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The goal of the collaborative study was to calibrate the B19 DNA content of a candidate Biological Reference Preparation (BRP) that is intended to be used for the validation of the analytical procedure, as threshold control and/or as quantitative reference material in the Nucleic Acid Amplification Technique (NAT) test of plasma pools for detection of B19 contamination. The candidate BRP was calibrated against the 1st International Standard for B19 DNA NAT assays. According to the European Pharmacopoeia monograph Human anti-D immunoglobulin, the threshold control needs to have a titre of 10( 4) IU/ml of B19 virus DNA. The lyophilised candidate BRP was prepared from 0.5 ml aliquots of a plasma pool spiked with B19 virus. The B19 virus originated from a "B19 virus window phase" blood donation (anti-B19 negative, B19-DNA high titre positive) and was diluted in a plasma pool tested negative by both serological and NAT assays for Hepatitis B Virus, Hepatitis C Virus and Human Immunodeficiency Virus 1 to obtain a B19-DNA concentration level in the range of 10( 6) copies/ml. The residual water content of the lyophilised candidate BRP was determined as 0.98 +/- 0.65% (mean +/- relative standard deviation). Sixteen laboratories (Official Medicine Control Laboratories, manufacturers of plasma derivatives, NAT test laboratories and NAT kit manufacturers) from nine countries participated. Participants were requested to test the candidate BRP and the International Standard (99/800) in four independent test runs on different days using their in-house qualitative and/or quantitative NAT methods. Sixteen laboratories reported results. Thirteen laboratories reported results from qualitative assays and 5 laboratories reported results from quantitative assays. Two laboratories reported results from both types of assay. For the qualitative assays a weighted combined potency of 5.64 log( 10) IU/ml with 95 per cent confidence limits of +/- 0.17 log( 10) which corresponds to 67 to 150 per cent of the estimated potency was determined. For the quantitative assay the semi-weighted combination of the 5 potency estimates lead to a combined potency of 5.83 log( 10) IU/ml with 95 per cent confidence limits of +/- 0.04 log( 10) which corresponds to 91 to 110 per cent of the estimated potency. The semi-weighted combination of the results from both types of assay lead to a final potency estimate of 5.80 log( 10) IU/ml with 95 per cent confidence limits of +/- 0.05 log( 10) which corresponds to 86 to 117 per cent of the estimated potency. A threshold control suitable for quantitative testing of B19 DNA and reflecting the requirements of the European Pharmacopoeia monograph Human anti-D immunoglobulin should contain 104 IU/ml of B19 DNA. Taking into account the assigned titre of 5.80 log( 10) IU/ml (630.957 IU/ml), a dilution of 10(-1.8) (1/63) of the candidate BRP should yield a positive response. This concentration was easily detected by all participating laboratories in a

Investigations on the replacement of the mouse neutralisation test for proving vaccine batches of Clostridium (C.) perfringens toxoid vaccines were performed since several years. The European Pharmacopoeia (Ph. Eur.) monograph Clostridium perfringens vaccines for veterinary use (0363) is prescribing a potency test by immunisation of rabbits and checking the induction of specific antibodies against the toxins in a mouse neutralisation test. Since the monograph was revised, immunochemical methods are favoured to detect directly specific antibodies in the rabbit sera. An indirect competitive ELISA using a monoclonal antibody was established at the Paul-Ehrlich-Institut for the detection of antibodies against the epsilon toxin component of C. perfringens. It was revised using the Clostridia rabbit antiserum Ph. Eur. Biological Reference Preparation (BRP) Batch 1 as reference serum. With a defined content of 11 International Units (IU) of C. perfringens epsilon antitoxin this reference serum enables the calculation of the potency of rabbit sera under test. For the collaborative study vaccine products of different composition licensed for the German and European markets were used. Seven international laboratories were included. Aim was to make a prediction on the transferability and precision of the test method. The results showing a satisfactory intermediate precision and transferability of the test confirmed the applicability of the ELISA method for the batch control of C. perfringens vaccines. Therefore a replacement of the mouse neutralisation test is available.

A collaborative study was initiated by the European Directorate for the Quality of Medicines (EDQM), to assign a potency value for candidate batch 2 of European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) for Hepatitis B (rDNA) antigen in vitro assays, for both method A and method B by calibrating them against the Ph. Eur. BRPs, batch 1 for methods A and B respectively. The study was prompted by the observation that the first batch of BRP for method B appeared to have lost potency over time. BRP 1 for method A showed no loss in potency, however stocks of the material were nearing depletion. Eleven laboratories participated in the study and all reported results. Participants performed 3 independent assays using both method A and method B. Method A was used to assess BRPs for method A and method B was used to assess BRPs for method B. Since BRP 1B was suspected to have lost potency, an additional sample was included in the method B test in an attempt to clarify the situation. BRP 1B was also assayed in method A against BRP 1A in the hope of also attaining further information by comparing the results from this study to those obtained in the original study to establish the first batch of BRP [1]. Although it was not the primary aim of this study to correlate in vitro potency with the immunogenicity assay in mice, a number of interested parties also performed the mouse in vivo assay to obtain data on the behaviour of the candidate BRPs in this assay. For method A, potency estimates were satisfactory in terms of repeatability and reproducibility. The candidate material was therefore assigned a value of 16.6 micrograms/ml. For method B, it appeared that the observation of reduced in vitro potency of BRP1 was confirmed. Despite the attempt to clarify the situation with additional studies, it was not possible to assign a potency value with the results obtained. A small-scale collaborative study will be organised to determine an appropriate value for the candidate BRP for method B. The results from the in vivo study while highly variable showed no evidence of a shift in the in vivo potency for either BRP 1A or BRP 1B. It should be noted that the in vitro method for determination of hepatitis B vaccine potency is under revision due to the discontinuation of the Auszyme kit from Abbott, which is required to perform the current assays. Once an alternative assay has been established, the suitability of the reference preparations or establishment of new reference preparations will be required. The candidate material for method A BRP was adopted by the European Pharmacopoeia Commission at its session in November 2003, as the European Pharmacopoeia Hepatitis B vaccine (rDNA) method A, batch 2.

Collaborative studies were initiated by the European Directorate for the Quality of Medicines (EDQM) to assign potency values for candidate European Pharmacopoeia Chemical Reference Substances (Ph. Eur. CRSs) used for the microbiological assay of antibiotics. The candidates were assayed against their respective International Standard (IS), using the methods by diffusion or turbidimetry. Potencies were assigned to all the antibiotics concerned, which were adopted by the European Pharmacopoeia Commission.

A collaborative study on the evaluation of an alternative functional assay, the Vero cell method, to the Ph. Eur. in vivo challenge procedures for potency determination of diphtheria toxoid in 6 different combined vaccines was initiated in January 2001. The study was an extension of a previous study for the validation of serological methods for potency testing of tetanus toxoid vaccines for human use. To allow interim evaluation of test results and to monitor study progress, the project was divided into three consecutive phases. The results of Phase I and II studies are presented in this report. Pre-validation (Phase I) study, performed in two laboratories, indicated that comparable diphtheria potency estimates were obtained in the Ph. Eur. direct intradermal challenge assay in guinea pigs, in Vero cell assay and in indirect ELISA for five vaccines of different potencies (range of estimates: ca. 20-200 IU/ml). The correlation coefficients between the challenge assay and the Vero cell assay corresponded to those between the challenge assay and ELISA, confirming that the antibodies play an important role in protection and that predominantly protective/neutralising antibodies are present in guinea pigs, at the time point investigated. It was observed, for Vero cell assays, that about 16-35 (9-28 in Phase II study) fold lower titre of individual serum samples were obtained when using equine, rather than guinea pig reference serum. The study also provided preliminary information that sera from the same guinea pigs may be used for potency determination of both diphtheria and tetanus toxoid components of vaccines. In Phase II, another five laboratories analysed a subset of the vaccines included in Phase I study plus an additional vaccine. Four laboratories performed the lethal challenge assay and one laboratory carried out the intradermal challenge assay. All laboratories also performed the Vero cell assay and both ELISA for diphtheria antitoxin and ELISA for tetanus antitoxin. One laboratory also performed the tetanus ToBI assay. The correlation coefficient (r) between Vero cell assay and ELISA for diphtheria antitoxin ranged from 0.76 to 0.91 in the different laboratories. The correlation between diphtheria serological assays and challenge assays were confirmed satisfactory as ca. 90 per cent of serum-estimates lead to correct prediction of mortality. All laboratories had identical rankings of the vaccines in all serological assays and in the valid challenge assays. The ranking order was identical to assumed/provided potency for the highest and the lowest vaccine. Two of the vaccines had an inversion in some assays and laboratories. As these two vaccines have almost identical potencies in all assays, these inversions are not significant. As the vaccine doses were optimised for the diphtheria component, serum anti-tetanus toxoid/toxin activities varied widely between the vaccines, making it questionable to apply a parallel line model to calculate

An international collaborative study aimed at establishing a global standard for the potency assay of anti-D immunoglobulin was started in 2002. 25 laboratories participated in this study run under the common aegis of the World Health Organization, the United States Food and Drug Administration (US-FDA) and the European Directorate for the Quality of Medicines (EDQM). The potencies of three candidate materials and the US-FDA standard (lot 3) included for comparison were evaluated using AutoAnalyzer, competitive enzyme-linked immunoassay (competitive EIA), flow cytometric methods or own "in-house" methods. Critical reagent, standardised procedures and standardised assay design were provided for either method, where appropriate. Central statistical evaluation of the potency data submitted by the participants was performed using a parallel line model. Agreement between laboratories and assay methods for all samples was observed. Intra-laboratory variability was lowest for laboratories performing flow cytometry and highest for laboratories that performed their in-house methods. Inter-laboratory variability was acceptable for all samples when assayed by AutoAnalyzer, competitive (EIA) and flow cytometric methods. It was concluded that sample A is most suitable to serve as a global standard and that sample C could serve as a reserve European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) batch provided that suitable stability is demonstrated. Sample A was adopted by the Ph. Eur. Commission at its 115th session (March 2003) as the first Ph. Eur. BRP (available from the EDQM: catalog number Y0000219) with the assigned potency of 285 IU/ampoule.

A stable liquid candidate Biological Reference Preparation (BRP) for diphtheria toxin was prepared in peptone buffer (nominal content of diphtheria toxin: 1 Lf/ml, 0.4 micro g/ml), filled in ampoules (filling volume: 1 ml) and characterised in a collaborative study. The toxin is to be used in the test "Absence of toxin and irreversibility of toxoid" as described in the current European Pharmacopoeia (Ph. Eur.) monograph Diphtheria Vaccine (Adsorbed) (2002:0443). Eleven laboratories assessed the specific activity of the preparation by in vivo and in vitro assays. The material is assumed to have satisfactory stability with a calculated predicted loss of activity of <1% per year at 4-8 degrees C. From the collaborative study, the specific activity was calculated as 77.6 (45-113) LD( 50)/ml (lethal challenge) and >75 000 Lr/Lf (intradermal challenge). The candidate BRP was successfully used in nine laboratories and confirmed suitable for use in the Vero cell test for "Absence of toxin and irreversibility of toxoid" as described in the Ph. Eur. monograph 2002:0443; i.e., concentrations of 5 x 10( -5) Lf/ml and below caused cytotoxic effects in the Vero cell test. Due to its liquid nature, the stability of the material will be monitored at regular intervals and preparation of a stable freeze-dried formulation will be considered for long-term use. Additional studies will be performed to confirm suitability of this BRP for other applications. The candidate BRP was adopted as the Ph. Eur. reference material for Diphtheria Toxin Batch 1 by the Ph. Eur. Commission at its session in March 2003.

A collaborative study was initiated by the European Directorate for the Quality of Medicines (EDQM) to assign a potency value for the candidate Ph Eur BRP batch 2 against the 2nd International Standard (IS) in order to replace the dwindling stocks of Ph Eur BRP batch 1. The candidate material is a concentrated trivalent bulk (Type 1 (Mahoney), Type 2 (MEF1) and Type 3 (SAUKETT)) from a commercially available IPV vaccine. Nine laboratories participated in the collaborative study. Eight laboratories reported results. Participants performed in-house ELISA assays on the candidate BRP, the 2nd International Standard (IS) and the current BRP (BRP batch 1). An additional sample was included to acquire information on the correlation between the in vitro and in vivo assays based on comparison with a previous study. Results of that comparison are included as an annex. Potency estimates were satisfactory in terms of repeatability and reproducibility, however the estimates for the 2nd IS were significantly lower than those for Ph Eur BRP batch 1. These two reference standards are derived from the same material and were originally assigned the same potency value after a joint study run by EDQM and the WHO in 1994. A reconciliation study was therefore designed to determine if the IS stored at NIBSC and the IS which had been sent from NIBSC to EDQM for use in the initial study were equivalent. 3 of the laboratories from the initial study participated. Results revealed no significant difference between the 2nd IS stocks stored in the two different locations at NIBSC nor between BRP batch 1 and the standards stored at NIBSC for types 1 and 2. For type 3 the 2nd IS standards stored at NIBSC are 13 % less potent than the Ph Eur BRP batch 1. The 2nd IS which had been shipped from NIBSC to EDQM was significantly less potent than BRP batch 1 and the 2nd ISs stored at NIBSC for all three types, confirming the observation of the initial study. Possible explanations for this apparent loss of potency of the 2nd IS used in the study are under investigation. Since Ph Eur BRP batch 1 and the 2nd IS in stock at NIBSC appear no more different than when their original potency assignment was made at their establishment, and since the 2nd IS standard used in the initial part of this study was compromised, a consensus potency value for the candidate BRP was determined using Ph Eur BRP batch 1 as the reference standard. The candidate material was therefore assigned a potency of 320-67-282 D Antigen units/ml (IU) for types 1, 2 and 3 respectively. A stability monitoring program will be initiated. The candidate material was adopted by the European Pharmacopoeia Commission at its session in March 2003 as European Pharmacopoeia IPV vaccine BRP batch 2 for D Ag in vitro assay.

A Newcastle disease virus antigen quantification assay has been developed at CIDC-Lelystad as a candidate in vitro potency test for inactivated Newcastle disease vaccines. In studies performed at CIDC-Lelystad, a high correlation was demonstrated between the results of this candidate in vitro potency assay and the results of the serological potency assay (European Pharmacopoeia monograph 0870; test A). Furthermore, a high correlation between the serological data (Haemagglutination Inhibition-antibody titres) and clinical protection after challenge was demonstrated. The aim of the feasibility study was to confirm the correlation between the results obtained using the candidate in vitro potency assay and the results from both the in vivo potency assays currently prescribed in Ph Eur monograph 0870, in different laboratories and to determine whether a large-scale validation study of the in vitro method should ensue. In the feasibility study three Official Medicines Control Laboratories tested the potency of 5 different inactivated Newcastle disease vaccines and one experimental vaccine, using both of the in vivo methods described in the European Pharmacopoeia and the candidate in vitro method. The 6 vaccine batches represented a quantitative range of Newcastle disease virus antigen content and were produced by different manufacturers. Statistical evaluation of all results indicated that a satisfactory correlation was found in all laboratories between the two types of in vivo tests currently in place, and the candidate in vitro test. An excellent reproducibility of the proposed in vitro method was observed with respect to the ranking of the vaccines included in this study. It is concluded that the results of this feasibility study indicate that a large-scale collaborative study can be organised to validate the in vitro method and the suitability of the reference preparation.