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Limitations of the rabbit pyrogen test for assessing meningococcal OMV based vaccines
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Caroline Vipond1, Lucy Findlay2, Ian Feavers1 and Rory Care1
Department of Bacteriology 1, Department of Biotherapeutics 2, National Institute of Biological Standards and Control, South Mimms, Potter Bar, UK
The rabbit pyrogen test was developed in the early 1900’s to detect contaminating pyrogens in parenteral medicines. Since its conception alternative methods with improved sensitivity, relevancy and which are ethically more acceptable have been developed. However, the test is still a current pharmacopeial method and is used to evaluate the pyrogen content of some vaccines. In this article the limitations and pitfalls of using the test to measure pyrogenicity of vaccines containing outer membrane vesicles are described. The method is unsuitable as a safety test for these products due to the high levels of endotoxin present in the vaccine which generate a pyrogenic response in rabbits when delivered intravenously without dilution. Its use as a consistency test is also ambiguous as the test gives a qualitative rather than quantitative response, and the rabbit models are highly variable. In addition there is evidence that measuring the temperature rise of the animals over three hours does not capture the maximum fever response. Finally the article considers the use of alternative methods and the validity of animal models when applying a consistency based approach for assessing the quality of licensed products.
Keywords: outer membrane vesicles (OMV), meningococcal vaccine, rabbit pyrogen test (RPT), monocyte activation test (MAT)
ALTEX 33(1), 47-53