Production and characterisation of a candidate hyper-immune serum for the replacement of the Bordetella pertussis mouse antiserum Biological Reference Preparation.

For acellular pertussis (aP) vaccines, the current European Pharmacopoeia (Ph. Eur.) monograph Pertussis vaccine (acellular, component, adsorbed) (1356) requires an immunogenicity assay in mice or guinea pigs to assess the potency of each lot of vaccine (Ph. Eur. general method 2.7.16. Assay of pertussis vaccine (acellular)). This biological assay, carried out on the final bulk of the vaccine lot, is based on the measurement of the specific antibody response to the 5 antigenic components (pertussis toxin (PT), Fimbrial haemagglutinin (FHA), pertactin (PRN) and Fimbriae 2 and 3 (FIM2/3)) that are present in the combined aP vaccines. In the mouse assay, serum antibody levels are measured by ELISA. The immunogenicity of a vaccine under test is estimated versus a homologous reference vaccine and a reference antiserum e.g. the first Ph. Eur. Biological Reference Preparation for Bordetella (B.) pertussis mouse anti-serum (BRP1), established in 1998, is used to normalise the titre of antibodies (expressed in ELISA Units (ELU)/mL). In anticipation of the depletion of BRP1 stocks, a project was launched in 2013 by the Biological Standardisation Programme (BSP) of the European Directorate for the Quality of Medicines & HealthCare (EDQM) in order to establish a new standardised reference serum. The project, referred to herein as BSP129, was conducted in 2 phases: 1) the production and characterisation of a mouse serum pool (using a multicomponent aP vaccine marketed in Canada similar to the vaccine used in the BRP1 production as immunogen) and of candidate BRP batches (cBRPs) and 2) an international collaborative study aimed at calibrating the cBRPs in terms of antibody levels against PT, FHA, PRN and FIM2/3. This article presents the design and results of the first phase of the collaborative study to establish the optimal conditions for immunisation and bleeding of mice in order to produce a large pool of hyper-immune serum against the 5 antigens. After the characterisation of this pool, cBRP pilot lots were manufactured by freeze-drying diluted solutions of the hyper-immune serum pool. The pilot lots were then characterised in two Official Medicines Control Laboratories (OMCLs) for their antibody contents against aP vaccine antigens using in-house ELISA (based on methods developed by 2 European vaccine manufacturers) and Multiplex Immunoassay (MIA) methods. The antibody titres recovered demonstrated that a dilution factor of 1/40 could be considered for the scaled-up manufacture of candidate reference preparations (cBRPs). Three batches (15 000 vials) of cBRP were manufactured and fully characterised. In light of the data obtained, and although titration results between the ELISA methods were sometimes discrepant, it was agreed that the establishment study (phase 2) could be launched. Real-time and accelerated stability studies were also included in the first study phase to document the stability of the cBRPs in freeze-dried form and after reconstitution and storage at -20°C±5°C. The results showed that the stability of the freeze-dried cBRPs at usual storage and shipment temperatures is acceptable and that reconstituted cBRP solutions are stable for 12 months at -20°C±5°C. It could therefore be recommended to freeze small aliquots of the 1 mL solution obtained by the reconstitution of one BRP vial in order to store them for use in separate assays. With the application of this strategy, the stocks of the BRP1 replacement batches should cover the needs of OMCLs and manufacturers for at least the next decade.

Establishment of Ph. Eur. Bordetella pertussis mouse antiserum Biological Reference Preparation batches 2, 3 and 4.

A project aimed at establishing replacement batches for the European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) Bordetella (B.) pertussis mouse antiserum was started in 2013 under the aegis of the Biological Standardisation Programme (BSP) of the European Directorate for the Quality of Medicines & HealthCare (EDQM). This BRP is used for the immunogenicity assay in mice to assess the potency of acellular pertussis (aP) vaccines as described in Ph. Eur. general method 2.7.16. Assay of pertussis vaccine (acellular). In a preliminary phase of the project (referred to herein as BSP129 phase 1) a hyper-immune serum pool was produced in mice using a combined aP vaccine as immunogen. This pool was used to generate 3 freeze-dried candidate (c) B. pertussis anti-mouse serum BRP batches (cBRP2, cBRP3 and cBRP4). After the pre-qualification that showed their suitability as candidate batches, an international collaborative study (BSP129 phase 2) was carried out in order to standardise these 3 batches against the current BRP1 in terms of anti-PT, -FHA, -PRN and -FIM2/3 antibody contents. For the sake of continuity with the standardisation of BRP1, the corresponding WHO standard (1RR 97/642) was introduced as a second reference for the calibration of the 3 candidate BRPs. Eleven laboratories took part in phase 2. Ten of them performed the ELISA method they use routinely for aP vaccine batch release and one laboratory performed the Multiplex Immunoassay (MIA) as an alternative test. Four participants titrated the antibodies against all 5 pertussis antigens, 5 participants determined the antibody content against 3 antigens (PT, FHA, PRN), one participant titrated the antibodies against PT and FHA antigens and one laboratory determined the antibody content for the PT antigen only. Details of all ELISA methods used were analysed to evaluate their impact on the calibration of the cBRPs. The variability of the results in relation to the nature and methodology of the tests appeared rather limited. Discrepant titres of cBRPs were measured depending on the reference used: the use of the 1RR induced an overestimation (in 8 out of 11 laboratories) and a large inter-laboratory variation in the calculated titres. Regardless of the reference used, equivalency between the calculated titres of cBRP2 and cBRP3 was observed, whilst cBRP4 had systematically lower titres for all antibodies against the 5 acellular pertussis vaccine components. Based on these observations, it was decided to establish the candidate BRP batches against BRP1 and to assign the following potencies based on the mean values determined through centrally calculated results of the calibration assays performed by ELISA in BSP129 phase 2: For cBRP2 and cBRP3 Anti-pertussis toxin: 37 ELISA Units (ELU) per vial Anti-filamentous haemagglutinin: 114 ELU per vial Anti-pertactin: 44 ELU per vial Anti-fimbrial agglutinogens (FIM2/3): 25 ELU per vial For cBRP4 Anti-pertussis toxin: 32 ELU per vial Anti-filamentous haemagglutinin: 98 ELU per vial Anti-pertactin 38 ELU per vial Anti-fimbrial agglutinogens (FIM2/3):23 ELU per vial In February 2018, BRP2, BRP3 and BRP4 were adopted by correspondence by the Ph. Eur. Commission.

Rapid PCR-based procedure to identify lactic acid bacteria: application to six common Lactobacillus species.

The goal of this study was to develop a method allowing rapid identification of the lactic acid bacteria strains in use in the laboratory (Lactobacillus plantarum NCIMB8826; L. fermentum KLD; L. reuteri 100-23; L. salivarius UCC43321; L. paracasei LbTGS1.4; L. casei ATCC393), based on PCR amplification of 16S RNA coding sequences. First, specific forward oligonucleotides were designed in the variable regions of 16S RNA coding sequences of six Lactobacillus strains. The reverse oligonucleotide was designed in the region where the sequences were homologous for the six strains. The expected size of the amplification product was +/-1000 bp. The specificity of the method was tested on total chromosomal DNA. For five out of the six strains, the amplification of the fragment was strain-specific and the method was directly applicable to colonies. For the strain L. casei ATCC393, an additional argument to the classification of this bacteria in the paracasei group could be proposed. Validation of the developed method was performed by applying it to six Lactobacillus reference strains and to various species of bacteria.

Expression of muscovy duck parvovirus capsid proteins (VP2 and VP3) in a baculovirus expression system and demonstration of immunity induced by the recombinant proteins.

The gene encoding the muscovy duck parvovirus (DPV)-strain 89384 capsid proteins VP2 and VP3 was cloned in a baculovirus expression system and expressed in insect cells. The recombinant proteins were found to react with specific anti-DPV serum by Western blotting and to be located in the nucleus of insect cells (Sf9) as shown by immunofluorescence. Empty virus-like particles (VLPs) identical in size and appearance to DPV virions were observed by electron microscopy. The antigenicity and immunogenicity of the recombinant proteins were evaluated by ELISA and seroneutralization. Immunization of 3-week-old muscovy ducklings induced anti-DPV antibodies; neutralizing antibody titres were consistent with those observed in ducklings inoculated with a commercial inactivated vaccine. The way to develop these promising results is discussed.

Construction of a new shuttle vector for Lactobacillus.

To clone the malolactic enzyme gene from Lactobacillus sp. 89, construction of a shuttle vector able to express itself in Lactobacillus sp. 89 and Escherichia coli was undertaken. The shuttle plasmid pLE16 resulted from the union of pBR328 and of the pLB10 plasmid extracted from Lactobacillus bulgaricus 10. The bacterial transformation in Lactobacillus sp. 89 was performed by electroporation, and the clones were selected on MRS medium with 30 micrograms.mL-1 chloramphenicol added. Fifty percent of the clones from Lactobacillus sp. 89 lost their resistance to chloramphenicol following 28 generations when the selection pressure was not maintained. The restriction map of pLE16 (7600 bp) was established using several restriction enzymes.

Purification and properties of a malolactic enzyme from Leuconostoc oenos ATCC 23278.

The malolactic enzyme of Leuconostoc oenos ATCC 23278 was purified 136fold. The molecular weight was estimated at 132,000 when determined by gel filtration. The enzyme contained two identical subunits (Mw = 66,000 using sodium dodecyl sulfate gel electrophoresis). The malolactic enzyme catalyzes the NAD(+)- and Mn(+)-dependent reaction L-malate----L-lactate + CO2. The apparent Km values for malic acid, NAD+, and Mn2+ were 17 mM, 0.044 mM, and 0.017 mM, respectively. The optimal pH and the optimal temperature for activity were 5.0, and 37 degrees C, respectively and the isoelectric point was pH 4.30. L-lactate and ethanol were non-competitive inhibitors, whereas succinate, citrate, and D-tartrate showed competitive type inhibitions.