Determination of Chikungunya Virus Infectious Titer Using Plaque Assays

The plaque-forming assay is the gold-standard method for measuring infectious viral particles. In this technique, lytic viruses infect and destroy host cells, but their spread is restricted by a viscous overlay medium. As a result, new viral particles can only infect neighboring cells, leading to localized clear areas known as plaques, which become visible after staining the remaining living cells. The number of plaques reflects the number of infectious viral particles initially present in the sample and is reported as plaque-forming units (PFU) per sample volume. In this protocol, we describe step by step how to perform a plaque-forming assay to determine the concentration of chikungunya virus in a cell culture supernatant.