What machinery is used to efficiently sediment even the smallest viruses?
Ultracentrifuge
*used for concentration and purification
Rate zonal centrifugation will separate viruses based on what?
Their mass
Isopycnic centrifugation separates viruses based upon what?
Their density
Aka buoyant or equilibrium separation
What method is used for virus purification?
Membrane chromatography
What is virus quantification?
Counts the number of the viruses in a specific volume to determine the concentration
What is the virus titer?
is the minimum concentration of virus in a given volume of solution that will still infect cells
number of infectious units per ml of sample
What are the two basic types of viral quantification tests?
Biological and physical
Direct particle counts by transmission electron microscopy is an example of what kind of quantification test?
PHYSICAL
direct counting of viral particles in solution
Using the virus counter 2100 is an example of what kind of quantification test?
PHYSICAL
direct counting of viral particles in solution
Hemagglutination assay measures what? What kind of quantification test is this?
Quantification assessment based on antigen concentration
(hemagglutination titer)
This is a physical test
Single Radial Immunodiffusion (SRID) is an example of what kind of quantification test?
Physical test
Radial diffusion of purified viral antigens (standards) and viral particles through agarose gel seeded with polyclonal antiserum against the viral antigen
T/F: Quantitative PCR is considered a physical quantification test
TRUE
assessment based on gene expression
Biological assays that assess viral quantification include what tests?
Monolayer Plaque Assay
Pock assay
Various endpoint titration methods
What is the unit used to express virus concentration when using the Monolayer plaque assay technique?
Plaque-forming units/ml = PFU
the number of virus particles capable of forming plaques per unit volume.
Ex: a solution has a PFU of 1000 pfu/ml; then every ml of solution contains enough viruses to make 1000 plaques
What unit is used when performing a pock assay?
Pock forming units/ml
Pock = necrotic area on the CAM of embryonated egg
What test results in quantitative determination of titers of oncogenic viruses?
Transformation assay
Unit: Focus-forming units/ml
T/F: Quantal assays are a biological quantitative test
True
Results in the ENDPOINT = virus dilution that affects 50% of test subjects
What is the TCID50?
The tissue culture infectious dose which will infect 50% of the cell monolayers challenged with the defined inoculum
