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| Development of in vitro quality control tests to replace animal based potency tests for diphtheria and tetanus toxoid vaccines |
Applicants:
Prof. Dr. Coenraad F.M.Hendriksen
Netherlands Vaccine Institute (NVI)
P.O.Box 457
3720 AL Bilthoven
Netherlands
Netherlands Centre Alternatives to Animal Use (NCA)
Utrecht University
P.O.Box 80.166
3508 TD Utrecht
Netherlands
Dr. Gideon F.A. Kersten
Netherlands Vaccine Institute (NVI)
P.O.Box 457
3720 AL Bilthoven
Netherlands
Dr. Bernard Metz
Netherlands Vaccine Institute (NVI)
P.O.Box 457
3720 AL Bilthoven
Netherlands |
Background and problem definition:
Vaccines play a crucial role in preventive health care and consequently these products are being produced worldwide. To guarantee that vaccine lots produced are safe and potent, quality control of each lot is statutory required, many tests have to be performed. Traditionally, tests for quality control of the conventional vaccines, the products still widely used, are based on animal models. Especially potency testing requires large numbers of animals while these animals experience severe distress due to the procedures applied. In the late 1980s NVI (then part of the RIVM) started a programme to gradually replace, refine and reduce the number of animals in statutory required quality control by modifying existing test procedures and developing new test methods. Thus, we introduced the use of humane endpoints in tests based on lethal endpoints, we statistically analysed animal numbers per dose group, we evaluated the replacement of multi-dose potency tests by single dose tests and for several products we were able to replace the challenge procedure by serology (Vero cell test for D toxoid and ToBI test for D and T toxoid vaccines). Several methods and approaches have now been accepted by the European Pharmacopoeia and by regulatory authorities. Animal studies are still needed, both for human and veterinary vaccines using rodents, guinea pigs and rabbits, but substantial refinement and animal reduction has been achieved. Currently, our focus of research is to replace the still existing animal models by non-animal models, particularly analytical, immunochemical and in vitro methods. We believe this is possible by introducing a paradigm shift in vaccine quality control based on the concept of demonstration of consistency. The red line in the consistency approach is that a new batch of vaccine is no longer seen as a unique product but as only one of a series of batches produced from the same starting material (seed lot). Consequently, the new batch shares many of the characteristics of the previous batches produced from the same seed lot. This allows for a new strategy of vaccine quality control, demonstrating consistency in production, giving emphasis to aspects such as in-process testing, the implementation of Good Manufacturing Practice (GMP) and to Quality Assurance (QA). The new strategy particularly focuses on non-animal test models such as physicochemical methods and in vitro models.
Previous studies to apply this concept to toxoid vaccines have been performed successfully. The toxoid quality was studied by assessing comparability in structure using a panel of in vitro test based on chemical and immunochemical characterisation. In two ECVAM workshops and in a recent meeting organised by the European Department for the Quality of Medicines (EDQM) this approach was evaluated positively [7-8]. However, these consistency tests still need further improvement as well as new methods need to be developed, particularly with regard interaction of antigen and adjuvant in the final product.
In a PhD study and a post-doc study, financed by the Dutch funding organisation ZonMw, we are now aiming to fine tune and extend the concept of the consistency approach to testing of the final lot, using the Diphtheria and Tetanus vaccine as model compounds.
Aims:
- Get more insight into the binding characteristics of the monoclonal antibodies used for the antigenic characterisation of the toxoids and the relation with the antibody profile that is formed after immunisation of experimental animals and humans.
- Redevelop or qualify the in vitro methods that are already available for diphtheria toxoid for tetanus toxoid.
- Select easy to use methods to characterise toxoids in vitro when they are adsorbed to aluminium salts. Recently, results from fundamental research into this issue have become available that might be relevant for routine vaccine quality control. We are currently performing a project on adsorbed products.
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