Virus Quantitation

Question 1

Describe virus quantification VS virus titer.

Answer 1

1. Virus quantification
   -counts # of viruses in vol to determine virus conc
2. Virus titer
   -lowest conc of virus that infects cell
   -# of infectious units per ml

Question 2

Describe the 2 types of viral quantification tests.

Answer 2

1. Biological = depend on virus particle initiating a successful replication cycle
   -plaque assays
   -pock assays
   -various endpoint titration methods
2. Physical = dont depend on biological activity
   -electron microscopy particle count
   -hemagglutination
   -immunological assays (ELISA)
   -quantitative PCR assays
   -flow cytometry

Question 3

Describe the two different physical tests to direct count viral particles in solution.

Answer 3

1. Transmission electron microscopy (TEM)
   -most direct method to determine conc of virus particles in sample
2. Virus counter 2100

Question 4

Describe the two types of physical tests used as an assessment based on antigen conc.

Answer 4

1. hemagglutination assay
2. Single radial immunodiffusion (SRID)

Question 5

Describe the physical test used as an assessment based on gene expression.

Answer 5

-quantitative polymerase chain receptor (qPCR)

Question 6

Describe the different types of traditional assays/biological assays used as a viral quantification test. (Not a physical test)

Answer 6

1. Monolayer plaque assay
2. Pock assay
3. Transforming assay
4. Quantal assay

Question 7

Describe monolayer plaque assay.

Answer 7

-plaque: circular zone of necrotic cells surrounded by viable cells in a monolayer
-units: plaque forming units/ml (PFU)
>measures # of virus particles capable of forming plaques per unit vol
>ex: if a solution has a PFU of 1000 PFU/ml -> every ml of solution has the ability to form a minimum of 1000 plaques

Question 8

Describe pock assay.

Answer 8

-pock: necrotic area on chorioallantoic membrane (CAM) of embryonated egg
-unit: pock forming units/ml

Question 9

Describe transforming assay.

Answer 9

-quantitative determination of titers of oncogenic virus
-unit: focus forming units/ml

Question 10

Describe quantal assay.

Answer 10

-endpoint: virus dilution that affects 50% of test subjects
>TCID50 = tissue culture infectious dose that infect 50% of cell monolayer challenged w defined inoculum