Plaque Forming Units per milliliter (PFU/mL) is a measure of the concentration of infectious virus particles in a sample. This value represents the number of plaques, or areas of cell lysis, formed when a diluted virus sample infects a susceptible cell monolayer. The process involves infecting cells with serial dilutions of the viral stock, allowing plaques to form, and then counting the plaques to determine the original viral titer. For example, if a 10-6 dilution results in 50 plaques on a plate, the original viral stock has a titer of 5.0 x 107 PFU/mL.
Determining the infectious titer of a viral stock is crucial for many virology and biotechnology applications. Precise quantification ensures reproducibility in experiments, allows for accurate dose determination in viral vector-based gene therapy, and aids in monitoring viral production during vaccine development. Historically, plaque assays have been a gold standard for measuring viral infectivity due to their simplicity and direct measurement of functional viral particles, setting a reliable benchmark for comparison across different assays and research groups.
