Plaque Assay Technique
Plaque Assay Technique - Related Videos
10:53
Plaque Assay for Murine Norovirus
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Cited by 99 •
2012
Here we describe a method to quantify infectious particles of murine norovirus (MNV), which is the only norovirus that efficiently replicates in cell culture. The plaque assay takes advantage of MNV’s tropism for murine macrophages and can be adapted for use with biological or environmental samples containing MNV.
13:00
Plaque Assay: A Method to Determine Viral Titer as Plaque Forming Units (PFU)
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2023
Source: Tilde Andersson1, Rolf Lood1 1 Department of Clinical Sciences Lund, Division of Infection Medicine, Biomedical Center, Lund University, 221 00 Lund, Sweden Viruses that infect prokaryotic organisms, called bacteriophages or simply phages, were identified in the early 20th century by Twort (1) and d'Hérelle (2) independently. Phages have since been widely recognized for their therapeutic value (3) and their influence on human (4), as well as global, ecosystems (5). Current concerns have...
03:30
Assessing Rotavirus Growth Curve by Plaque Assay
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2026
Source: Kadoya, S., Sano, D. Assays for the Specific Growth Rate and Cell-binding Ability of Rotavirus. J. Vis. Exp. (2019).This video demonstrates the use of a plaque assay to assess the rotavirus growth curve. The method involves infecting host cells with diluted virus, overlaying with agarose to restrict spread, and staining to visualize plaques formed by viral replication. By counting plaque-forming units at defined time points, the resulting growth curve reveals the lag, exponential, and...
04:33
Evaluation of a Liquid Overlay System for Viral Plaque Assays
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2026
Source: Baer, A. and Kehn-Hall, K. Viral Concentration Determination Through Plaque Assays: Using Traditional and Novel Overlay Systems. J. Vis. Exp. (2014).This video demonstrates the use of a liquid microcrystalline cellulose-based overlay in a plaque-based assay by comparing its effectiveness in viral plaque formation with that of a traditional semi-solid agarose overlay.
03:25
Quantification of Pseudovirus Particles by Plaque Assay
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2026
Source: Jamieson, T. R., et al., Detection of SARS-CoV-2 Neutralizing Antibodies using High-Throughput Fluorescent Imaging of Pseudovirus Infection. J. Vis. Exp. (2021)This video describes the virus plaque assay using coronavirus pseudovirus particles. The diluted pseudovirus is added to a monolayer of mammalian cells, followed by incubation with a methylcellulose overlay. Plaques formed by infected cells are counted visually to determine the infectious virus titer.
FAQs
The overlay restricts movement of virus or bacteriophage particles after they infect the host-cell layer. This confinement keeps successive rounds of replication and cell lysis localized rather than allowing particles to spread throughout the culture. As a result, each infectious unit produces a discrete clear zone that can be observed and counted for quantitative analysis.
A plaque represents localized destruction of susceptible cells following infection and replication by an infectious unit. Researchers count these clear zones and relate the count to the diluted sample used in the assay, reporting the result as plaque-forming units per milliliter. Thus, the measurement reflects particles capable of producing detectable infection and lysis under the assay conditions.
Susceptible cells provide the biological system required for infection, replication, and lysis. A confluent monolayer creates a continuous layer in which neighboring cells can be reached during localized replication. If the cells cannot support the infectious agent, or if the layer is not suitable for localized growth, the assay will not produce plaques that accurately represent infectivity.
Dilution places the sample into a form that can be evaluated through its resulting plaque count and then related back to the original material. Because the assay converts visible plaques into PFU/mL, the dilution used is essential for interpreting the observed number quantitatively. This step supports comparisons of infectious levels among samples analyzed under the assay.
The workflow begins by preparing a diluted sample and applying it to a confluent layer of susceptible host cells. A semisolid agar or agarose overlay is then added to limit particle movement while infection and lysis proceed. After plaques develop as clear zones, researchers count them and use the dilution information to calculate infectious titer in PFU/mL.
This technique is useful when a study requires a measurement of infectious virus or bacteriophage rather than only a general sample description. The resulting titer can support virus characterization, vaccine research, antiviral research, and phage biology. It also provides a way to investigate infectivity, replication, and neutralization through changes in plaque formation or infectious levels.
The same core logic applies to viruses and bacteriophages: a diluted infectious sample interacts with a suitable host-cell layer, localized replication produces lysis, and clear plaques provide a measurable outcome. In biology, this makes the assay relevant across virus characterization and phage biology. Its shared readout also supports comparisons of infectivity and replication within the systems studied.