2008 PBL Cat_mech_r.qxd:PBL Catalog.mech 11/29/07 1:51 PM Page 42
Bioassay Testing Services
Through its laboratory facilities in Piscataway, NJ, PBL InterferonSource Graph Pad Analysis
offers bioassay testing services. PBL's bioassays for interferons are We now offer an additional analysis for customers who prefer graphic
cytopathic effect inhibition assays, also known as CPE and antiviral results. In this process the same plates that have been read by visual
assays. In these assays, one unit is defined by comparison to the read are used. The Crystal Violet is solublized from the cells with
International standards established by WHO/NIH. For samples where no methanol and the OD read on a plate reader at 562-570 nm. These OD
established standard exists, the closest homologue is used (mouse for values are then transformed to % protection by setting the cell control
rat, etc.). The assay system, specifically the cell and virus types, varies as 100% and the virus control as 0%. The data is then graphed and
depending on the species of interferon to be analyzed. For example, analyzed in GraphPad Prism using a variable slope sigmoidal curve
human interferon alpha bioactivity can be measured on either bovine fitting function. This option offers a few advantages: It considers all
MDBK cells, or human A549 cells with Vesicular Stomatitis Virus (VSV). the data points in determining the EC
50
; Examines the slope of
PBL also offers neutralization assay services, which measure an different samples; and provides a sliding scale for the EC
50
value
antibody's ability to neutralize the CPE activity of the cytokine. The cells compared to the visual read. The actual raw OD values are provided for
and virus listed in the table are used to measure the neutralizing your in-house analysis. Please see page 39 for an example of
activity of the corresponding antibody. For example, the neutralizing GraphPad Prism analysis.
activity of anti-human interferon alpha may be measured using MDBK
cells, VSV and interferon alpha. In addition to Bioassay services, we also provide cytokine assay and
PBL has worked with many laboratories and Contract Research novel reagent development services.
Organizations to provide fast and accurate CPE results.
Sample Requirements
• 100 µl per sample is needed if activity is greater than 2,000 units per ml
• 1 ml is needed if activity is less than 2,000 units per ml
• A completed Viral Inhibition Assay Submission Form. The form can be
obtained by writing to bioassay@interferonsource.com
*Results are normally provided 2 to 3 weeks after receipt of samples,
although assay times may vary.
Visual Read: Our standard antiviral assay service is based on a visual
read of the protection of cells from cytopathic effect (CPE) due to viral
challenge. Samples are titrated in 96 well plates and protection is
determined in comparison to virus (no IFN) and cell (no virus) controls.
After maturation of the viral CPE, the live cells are fixed and stained with
a Crystal Violet solution. The wells are then examined under a
microscope to determine which dilution protects 50% of the cells from
cytopathic effect. This dilution is calibrated to a standard interferon
solution to obtain Units/ml of the sample.
PBLInterferonSource Toll Free: 1 877- PBL-8881
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