Prevalidation of the cAMP-PTx reporter assay for quantitative assessment of pertussis toxin activity.

Testing for inactivation of pertussis toxin and reversion to toxicity in aP vaccines has historically relied on the murine histamine sensitization test, that lacks mechanistic understanding, suffers from standardization problems and is associated with severe animal suffering. Though the regulatory requirements for in vivo testing of acellular pertussis (aP) vaccine products have been waived in Europe, it is still common practice globally. Easy and quantitative in vitro methods are therefore urgently needed. One of the alternatives under development is our reporter cell line - CHO-CRE cells - that carries a cAMP-reporter construct. After exposure to pertussis toxin, cells are stimulated with a low concentration of forskolin to allow detection of pertussis toxin dependent changes in intracellular cAMP levels. Here, the results of two prevalidation studies with purified pertussis toxin and pertussis toxin spiked aP vaccines are described that were performed according to the principles of the ICH Q2(R1) guidelines for a content assay. We confirmed the assay's specificity, accuracy, precision, linearity and range. The cAMP-PTx reporter assay allows for objective, reliable and quantitative assessment of pertussis toxin levels in aP vaccines and can thereby boost broad and global replacement of the histamine sensitization test.

Molecular and cellular signatures underlying superior immunity against Bordetella pertussis upon pulmonary vaccination.

This corrects the article DOI: 10.1038/mi.2017.81.

Molecular and cellular signatures underlying superior immunity against Bordetella pertussis upon pulmonary vaccination.

Mucosal immunity is often required for protection against respiratory pathogens but the underlying cellular and molecular mechanisms of induction remain poorly understood. Here, systems vaccinology was used to identify immune signatures after pulmonary or subcutaneous immunization of mice with pertussis outer membrane vesicles. Pulmonary immunization led to improved protection, exclusively induced mucosal immunoglobulin A (IgA) and T helper type 17 (Th17) responses, and in addition evoked elevated systemic immunoglobulin G (IgG) antibody levels, IgG-producing plasma cells, memory B cells, and Th17 cells. These adaptive responses were preceded by unique local expression of genes of the innate immune response related to Th17 (e.g., Rorc) and IgA responses (e.g., Pigr) in addition to local and systemic secretion of Th1/Th17-promoting cytokines. This comprehensive systems approach identifies the effect of the administration route on the development of mucosal immunity, its importance in protection against Bordetella pertussis, and reveals potential molecular correlates of vaccine immunity to this reemerging pathogen.

Adaptive immune response to whole cell pertussis vaccine reflects vaccine quality: A possible complementation to the Pertussis Serological Potency test.

Whole cell Bordetella pertussis (wP) vaccines are still used in many countries to protect against the respiratory disease pertussis. The potency of whole-cell pertussis vaccine lots is determined by an intracerebral challenge test (the Kendrick test). This test is criticized due to lack of immunological relevance of the read-out after an intracerebral challenge with B. pertussis. The alternative in vivo test, which assesses specific antibody levels in serum after wP vaccination, is the Pertussis Serological Potency test (PSPT). Although the PSPT focuses on a parameter that contributes to protection, the protective immune mechanisms after wP vaccination includes more elements than specific antibody responses only. In this study, additional parameters were investigated, i.e. circulating pro-inflammatory cytokines, antibody specificity and T helper cell responses and it was evaluated whether they can be used as complementary readout parameters in the PSPT to assess wP lot quality. By deliberate manipulation of the vaccine preparation procedure, a panel of high, intermediate and low quality wP vaccines were made. The results revealed that these vaccines induced similar IL-6 and IP10 levels in serum 4h after vaccination (innate responses) and similar antibody levels directed against the entire bacterium. In contrast, the induced antibody specificity to distinct wP antigens differed after vaccination with high, intermediate and low quality wP vaccines. In addition, the magnitude of wP-induced Th cell responses (Th17, Th1 and Th2) was reduced after vaccination with a wP vaccine of low quality. T cell responses and antibody specificity are therefore correlates of qualitative differences in the investigated vaccines, while the current parameter of the PSPT alone was not sensitive enough to distinguish between vaccines of different qualities. This study demonstrates that assessment of the magnitude of Th cell responses and the antigen specificity of antibodies induced by wP vaccination could form valuable complementary parameters to the PSPT.

In vitro innate immune cell based models to assess whole cell Bordetella pertussis vaccine quality: a proof of principle.

Lot release testing of vaccines is primarily based on animal models that are costly, time-consuming and sometimes of questionable relevance. In order to reduce animal use, functional in vitro assays are being explored as an alternative approach for the current lot release testing paradigm. In this study, we present an evaluation of APC platforms assessing innate immune activation by whole cell Bordetella pertussis (wP) vaccines. Primary monocytes, monocyte-derived DC (moDC) and human monocyte/DC cell lines (MonoMac6 and MUTZ-3) were compared for their capacity to respond to wP vaccines of varying quality. To produce such vaccines, the production process of wP was manipulated, resulting in wP vaccines covering a range of in vivo potencies. The responses of MUTZ-3 cells and primary monocytes to these vaccines were marginal and these models were therefore considered inappropriate. Importantly, moDC and MonoMac6 cells responded to the wP vaccines and discriminated between vaccines of varying quality, although slight variations in the responses to wP vaccines of similar quality were also observed. This study provides a proof of principle for the use of in vitro APC platforms as part of a new strategy to assess wP vaccine lot consistency, though careful standardisation of assay conditions is necessary.