What is plaque assays?

Plaque assays are a virological technique used to quantify infectious virus particles in a sample. The assay involves infecting a monolayer of susceptible cells with a diluted virus sample, overlaying the cells with a semi-solid medium (like agar or carboxymethylcellulose) to restrict virus diffusion, and then counting the resulting plaques (areas of cell lysis or infection). Each plaque is assumed to originate from a single infectious virus particle, allowing the determination of viral titer, typically expressed as plaque-forming units (PFU) per milliliter. Plaque assays are commonly used to determine viral infectivity, study viral replication kinetics, and assess the effectiveness of antiviral agents.