Plaque reduction neutralization test
Encyclopedia
The Plaque reduction neutralization test is used to quantify the titre of neutralising antibody
for a virus.
The serum sample or solution of antibody to be tested is diluted and mixed with a viral suspension. This is incubated to allow the antibody to react with the virus. This is poured over a confluent monolayer of host cells. The surface of the cell layer is covered in a layer of agar
or carboxymethyl cellulose
to prevent the virus from spreading indiscriminately. The concentration of plaque forming units can be estimated by the number of plaques (regions of infected cells) formed after a few days. Depending on the virus the plaque forming units are measured by microscopic observation, florescent antibodies or specific dyes that react with infected cells.
The concentration of serum to reduce the number of plaques by 50% compared to the serum free virus gives the measure of how much antibody is present or how effective it is. This measurement is denoted as the PRNT50 value.
Currently it is considered to be the "gold standard" for detecting and measuring antibodies that can neutralise the viruses that cause many diseases. It has a higher sensitivity
than other tests like hemagglutination
and many commercial Enzyme immunoassay without compromising specificity.
However, the test is relatively cumbersome and time intensive (few days) relative to EIA kits that give quick results (usually several minutes to a
few hours).
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
for a virus.
The serum sample or solution of antibody to be tested is diluted and mixed with a viral suspension. This is incubated to allow the antibody to react with the virus. This is poured over a confluent monolayer of host cells. The surface of the cell layer is covered in a layer of agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
or carboxymethyl cellulose
Carboxymethyl cellulose
Carboxymethyl cellulose or cellulose gum is a cellulose derivative with carboxymethyl groups bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone...
to prevent the virus from spreading indiscriminately. The concentration of plaque forming units can be estimated by the number of plaques (regions of infected cells) formed after a few days. Depending on the virus the plaque forming units are measured by microscopic observation, florescent antibodies or specific dyes that react with infected cells.
The concentration of serum to reduce the number of plaques by 50% compared to the serum free virus gives the measure of how much antibody is present or how effective it is. This measurement is denoted as the PRNT50 value.
Currently it is considered to be the "gold standard" for detecting and measuring antibodies that can neutralise the viruses that cause many diseases. It has a higher sensitivity
Sensitivity and specificity
Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...
than other tests like hemagglutination
Hemagglutination
Hemagglutination, or haemagglutination, is a specific form of agglutination that involves red blood cells . It has two common uses in the laboratory: blood typing and the quantification of virus dilutions.-Blood Typing:...
and many commercial Enzyme immunoassay without compromising specificity.
However, the test is relatively cumbersome and time intensive (few days) relative to EIA kits that give quick results (usually several minutes to a
few hours).
See also
- Viral quantification using the plaque assay
- ELISAELISAEnzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...