Quantification of Viruses

Question 1

Virus quantification counts the number of viruses in a specific volume to determine what?

Answer 1

Virus concentration

Question 2

What is the virus titer?

Answer 2

Lowest concentration of virus that still infects cells.

Question 3

What are the 2 types of viral quantification tests?

Answer 3

Biological

Physical

Question 4

Which type of viral quant test depends on a virus particle initiating a successful replication cycle?

Answer 4

Biological

Question 5

Plaque assays, Pock assays, and endpoint titration methods are examples of:

Answer 5

Biological quantification tests

Question 6

Electron microscope particle counts, hemagglutination, Immuno assays (ELISA), quantitative PCR, and flow cytometry are examples of:

Answer 6

Physical quantification tests

Question 7

What is the most direct method of determining the conc of virus particles in a sample?

Answer 7

Direct particle counts by TEM (physical test)

Question 8

Besides TEM, what is another way to directly count virus particles in solution?

Answer 8

Virus Counter 2100 (flow cytometry)

Question 9

What are examples of physical quantification tests based on antigen concentration?

Answer 9

Hemagglutination assay
ELISA
High Performance Liquid Chromatography
Single Radial Immunodiffusion (SRID)

Question 10

What quantification method works by amplifying viral DNA or RNA?

Answer 10

Quantitative PCR

Question 11

The ______ _____ _____ is a biological test that involves counting the number of necrotic plaques on a monolayer cell culture.

Answer 11

Monolayer plaque assay

Question 12

If a diluted solution has a PFU (plaque forming unit) of 500 pfu/ml, each ml of solution contains enough virus particles to form how many plaques?

Answer 12

500

Question 13

Each necrotic plaque on a monolayer cell culture represents cell lysis initiated by how many viral particles?

Answer 13

ONE

Question 14

A ____ _____ is a biological test that measures necrotic areas on the chorioallantoic membrane (CAM) of an embryonated egg.

Answer 14

Pock assay

Question 15

The ______ ______ is used to determine titers of oncogenic viruses.

Answer 15

Transformation assay

Question 16

The transformation assay measures focus-forming units/ml based on what characteristic of the cells?

Answer 16

Transformed cells lose contact inhibition and clump together. Foci (clumps) are counted to determine focus-forming units.

Question 17

_______ _____ measure viruses by determining the number of viruses needed to affect 50% of the test subjects. (Lethal Dose 50)

Answer 17

Quantal assays

Question 18

What is the TCID50?

Answer 18

Tissue culture infectious dose. (number of virus particles needed to infect half of the cell monolayers they contact)

Question 19

What is the formula for calculating TCID50? (Reed and Muench Method)

Answer 19

% inf above 50% - % inf below 50%