Virus Quantitation

Question 1

Virus Quantification

Answer 1

Count the number of viruses in a specific volume to DETERMINE THE VIRUS CONCENTRATION

Question 2

Virus Titer

Answer 2

The LOWEST concentration of a virus that still infects cells. Also defined as the NUMBER OF INFECTIOUS UNITS PER mL OF SAMPLE.

Question 3

What are the two types of virus quantification tests?

Answer 3

1) Biological

2) Physical

Question 4

Biological virus quantification tests depends on what?

Answer 4

Depends on a virus particle to initiate a successful replication cycle.

Question 5

T/F: A Physical virus quantification test DOES NOT depend on any biological activity of the virus particle

Answer 5

True

Question 6

List the biological quantification tests

Answer 6

1) Plaque assays
2) Pock assays
3) Various endpoint titration methods
4) Transformation assay
5) Quantal assay

Question 7

Monolayer Plaque Assay- Is this a biological or physical virus quantification test?

Answer 7

Biological

Question 8

Plaque

Answer 8

A circular zone of necrotic cells surrounded by viable cells in a monolayer
(part of Plaque assay - a biological virus quantification test)

Question 9

What does Plaque- forming units/ mL (PFU) measure?

Answer 9

Measures the number of virus particles capable of forming plaques per unit volume.

Question 10

If a solution has a PFU ( plaque- forming units) of 1000 pfu/ mL, then every mL of solution contains enough virus to form, how many plaques?

Answer 10

1000 plaques

Question 11

Pock

Answer 11

Necrotic area on chorioallantoic membrane (CAM) of embryonate egg. (unit: Pock-forming unit/ mL)
(part of Pock assay - a biological virus quantification test)

Question 12

Transformation assay

Answer 12

A biological quantification test that quantitatively determines titers of ONCOGENIC VIRUSES!

Question 13

Endpoint

Answer 13

Virus dilution that affects 50% of the TEST SUBJECTS.

part of quantal assay - a biological virus quantification test

Question 14

TCID50

Answer 14

The tissue culture infectious dose which will infect 50% of the CELL MONOLAYER challenged with the defined inoculum.
(part of quantal assay - a biological virus quantification test)

Question 15

List Physical quantification tests

Answer 15

1) Electron microscopic particle counts
2) Hemagglutination
3) Immunological assay, such as ELISA
4) Quantitative PCR assay
5) Flow cytometry

Question 16

Which of the following is NOT a biological virus quantification test?

A. Pock assay
B. ELISA
C. Plaque assay
D. Various endpoint titration methods

Answer 16

B. ELISA – This is a physical virus quantification test.

Question 17

Which of the following is(are) physical virus quantification tests?

A. Flow cytometry
B. Hemagglutination
C. ELISA (Immunological assay)
D. Electron Microscopic particle counts 
E. Quantitative PCR assay
F. Pock assay 
G. Answers A. through E. are correct 
H. All of the above are correct

Answer 17

G. Answers A - E are correct

Question 18

Which physical virus quantification test(s), use(s) direct counting of virus particles in solution?

Answer 18

1. Direct particle counts by TEM (Transmission Electron Microscopy)
2. Virus Counter 2100

Question 19

Which physical virus quantification test(s), use(s) assessment based on antigen concentration?

Answer 19

1. Hemagglutination

2. Single Radial Immunodiffusion (SRID)

Question 20

Which physical virus quantification test(s), use(s) assessment based on gene expression?

Answer 20

Quantitative PCR assays

Question 21

Which virus quantification test is the MOST DIRECT method to determine the concentration of virus particles in a sample?

Answer 21

Direct particle counts by TEM (Transmission Electron Microscopy)