Viral Titer Determination
Viral Titer Determination - Related Videos
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...
08:35
Production and Titering of Recombinant Adeno-associated Viral Vectors
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Cited by 149 •
2011
Recombinant adeno-associated virus (rAAVs) vectors are becoming increasingly valuable for in vivo studies in animals. We describe how rAAVs can be produced in the laboratory and how these vectors can be titered to give an accurate reading of the number of infectious particles produced.
02:54
Crystal Violet Staining for Estimating Viral Infectious Titer in Cell Cultures
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2026
Source: Frias-De-Diego and A., Crisci, E. Use of Crystal Violet to Improve Visual Cytopathic Effect-based Reading for Viral Titration using TCID50 Assays. J. Vis. Exp., (2022)This video demonstrates a crystal violet staining method to visualize cytopathic effects in virus-infected cell cultures. The pattern of stained and unstained wells across serial dilutions enables rapid, cost-effective estimation of the viral infectious dose.
09:28
Viral Concentration Determination Through Plaque Assays: Using Traditional and Novel Overlay Systems
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Cited by 466 •
2014
Plaque assays are the gold standard for viral quantification, utilizing entrapping overlays on host cellular monolayers to determine viral titers. While various semisolid overlays have traditionally been used, here we demonstrate plaque techniques comparing semisolid overlays to a novel liquid microcrystalline cellulose among several families of viruses.
08:01
A Streamlined, Label-Free Real-Time 50% Tissue Culture Infectious Dose (TCID50) Assay using Impedance for Automated Viral Titer Quantification
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2026
The TCID50 assay reported here leverages label-free real-time impedance measurements and the system's Virology module to objectively monitor virus-induced cytopathic effects (CPE) in real time. This streamlined assay significantly reduces hands-on time while supporting high-throughput, quantitative kinetic CPE measurements and enabling automated, real-time TCID50 calculations.
FAQs
Serial dilution separates the virus suspension into concentrations that can be evaluated through plaque formation. After infection, each visible plaque represents a localized outcome of viral replication and lysis in the cell layer. Researchers combine the observed plaque count with the corresponding dilution factor to calculate an infectivity value, commonly expressed as PFU/mL, for the original sample.
A susceptible cell monolayer provides the living biological system required for the assay’s signal. Virus must infect cells, replicate, and spread to neighboring cells before lysis produces a clear zone. If the cells cannot support this sequence, plaque formation cannot reflect the sample’s infectious virus concentration, so cell susceptibility directly affects whether the assay can reveal infectivity.
Plaque formation links a measurable visual outcome to successful viral infection. Replication within initially infected cells, followed by spread and lysis in neighboring cells, creates a clear zone that can be counted. Because the result reflects infectious activity rather than merely the presence of virus in a suspension, it helps relate experimental conditions to infectious dose.
Dilution factors connect the plaque count observed in a tested portion of the sample to the concentration in the original virus suspension. Without accounting for dilution, the measured count would describe only the reduced concentration used in the assay. Including the factor allows results from differently diluted samples to be expressed as a comparable infectivity value.
The measured infectivity value provides a basis for adjusting the amount of virus introduced into an experiment. Rather than relying only on sample volume, researchers can relate the inoculum to infectious virus concentration. This standardization makes it easier to compare outcomes between samples and to connect observed biological effects with the amount of infectious virus used.
Viral titer determination supports several areas of biology, including pathogenesis studies, vaccine development, antiviral activity testing, and virus production. In each setting, the infectivity value helps researchers compare viral growth or experimental conditions and control the infectious dose. It therefore connects quantitative sample characterization with biological outcomes that depend on viable, infectious virus.