PRNT50

PRNT50, short for Plaque Reduction Neutralization Test 50%, is a quantitative serological assay used to measure the neutralizing antibody activity of a serum against a specific virus. The test evaluates the ability of antibodies in the serum to prevent viral infection of susceptible cells.

In principle, virus is incubated with serial dilutions of the test serum and then exposed to a susceptible cell monolayer. After allowing infection, an overlay is applied to restrict viral spread, and plaques caused by virus-infected cells are counted after an incubation period. The neutralizing antibody titer is defined as the reciprocal of the highest serum dilution that reduces the number of plaques by 50% relative to a virus-only control.

PRNT50 is one of several PRNT formats, with PRNT90 and others using different plaque-reduction thresholds. Results are typically reported as the dilution factor or as a titer (e.g., 1:100). The assay requires live virus, appropriate cell lines, and containment appropriate to the virus, as well as standardized procedures and controls to ensure reproducibility.

Advantages of PRNT50 include its functional assessment of antibodies capable of blocking viral replication and its longstanding use in vaccine evaluation and serosurveillance. Limitations include labor intensity, time consumption, and potential variability in plaque counting and interpretation. Differences in virus strains, cell lines, and assay conditions can affect results, necessitating careful standardization and, when possible, corroboration with other neutralization assays.

PRNT50 is widely used in research and clinical settings to gauge immune responses to viruses such as flaviviruses and coronaviruses, contributing to vaccine development and epidemiological studies.