Evaluation of fourth international standard for whole cell pertussis vaccine

Whole cell pertussis vaccine is still widely used in many countries. An International Standard is needed for its potency control. The Third International Standard for Pertussis Vaccine was prepared about 40 years ago and its replacement was recommended by the Expert Committee for Biological Standardisation (ECBS) of the WHO. Material in ampoules coded 94/532 was prepared as a candidate replacement and has been evaluated in international collaborative studies which consisted of two parts. The first part, to assess the suitability of the candidate standard by comparing it with the Second International Standard for Pertussis Vaccine (IS2) involved 14 laboratories in 11 countries. The second part to compare the candidate standard with the Third International Standard for Pertussis Vaccine (IS3) involved 16 laboratories in 14 countries. Since 1995 various other studies have included the international standards and the results of these are also considered in assessing likely continuity of the IU for potency of whole cell pertussis vaccine. The preparation in ampoules coded 94/532 was adopted by the WHO ECBS in October 2006 as the 4th International Standard for whole cell pertussis vaccine and assigned an activity of 40 IU per ampoule on the basis of the studies reported here.

The CREATE project: development of certified reference materials for allergenic products and validation of methods for their quantification

Allergen extracts have been used for diagnosis and treatment of allergy for around 100 years. During the second half of 20th century, the notion increasingly gained foothold that accurate standardization of such extracts is of great importance for improvement of their quality. As a consequence, manufacturers have implemented extensive protocols for standardization and quality control. These protocols have overall IgE-binding potencies as their focus. Unfortunately, each company is using their own in-house reference materials and their own unique units to express potencies. This does not facilitate comparison of different products. During the last decades, most major allergens of relevant allergen sources have been identified and it has been established that effective immunotherapy requires certain minimum quantities of these allergens to be present in the administered maintenance dose. Therefore, the idea developed to introduce major allergens measurements into standardization protocols. Such protocols based on mass units of major allergen, quantify the active ingredients of the treatment and will at the same time allow comparison of competitor products. In 2001, an EU funded project, the CREATE project, was started to support introduction of major allergen based standardization. The aim of the project was to evaluate the use of recombinant allergens as reference materials and of ELISA assays for major allergen measurements. This paper gives an overview of the achievements of the CREATE project.

Implications of experimental technique for analysis and interpretation of data from animal experiments: outliers and increased variability resulting from failure of intraperitoneal injection procedures

Intraperitoneal (i.p.) injections are widely used in laboratory animal experiments. This technique has a failure rate that is typically reported to be of the order of 10-20%. It is not apparent that failures of i.p. injection and their consequences for the experimental results are as widely recognized as the use of the technique. We illustrate the consequences of i.p. injection failure for the analysis and interpretation of several bioassays. We suggest approaches to data analysis that should be considered, and emphasize the need to recognize and allow for the possibility of i.p. injection failure in the analysis and interpretation of laboratory animal experiments involving this technique.

Standardization of antibody preparations for use in immunogenicity studies: a case study using the World Health Organization International Collaborative Study for Islet Cell Antibodies

The immunogenicity of biological therapeutic products is currently a high profile regulatory and biotechnology industry issue. The immune responses raised against biotechnology products range from the benign, to affecting product efficacy, to those that have serious deleterious clinical impact. The most widely used marker of immunogenicity is the detection and measurement of antibody responses induced in vivo to a product. This relies on assays that are sensitive and robust. In order to assess the parameters of an assay during its design, development and validation, it is extremely useful to have a reference standard to compare assay results. However, immune responses lead to polyclonal antibody preparations that can vary by affinity and avidity. This makes it extremely difficult to select a preparation that will behave similarly in different test systems and against different antibody samples. The case example of the WHO standardization of islet cell antibodies illustrates the difficulties in the process and the mechanisms required to produce a suitable antibody standard.

Comparison of the bioactivity of reference preparations for assaying Bordetella pertussis toxin activity in vaccines by the histamine sensitisation and Chinese hamster ovary-cell tests: assessment of validity of expression of activity in terms of protein concentration

Pertussis toxin (PT) in its detoxified form is an important antigenic component of both acellular and whole cell pertussis vaccines. Limits on the content of active PT in acellular vaccines are set in official monographs (EP, WHO, USP) and evidence of compliance is therefore, required by regulatory authorities. The two assay methods which are currently used by most manufacturers and official national control laboratories to monitor residual PT activity in acellular pertussis vaccines (and also in whole cell vaccines) are histamine sensitising (HIST) assays and Chinese hamster ovary (CHO) cell assays. Currently, different reference preparations of PT are used by individual laboratories for these tests. We therefore organised an international collaborative study to examine, by these two assay methods, two freeze-dried purified preparations of PT, one preparation in ampoules coded JNIH-5 and one preparation in ampoules coded 90/518, together with in-house reference (IHR) preparations in current use. Data from this study confirm that both JNIH-5 and 90/518 show biological activity both in HIST assays and in CHO-cell assays. Both HSD50 and ED50 values obtained in this study differ significantly between laboratories and thus show that biological activity is not determined by the nominal masses of preparations. Estimates of relative potency of 90/518 in terms of JNIH-5 per ampoule for the HIST assays do not differ significantly between laboratories. The overall mean estimates of relative potency of 90/518 in terms of JNIH-5 do not differ significantly between the two methods. Data from this study further indicate that the biological activity of different preparations was not directly related to their stated protein content. The use of protein content to indicate the level of PT activity in different preparations would give misleading results. Thus, use of a common standard is shown to greatly improve between laboratory agreement of estimates.

Cytokine levels as performance indicators for white blood cell reduction of platelet concentrates

BACKGROUND AND OBJECTIVES

With the implementation of universal white blood cell (WBC) reduction in the UK, in-process WBC-reduction filters for pooled buffy coat (BC)-derived platelet concentrates (PCs) and apheresis methods are used routinely for the production of WBC-reduced PCs. While these strategies meet the specification for WBC reduction (< 5 x 10(6) WBCs/unit), the products from these processes may differ depending on the process employed and its performance. The aim of this study was therefore to investigate whether PCs prepared using various WBC-reduction processes are sufficiently depleted of WBCs to limit cytokine accumulation during storage and to assess if cytokine levels detected in platelet products can serve as indicators of acceptable platelet activation as a result of the WBC-reduction process.

MATERIALS AND METHODS

We measured the levels of cytokines predominantly derived from WBCs [e.g. interleukin-8 (IL-8)] and platelets [e.g. regulated on activation, normal, T-cell expressed, and secreted (RANTES) and transforming growth factor-beta(1) (TGF-beta(1))] under the present experimental conditions in different WBC-reduced PCs, i.e. PCs prepared from three different WBC-reduction filters and control non-filtered PCs using pooled BCs from the same donors and three apheresis types. Supernatant plasma was collected at the beginning (day 1) and end (day 5) of the shelf life of each PC, and the cytokine content was determined using appropriate enzyme-linked immunosorbent assays (ELISAs). Process efficiency was assessed by platelet yield and residual WBC count.

RESULTS

We found that products from the apheresis process involving a filtration step (Haemonetics MCS+) showed a lower cytokine content on both day 1 and day 5 in comparison with the fluidized bed (COBE Spectra) or elutriation (Amicus) processes. WBC reduction of BC-PCs of the same origin using three different filters showed comparable levels of cytokines on day 1 in all units. After storage for 5 days, the levels of IL-8 remained essentially unchanged in filtered BC-PCs but increased by more than threefold in control non-filtered BC-PCs, suggesting IL-8 release by residual WBCs present in the control PCs. The concentration of platelet-derived cytokines such as RANTES and TGF-beta(1), however, increased significantly in all filtered and control non-filtered PCs during the storage period.

CONCLUSION

These results show that markers of cytokine release from both WBCs and platelets are useful indicators of the performance and efficacy of the WBC-reduction process and of platelet quality.

Laboratory testing of whole cell pertussis vaccine: a WHO proficiency study using the Kendrick test

Whole cell pertussis vaccine (WCV), commonly in combination with vaccines for diphtheria and tetanus, has an important role in reducing morbidity and mortality among children in most parts of the world. Testing to assure the efficacy of such vaccines is essential. We have, therefore, carried out, under the Global Training Network (GTN) of the Department of Vaccines and Biologicals at the World Health Organization (WHO), a proficiency study involving 13 laboratories in 12 countries that routinely test WCV. Two vaccine samples were tested in this study and represented samples which were expected clearly either to pass (sample B, a full strength vaccine) or to fail (sample A, 1/8 strength of vaccine B). Data from this study showed good performance by the majority of participants. Most assays were statistically valid and were carried out to the level of precision achieved for these assays in previous studies. This study also indicated that, relative to the assay precision, the in-house reference (IHR) preparations are in general accurately calibrated. Statistically valid assays of the sub-potent vaccine, A, showed it to fail in all except one laboratory. Statistically valid assays of the potent vaccine, B, showed it to pass in all laboratories. Nevertheless, the between laboratory variability of estimates for vaccine B, and for comparisons of the two vaccine samples suggested that there are some differences in results in different laboratories. The introduction of a common working standard may assist in reducing inter-laboratory variation. This study has shown clearly satisfactory performance by most laboratories. However, a serious problem was detected in one laboratory where the sub-potent vaccine A could have been passed and was not distinguished from the eight-fold more potent vaccine B. There were also indications of possible problems in several other laboratories, where IHR preparation may not be accurately calibrated or where vaccine samples A and B may not be completely distinguished. Although this study provides reassurance that most laboratories perform well, it demonstrates the essential role of ongoing proficiency studies in high-lighting problems.

Establishment of new and replacement World Health Organization International Biological Standards for human interferon alpha and omega

The complexity of the human interferon-alpha (IFN-alpha) family, with its multiple molecular forms and various biological activities, raises a number of scientific issues with regard to the biological standardisation of natural and recombinant IFN-alpha products. To address such issues and to achieve an appropriate biological standardisation of human interferon-alpha (IFN-alpha) preparations, the National Institute for Biological Standards and Control (NIBSC) of the United Kingdom (UK), in association with the Centre for Biologics Evaluation and Research (CBER) of the United States of America (USA), organised an international collaborative study, which was subsequently divided into two parts. Ninety-three participating laboratories from 29 countries worldwide participated in the first part of the study. They performed titrations on up to 15 different IFN-alpha preparations and one IFN-omega (omega) preparation in a variety of assays, including those based upon antiviral, antiproliferative, and other biological activities of IFN, and contributed raw data from these assays to NIBSC for analysis and calculation of relative activities. Analysis of data from this part of the study showed a greater than expected assay-dependent disparity between the relative activities of different IFN-alpha preparations. This disparity was found when only antiviral assays were considered and even when there were only small molecular dissimilarities between two otherwise closely related IFN-alpha preparations. The lack of assay independence and relative activity equivalence has indicated that a single biological potency standard for all IFN-alpha subtypes and mixtures would be inappropriate. Hence, individual, homologous standards, each with a separate unitage, were required for biological standardisation and potency determinations of individual IFN-alpha subtypes. At this stage, potency assignments to the IFN-alpha and -omega preparations included in the study were made as far as possible on the basis of comparison of antiviral activity with that of the 1st International Reference Preparation (IRP) for IFN, human leukocyte, 69/19. However, it was recognised that other standards had been used in assays to estimate potencies of widely available, current, therapeutic IFN-alpha products. Thus, to ensure the continuity of unitages already in use for IFN-alpha products, the second part of the study, which involved 12 members of the International Federation of Pharmaceutical Manufacturers Association (IFPMA), was carried out using for calibration of antiviral assays those IFN-alpha preparations that most closely matched manufacturers' products or that had been previously used for assay calibration by a manufacturer for a particular product. On the basis of data analysis from the second part of the study, potency assignments to the IFN-alpha preparations, as made in the first part of the study, were either left unchanged or changed to potency assignments that ensured as far as possible continuity with existing unitages. From among the IFN preparations evaluated, the following were recommended as the most suitable to continue or replace existing WHO international standards (IS) and have subsequently been formally established as WHO IS at the 51st meeting (October 1999) of the WHO ECBS: 83/514, 1st WHO IS for human IFN-alpha1 8000 international units (IU); 95/650, 2nd WHO IS for human IFN-alpha2a, 63,000 IU; 95/566, 2nd WHO IS for human IFN-alpha2b, 70,000 IU; 95/580, 1st WHO IS for human IFN-alpha2c, 40,000 IU; 95/572, 1st WHO IS for human IFN-alpha1/8, 27,000 IU; 94/786, 1st WHO IS for human IFN-alphaCon1, 100,000 IU; 94/784, 2nd WHO IS for human IFN-alpha (leukocyte), 11,000 IU; 95/574, 1st WHO IS for human IFN-alpha (leukocyte n3), 60,000 IU; 95/568, 2nd WHO IS for human IFN-alpha (lymphoblastoid n1), 38,000 IU; 94/754, 1st WHO IS for human IFN-omega, 20,000 IU. These WHO IS are available upon request to NIBSC.

The first international standard for human leptin and the first international standard for mouse leptin: comparison of candidate preparations by in vitro bioassays and immunoassays

In an international collaborative study, two preparations of human sequence recombinant leptin and two preparations of mouse sequence recombinant leptin were evaluated, using in vitro bioassays and immunoassays, by eight laboratories, in three countries, for their suitability to serve as the international standard (IS) for human and mouse leptin respectively. The bioassays detected the human and mouse leptin with similar potency, while the immunoassays showed a greater response to the leptin of the species against which the antibody preparation had been raised. Comparison of the candidate standards with the various preparations of leptin of the same species currently assayed in the participating laboratories showed that immunoassay measurements cannot be used to predict the biological potency. On the basis of the results reported here, in October 1999 the Expert Committee on Biological Standardization of the World Health Organization established the preparation coded 97/594 as the first IS for human leptin, with an assigned unitage of 4000 IU/ampoule, and the preparation coded 97/626 as the first IS for mouse leptin, with an assigned unitage of 4000 IU/ampoule. The ISs for leptin are distributed by the National Institute for Biological Standards and Control, UK, http://www.nibsc.ac.uk.

Third International Standard for pertussis vaccine: international confirmation study of activity of British Standard for pertussis vaccine, coded 66/303

The first British Standard (BS) (Code 66/303) for pertussis whole cell vaccine was prepared from the same suspension of Bordetella pertussis as the now exhausted Second International Standard for Pertussis Vaccine (2ndIS). The BS and the 2ndIS were compared and calibrated in a previous international study. This report describes a small international study, which included the BS, the 1stIS and the 2ndIS so that the present relationship of these preparations to one another could be assessed. The results of this study show that the relationship of the BS to the 1stIS is consistent with its established unitage of 46 IU per ampoule. The results further show that the potency of the BS is broadly consistent with that of the 2ndIS and that the BS has not lost activity relative to the 2ndIS (from which it was previously found to be indistinguishable). Based on its original calibration and supported by the results of this present study, the BS has been established as the Third International Standard for Pertussis Vaccine, with an assigned unitage of 46 IU per ampoule.

International collaborative study: evaluation of proposed International Reference Reagent of pertussis antiserum (mouse) 97/642

A freeze dried preparation of mouse serum in vials coded 97/642 containing antibodies to five pertussis antigens [pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (PRN), fimbriae type 2 and 3 (Fim 2 and 3)] has been assessed for its suitability as an international reference reagent in an international collaborative study by thirteen laboratories in nine countries. This serum has been compared with U.S. Standard Pertussis Antiserum (mouse) Lot No. 1 (US Lot 1), which has been in use since 1995, for antibodies for each antigen. Calibration of the proposed International Reference Reagent of Pertussis Antiserum (pIRR) in terms of US Lot 1 gives results which are broadly consistent between laboratories for antibodies to each antigen, although the between-laboratory differences are larger than those seen for comparison of identical sera. Calibration of two positive control sera in terms of the pIRR gave similar between laboratory variability of estimates to that obtained when the same sera were calibrated in terms of US Lot 1. Overall continuity of estimates is maintained if units are assigned to the pIRR based on its calibration in terms of US Lot 1 in this study. Data presently available indicate that the pIRR is sufficiently stable to serve as a reference reagent. It was therefore recommended, with the agreement of all participants, that the preparation in vials coded 97/642 be established as the First International Reference Reagent for Pertussis Antiserum, mouse, with assigned unitages 16 units of anti-PT per vial, 143 units of anti-FHA per vial and 30 units of anti-PRN per vial based on its calibration in terms of US Lot 1. These unitages are also consistent with calibration of 97/642 in terms of the Japanese preparations JNIH-11 for anti-FHA and of JNIH-12 for anti-PT. Purified antigens for Fim 2 and Fim 3 are not readily available and an arbitrary value of 32 units per vial is suggested for anti-Fim 2 and 3 mixture. These recommendations were agreed by the Expert Committee on Biological Standardization of the World Health Organization.

The World Health Organization International Collaborative Study for islet cell antibodies

AIMS/HYPOTHESIS

Islet cell autoantibodies are a specific marker for Type 1 (insulin-dependent) diabetes mellitus. Standardisation of islet cell antibodies and the uniform reporting in International units is critical to research and the development of assays for islet cell autoantibodies as diagnostics.

METHODS

The suitability of a candidate serum to serve as the international standard for islet cell antibodies was studied by 19 participants in 8 countries. In addition, the purpose was to investigate whether the serum could also serve as a standard for antibodies to the 65000 Mr isoform of glutamic acid decarboxylase (GAD65) and islet antigen-2 (IA-2). Control sera were included in the study to assess the validity of the various assay systems. The sera were lyophilized to World Health Organization criteria and the candidate serum assigned the ampoule code number 97/550.

RESULTS

The use of 97/550 was shown to notably reduce inter laboratory variability in the measurement of islet cell antibodies. In addition, there was a pronounced reduction in inter laboratory variability in the measurement of GAD65 and IA-2 antibodies.

CONCLUSIONS/INTERPRETATION

On the basis of the results reported here and with agreement of the participants, the preparation 97/550 has been established by the World Health Organization Expert Committee on Biological Standards for establishment as the first international standard for islet cell antibodies, with an assigned potency of 20 international units. In addition, 97/550 can serve as an international reference reagent for specific GAD65 antibodies, with an assigned potency of 100 units. It can also serve as a National Institute of Biological Standards and Control (NIBSC) reference reagent for IA-2 antibodies for evaluation of assays for this material.

Reference reagents for prostate-specific antigen (PSA): establishment of the first international standards for free PSA and PSA (90:10)

BACKGROUND

Prostate-specific antigen (PSA) measurements in serum by immunoassay are widely used in the screening, diagnosis, and monitoring of patients with prostate cancer although the lack of common reference reagents has led in the past to wide differences in estimates. We report here the results of a WHO international collaborative study in which two preparations of PSA representative of the main immunoreactive components in serum, free PSA and PSA 90:10, and a preparation of recombinant DNA-derived PSA were assessed as potential standards for the calibration of diagnostic immunoassays for PSA.

METHODS

Coded vials of the candidate materials and serum preparations containing PSA in the clinically important range were provided to the 10 laboratories in the study, and participants were asked to perform PSA assays currently in use in their laboratories. Data from 89 immunoassays by 26 different method-laboratory combinations were contributed to the study and analyzed centrally at the National Institute for Biological Standards and Control.

RESULTS

Potency estimates of the preparations relative to the in-house calibrators were in good agreement with the target value of 1 microg of total PSA/vial, the preparation of free PSA giving 1.10 microg/vial (95% confidence interval, 0.99-1.21 microg/vial) and PSA 90:10, 1.11 microg/vial (95% confidence interval, 1.04-1.18 microg/vial). No immunoreactivity was detected in ampoules containing the recombinant material. Use of a common standard of PSA 90:10 significantly reduced the between-laboratory geometric coefficients of variation for serum samples included in the study and gave a much narrower range of potency estimates.

CONCLUSIONS

The preparation of free PSA was established by WHO as the First International Standard for PSA (free) with an assigned content of 1 microg of total PSA per vial. In addition, the preparation of bound PSA was established as the First International Standard for PSA (90:10) with an assigned content of 1 microg of total PSA per vial.

Neutralizing antibodies to granulocyte-macrophage colony-stimulating factor, interleukin-1alpha and interferon-alpha but not other cytokines in human immunoglobulin preparations

Human immunoglobulin preparations are used therapeutically for various disorders. Such therapy is generally safe but adverse effects occasionally occur in recipients. It has been suggested that antibodies to cytokines present in clinical immunoglobulin products may contribute to undesirable effects in recipients. Therefore, we investigated intravenous and intramuscular immunoglobulin products for the presence of cytokine-specific neutralizing antibodies. Using validated bioassays, we detected neutralizing activity against human granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-alpha2a (IFN-alpha2a) and interleukin-1alpha (IL-1alpha) in immunoglobulin products. We found no neutralization of granulocyte colony-stimulating factor, macrophage colony-stimulating factor, stem cell factor, IL-1beta, IL-2, IL-3, IL-4, IL-6, IL-9, IL-10, IL-12, tumour necrosis factor-alpha, oncostatin M (OSM) and IFN-gamma. Most batches which neutralized IFN-alpha2a activity also neutralized other IFN-alpha subtypes, IFN-omega and IFN-beta. Most products (94%) neutralized the biological activity of GM-CSF. No correlation between batches and their ability to neutralize bioactivities of GM-CSF, IFN-alpha2a and IL-1alpha was found. This neutralizing activity could be traced to plasma pools used for manufacture of immunoglobulins. The neutralization was mediated by specific cytokine antibodies contained within immunoglobulin products as it was present in specific immunoglobulin G (IgG) fractions eluted from cytokine affinity chromatography columns. Specific binding of such IgG fractions to cytokines in immunoblots and in enzyme-linked immunosorbent assays (ELISAs) was observed. This contrasts with the broad non-specific recognition of cytokine proteins observed using unfractionated immunoglobulins in ELISAs. This is the first comprehensive study showing the presence of neutralizing antibodies against GM-CSF, IL-1alpha, or IFN-alpha2a in immunoglobulin products.

Comparison of pituitary and recombinant human thyroid-stimulating hormone (rhTSH) in a multicenter collaborative study: establishment of the first World Health Organization reference reagent for rhTSH

BACKGROUND

The increasing use of recombinant-DNA-derived materials in therapy and diagnosis poses a new challenge for biological standardization, that of developing reference preparations appropriate for both the native and recombinant products. Here we report the results of an international collaborative study that was carried out under the auspices of WHO to assess the suitability of a preparation of recombinant thyroid-stimulating hormone (rTSH; 94/674) to serve as a potential standard for the calibration of diagnostic immunoassays compared with the International Reference Preparation (IRP) for human TSH (80/558).

METHODS

Coded samples were provided to the 33 laboratories in the study, and participants were asked to perform TSH assays currently in use in their laboratories. Twenty-eight laboratories contributed 93 immunoassays in 41 different method-laboratory combinations, and an additional 5 laboratories contributed bioassay data. All data were analyzed centrally at the National Institute for Biological Standards and Control.

RESULTS

The results obtained in different laboratories and with different assay systems revealed significant variability between estimates of rTSH relative to the IRP. These ranged from 5. 51 mIU (95% limits, 3.95-7.67 mIU) per ampoule by RIA to 7.15 mIU (95% limits, 6.7-7.63 mIU) per ampoule by immunofluorometric assay. However, the results showed that the assignment of a value of 6.70 mIU per ampoule of 94/674 would give reasonable continuity with the IRP in many assay systems.

CONCLUSIONS

The preparation was established as the First WHO Reference Reagent for TSH, human, recombinant, to provide a means of validating assay performance and to maintain continuity with the IRP without compromising clinical data.

Biological standardization of cytokines and growth factors

To quantify the biological activity of different cytokine preparations with different specific activities by bioassay, mass units cannot be used and biological activity has to be expressed as << biological potency units >>. The biological unit requires definition by a standard that is assay-independent (especially when measuring a particular type of biological activity). Once the unit is defined, it can be used in any laboratory, thus providing a means of ensuring uniformity throughout the world in the designation of potency of different biological preparations. The World Health Organisation (WHO) standardization programme involves the production of biologically stable, well-characterised potency and immunoassay standards that are available world-wide using a single international unitage. These international standards have been used to reduce dramatically the variation in estimates of cytokine preparations within and between laboratories for immunoassays and bioassays.

An aerosol challenge model of Bordetella pertussis infection as a potential bioassay for acellular pertussis vaccines

Whole cell and five different types of acellular pertussis vaccine were assayed using a mouse aerosol challenge model which permitted delivery of a controlled, consistent dose of Bordetella pertussis to the lower respiratory tract. Using this system, the viable counts in the lungs of vaccinated mice were immunisation dose-dependent and allowed the protective capacity of different vaccine preparations to be distinguished. This model may thus provide the basis for a protection assay for pertussis vaccines. Comparison of acellular vaccines with a whole cell pertussis vaccine showed that the latter gave better active protection in mice but with a different dose-response relationship. Thus the two types of vaccine are not directly comparable in the same assay and require different reference standards. A pentavalent type acellular vaccine is suggested as a possible candidate standard for the acellular vaccine potency test. The results suggest that this aerosol challenge model has potential for use as a potency test for acellular pertussis vaccines.

The development of a World Health Organisation international standard for islet cell antibodies: the aims and design of an international collaborative study

Islet cell antibodies (ICA) are a specific marker for Type 1 (insulin-dependent) diabetes mellitus. ICA are found in the serum of over 80% of newly diagnosed patients and the levels of ICA are directly of prognostic value. Standardisation of ICA and the uniform reporting of ICA levels in international units is critical to preclinical/clinical research and the development of assays for ICA as diagnostics, in particular for the differential diagnosis of late onset Type 1 and Type 2 diabetes. Proficiency studies carried out by the Immunology of Diabetes Workshops on Standardization have clearly shown that a single reference material, serum sample 673, obtained by Dr J. Ludvigsson, has significantly reduced inter- and intra-assay variability in the reporting of ICA levels. Nevertheless, this material is a frozen serum of limited shelf-life and is difficult to distribute on a worldwide and routine basis. Therefore, the Immunology of Diabetes Workshop Standardization Committee and the Juvenile Diabetes Foundation International requested that the National Institute for Biological Standards and Control (NIBSC) organise an international collaborative study to compare the activities of lyophilised, stable ICA preparations. In addition, the purpose was to investigate if sample 673 could also serve as a standard for GAD65 and IA-2 antibodies. Twenty participants in eight countries have been recruited to the study.

WHO cytokine standardization: facilitating the development of cytokines in research, diagnosis and as therapeutic agents

The development and widespread application of recombinant DNA technology has dramatically increased the number of cytokines available for clinical evaluation. New and novel cytokines are being discovered, cloned and entered into clinical trials at such a rate that it is often the case that the biological activities of these proteins are poorly understood during their development as therapeutic agents. In addition, manufacturers of any one cytokine can produce the protein from different cellular sources resulting in materials that exhibit markedly different specific activities. When estimating the amount of biological activity of different preparations with different specific activities by bioassay, mass units cannot be used and biological activity is therefore expressed as 'biological potency units'. The biological unit requires definition by a standard that is assay-independent (especially when measuring a particular type of biological activity). In many cases, a variety of assay methods will be available and the material chosen for a standard should ideally be suitable for use with as many of them as possible. Once the unit is defined, this can be used in any laboratory, thus providing a means of ensuring uniformity throughout the world in the designation of potency of different biological preparations. The World Health Organisation (WHO) standardization programme involves the production of biologically stable, well characterised potency and immunoassay standards that are available world-wide using a single international unitage. Over the years, WHO international standards have been used to dramatically reduce the variation in estimates of cytokine preparations within and between laboratories for immunoassays and bioassays. WHO international standards are primary reference preparations against which secondary, or working standards (including regional standards, national standards, pharmacopoeial standards and in-house working standards) can be calibrated.

Implications for the assay and biological activity of interleukin-8: results of a WHO international collaborative study

Eight ampouled preparations of interleukin-8 (IL-8) have been evaluated for their suitability to serve as an international standard for IL-8 by 30 laboratories in 12 countries in an international collaborative study. The preparations were assayed in a wide range of in vitro bioassays and immunoassays. It is clear from the study that different recombinant preparations of IL-8 can have different biological specific activities, even though all were produced using E. coli. It is of interest that the intra-laboratory variability of estimates provided by several neutrophil degranulation bioassays was less than that of the immunoassays, suggesting that these bioassays can be as precise, if not more so, than immunoassays. In addition, immunoassay estimates of IL-8 preparations differed from those of bioassays, illustrating the fact that immunoassays do not necessarily measure biologically active cytokine. The large reduction in the inter-laboratory variability of estimates in terms of a common reference preparation clearly illustrates the need for a standard for IL-8. On the basis of the results reported here, with the agreement of the participants of the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO) the preparation of IL-8 (89/520) was established as the International Standard for IL-8 with an assigned unitage of 1000 IU/ampoule.

The biological properties, assay, and standardization of interferon-alpha: a need for a WHO collaborative study

Interferon-alpha (IFN-alpha) exists as a range of closely related, biologically active proteins and has been the subject of extensive research and clinical investigation. Standardization of IFN-alpha and the uniform reporting of IFN-alpha activity in International Units (IU) is critical to preclinical research and the clinical development of IFN-alpha products as therapeutic agents. Currently, several different IFN-alpha-containing reference preparations, established as World Health Organization (WHO) International Standards (IS) for particular IFN-alpha proteins (mixtures or single molecular species) are available for assay calibration. Nevertheless, the heterogeneous nature of IFN-alpha has raised standardization issues relating to the activity of individual IFN-alpha proteins, hence-forth termed subtypes, in the various biologic assays used for determining IFN-alpha levels. These issues include the question of parallelism of dose-response curves among particular IFN-alpha subtypes and different, naturally produced IFN-alpha subtype mixtures, for example, leukocyte IFN-alpha, and the applicability of IU of IFN-alpha activity defined by antiviral assays to alternative biologic assays, for example, antiproliferative assays. To address such issues, a WHO Consultative Group on Cytokine Standardization requested that the National Institute for Biological Standards and Control (NIBSC) and the Centre for Biologics Evaluation and Research (CBER) organize an international collaborative study to compare the activities and relative potencies of the several available IFN-alpha preparations, including those derived from human cells containing mixtures of IFN-alpha subtypes and those derived by rDNA methods containing single IFN-alpha subtypes, in different assays. To date, 111 participants in 32 countries have been recruited to the study and have agreed to assay a total of 17 different natural and recombinant IFN-alpha preparations or a defined subset thereof in specific in-house assays. The assay results generated will be statistically analyzed and evaluated to address the stated issues and to assess whether any individual IFN-alpha preparation is suitable to serve as an IS for all IFN-alpha preparations or whether more than one IS will be needed for this purpose.

Catalytic properties and stability of lipase purified from human pancreatic juice

Catalytic properties of a preparation of human pancreatic lipase purified from pancreatic juice have been compared to those of the enzyme present in pooled plasma from patients suffering from acute pancreatitis. They were very similar as regards influence of effectors (sodium deoxycholate, colipase and Ca2+), optimal pH and apparent KM in optimized conditions. The stability of the preparation appeared to be satisfactory. It was found to be stable for at least 200 days in a liquid form at +4 degrees C and predictive degradation rates per year of the lyophilized form at +4 degrees C and -20 degrees C were 0.06% and 0.00%, respectively. The close similarity of properties of this preparation with those of a recombinant human pancreatic lipase produced in V79 Chinese hamster lung cells suggests that both approaches (purification from human pancreatic juice and gene transfer technology) could be used to produce a suitable reference material for this enzyme.

Implications for the assay and biological properties of interleukin-3. Results of a WHO international collaborative study

Five preparations of interleukin-3 (IL-3) have been evaluated by 28 laboratories in 12 countries for their suitability to serve as an international standard for this material in a joint international collaborative study for IL-3 and interleukin-4 (IL-4). The preparations were assayed in a wide range of in vitro bioassays and immunoassays. It is clear from the biological assays contributed to this study that different recombinant preparations of IL-3 can have very different biological specific activities, including those from the same source (i.e., E. coli). Biological assays of IL-3 were significantly more consistent in their estimates of levels of IL-3 than the immunoassays, suggesting an unusual pattern of epitope recognition amongst the antibodies included in the immunoassays. This study also illustrates the point that the level of cytokine measured by immunoassay does not necessarily reflect the biological potency of the cytokine. On the basis of results reported here, with the agreement of the participants of the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO) the preparation of IL-3 (91/510) was established as the international standard for interleukin-3 with an assigned unitage of 1700 IU/ampoule.

Implications for the assay and biological activity of interleukin-4. Results of a WHO international collaborative study

Five ampouled preparations of interleukin-4 (IL-4) have been evaluated by 36 laboratories in 14 countries for their suitability to serve as an international standard for this material in a joint international collaborative study for interleukin-3 (IL-3) and IL-4. The preparations were assayed in a wide range of in vitro bioassays and immunoassays. It is clear from the study that different recombinant preparations of IL-4 can have very different biological specific activities, including those from the same source (i.e., E. coli). In addition, immunoassay estimates of IL-4 levels did not correlate with those of bioassays, illustrating the fact that immunoassays do not necessarily measure biologically active cytokine. It is of interest that the estimates provided by the different bioassays were less variable than those produced by the immunoassays, suggesting that bioassays can be as accurate, if not more so, than immunoassays. The large reduction in the variability of estimates with the inclusion of a single reference preparation clearly illustrates the need for a single standard to assay IL-4. On the basis of the results reported here, with the agreement of the participants of the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO) the preparation of IL-4 (88/656) was established as the international standard for interleukin-4 with an assigned unitage of 1000 IU/ampoule.

Refinement and validation of an alternative bioassay for potency testing of therapeutic botulinum type A toxin

The type A neurotoxin produced by Clostridium botulinum is a potent neuromuscular blocking agent which causes paralysis by preventing the release of neurotransmitter from motor neurones. This property has led to the use of the toxin in the treatment of a number of neuromuscular diseases involving muscle spasms. At present, the only recognised assay with the specificity and sensitivity to estimate accurately the potency of botulinum toxin in clinical preparations is bioassay, in which lethality is used as the end point. Refinement of this assay, with respect to the end point, was explored on the basis of the development of flaccid paralysis of muscles following subcutaneous injection of the toxin at the inguinocrural region. Potency estimates, relative to in house reference preparations, for different therapeutic preparations obtained using flaccid paralysis as a scored response gave excellent agreement with estimates obtained in independent assay using the currently required control method. This study demonstrates that an alternative, more humane bioassay for potency testing of clostridia neurotoxins gives valid estimates equivalent to those currently in use.

The international standard for macrophage colony stimulating factor (M-CSF). Evaluation in an international collaborative study

Three ampouled preparations of macrophage colony stimulating factor (M-CSF) were evaluated by 23 laboratories in nine countries for their suitability to serve as international standards for this material. The preparations were assayed in a wide range of in vitro bioassays and immunoassays. On the basis of results reported here, with the agreement of the participants in the study and with the authorization of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO), the preparation in ampoules coded 89/512 was established as the international standard for M-CSF.

The international standard for granulocyte colony stimulating factor (G-CSF). Evaluation in an international collaborative study. Participants of the Collaborative Study

Three ampouled preparations of granulocyte colony stimulating factor (G-CSF) have been evaluated by 29 laboratories in 11 countries for their suitability to serve as international standards for these materials. The preparations were assayed in a wide range of in vitro bioassays and immunoassays. On the basis of results reported here with the agreement of the participants in the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO) one of the preparations (88/502) was established as the international standard for G-CSF.

The international standard for granulocyte-macrophage colony stimulating factor (GM-CSF). Evaluation in an international collaborative study. Participants of the Collaborative Study

Two ampouled preparations of granulocyte-macrophage colony stimulating factor (GM-CSF) have been evaluated by twenty nine laboratories in eleven countries for their suitability to serve as international standards for these materials. The preparations were assayed in a wide range of in vitro bioassays and immunoassays. On the basis of results reported here, with the agreement of the participants in the study and with the authorisation of the Expert Committee on Biological Standardization (ECBS) of the World Health Organization (WHO) one of the preparations (88/646) was established as the international standard for GM-CSF.

Aluminium-adjuvanted vaccines transiently increase aluminium levels in murine brain tissue

Aluminium is widely used as an adjuvant in human vaccines, and children can often receive up to 3.75 mg of parenteral aluminium during the first six months of life. We show that intraperitoneal injection of aluminium adsorbed vaccines into mice causes a transient rise in brain tissue aluminium levels peaking around the second and third day after injection. This rise is not seen in the saline control group of animals or with vaccine not containing aluminium. It is likely that aluminium is transported to the brain by the iron-binding protein transferrin and enters the brain via specific transferrin receptors.