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Our FociSpot products

Published: December 14, 2023

Updated: January 12, 2024

The principles of FociSpot

FociSpot is an innovative assay kit designed to precisely detect and quantify focus-forming units (FFUs). This assay is an essential tool for virology research, combining the precision and reliability of focus-forming assays with optimized protocols and reading.

We know each viral assay is unique, but we've streamlined the detection and reading steps. If we take a typical focus reduction neutralization test (FRNT) for example, dilutions of a serum sample containing potential neutralizing antibodies (nAbs) is mixed with a known titer of virus. This mixture is then added to a monolayer of cells in a 96-well plate and incubated overnight. The following day, the virus-sample mixture is removed and this is where the FociSpot kit protocol comes into play. Following fixation, a virus-specific biotinylated mAb is added to detect viral proteins in the cells. Then a steptavidin-ALP conjugate is added just like in ELISpot so that when substrate is added, foci are visualized and can be counted in IRIS 2.

FociSpot staining schematic - virus protein detection
FociSpot neutralization assay (FRNT) step-by-step

An example of a typical FRNT assay using FociSpot to enumerate neutralizing antibody titers in a given sample.


What are the benefits of FociSpot?

FociSpot represents a new advancement in viral research tools, particularly due to the limited availability of standardized commercial focus-forming assay (FFA) kits. By offering a consistent and reliable FFA solution, FociSpot lowers the threshold for new virology research and streamlines the process for established scientists. Its standardized approach brings much-needed uniformity to a field where such resources have been scarce, ensuring accuracy and comparability across various research endeavors.

Our FociSpot kits have the potential to be an essential tool for detecting neutralizing antibodies (nAbs), determining viral titers, and other key virological applications. It enables researchers to conduct more efficient and effective studies, thereby accelerating advancements in the field of virology. With FociSpot, both new and seasoned researchers can achieve reliable results, enhancing their viral research's overall quality and impact.


FociSpot applications and usage

FociSpot is our umbrella name for FFA kits. FFAs can be used in a number of ways for your virus research.

Virus quantification: FFA techniques like TCID50 are used to estimate the amount of infectious virus in a sample. This is vital for understanding viral load and its impact on disease severity or transmission.

Antiviral drug testing: FFAs are instrumental in testing the effectiveness of antiviral drugs. They allow researchers to determine the concentration of a drug needed to inhibit viral replication, providing crucial data for drug development and approval.

SARS-CoV-2 FociSpot virus titration

Increasing dilutions of SARS-CoV-2 added to cells and detected with FociSpot

Vaccine efficacy: FRNT is commonly used to assess the neutralizing capacity of antibodies generated by vaccines as well as nAb titers. By measuring how well these antibodies can prevent virus infection in cell cultures, researchers can evaluate and compare the efficacy of different vaccine candidates.

Viral pathogenesis: These assays help in understanding how different viral strains or mutations affect infectivity and virulence. By comparing the infectivity rates of different viral variants, researchers can gain insights into the mechanisms of viral pathogenesis.


Automated foci counting

In the Apex software of IRIS 2, you can now find a new assay format below ELISpot and FluoroSpot. Simply choose FociSpot as well as the plate format, insert your plate, and press read. IRIS 2 quickly and precisely enumerates foci getting you right to your data.

Counting foci has never been easier and, most importantly, more accurate.



FociSpot on IRIS 2

To get the most out of your FociSpot experiment, please read our Step-by-step guide to FociSpot.


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