Biomedical subjects

A R Mire-Sluis

Publications and source records attributed to A R Mire-Sluis.

At least 19 recordsLinked to original sources

PubMed2003

An overview of scientific and regulatory issues for the immunogenicity of biological products.

Immunogenicity of biological products can occur pre-clinically and clinically when products elicit immune responses in animals or humans receiving the products. This is a concern for manufacturers, regulatory agencies and clinicians as immune responses can result in effects on product effectiveness and safety. The clinical sequelae of immunogenicity range from no effects to serious, life-threatening syndromes. However, although many biological products are immunogenic to some extent, it is quite rare that immunogenicity leads to serious adverse events. Whilst there are methods to detect immunogenicity, they currently rely on detecting the humoral rather than the cellular response of the immune system. The design and validation of assays such as immuno-assays and bio-assays are critical for a meaningful assessment of immunogenicity. There are a growing number of computational and laboratory-based methods for the prediction of immunogenicity, as well as methods to reduce potential immunogenicity and these may lead to less immunogenic biological products in future.

Animals↗

PubMed2002

Immune responses to therapeutic proteins in humans--clinical significance, assessment and prediction.

There is a large and increasing number of therapeutic proteins approved for clinical use and many more undergoing preclinical studies and clinical trials in humans. Most of them are human or 'humanized' recombinant molecules. Virtually all therapeutic proteins elicit some level of antibody response, which in some cases, can lead to potentially serious side effects. Therefore, immunogenicity of therapeutic proteins is a concern for clinicians, manufacturers and regulatory agencies. In order to assess immunogenicity of these molecules, appropriate detection, quantitation and characterization of antibody responses are necessary. Immune responses to therapeutic proteins in conventional animal models has not been, except in rare cases, predictive of the response in humans. In recent years there has been a considerable progress in development of computational methods for prediction of epitopes in protein molecules that have the potential to induce an immune response in a recipient. Initial attempts to apply such tools in early development of therapeutic proteins have already been reported. It is expected that computer driven prediction followed by in vitro and/or in vivo testing of any potentially immunogenic epitopes will help in avoiding, or at least minimizing, immune responses to therapeutic proteins.

Antigens↗

PubMed2002

Setting specifications for potency assays--basic principles.

To develop any biological therapeutic successfully, it is necessary to characterise the product thoroughly, both physicochemically and biologically. To ensure that consistency of production is maintained, some level of control is required to limit the variability of the product from batch to batch. This premise forms the basis of specification setting. The biological activity or potency of the product must be appropriately assessed through a functional assay unless specifically justified otherwise e.g. for binding proteins where binding has been correlated with biological activity. Biological assays are particularly prone to assay variability and therefore it is necessary to design and execute the assay to reduce variability as much as possible while providing a statistically valid measure of the reproducibility of potency estimates. Therefore, specifications for potency should only be derived following establishment of a well validated and controlled bioassay and should include some measure of the variability of the estimate in addition to the actual potency estimate itself. The limits applied to those specifications need to reflect the true batch to batch consistency of the product, its nature and toxicity as well as its intended use.

Biological Assay↗

PubMed2002

Challenges with current technology for the detection, measurement and characterization of antibodies against biological therapeutics.

The primary concern with immunogenicity of biological products for manufacturers, regulatory agencies and clinicians is whether antibodies produced by patients receiving the product have clinical sequelae. However, the assessment of this concern is entirely dependent on the appropriate detection, measurement and characterisation of antibodies against biological therapeutics. The current assays for antibodies in biological fluids are prone to a wide range of technical difficulties in addition to scientific challenges in their interpretation. Problems such as matrix effects, selecting controls, antibody affinity, neutralizing capacity, antigen presentation and antigen/antibody complexes all require consideration in the design of antibody assays. Following the design of antibody assays, rigorous validation must be carried out to assure that the results they produce are meaningful. The relevance of quantitative measurement is particularly difficult to assess, as is the comparability of assay results between laboratories. Therefore considerable care is required in the design, execution, analysis and interpretation of antibody assays.

Antibodies↗

PubMed2001

Progress in the use of biological assays during the development of biotechnology products.

The complexity of the structure and function of many biotechnology derived products necessitates a wide range of analytical procedures to adequately characterize the product. In-depth characterization is required for the assessment of several criteria vital to the success of product development such as consistency, purity, stability, and potency. More recently, the concern over the immunogenicity of biologics has increased the need to develop assays to detect neutralizing anti-product antibodies. Although many physicochemical tests are available to characterize the structure of a protein and detect the presence of contaminants, they provide little, if any, information regarding biological potency or the neutralizing capacity of antibody responses in immunogenicity studies. There is a continual need to refine biological assays to increase their accuracy and reproducibility, in particular to replace in vivo bioassays with appropriate in vitro assays. There have also been several recent technological developments that could lead to more rapid and reproducible bioassays.

Allergy and Immunology↗

PubMed2000

Development of a continuous IL-7-dependent murine pre-B cell line PB-1 suitable for the biological characterisation and assay of human IL-7.

Human interleukin-7 (IL-7) is a cytokine that appears to be critical for early T- and B-cell development and although IL-7 is currently under investigation as a therapeutic agent in a variety of hematolymphopoietic disorders, there have been few instances of the detection or investigation of this cytokine using a biological assay. This has been due, in the main, to the lack of a widely available, stable, easy to maintain and use, IL-7 responsive cell line. We have developed a pre-B-cell line, PB-1, from murine bone marrow, that is dependent on IL-7 for growth and has been maintained continually for up to 1 year without loss of responsiveness. The cells survive freezing and reviving, having been stored for periods of up to 4 years. The IL-7 bioassay is reproducible and sensitive, able to reliably detect 50 pg/ml IL-7. The assay is completely unresponsive to any other stimulatory cytokines tested and is not affected by a wide variety of inhibitory cytokines, with the exception of high levels of interferon alpha. The assay can be made completely specific for human IL-7 by including specific neutralizing antibodies for IL-7 and has been shown to be suitable for the estimation of IL-7 in both plasma and serum samples.

Animals↗

PubMed2000

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.

Autoantibodies↗

PubMed1999

Cytokines: from technology to therapeutics.

Cytokines are playing an ever-increasing role in the treatment of human disease. The characterization of these proteins plays a vital role in their development as useful therapeutic agents. Physicochemical techniques can produce information about the structure and composition of cytokine therapeutics but cannot yet predict their biological activity, for which biological assays are required. Because of the large number of techniques available and the variety of products requiring analysis, the tests used to characterize cytokine products must be both appropriate for the product and adequately controlled if the information they provide is to be of value.

Biological Assay↗

PubMed1999

Analytical characterisation of cytokines and growth factors.

Cytokines (including growth factors) are playing an ever-increasing role in the therapy of human disease. The rapidity by which new cytokines are discovered, cloned and enter the clinics has placed a burden on control authorities and manufacturers to ensure their safety, quality and efficacy. The appropriate characterisation of these proteins plays a vital role in ensuring the development of cytokines as useful therapeutic agents. Highly sophisticated physicochemical techniques exist that can produce specific information about the structure and composition of cytokines including methods such as nuclear magnetic resonance (NMR) and mass spectrometry. However, even a bank of such techniques cannot yet predict the biological activity of cytokines. Biological assays are essential to assess the potency of cytokines and can take several forms, from in vivo assays to in vitro cell-line bioassays and more recently biochemically-based assays. Bioassays require a biological reference standard to define an appropriate unit that can be used to assess the potency of a biological therapeutic. However, bioassay-derived potency is a quality issue and should not have an impact on the perceived efficacy of a biological therapeutic.

Biological Assay↗

PubMed1999

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.

Biological Assay↗

PubMed1999

The development of non-animal-based bioassays for cytokines and growth factors.

Cytokines (including growth factors) exist as a family of proteins that possess a vast array of pleiotropic biological activities and therapeutic potential. As with any biological therapeutic, appropriate assessment of biological potency is vital to the development of cytokines as medicinal products. In early investigations of cytokine activity, in vivo bioassays were used to assess the whole body effects of cytokines in animals. The identification of the cellular targets of each cytokine allowed the extraction of tissue and the use of cells to produce in vitro bioassays, with the drastic reduction in the number of animals required. The discovery of cytokine-responsive tumours introduced a range of immortal, homogeneous tumour cell lines that are dependent on cytokines for proliferation. This allows cell lines to be made available for general distribution to laboratories internationally for bioassays, without the need for animals. More recently, the use of recombinant DNA technology to clone the specific receptor for the cytokine required for bioassay into an unresponsive cell line has led to a highly specific 'receptor-transduced' cell line. The most recent advances include the development of receptor signalling-based biochemical bioassays for cytokines.

Animal Testing Alternatives↗

PubMed1999

Cytokine and growth factor standardization: the need for research to answer modern issues.

New and novel cytokines are being discovered, cloned and entered into clinical trials at such a rate that often the biological activities of these proteins are poorly understood during their development as therapeutic agents. When estimating the biological activity of different preparations with different specific activities by bioassay, mass units cannot be used. Biological activity is therefore expressed as "biological potency units". Due to the pleiotropic nature of cytokine activity, the biological unit requires definition by a standard that is assay-independent. The need to investigate the biological activity of any proposed standard material in a variety of assays, with statistically valid numbers of participants and with appropriate scientific rationale, has led to the design of international collaborative studies that have provided extremely useful data about the biological activity of cytokines. Such information has had a great impact on the choice of material to serve as a standard and has prevented the establishment of inappropriate preparations. Over the years, WHO international standards have been used to reduce the variation in estimates of cytokine preparations within and between laboratories for both immunoassays and bioassays.

Cytokines↗

PubMed1998

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.

Cytokines↗

PubMed1998

Laboratory protocols for the quantitation of cytokines by bioassay using cytokine responsive cell lines.

Cytokines have been shown to be involved in many physiological processes, including the maintenance and control of a competent haematopoietic/immune system. Abnormal cytokine secretion or synthesis can cause a wide range of pathological disorders. Cytokines have also been shown to have therapeutic potential in many diseases. In order for the role of cytokines to be evaluated in normal and pathogenic processes, it is vital that appropriate assay systems are used to measure their levels in different biological fluids. Whilst immunoassays maybe a more convenient method for quantitating cytokines, they only measure immunologically reactive material. They may or may not detect biologically inactive material, such as cytokines bound to soluble receptors or degraded cytokine molecules. Bioassays, however, detect biologically active cytokines and can be as accurate and precise as immunoassays. The purpose of these protocols is to provide practical stepwise methods for the bioassay of cytokines using cytokine responsive cell lines. They include tables of the most useful currently available cell lines for the detection of cytokines and how to maintain them. In addition, these protocols provide all the materials and methods in a logical step-by-step procedure to carry out bioassays. Information is provided on possible pitfalls and general problems associated with bioassays and how to overcome them. These protocols should be valuable to scientists new to the cytokine field as well as experienced scientists who require a consensus methodology and access to information on cell lines useful for cytokine bioassays.

Animals↗

PubMed1998

Blood polymorphonuclear leukocytes from the majority of sickle cell patients in the crisis phase of the disease show enhanced adhesion to vascular endothelium and increased expression of CD64.

There is increasing interest in the role of blood polymorphonuclear leukocytes (PMNs) in the pathogenesis of sickle cell crisis. We studied the adherence of PMNs from 18 sickle cell patients in crisis, 25 out of crisis, and 43 healthy subjects (controls) to monolayers of human umbilical cord endothelium that were either untreated or pretreated with tumor necrosis factor alpha (TNFalpha). Overall, the PMNs from patients in crisis were more adherent than control PMNs to untreated endothelial monolayers (mean 53% increase; P < .001) and TNFalpha-treated monolayers (mean 41% increase; P < .002). Increased adhesiveness was not associated with an abnormal expression of CD11a, CD11b, CD11c, CD18, CD62L, or CD15. There was an increase in the number of PMNs expressing CD64 in patients in crisis (median value, 44%) compared with patients out of crisis (median, 21%; P = .025) and controls (median, 6.5%; P < .001). Sera from patients in crisis had normal levels of granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interferon-gamma, TNFalpha, interleukin-1 (IL-1), IL-6, or IL-8 and did not modify the adherence of PMNs or their expression of CD64. Only IFN-gamma induced CD64 expression on PMNs, but this effect was not associated with enhanced binding to endothelium. Because PMNs bound to endothelial monolayers were CD64(+) and CD64-enriched PMNs were 7 times more adherent to endothelial monolayers than CD64-depleted PMNs, it is likely that CD64 is a marker of adherent PMNs. Two of the three anti-CD64 antibodies used in our antibody blocking studies (clones 32.2 and 197) partially inhibited the binding of sickle cell PMNs to untreated endothelium (mean inhibitions of 33% [P = .01] and 21% [P = .03], respectively), whereas only one (clone 197) inhibited binding to TNFalpha-treated endothelium (mean inhibition, 29%; P = . 004). In some patients with sickle cell disease, an enhanced PMN adhesion to vascular endothelium could contribute to the vascular occlusion that characterizes the acute crisis of the disease.

Acute Disease↗

PubMed1997

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.

Biological Assay↗

PubMed1997

Transforming growth factor-beta induced by live or ultraviolet-inactivated equid herpes virus type-1 mediates immunosuppression in the horse.

Up to 21 days after exposure to live or ultraviolet-inactivated equid herpesvirus type-1 (EHV-1) autologous serum from ponies caused an immunosuppressive effect if incorporated into T-cell proliferation assays to EHV-1. The suppressive factor in the sera of ponies also inhibited T-cell response to phytohaemagglutinin. Increased levels of circulating activated transforming growth factor-beta 1 (TGF-beta 1) were detected, and the suppressive activity of the serum could be reversed by antibody to TGF-beta 1. In a challenge experiment the ponies which exhibited circulating TGF-beta 1 activity succumbed to infection while the ones with similar magnitudes of T-cell responses, but no TGF-beta 1 activity, were protected. A definition of this immunosuppressive mechanism and its mode of induction must be central to the design of vaccines and to an understanding of the pathogenesis of EHV-1.

Animals↗

PubMed1996

An anti-cytokine bioactivity assay for interferons-alpha, -beta and -omega.

Interferons-alpha and -beta (IFN-alpha and -beta) are cytokines that are widely known to induce potent anti-viral activity. However, it has become increasingly apparent that IFN-alpha and -beta exert a variety of other biological effects, including anti-tumour and immunomodulatory activities and are increasingly used clinically to treat a range of malignancies, myelodysplasias and autoimmune diseases, e.g., IFN-beta for multiple sclerosis. The most widely used bioassays for the IFNs are based on their anti-viral activity, but these do not predict the biological activity of the IFNs in anti-tumour and immunomodulatory therapies. Thus, we have developed anti-cytokine-based bioassays that may be more reflective of such activity and which have several advantages over existing anti-viral bioassays. The anti-cytokine bioassay is based on the ability of IFN-alpha, -beta and -omega to inhibit granulocyte-macrophage-colony-stimulating factor (GM-CSF) induced proliferation of the erythroleukaemic cell line TF-1. This assay can take only 24 h, is sensitive to 200 fg (0.04 IU) IFN-alpha or -beta and 100 fg (0.02 IU) IFN-omega and is able to detect down to these levels in serum or plasma samples. The usefulness of anti-cytokine bioassays for IFN-alpha, -beta and -omega is not restricted to the GM-CSF/TF-1 cell format and other alternatives are available, such as erythropoietin (EPO)/TF-1 cells and EPO/UT-7-EPO cells. These assays can be made specific for each of the IFNs by including neutralising antibodies in the bioassay.

Humans↗