Novel pyrogen tests based on the human fever reaction. The report and recommendations of ECVAM Workshop 43. European Centre for the Validation of Alternative Methods. European Centre for the Validation of Alternative Methods

A novel alternative for pyrogen detection based on a transgenic cell line

Pyrogen, often as a contaminant, is a key indicator affecting the safety of almost all parenteral drugs (including biologicals, chemicals, traditional Chinese medicines and medical devices). It has become a goal to completely replace the in vivo rabbit pyrogen test by using the in vitro pyrogen test based on the promoted 'reduction, replacement and refinement' principle, which has been highly considered by regulatory agencies from different countries. We used NF-κB, a central signalling molecule mediating inflammatory responses, as a pyrogenic marker and the monocyte line THP-1 transfected with a luciferase reporter gene regulated by NF-κB as an in vitro model to detect pyrogens by measuring the intensity of a fluorescence signal. Here, we show that this test can quantitatively and sensitively detect endotoxin (lipopolysaccharide from different strains) and nonendotoxin (lipoteichoic acid, zymosan, peptidoglycan, lectin and glucan), has good stability in terms of NF-κB activity and cell phenotypes at 39 cell passages and can be applied to detect pyrogens in biologicals (group A & C meningococcal polysaccharide vaccine; basiliximab; rabies vaccine (Vero cells) for human use, freeze-dried; Japanese encephalitis vaccine (Vero cells), inactivated; insulin aspart injection; human albumin; recombinant human erythropoietin injection (CHO Cell)). The within-laboratory reproducibility of the test in three independent laboratories was 85%, 80% and 80% and the interlaboratory reproducibility among laboratories was 83.3%, 95.6% and 86.7%. The sensitivity (true positive rate) and specificity (true negative rate) of the test were 89.9% and 90.9%, respectively. In summary, the test provides a novel alternative for pyrogen detection.

Standardized pyrogen testing of medical products with the bacterial endotoxin test (BET) as a substitute for rabbit Pyrogen testing (RPT): A scoping review

The Bacterial Endotoxin Test (BET) is a method for exclusion of endotoxin-related pyrogen contamination in pharmaceutical products, as an alternative to the Rabbit Pyrogen Test (RPT). However, BET does not detect a broad range of biologically relevant pyrogens, and interferences can limit its practical use for different medical products. This work aimed to scope the evidence in the scientific literature for case-by-case validity assessments of BET in different uses for medical products. A search strategy was conducted in PubMed, Scopus, and Web of Science in April 2020, according to the PRISMA-ScR statement. Twenty-two references were included, evaluating medical products for endotoxin contamination through both BET and RPT according to standardized protocols. A critical appraisal was performed through ToxRTool, followed by data extraction and qualitative synthesis of outcomes and methodological issues. Four classes of products assessed by BET were identified, including nanoparticles, drugs, blood and biological products. A considerable variation was observed on the BET methods used. Collectively, the evidence indicates different factors influencing the outcome of BET, including the chemical nature of samples that may cause interference depending on the selected method. While some applications to medical products appear adequate, others, such as nanoparticles, may require the use of different in vitro pyrogen testing methods, reinforcing the need for case-by-case validation for each BET method and type of medical product.

A Novel Reporter Gene Assay for Pyrogen Detection

Fever is a systemic inflammatory response of the body to pyrogens. Nuclear factor κB (NF-κB) is a central signaling molecule that causes the excessive secretion of various pyrogen-induced pro-inflammatory factors. This study explored the feasibility of a novel reporter gene assay (RGA) for pyrogen detection using RAW264.7 cells stably transfected with the NF-κB reporter gene as a pyrogenic marker. The RGA could detect different types of pyrogens, including the lipopolysaccharide of gram-negative bacteria, the lipoteichoic acid of gram-positive bacteria, and the zymosan of fungi, and a good dose-effect relationship was observed in terms of NF-κB activity. The limits of detection of the RGA to those pyrogens were 0.03 EU/ml, 0.001 μg/ml, and 1 μg/ml, respectively. The method had good precision and accuracy and could be applied to many molecules (e.g., nivolumab, rituximab, bevacizumab, etanercept, basiliximab, Haemophilus influenzae type b conjugate vaccine, 23-valent pneumococcal polysaccharide vaccine, group A and group C meningococcal conjugate vaccine, diphtheria, tetanus, pertussis [acellular, component], poliomyelitis [inactivated] vaccine, and imject alum adjuvant). The results of this study suggest that the novel RGA has a wide pyrogen detection spectrum and is sufficiently sensitive, stable, and accurate for various applications.

Evaluation of the monocyte activation test for the safety testing of meningococcal B vaccine Bexsero: A collaborative study

The aim of this collaborative study was to evaluate the robustness of the monocyte activation test (MAT) for quantifying the pyrogenic content in the outer membrane vesicle (OMV)-containing vaccine Bexsero: the first meningococcal B vaccine to be licenced. We analysed datasets from 9 laboratories covering 15 test systems for 3 batches of Bexsero with higher, equivalent and lower activity relative to a reference lot in the MAT. Activity was measured in terms of relative pyrogen units (RPU) based on European Pharmacopoeia (Ph. Eur.) MAT Chapter 2.6.30 Method C: Reference Lot Comparison Test. We report that all 15 test systems were consistent in that they showed sample A to be the most active in the MAT; that 13 of 15 test systems had an accuracy of more than 80% and an overall geometric mean RPU of 1.03 with lower and upper 95% confidence limits of 0.97 and 1.09 respectively for a sample with an expected value of 1.00 RPU. We also report larger variability in the results for test systems involving cells from individual blood donations for sample A suggesting that there could be donor to donor differences in sensitivity to the vaccine constituents responsible for the higher activity of this batch. Overall, the consistency and accuracy of the MAT was remarkable given the range of test systems used by participants, all of which are permitted by the Ph. Eur. General MAT Chapter. This is important given the limitations of the rabbit pyrogen test for the control of pyrogenicity in general and particularly with products with intrinsic pyrogenicity such as Bexsero.

Monocyte-activation test to reliably measure the pyrogenic content of a vaccine: An in vitro pyrogen test to overcome in vivo limitations

Pyrogen content is one of the critical quality attributes impacting the safety of a product, and there is an increasing need for assays that can reliably measure this attribute in vaccines. The Limulus amebocyte lysate (LAL) assay and the rabbit pyrogen test (RPT) are the canonical animal-based pyrogen tests currently used to release vaccines; however, there are several drawbacks associated with these tests when applied to Bexsero, intrinsically pyrogenic product, containing a meningococcal Outer Membrane Vesicle component. While the RPT, as applied to Bexsero at its given dilution, ensures safe vaccine, it is highly variable and prone to false positive results. On the other hand, the LAL assay although quantitative, can detect only endotoxin pyrogens and is not sufficient for monitoring the safety of Bexsero, which contains both LPS and non-endotoxin pyrogens. Being aware of these limitations of the RPT and LAL when applied to Bexsero, the Monocyte Activation Test (MAT) which is sensitive to both endotoxin and non-endotoxin based pyrogens has been developed as an alternative pyrogen test. Here, the development and the validation of a MAT assay adapted from the European pharmacopoeia for Bexsero, is described. The MAT assay is then used for monitoring the safety and consistency of Bexsero vaccines at release, providing great advantages in terms of reduced variability with respect to RPT, reduction of animal use, in line with the 3Rs principle concerning the protection of animals and faster time to market. In addition the correlation of the MAT to the RPT has been demonstrated supporting the replacement of the in vivo method and the potential application of the assay to other intrinsically pyrogenic vaccines.

Analysis of IL-6 and IL-1β release in cryopreserved pooled human whole blood stimulated with endotoxin

To overcome the lack of availability of fresh human whole blood for pyrogen detection, we explored the feasibility of utilizing cryopreserved pooled human blood to detect the responses of the pro-inflammatory cytokines IL-6 and IL-1β to LPS. Whole blood was obtained from five donors and incubated with LPS. The quantities of pro-inflammatory cytokines were measured using ELISA, and the results were compared among the samples. After the blood was cryopreserved with Dimethyl sulfoxide (DMSO) (10% v/v) and stored for 4 mo at –196℃, the detection limits of the IL-6/IL-1β responses to LPS were 0.2/0.4 endotoxin units (EU)/ml, respectively, and IL-6/IL-1β release increased in response to LPS in a dose-dependent manner. When these experiments were performed in three separate laboratories, the within-laboratory reproducibility of the IL-6/IL-1β responses was 100%/86.7%, 93.3%/100%, and 86.7%/80%, and the inter-laboratory reproducibility was 92.9%/85.7%, 64.3%/63.6%, and 57.1%/66.7%, respectively. The sensitivity (the probability of correctly classifying positive samples) and specificity (the probability of correctly classifying negative samples) of the IL-6/IL-1β tests were 81.7%/82.5% and 100%/100%, respectively. The results of this study suggest that cryopreserved pooled blood is a convenient and viable alternative for evaluating in vitro pyrogenicity. Additionally, maintaining cryopreserved pooled blood promotes safety for the user because it is released only after pretesting for infection parameters and has lower variation than fresh donations from a variety of donors.

Optimisation of pyrogen testing in parenterals according to different pharmacopoeias by probabilistic modelling

The rabbit test to detect pyrogenic contamination in parenterals is crucial to ensure patient safety. The pharmacopoeial tests in Europe, the US and Japan are based on the fever reaction of rabbits, but differ in their experimental design and in their algorithms to assess contamination. Employing an international reference endotoxin, fever can be induced in rabbits. Data from 171 rabbits built the base for probabilistic modelling of the fever reaction and for the comparison of the pharmacopoeial tests. The rabbit fever reaction could be modelled as a function of the amount of injected endotoxin (per kg body weight) by linear regression. Combining the pharmacopoeial algorithms of the rabbit pyrogen test with the developed model allowed analysis of differences regarding test results and animal consumption. This showed that the assessment of pyrogenic contamination strongly depends on the respective pyrogen test stipulated by regulations. Additionally, the approach was used to develop a new experimental design. Two specific versions of this design resulted in a reduction of the number of animals used by about 30% while the safety of the test was maintained. A need for harmonisation is evident, allowing optimisation of the experimental design, which promotes animal welfare.

In Vivo Analgesic and Antipyretic Activities of N-Butanol and Water Fractions of Ocimum Suave Aqueous Leaves Extract in Mice

BACKGROUND

Ocimum suave willd is one of the plants traditionally used for the treatment of inflammation and related disorders in different parts of Ethiopia. The aim of the current study was to evaluate the analgesic and antipyretic activities of the solvent fractions (n-butanol and water) of O. suave aqueous leaves extract.

MATERIALS AND METHODS

Acetic acid writhing and tail flick tests were used to evaluate the analgesic activity, and yeast-induced fever in mice was used to evaluate the antipyretic activity of the solvent fractions.

RESULTS

Both solvent fractions exhibited inhibitory effect against acetic acid induced writhing at all tested dose levels in a dose dependent manner. The water fraction inhibited writhing by 47.69% at a dose of 200 mg/kg which was comparable to that by ASA, the standard drug. In the tail flick test, 200 mg/kg dose of both solvent fractions showed significant activity (P<0.05) after 0.5h, 1h and 3hrs of their administration. Both n- butanol and water fractions produced significant reduction in yeast induced fever at all doses employed.

CONCLUSION

From these findings, it can be concluded that the n-butanol and water fractions of O. suave aqueous leaves extract have potential analgesic and antipyretic activity in mice.

Soluble β-(1,3)-glucans enhance LPS-induced response in the monocyte activation test, but inhibit LPS-mediated febrile response in rabbits: Implications for pyrogenicity tests

In the present study, we aimed to determine the influence of β-(1,3)-d-glucans on the LPS-induced pro-inflammatory cytokine response in the Monocyte Activation Test (MAT) for pyrogens, and on the LPS-induced febrile response in the Rabbit Pyrogen Test (RPT), thus evaluating the resulting effect in the outcome of each test. It was found that β-(1,3)-d-glucans elicited the production of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α, also known as endogenous pyrogens, but not enough to classify them as pyrogenic according to MAT. The same β-(1,3)-d-glucans samples were non-pyrogenic by RPT. However, β-(1,3)-d-glucans significantly enhanced the LPS-induced pro-inflammatory cytokines response in MAT, insomuch that samples containing non-pyrogenic concentrations of LPS become pyrogenic. On the other hand, β-(1,3)-d-glucans had no effect on sub-pyrogenic LPS doses in the RPT, but surprisingly, inhibited the LPS-induced febrile response of pyrogenic LPS concentrations. Thus, while β-(1,3)-d-glucans could mask the LPS pyrogenic activity in the RPT, they exerted an overstimulation of pro-inflammatory cytokines in the MAT. Hence, MAT provides higher safety since it evidences an unwanted biological response, which is not completely controlled and is overlooked by the RPT.

Reconfigurable microfluidic device with integrated antibody arrays for capture, multiplexed stimulation, and cytokine profiling of human monocytes

Monocytes represent a class of immune cells that play a key role in the innate and adaptive immune response against infections. One mechanism employed by monocytes for sensing foreign antigens is via toll-like receptors (TLRs)-transmembrane proteins that distinguish classes of foreign pathogens, for example, bacteria (TLR4, 5, and 9) vs. fungi (TLR2) vs. viruses (TLR3, 7, and 8). Binding of antigens activates a signaling cascade through TLR receptors that culminate in secretion of inflammatory cytokines. Detection of these cytokines can provide valuable clinical data for drug developers and disease investigations, but this usually requires a large sample volume and can be technically inefficient with traditional techniques such as flow cytometry, enzyme-linked immunosorbent assay, or luminex. This paper describes an approach whereby antibody arrays for capturing cells and secreted cytokines are encapsulated within a microfluidic device that can be reconfigured to operate in serial or parallel mode. In serial mode, the device represents one long channel that may be perfused with a small volume of minimally processed blood. Once monocytes are captured onto antibody spots imprinted into the floor of the device, the straight channel is reconfigured to form nine individually perfusable chambers. To prove this concept, the microfluidic platform was used to capture monocytes from minimally processed human blood in serial mode and then to stimulate monocytes with different TLR agonists in parallel mode. Three cytokines, tumor necrosis factor-α, interleukin (IL)-6, and IL-10, were detected using anti-cytokine antibody arrays integrated into each of the six chambers. We foresee further use of this device in applications such as pediatric immunology or drug/vaccine testing where it is important to balance small sample volume with the need for high information content.

An improved monocyte activation test using cryopreserved pooled human mononuclear cells

The monocyte activation test (MAT) is a promising replacement of the currently used rabbit pyrogen test to detect the presence of pyrogens in injectable drugs. In the MAT, drugs are incubated with a source of human monocytes and production of pyrogenic cytokines used as readout. The best results are obtained with human mononuclear cells (MNC). However, donor variation requires testing on four different donors, and for most laboratories access to fresh MNCs is a problem. The current study shows how to overcome these problems using frozen pooled MNCs. The MAT is performed by thawing pooled MNC and co-culture overnight with a test substance, LPS or non-endotoxin pyrogens, with IL-6 production as the readout. The study demonstrates that fresh and frozen pooled MNC have comparable sensitivity. The reproducibility of the MAT performed with different batches of frozen pooled MNC was excellent. Different non-endotoxin pyrogens induce IL-6, confirming the ability of the MAT to detect a variety of pyrogens. In conclusion, the MAT using frozen pooled MNC is a highly sensitive, specific and reproducible pyrogen test, able to detect and quantify endotoxin and non-endotoxin pyrogenic contaminations in parenteral pharmaceuticals.

Evaluation of the bioactivity of influenza vaccine strains in vitro suggests that the introduction of new strains in the 2010 Southern Hemisphere trivalent influenza vaccine is associated with adverse events

In Australia, during the 2010 Southern Hemisphere (SH) influenza season, there was an unexpected increase in post-marketing adverse event reports of febrile seizures (FS) in children under 5 years of age shortly after vaccination with the CSL trivalent influenza vaccine (CSL 2010 SH TIV) compared to previous CSL TIVs and other licensed 2010 SH TIVs. The present study describes the outcomes of a series of in vitro experiments directed at elucidating the root cause. The scientific investigations found that a subset of paediatric donors displayed elevated cytokine/chemokine responses to the CSL 2010 SH TIV but not to previous CSL TIVs nor other 2010 SH TIVs. The induction of elevated cytokines/chemokines in paediatric whole blood correlated with elevated NF-κB activation in a HEK293 cell reporter assay. The data indicate that the introduction of the B/Brisbane/60/2008 strain within the CSL manufacturing process (such as occurred in the preceding 2009/10 NH season) appears to have raised the pyrogenic potential of the CSL 2009/10 NH TIV but that this was insufficient to elicit FS in children <5 years. The 2010 SH season coincided with the first introduction of the H1N1 A/California/07/2009 in combination with the B/Brisbane/60/2008 strain. Our data demonstrates that the introduction of the H1N1 A/California/07/2009 (and to a much lesser degree, H3N2 A/Wisconsin/15/2009) in combination with B/Brisbane/60/2008 (as expressed through the CSL method of manufacture) combined and likely compounded the bioactivity of the CSL 2010 SH TIV. This was associated with stronger immune responses, which in a proportion of children <5 years were associated with FS. The assays and systems developed during these investigations should greatly assist in determining the bioactivity of new influenza strains, and thus aid with the manufacture of CSL TIVs indicated for use in the paediatric population.

Highly sensitive pyrogen detection on medical devices by the monocyte activation test

Pyrogens are components of microorganisms, like bacteria, viruses or fungi, which can induce a complex inflammatory response in the human body. Pyrogen contamination on medical devices prior operation is still critical and associated with severe complications for the patients. The aim of our study was to develop a reliable test, which allows detection of pyrogen contamination on the surface of medical devices. After in vitro pyrogen contamination of different medical devices and incubation in a rotation model, the human whole blood monocyte activation test (MAT), which is based on an IL-1β-specific ELISA, was employed. Our results show that when combining a modified MAT protocol and a dynamic incubation system, even smallest amounts of pyrogens can be directly detected on the surface of medical devices. Therefore, screening of medical devices prior clinical application using our novel assay, has the potential to significantly reduce complications associated with pyrogen-contaminated medical devices.

Analysis of IL-1 β release from cryopreserved pooled lymphocytes in response to lipopolysaccharide and lipoteichoic acid

Pyrogens are heterogeneous group of fever-inducing substances derived from Gram-positive and Gram-negative bacteria, fungi, and viruses. They incite immune response by producing endogenous pyrogens such as prostaglandins and other proinflammatory cytokines like IL-1β, IL-6, and TNF-α. The present study was to analyze the influence of cryopreservation in IL-1β release, a marker for inflammatory response from human lymphocytes, in response to exogenous pyrogenic stimulants. Lymphocytes isolated from pooled blood of multiple healthy individuals were cryopreserved in DMSO and glycerol for periods of 7, 14, 30, and 60 days and were challenged with LPS and LTA in vitro. The inflammatory cytokine, IL-1β release, was measured by ELISA method. It was observed that the release of IL-1β increases instantaneously after the initiation of incubation and reaches a maximum at 3 to 5 hours and then gradually decreases and gets stabilized for both pyrogens. Moreover it was also observed that the effect of cryoprotectants, DMSO (10%) and glycerol (10%), showed almost similar results for short-term storage, but DMSO-preserved lymphocytes yielded a better viability for long-term storage. Thus, the isolated cryopreserved lymphocytes system can be a promising approach for the total replacement/alteration to animal experimentation for pyrogenicity evaluation.

Detection of interleukin -1β from isolated human lymphocyte in response to lipopolysaccharide and lipoteichoic acid

Aim:

To detect the interleukin -1β levels from single and pooled isolated human lymphocytes in response to lipolysaccharide and lipoteichoic acid.

Materials and Methods:

Blood collected from healthy individuals (O +ve, A +ve, B +ve, and AB +ve) were subjected to gradient centrifugation to isolate lymphocytes. Different lymphocyte concentrations were used for in vitro pyrogen assay. Lymphocytes isolated were challenged with 5 EU of Gram negative (LPS) and 1 μg/μl of Gram positive (LTA) pyrogens in vitro and the inflammatory cytokine, Interleukin 1β (IL-1β) release was measured by Sandwich ELISA method.

Results:

The results indicated that the release of IL-1β increases immediately after the initiation of incubation and reaches a maximum at 4 to 6^th hour and then stabilizes for both the pyrogens. Furthermore, IL-1β release by 5 EU of LPS and 1 μg/μl of LTA is dependent on lymphocytes concentration. It was also observed that the difference in blood group did not interfere with the IL-1β release.

Conclusion:

The isolated lymphocyte system can be used as an alternative to the in vivo rabbit pyrogen assay.

Systematic review of membrane components of gram-positive bacteria responsible as pyrogens for inducing human monocyte/macrophage cytokine release

Fifty years after the elucidation of lipopolysaccharides (LPS, endotoxin) as the principal structure of Gram-negative bacteria activating the human immune system, its Gram-positive counterpart is still under debate. Pyrogen tests based on the human monocyte activation have been validated for LPS detection as an alternative to the rabbit test and, increasingly, the limulus amebocyte lysate test. For full replacement, international validations with non-endotoxin pyrogens are in preparation. Following evidence-based medicine approaches, a systematic review of existing evidence as to the structural nature of the Gram-positive pyrogen was undertaken. For the three major constituents suggested, i.e., peptidoglycan, lipoteichoic acids (LTA), and bacterial lipoproteins (LP), the questions to be answered and a search strategy for relevant literature was developed, starting in MedLine. The evaluation was based on the Koch–Dale criteria for a mediator of an effect. A total of 380 articles for peptidoglycan, 391 for LP, and 285 for LTA were retrieved of which 12, 8, and 24, respectively, fulfilled inclusion criteria. The compiled data suggest that for peptidoglycan two Koch–Dale criteria are fulfilled, four for LTA, and two for bacterial LP. In conclusion, based on the best currently available evidence, LTA is the only substance that fulfills all criteria. LTA has been isolated from a large number of bacteria, results in cytokine release patterns inducible also with synthetic LTA. Reduction in bacterial cytokine induction with an inhibitor for LTA was shown. However, this systematic review cannot exclude the possibility that other stimulatory compounds complement or substitute for LTA in being the counterpart to LPS in some Gram-positive bacteria.

Nonclinical vaccine safety evaluation: advantages of continuous temperature monitoring using abdominally implanted data loggers

Fever has been reported as the most common adverse event after vaccination in infants and children. For this reason it is important that, prior to clinical testing of a new vaccine, change in body temperature following vaccination is tested carefully in nonclinical animal studies. Since both the timing and the height of the temperature peak after vaccination may differ from vaccine to vaccine, it is important that the time point for body temperature measurement should be chosen on a case-by-case basis with sufficient knowledge of the specific vaccine. In order to determine the best time point for rectal body temperature measurement after vaccination with a new vaccine candidate against N. meningitidis serogroup B, to be applied in a formal Good Laboratory Practice (GLP) toxicology study, miniature temperature data loggers were implanted into the peritoneal cavity of rabbits. The continuous body temperature monitoring appeared to give a complete picture of the entire body temperature kinetics after vaccination. The body temperature peaked at 4 h after vaccination, and this time point was subsequently applied in the toxicology study. Measured body temperature values at the selected time point of 4 h after vaccination were comparable in the continuous temperature setting and in the formal toxicology study, i.e. rectal temperature measurement at one time point. In the present study implanted temperature loggers were successfully used to define an adequate time point to be applied in determining rectal body temperature in a formal GLP toxicology study with a new vaccine candidate.

Alternatives to animal testing: current status and future perspectives

On the occasion of the 20th anniversary of the Center for Alternative Methods to Animal Experiments (ZEBET), an international symposium was held at the German Federal Institute for Risk Assessment (BfR) in Berlin. At the same time, this symposium was meant to celebrate the 50th anniversary of the publication of the book “The Principles of Humane Experimental Technique” by Russell and Burch in 1959 in which the 3Rs principle (that is, Replacement, Reduction, and Refinement) has been coined and introduced to foster the development of alternative methods to animal testing. Another topic addressed by the symposium was the new vision on “Toxicology in the twenty-first Century”, as proposed by the US-National Research Council, which aims at using human cells and tissues for toxicity testing in vitro rather than live animals. An overview of the achievements and current tasks, as well as a vision of the future to be addressed by ZEBET@BfR in the years to come is outlined in the present paper.

Induced cytokine response of human PMBC-cultures: correlation of gene expression and secretion profiling and the effect of cryopreservation

The immune system is regulated by the complex interaction of multiple cytokines, which are secreted signaling molecules affecting other cells. In this work, we studied the cytokine response to several well-known stimulants, such as OKT-3, Con A, PWM, and SEB. Healthy donor cells (PBMCs) were cultivated for up to 72 h and the mRNA levels and cytokine release of four key cytokines (IL-2, IL-4, IFN-γ, and TNF-α) were analyzed by RT-PCR and bead-based multiplex analyses. The generated cytokine profiles showed characteristic expression patterns and secretion kinetics for each cytokine and substance. PWM/SEB and OKT-3 led to a very fast and long-lasting immune response, whereas Con A induced the slowest cytokine production. Cytokine concentrations also differed greatly. The highest IFN-γ concentration was 1000 times higher than the respective IL-4 concentration. Gene expression and cytokine concentration profiles were strongly correlated during the time course. The chronological response of the donors' cytokine profiles coincided, but showed individual characteristics regarding the strength of the cytokine release. The comparison of stimulation experiments using freshly isolated and cryopreserved PBMCs showed that, for the observation of an immunological response at early points in time, gene expression experiments are more reliable than the measurement of cytokines in the cell culture supernatant. However, the freezing of cells influences the response significantly. The measurement of secreted proteins is the superior method at later points in time.

Investigation of interleukin-1β release from cryopreserved blood stimulated with endotoxin

The feasibility of an indigenously developed ELISA method to determine cytokine response to wide spectrum of pyrogenic stimuli utilizing fresh human whole blood is limited by the availability of healthy donors. The possibility of using cryopreservation of pooled human blood for detection of cytokine response to lipopolysaccharide is explored in this study. The effect of cryopreservation on blood parameters, cellular morphology and cytokine response were compared with that of the pooled fresh blood and cryopreserved blood from single and multiple donors. In vitro pyrogenic stimulation with 0.5 and 5 EU of LPS was monitored on fresh and cryopreserved pooled blood from single and multiple donors. The release of IL-1β was quantitated by Sandwich ELISA (1, 10, 25, 45 and 75 days) after storage. The results indicated that the cryopreserved blood displayed enhanced IL-1β release on stimulation with LPS, when compared to fresh blood. The maximum release of IL-1β level was observed at 2h when 5 EU of LPS was treated with pooled fresh blood which is similar to that of fresh blood. After 75 days storage of pooled cryopreserved blood the IL-1β release was maximum at 9 and 15 h when treated with 5 and 0.5 EU of LPS. Observations of the study suggest that cryopreserved pooled blood is an economically and experimentally viable alternative to fresh blood. This investigative study promises short term storage and regular supply of non-allergic, pathogen free human blood for the detection of interleukin-1β for the evaluation of in vitro pyrogenicity.

Production and comprehensive quality control of recombinant human Interleukin-1beta: a case study for a process development strategy

We describe an efficient strategy to produce high-quality proteins by using a single large IMAC chromatography column and enzymatic His-tag removal via the TAGZyme system in pilot scale. Numerous quality assays demonstrated a high purity of the final product, the human cytokine Interleukin-1beta (IL-1beta). The protein preparation was apparently free of host cell proteins, endotoxins, protease, and aggregates. The N-terminal amino acid sequence of IL-1beta was in full agreement with the natural mature form of IL-1beta. The homogeneity of the product was further shown by X-ray structure determination which confirmed the previously solved structure of the protein. We propose the applied workflow as a strategy for industrial production of protein-based biopharmaceuticals.

In vitro pyrogen test for toxic or immunomodulatory drugs

Pyrogenic contaminations of some classes of injectable drugs, e.g. toxic or immunomodulatory as well as false-positive drugs, represent a major risk which cannot yet be excluded due to the limitations of current tests. Here we describe a modification of the In vitro Pyrogen Test termed AWIPT (Adsorb, Wash, In vitro Pyrogen Test), which addresses this problem by introducing a pre-incubation step in which pyrogenic contaminations in the test sample are adsorbed to albumin-coated beads. After rinsing, the beads are incubated with human whole blood and the release of the endogenous pyrogen interleukin-1beta is measured as a marker of pyrogenic activity. Intentional contaminations with lipopolysaccharide were retrieved from the chemotherapeutic agents paclitaxel, cisplatin and liposomal daunorubicin, the antibiotic gentamicin, the antifungal agent liposomal amphotericin B, and the corticosteroid prednisolone at lower dilutions than in the standard in vitro pyrogen test. This represents a promising new approach for the detection of pyrogenic contamination in drugs or in drugs containing interfering additives and should lead to improved safety levels.

Utilization of the human cell line HL-60 for chemiluminescence based detection of microorganisms and related substances

In this paper we describe a new pyrogen assay using the human leukemia cell line HL-60. The cell line is differentiated using all-trans retinoic acid (ATRA) to generate a cell population that resembles mature granulocytes. The differentiated HL-60 cell is capable of generating reactive oxygen species (ROS) when challenged with pyrogenic substances. In a luminol enhanced chemilumimetric assay the responsiveness of differentiated HL-60 cells is tested towards Salmonella typhimurium, Bacillus subtilis, Saccharomyces cerevisiae, Candida albicans, lipopolysaccharide (LPS) and lipoteichoic acid (LTA). The results show a poor sensitivity to S. typhimurium but displays good sensitivity towards B. subtilis, LTA and LPS. Furthermore, the sensitivity towards the yeasts C. albicans and S. cerevisiae is considerably better than obtained in other in vitro cell systems. Overall these results indicate that the HL-60 cell assay possibly could be evolved to a supplementary assay for the known pyrogenic detection assays. Furthermore, the utilization of the assay for pyrogenic examination of recombinant drugs derived from yeast expression systems would be relevant to examine.

ESTIV questionnaire on the acquisition and use of primary human cells and tissue in toxicology

The ability to use human cells and tissues in toxicology research and testing has the benefit that it obviates the need to undertake species extrapolation when assessing human hazard. However, obtaining and using human cells and tissues is logistically difficult, ethically complex and is a potential source of infections to those coming into contact with human cell material. The issue is also controversial, with the recent EU legislation draft on tissue engineering, and also due to some instances of human material being obtained and used without informed consent. There are also varying regulations and attitudes relating to the use of human cells and tissues throughout Member States of the EU, and there is a need for harmonisation. The European Society of Toxicology in Vitro (ESTIV) Executive Board and the European Network of Human Research Tissue Banks (ENRTB) have conducted a survey to ascertain the extent to which human cells and tissues are used by its members, how these are obtained, what local regulations are in force, how the material is used, and the advantages and disadvantages experienced by members in using such material, as opposed to cell lines. The results obtained have been compared with the results from a previous survey conducted in 2000. It is hoped that this information will help to facilitate the process of acquiring and using human cells and tissues in a safe and effective way to promote the use of non-animal approaches for investigating the mechanisms of toxicity, and for predicting the toxic hazard of substances.

International validation of novel pyrogen tests based on human monocytoid cells

It is a requirement that parenteral medicines be tested for pyrogens (fever causing agents) using one of two animal-based tests: the rabbit pyrogen test and the bacterial endotoxin test. Understanding the human fever reaction has led to novel non-animal alternative tests based on in vitro activation of human monocytoid cells in response to pyrogens. Using 13 prototypic drugs, clean or contaminated with pyrogens, we have validated blindly six novel pyrogen tests in ten laboratories. Compared with the rabbit test, the new tests have a lower limit of detection and are more accurate as well as cost and time efficient. In contrast to the bacterial endotoxin test, all tests are able to detect Gram-positive pyrogens. The validation process showed that at least four of the tests meet quality criteria for pyrogen detection. These validated in vitro pyrogen tests overcome several shortcomings of animal-based pyrogen tests. Our data suggest that animal testing could be completely replaced by these evidence-based pyrogen tests and highlight their potential to further improve drug safety.

A model of human whole blood lymphokine release for in vitro and ex vivo use

Endotoxin (lipopolysaccharide, LPS) inducible cytokine release by human whole blood is increasingly used to model inflammatory responses in vitro, to detect the presence of pyrogenic contaminations as well as to monitor disease states or immunomodulatory treatments ex vivo. However, the LPS-stimulated blood model primarily allows the assessment of monocyte responses. Here, a whole blood model was established which allows assessment of lymphocyte responses. Four different superantigens, namely staphylococcal enterotoxin A and B (SEA, SEB), toxic shock syndrome toxin-1 (TSST-1) or streptococcal exotoxin A (SPEA) were tested with respect to the induction of lymphokine release. All superantigens were capable of inducing significant amounts of the lymphokines interferon-gamma (IFNgamma), interleukin 2 (IL-2), IL-4, IL-5, IL-13 and tumor necrosis factor beta (TNFbeta) after 72 h of incubation. Concentration-dependencies and kinetics were determined. Blood from 160 healthy donors was used to assess the variability of SEB-inducible lymphokine release. Interindividual differences were more pronounced compared to LPS-inducible monokine release. However, the individual response was maintained when blood from six donors was tested once a week for 8 weeks, suggesting that the individual response represents a donor characteristic. The model appears to be suitable for the evaluation of immunomodulatory agents in vitro as well as ex vivo.

A rapid 'one-plate' in vitro test for pyrogens

A rapid, 'one-plate' monocyte-activation test is described for detecting endotoxin and non-endotoxin pyrogens in parenteral medicinal products. The one-plate test offers useful gains over conventional 'two-plate' (cell culture plate+ELISA plate) tests in terms of its limit of detection, robustness, speed and cost. The 'one-plate' test is likely to be applicable to a wide range of products because it allows less time for product interference in the test. The 'one-plate' test utilises pyrogen-free anti-cytokine (interleukin (IL)-6 or tumour necrosis factor alpha (TNFalpha)) antibodies (Ab), coated and stabilised onto (pyrogen-free) 96-well plates. Monocytes/monocytic cells, endotoxin (lipopolysaccharides, LPS) standard or sample and (pyrogen-free) second (labelled) Ab are cultured together (usually for 2-4 h) on the Ab-coated plate and then the plate is washed and the ELISA completed. There is no transfer from one plate to another and no (further) incubations of (released) cytokine with, first, coating Ab and, then, developing Ab since these steps have already taken place during the initial cell culture. The rapid, 'one-plate' test is readily automated. The preferred readout is IL-6, which gives a limit of detection of 0.015 endotoxin units (EU)/ml with peripheral blood mononuclear cell (PBMNC), 0.03 EU/ml with diluted whole blood and 0.05 EU/ml with a monocytic cell line (MONO MAC 6).