Evaluation of Whole Cell Vaccine-induced humoral antibody responses in the Pertussis Serological Potency Test in relation to the Mouse Protection Test
Evaluatie van Whole Cell-vaccin geinduceerde humorale antilichaamresponsen in de Pertussis Serological Potency Test in relatie met de Muisbeschermingstest
26 May 2012, PDF |
29 pages |
van der Ark AAJ, van Straaten-van de Kapelle I, van de Donk HJM, Hendriksen CFM
RIVM Report 623860004
The Pertussis Serological Potency Test (PSPT) has been developed as an alternative for the current MPT. The PSPT is based on in vitro assessment of the humoral immune response against the whole range of surface-antigens of B. pertussis in mice after immunisation with Whole Cell Vaccine (WCV). The concentration of pertussis antibodies in sera is measured in the 18323-Whole Cell ELISA (18323-WCE). In an in-house validation study 13 WCVs were tested in the PSPT and the MPT. Homogeneity of both test systems was proven by means of a modified chi-square test ; potencies were not significantly different (p = 0.95). Compared to the MPT, the PSPT is more reproducible as is indicated by its smaller 95% confidence intervals. Additionally, the immunogenicity of WCVs has been studied in antigen specific ELISAs and in vitro functional test systems to assess correlation with mouse protection. Estimation of WCV-potencies based on the antibody concentration against Pertussis Toxin (PT), Filamentous-Hemagglutinin (FHA) or 69-kDa Outer Membrane Protein (OMP) was not possible due to very low antibody responses which were not vaccine dose dependent. The anti-92-kDa OMP antibody response showed a poor correlation with the MPT, due to scattering. In conclusion, the protection of mice against a lethal intracerebral challenge is not related to a humoral immune response against a single 'protective' antigen, nor restricted to a single immune mechanism, but may be related to a synergistic effect of humoral responses against a wide range of 'protective' and 'non-protective' antigens. The PSPT is therefore a good alternative for the MPT and provides more precise information about immunogenicity, potency and hence on consistency in production of pertussis WCVs.