surrounded by viable cells in a monolayer

Question 10

plaque forming units/ml

Answer 10

Measures the number of virus particles capable of forming plaques per unit volume.
Number of plaques does not equal number of viruses

Question 11

Pock Assay

Answer 11

Biological assay
Pock: necrotic area on chorioallantoic membrane (CAM) of embryonated egg
Unit: pock-forming units/ml

Question 12

Transformation assay

Answer 12

Biological assay
Quantitative determination of titers of oncogenic viruses
Unit: focus-forming units/ml

Question 13

Quantal assay

Answer 13

Biological assay

Endpoint: virus dilution that affects 50% of the test subjects

Question 14

TCID50

Answer 14

Tissue culture infectious dose which will infect 50% of the cell monolayers challenged with the defined inoculum