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.

Animal-Friendly Affinity Reagents: Replacing the Needless in the Haystack.

The multibillion-dollar global antibody industry produces an indispensable resource but that is generated using millions of animals. Despite the irrefutable maturation and availability of animal-friendly affinity reagents (AFAs) employing naïve B lymphocyte or synthetic recombinant technologies expressed by phage display, animal immunisation is still authorised for antibody production. Remarkably, replacement opportunities have been overlooked, despite the enormous potential reduction in animal use. Directive 2010/63/EU requires that animals are not used where alternatives exist. To ensure its implementation, we have engaged in discussions with the EU Reference Laboratory for alternatives to animal testing (EURL ECVAM) and the Directorate General for Environment to carve out an EU-led replacement strategy. Measures must be imposed to avoid outsourcing, regulate commercial production, and ensure that antibody producers are fully supported.

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.

[Developments in the area of animal experiments in biomedical research]. / Ontwikkelingen op het gebied van dierproeven in het biomedisch onderzoek.

Although many would like to see it differently, animal experiments are still very important in biomedical research. The solution to fundamental questions in the area of cancer or chronic diseases as well as the legally-required registration and release of vaccines or drugs are all impossible without studies on laboratory animals. - The point of departure in existing legislation on animal experimentation is the principle of 'responsible use'. Important aspects in this connection are the education and training of those working with laboratory animals, the monitoring of animal welfare, and the ethical evaluation of proposed studies. - In addition, for various reasons, substantial attention is being given to possible ways of replacing, reducing or refining the use of experimental animals, the so-called 3Rs. Significant progress has been made in this field. - The number of animals used for research in the Netherlands has been reduced by about 50% in the last 25 years. In recent years, however, there is a trend of increase and decrease due to scientific and social developments such as the availability of genetically modified animals and the increased priority given to product safety. - Consequently, animal experimentation will for the time being remain indispensable in biomedical research, although its role will shift in the direction of the confirmation of results obtained by animal-free methods.

Decreased sensitivity to diphtheria toxin of Vero cells cultured in serum-free medium.

Vero cell cultures are used in the quality control of Diphtheria vaccines: to estimate vaccine potency and to determine residual toxicity and reversion to toxicity. The impact of replacing foetal calf serum containing medium (SCM) by serum free media (SFM) on the sensitivity of Vero cells to Diphtheria Toxin was studied. Compared to SCM, SFM showed an eight-fold decrease in sensitivity to Diphtheria Toxin. This decrease was almost immediate, indicating that this phenomenon was not caused by a change in membrane structure or protein expression. We investigated the effect of SFM on Diphtheria Toxin in order to determine the cause of the decrease in sensitivity. Our results show that oligopeptides, which are often used in SFM as part of the replacement of foetal calf serum, are the most likely cause.

An in vitro approach in quality control of toxoid vaccines.

For routine immunogenicity testing of traditionally produced vaccines, animal tests are required by regulatory authorities, with potency estimated in International Units. A new concept focuses on assuring immunogenicity by monitoring batch-to-batch consistency in production. This concept is used for well-defined biologicals such as hormones. Through the use of immunochemical and bio- and physiochemical techniques the traditional products can be characterised as completely as possible. Developments in in vitro methodologies offer opportunities for immunogenicity testing in vitro. This study describes the possibilities for applying the consistency concept to the traditional products, tetanus and diphtheria toxoids. The sources of variation in these products were studied by flocculation time, SDS-PAGE, biosensor analysis, gel permeation chromatography and in vitro cytokine production studies. Batch-to-batch variation was shown using these in vitro techniques. Results indicate that it is possible to apply the consistency concept in the quality control of traditional vaccines like tetanus and diphtheria toxoids.

Mepyramine but not cimetidine or clobenpropit blocks pertussis toxin-induced histamine sensitization in rats.

The effects of pertussis toxin (PT) and the role of histaminergic H(1), H(2) and H(3) receptor blockade on the actions of histamine on blood pressure, heart rate, blood gas values, and mortality were studied in anaesthetized rats. Four days after treatment with PT, histamine dose-dependently decreased mean arterial blood pressure (MAP) and PT enhanced the histamine-induced decrease in MAP. In the PT but not in the inactivated PT (IPT) or saline treated group three out of six animals died after the highest dose of histamine (300 mg kg(-1), i.v.) In order to determine the type of histamine receptor that mediates HS, 4 days after PT the selective antagonists mepyramine (H(1)), cimetidine (H(2)) and clobenpropit (H(3)) were administered 20 min before the challenge with histamine. Mepyramine completely inhibited both the enhanced histamine-induced decrease in MAP and mortality brought about by PT. Cimetidine and clobenpropit had no protective effects, but rather enhanced the histamine-induced mortality elicited by PT. The present study shows that PT caused HS in rats which is primarily mediated via H(1) and secondarily via H(2) and H(3) receptors. These results are considered to be a first step in the elucidation of the mechanism(s) of the HS test used in the quality control of acellular pertussis vaccine.

Evaluation of toxin neutralisation in test systems for diphtheria antibody assessment.

Over the past years, various authors have reported that the amount of toxin used in toxin neutralisation (TN) assays for diphtheria appears to influence the resulting relative antibody titre. Antibody affinity is thought to be an influencing factor. To confirm this observation and study the underlying mechanism of toxin neutralisation, a panel of sera was generated, differing in species of origin (mouse, guinea pig, and rabbit) and in affinity by using different immunisation schedules. The panel was then tested in relevant TN test systems for diphtheria antibody titration, namely the VERO cell test, the Toxin Binding Inhibition (ToBI) assay and the in vivo skin test in guinea pigs. A hyperimmune equine reference serum was used as the standard. Antibody affinity was measured in two different affinity ELISAs, the ammonium thiocyanate elution ELISA and the diethylamine inhibition ELISA. The VERO cell test clearly demonstrates the phenomenon; the higher the toxin dose used in the assay, the higher the resulting relative potency. The difference in relative antibody titre decreases as antibody affinity increases. This is especially evident when an equine hyperimmune reference serum is used as the standard. When a species homologous reference is used, the phenomenon is less distinct. The ToBI test, however, does not show the phenomenon. This discrepancy between these two test systems is being further investigated, and comparison will be made with the in vivo TN test. The findings confirm and support earlier observations. It is still unclear exactly which mechanisms are involved in the toxin neutralisation process. Antibody subclasses and class switching could play a role and will be further studied.

Validation of tests methods in the quality control of biologicals.

With increasing frequency new methods are being developed for the assessment of the quality of biological products. Before these methods can be considered for regulatory acceptance, their relevance and reliability must be established in a formal validation study. Such a study should be tailor-made, depending on the particular purpose and goal of the new method. However, a set of general principles can be given, according to which a validation study should be conducted. Essential ingredients in a validation study are the three Cs for Common sense, Commitment and Communication. Common sense in the design of the study, Commitment of the participating laboratories and Communication between the parties involved. An overview will be given of the various stages of a validation study, the time period needed (Table 1) and a number of problems that can be encountered will be discussed.

Statistical evaluation of numbers of animals to be used in vaccine potency testing: a practical approach.

Some of the guidelines for potency testing of vaccines issued by regulatory bodies such as the European Pharmacopoeia (EP) and WHO are detailed and stringent (e.g. EP monograph for Newcastle Disease (ND) Vaccine (inactivated)), whereas others only stipulate that the number of animals used should be sufficient to meet the required accuracy (e.g. EP monograph for Hepatitis A vaccine (inactivated)). Simulation studies in our laboratory using historical ND potency test data indicated that the number of animals specified in the monograph is too high; a considerable reduction from 10 to seven animals per group does not substantially influence the precision of the results. Multipoint models (e.g. EP monograph for Tetanus Vaccine (adsorbed)) require at least three dilutions per vaccine for testing for response linearity. However, when historical data clearly show that in the range used the response curves are linear, it is superfluous to verify this in every test. Furthermore, linearity has little priority for a valid parallel line assay calculation. A simulation study using historical Diphtheria potency test data showed that calculations using two dilutions per vaccine in relatively small groups of animals produced results comparable to those obtained from the full assay. This procedure still enables calculation of the relative potency, in contrast to the 1 + 1 method, which gives only a pass or fail result, while the number of animals required is only slightly higher. This method could be applied in cases where the 1 + 1 method fails. In conclusion, by providing guidelines on methods in which proven consistency in production and testing may be taken into account, manufacturers are more stimulated to look for other (cheaper) ways to test the potency of a vaccine using less animals.

The Production of Polyclonal Antibodies in Laboratory Animals. The Report and Recommendations of ECVAM Workshop 35.

This is the report of the thirty-fifth of a series of workshops organised by the European Centre for the Validation of Alternative Methods (ECVAM). ECVAM's main goal, as defined in 1993 by its Scientific Advisory Committee, is to promote the scientific and regulatory acceptance of alternative methods which are of importance to the biosciences and which reduce, refine or replace the use of laboratory animals. One of the first priorities set by ECVAM was the implementation of procedures which would enable it to become well informed about the state-of-the-art of non-animal test development and validation, and the potential for the possible incorporation of alternative tests into regulatory procedures. It was decided that this would be best achieved by the organisation of ECVAM workshops on specific topics, at which small groups of invited experts would review the current status of various types of in vitro tests and their potential uses, and make recommendations about the best ways forward (1). This joint ECVAM/FELASA (Federation of European Laboratory Animal Science Associations) workshop on The Immunisation of Laboratory Animals for the Production of Polyclonal Antibodies was held in Utrecht (The Netherlands), on 20-22 March 1998, under the co-chairmanship of Coenraad Hendriksen (RIVM, Bilthoven, The Netherlands) and Wim de Leeuw (Inspectorate for Health Protection, The Netherlands). The participants, all experts in the fields of immunology, laboratory animal science, or regulation, came from universities, industry and regulatory bodies. The aims of the workshop were: a) to discuss and evaluate current immunisation procedures for the production of polyclonal antibodies (including route of injection, animal species and adjuvant ); and b) to draft recommendations and guidelines to improve the immunisation procedures, with regard both to animal welfare and to the optimisation of immunisation protocols. This report summarises the outcome of the discussions and includes a number of recommendations and a set of draft guidelines (included in Appendix 1).

Assessment of side effects induced by injection of different adjuvant/antigen combinations in rabbits and mice.

We evaluated the side effects induced by injection of Freund's adjuvant (FA) and alternative adjuvants combined with different antigens. Rabbits and mice were injected subcutaneously, intramuscularly (rabbits) and intraperitoneally (mice) with different adjuvants (FA, Specol, RIBI, TiterMax, Montanide ISA50) in combination with several types of antigens (synthetic peptides, autoantigen, glycolipid, protein, mycoplasma or viruses). The effects of treatment on the animals' well-being were assessed by clinical and behavioural changes (POT and LABORAS assays) and gross and histopathological changes. In rabbits, treatment did not appear to induce acute or prolonged pain and distress. Mice showed behavioural changes immediately after (predominantly secondary) immunization. Injection of several adjuvant/antigen mixtures resulted in severe pathological changes, depending on adjuvant, type of antigen, animal species used and route of injection. Both rabbits and mice showed pathological changes ranging from marked to severe after injection of FA, and ranging from minimal to marked after Specol and Montanide injections. Pathological changes after RIBI injections were severe in rabbits, though slight in mice. After TiterMax injections, pathological changes were moderate in rabbits, though severe in mice. In conclusion, injection of FA according to present guidelines resulted mostly in severe pathological changes, whereas only very few clinical and behavioural signs indicated prolonged severe pain. Our findings indicate that Montanide ISA50 and Specol induce acceptable antibody titres, and cause fewer pathological changes than FA. Thus they are effective alternatives to FA.

Immune responses and side effects of five different oil-based adjuvants in mice.

In this study, five different oil based adjuvants were compared to assess efficacy and side effects. Mice were injected subcutaneously (s.c.) or intraperitoneally (i.p.) with a weak immunogen (synthetic peptide) emulsified in Freund's adjuvant (FA), Specol, RIBI, TiterMax or Montanide ISA50. Efficacy of adjuvants was evaluated based on their properties to induce peptide specific IgG1, IgG2a and total IgG antibodies, native protein cross-reactive antibodies and cytokine production. Side effects were evaluated based on clinical and behavioural abnormalities, and (histo)pathological changes. Although marked differences in isotype profile and height of titre are observed among the different adjuvants used, we found that FA, Montanide ISA50 and Specol worked equally well in the s.c. and i.p. route, TiterMax functioned only when given i.p. and RIBI also did not perform up to par. The number of cytokine (interferon-gamma and interleukin-4) producing spleen cells was significantly higher after injection of RIBI compared with other adjuvants. Injection of FA or TiterMax resulted in severe pathological changes while after RIBI injection minimal changes were observed. In conclusion, high peptide specific antibody levels with limited side effects can be obtained by s.c. injection of peptide combined with Montanide ISA50 or Specol as alternatives to FA.