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Updated: Jan 23, 2026
Determination of Vaccine Immunogenicity Using Bovine Monocyte-Derived Dendritic Cells
Published on: May 19, 2023
Development and validation of a monocyte activation test for the control/safety testing of an OMV-based meningococcal
Caroline Vipond1, Janet Sutherland2, Karin Nordgren2
1Department of Bacteriology, The National Institute for Biological Standards and Control, Blanche Lane, Potters Bar EN6 3QG, UK.
Abstract:
It is imperative to ensure biological products are free of contaminating pyrogenic material prior to administration to patients. Historically the rabbit pyrogen test (RPT) was used to screen for such contamination in medicines for intravenous delivery. This test was adapted for use to screen vaccines. However, some, including meningococcal vaccines containing outer membrane vesicles, are intrinsically pyrogenic. Indeed, this is the case for Bexsero which contains relatively high levels of endotoxin and other potential pyrogens such as lipoproteins and porins. The RPT proved a difficult method for measuring the pyrogenic content of Bexsero and differences between laboratories in different countries made repeat testing at the control laboratories problematic resulting in batches being wrongly identified as unsafe. At NIBSC a monocyte activation test (MAT) was adapted and validated as an alternative. This required setting of a specification in-house and deciding on a decisional procedure using multiple donors, allowing batches equally pyrogenic or less, than those batches shown to be safe in a clinical trial, to be certified as safe. The resulting format was a reference comparison method with an upper limit of 1.8 relative pyrogen units (RPU). The batch passed if an initial four donors had a response equal to or less than 1.8 RPU, if one donor is above this limit the batch was tested in a further four donors and seven of the eight must be equal to or below 1.8 RPU. If two donors have a response greater than 1.8 the batch failed.
Insights
The monocyte activation test (MAT) offers a reliable alternative to the rabbit pyrogen test (RPT) for pyrogen testing in vaccines like Bexsero. This validated method ensures vaccine safety by accurately measuring pyrogenic content.
Area of Science:
- Biotechnology
- Immunology
- Vaccine Development
Background:
- The traditional rabbit pyrogen test (RPT) faces challenges in accurately assessing pyrogenic material in certain vaccines, such as meningococcal vaccines (e.g., Bexsero).
- Bexsero contains high levels of endotoxin, lipoproteins, and porins, making it intrinsically pyrogenic and difficult to evaluate using the RPT.
- Inter-laboratory variations in RPT led to issues in batch release, with some batches incorrectly identified as unsafe.
Purpose of the Study:
- To adapt and validate a monocyte activation test (MAT) as a reliable alternative to the RPT for pyrogen testing of vaccines.
- To establish a robust in-house specification and decision-making procedure for the MAT, ensuring accurate pyrogen content assessment.
- To enable the certification of vaccine batches with pyrogenic content equal to or less than those proven safe in clinical trials.
Main Methods:
- Adaptation and validation of a monocyte activation test (MAT) at the National Institute for Biological Standards and Control (NIBSC).
- Development of an in-house specification and a multi-donor decision procedure for the MAT.
- Implementation of a reference comparison method with an upper limit of 1.8 relative pyrogen units (RPU) for batch assessment.
Main Results:
- The MAT was successfully validated as an alternative pyrogen testing method.
- A clear decision procedure was established: batches pass if initial four donors show ≤1.8 RPU; if one donor exceeds, seven of eight must be ≤1.8 RPU; two donors exceeding 1.8 RPU results in failure.
- This method allows for the reliable certification of vaccine batches based on their pyrogenic content.
Conclusions:
- The monocyte activation test (MAT) provides a more accurate and reproducible method for pyrogen testing of vaccines like Bexsero compared to the RPT.
- The validated MAT procedure ensures that vaccine batches are certified as safe, minimizing the risk of incorrect rejection.
- This advancement in pyrogen testing contributes to the quality control and safety assurance of biological products.
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