Publications (17)36.9 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: Monophosphoryl lipid A (MPLA), a non-toxic TLR4 ligand derived from lipopolysaccharide (LPS), is used clinically as an adjuvant in cancer, hepatitis, and malaria vaccines and in allergen-specific immunotherapy. Nevertheless, its cell activating effects have not been analyzed in a comprehensive direct comparison including a wide range of different immune cells. Therefore, the objective of this study was the side-by-side comparison of the immune modulating properties of MPLA and LPS on different immune cells. Immune activating properties of MPLA and LPS were compared in human monocytes and mast cells (MCs), a mouse endotoxin shock model (ESM), and mouse bone marrow-(BM-) derived myeloid dendritic cells (mDCs), T cells (TCs), B cells, and MCs. In a mouse in vivo ESM and a human ex vivo monocyte activation test (MAT), MPLA induced the same cytokine secretion pattern as LPS (ESM: IL-6, IL-12, TNF-α; MAT: IL-1β, IL-6, TNF-α), albeit at lower levels. Mouse mDCs and ex vivo isolated B cells stimulated with MPLA required a higher threshold to induce Trif-dependent cytokine secretion (IL-1β, IL-6, IL-10 and TNF-α) than did LPS-stimulated cells. In mDC:DO11.10 CD4 TC co-cultures, stimulation with MPLA, but not LPS resulted in enhanced OVA-specific IL-4 and IL-5 secretion from DO11.10 CD4 TCs. Unexpectedly, in both human and mouse MCs, MPLA, unlike LPS, did not elicit secretion of pro-inflammatory cytokines. Compared to LPS, MPLA induced a qualitatively similar, but less potent pro-inflammatory immune response, but was unable to activate human or mouse MCs. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
- [Show abstract] [Hide abstract] ABSTRACT: Conjugated vaccines consisting of flagellin and antigen activate TLR5 and induce strong innate and adaptive immune responses. Objective of the present study was to gain further insight into the mechanisms by which flagellin fusion proteins mediate their immune modulating effects. In a mouse model of Ova-induced intestinal allergy a fusion protein of flagellin and Ova (rflaA:Ova) was used for intranasal and intraperitoneal vaccination. Aggregation status of flaA, Ova and flaA:Ova were compared by light scattering, uptake of fluorescence labeled proteins into mDC was analyzed, processing was investigated by microsomal digestion experiments. Mechanism of DC-activation was investigated using proteasome and inflammasome inhibitors. Immune responses of wildtype, IL-10(-/-), TLR5(-/-) mDCs and Ova-transgenic T cells were investigated. Mucosal and i.p.-application of rflaA:Ova were able to prevent allergic sensitization, suppress disease-related symptoms, prevent body weight loss and reduction in food uptake. Intranasal vaccination resulted in strongest suppression of Ova-specific IgE production. These protective effects were associated with increased aggregation of rflaA:Ova and accompanied by tenfold higher uptake rates into mDC compared to the mixture of both proteins. Microsomal digestion showed that stimulation with rflaA:Ova resulted in faster degradation and the generation of different peptides compared to rOva. rflaA:Ova-mediated activation of mDC could be suppressed in a dose-dependent manner by the application of both inflammasome and proteasome inhibitors. Using TLR5(-/-) mDC the rflaA:Ova induced IL-10 secretion was shown to be TLR5 dependent. In co-cultures of IL-10(-/-) mDC with DO11.10 T cells the lack of rflaA:Ova-mediated IL-10 secretion resulted in enhanced levels of both TH2 (IL-4, IL-5) and TH1 (IL-2 and IFN-y) cytokines. In summary, mucosal vaccination with flaA:Ova showed strongest preventive effect. Stimulation with rflaA:Ova results in strong immune modulation mediated by enhanced uptake of the aggregated fusion protein, likely resulting in a different processing by DC as well as stronger TLR5 mediated cell activation.
- [Show abstract] [Hide abstract] ABSTRACT: Pertussis Toxin (PTx) is one of the most important virulence factors of Bordetella pertussis, the cause of whooping cough. Therefore, the inactivated toxin is an obligatory constituent of acellular pertussis vaccines. It is described in the literature that both native PTx and recombinant Pertussis Toxin (PTg) activate human monocytes whereas others report an inhibition of mammalian monocytes during pertussis infection. B. pertussis, as a Gram-negative bacterium, harbours naturally lipopolysaccharide (LPS, also known as endotoxin), one of the strongest stimulators of monocytes. The latter is triggered via the interaction of endotoxin with inter alia the surface receptor CD14. Consequently, it is necessary to consider a potential contamination of Pertussis Toxin preparations with LPS. First, we determined the LPS content in different preparations of PTx and PTg. All preparations examined were contaminated with LPS; therefore, possible PTx- and PTg-driven monocyte activation independently of LPS was investigated. To meet these aims, we examined monocyte response to PTx and PTg while blocking the LPS receptor CD14 with a specific monoclonal antibody (anti-CD14 mAb). In addition, all toxin preparations examined underwent an LPS depletion. Our results show that it is contaminating LPS, not Pertussis Toxin, which activates human monocytes. Blocking the CD14 receptor prevents Pertussis Toxin-mediated induction of pro-inflammatory cytokines in human monocytes. The depletion of LPS from Pertussis Toxin leads to the same effect. Additionally, the PTx toxicity after LPS depletion procedure was confirmed by animal tests. In contrast, the original Pertussis Toxin preparations not treated as mentioned above generate strong monocyte activation. The results in this publication allow the conclusion that purified Pertussis Toxin preparations do not induce the release of pro-inflammatory cytokines in human whole blood.
- [Show abstract] [Hide abstract] ABSTRACT: Die Sterilität von parenteral verabreichten Arzneimitteln wird heutzutage als selbstverständlich vorausgesetzt. In der pharmazeutischen Industrie wurden exakt definierte Verfahren etabliert, die einen effizienten Schutz vor Kontaminationen durch Bakterien und Pilze bieten. Im Gegensatz dazu ist die Gewährleistung der mikrobiellen Sicherheit der Mehrzahl der Advanced Therapy Medicinal Products (ATMP), insbesondere der Zelltherapeutika, eine bis dato nicht oder höchstens partiell gelöste Aufgabe. Sie stellt eine Herausforderung an Hersteller, Behörden und Ärzte dar. Eine ganze Reihe der oben genannten Prinzipien ist bei der Herstellung von Zelltherapeutika nicht anwendbar. So ist die Sterilität von Ausgangsmaterialien nicht garantiert, die bekannten Verfahren zur Sterilisation sind in der Regel nicht anwendbar, sodass auch die Sterilität der Endprodukte nicht garantiert werden kann. Angesichts extrem kurzer Laufzeiten vieler Zelltherapeutika von bis zu wenigen Stunden liegen die Ergebnisse der etablierten Methoden zur Sterilitätstestung häufig viel zu spät vor. Außerdem kann aus der Sterilität der Untersuchungsprobe nicht automatisch auf die Sterilität des gesamten Produktes geschlossen werden. Konventionelle Methoden zur Pyrogentestung sind für ATMP in den meisten Fällen nicht anwendbar. In dieser Arbeit wird versucht, die wesentlichen Unzulänglichkeiten in puncto Sterilität und Pyrogenfreiheit neuartiger Therapeutika aufzuzeigen. Möglichkeiten zur Überwindung dieser Probleme werden diskutiert, und es wird eine Reihe von Lösungsvorschlägen unterbreitet.
- [Show abstract] [Hide abstract] ABSTRACT: Today, sterility of parenteral drugs is practically guaranteed. Well-defined procedures in the pharmaceutical industry enable effective protection against contamination by bacteria and fungi. In contrast, problems regarding microbial safety of advanced therapy medicinal products (ATMPs), especially of cell therapeutics, are at best only partially solved. The latter should be understood as a challenge for manufacturers, regulators, and physicians. Many of the manufacturing principles mentioned above are not applicable in production of cell therapeutics. Sterility of source materials cannot be guaranteed and the hitherto known procedures for sterilization are, as a rule, not feasible. Thus, the sterility of the final product cannot be guaranteed. Considering the extremely short shelf life of many cell therapeutics, sometimes only a few hours, the results from established methods for sterility testing are often available too late. Furthermore, the sterility of a test sample does not indicate sterility of the whole product. In most cases, conventional methods for pyrogen testing are not applicable for ATMPs. This paper demonstrates relevant limitations regarding microbial safety and pyrogenicity. Possibilities to overcome these problems are discussed and some novel solutions are proposed.
- [Show abstract] [Hide abstract] ABSTRACT: In the present study, the feasibility to employ the in vitro pyrogen test (IPT) in the validation of depyrogenation process is presented. As one of the main advantages of IPT is its ability to determine pyrogen absorbed to the container surface, direct incubation of diluted whole blood with the endotoxin indicator was first attempted. It was not possible to quantify the endotoxin in control indicators due to the high content, which is discussed. However, it was possible to demonstrate that indicators subjected to the depyrogenation process were indeed pyrogen free, a quality that is difficult to assure when the LAL assay is employed in extract of indicators or medical devices. On the other hand, IPT performed as well as LAL when endotoxin was previously extracted from the indicator surface. Finally, some conditions for incubation of whole blood with the test surface and to dilute the supernatant obtained from the incubation are presented.
- [Show abstract] [Hide abstract] ABSTRACT: Pyrogens (fever inducing substances) in Pharmaceuticals may affect patients up to life-threatening consequences. The rabbit pyrogen test is the standard animal test in the Pharmacopeias since more than 50 years. Various efforts were made during the last decade to develop alternative pyrogen tests. The common basis of these alternative test is the employment of human monocytes. The chosen sources of monocytes were: human whole blood, peripheral blood mononuclear cells or monocytic cell lines. In an Euopean validation study most of these tests succeeded. Nevertheless the practical application (commercialisation) of these tests would have posed problems: human whole blood and PBMC could not be delivered together with the test, venipuncture at the test site is problematic in terms of safety (blood borne pathogens), legal and ethical issuses. Additionally, there is a individual response of donors towards Non-Endotoxin pyrogens, which makes the use of single donors (including cell lines) questionable. The aim of our work was to develop a simple method for the cryoconservation of human whole blood (single donors / pooled donors) to obtain safe (tested for infection markers) and reliable monocytes which can be shipped and stored at -80°C (dry ice).
- [Show abstract] [Hide abstract] ABSTRACT: The European Partnership for Alternative Approaches to Animal Testing (EPAA) pointed out the need to involve authorities throughout the process of validation and legal acceptance of alternatives to animal experiments. The Paul-Ehrlich-Institute (PEI), Federal Agency for Sera and Vaccines, is the national competent authority in Germany which is responsible for the quality and safety of biologicals including blood and cell-based products. This paper is intended to contribute to the discussion concerning the use of alternative methods in safety testing of medicinal products and considers the scientific work of the PEI in this field. From a regulator's perspective, adequate demonstration of safety and quality of medicinal products are of major interest. Additionally, the availability of the products to the patient has to be taken into consideration. It has to be carefully explored whether the respective in vitro method for demonstration of non-clinical safety as part of the non-clinical development programme is able to guarantee safety level comparable to the corresponding experiment in animals. The topics cited above shall be discussed in this paper using the example of the Alternative Pyrogen Test or also called Monocyte Activation Test. The Alternative Pyrogen Test could serve as paradigm to exemplify how an alternative test can provide at least a comparable level of safety estimation in comparison with a conventional animal test. Furthermore, this alternative test creates additional information which cannot be obtained from the animal experiment, and might also open further scientific insight into the mechanisms of pyrogenicity and acute pro-inflammatory reactions in patients. This test method allows the definition of pyrogen limits for medicinal products. Due to its use of relevant cell systems this in vitro test might contribute significantly to safety assessments of advanced medicinal products during the pre-clinical phase.
- [Show abstract] [Hide abstract] ABSTRACT: Pyrogens as fever-inducing agents can be a major health hazard in parenterally applied drugs. For the control of these contaminants, pyrogen testing for batch release is required by pharmacopoeias. This has been done either by the in vivo rabbit pyrogen test (since 1942) or the limulus amoebocyte lysate test (LAL), since 1976. New approaches include cell-based assays employing in vitro culture of human immune cells which respond e.g. by cytokine production (IL-1beta; IL-6) upon contact with pyrogens. Six variants of these assays have been validated in a collaborative international study. The recent successful development of cryopreservation methods promises to make standardized immunoreactive primary human blood cells available for widespread use. Furthermore, the pretesting of donors for infectious agents such as HIV or hepatitis has made it possible to develop a safe and standardised reagent for pyrogen testing. Using a total of 13 drugs, we have validated the pyrogen test based on fresh and cryopreserved human whole blood in four laboratories. The test reached >90% sensitivity and specificity. In contrast to the LAL, the test was capable of detecting non-endotoxin pyrogens derived from Gram-positive bacteria or fungi.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: Micronemes are characteristic secretory organelles located within the apical cell region of apicomplexan parasites. The protein contents are exocytosed during an early phase of host cell invasion and contribute to parasite motility and the invasion of target cells. We report here on the cloning and heterologous expression of a novel member of the Sarcocystis muris microneme lectin family. The deduced amino acid sequence is in total agreement with that obtained after sequencing the native protein and is characterized by two copies of the apple domain motif. The recombinant polypeptide is expressed in a biologically active conformation as demonstrated by its galactose binding properties.
- [Show abstract] [Hide abstract] ABSTRACT: A novel lectin (SML-2) consisting of 138 amino acids was isolated from cyst merozoites of Sarcocystis muris and sequenced by Edman degradation and mass spectrometry. All 12 cysteinyl residues are involved in disulfide bridges, four of which are attributed to a characteristic pattern of cysteines as found in the so-called PAN-module superfamily. Crystals of SML-2 diffracting to 2.1 A resolution at a synchrotron were grown by the hanging-drop vapour-diffusion technique. They belong to the space group P2(1)2(1)2(1), with unit-cell parameters a = 53.6, b = 128.8, c = 158.2 A and eight molecules in the asymmetric unit. SML-2 cocrystallized with Au galactose results in two different crystal forms. The first form is isomorphous with the native crystals and the second form adopts space group C222(1), with unit-cell parameters a = 74.7, b = 82.0, c = 131.0 A, and diffracts to 2.4 A at a rotating-anode X-ray generator.
- [Show abstract] [Hide abstract] ABSTRACT: The mature major microneme protein of Sarcocystis muris cyst merozoites, which is known as a dimeric lectin with high affinity to galactose and some of its derivatives, was expressed in Escherichia colias a histidine-tagged fusion protein. The recombinant polypeptide, which was recognized by a monoclonal antibody directed against the native lectin, was purified from inclusion bodies after solubilization and refolding, using a combination of metal chelate and lactose affinity chromatography. The apparent molecular mass of the refolded polypeptide as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoreses was 16 kDa, whereas gel filtration chromatography clearly demonstrated that the recombinant protein, like its native counterpart, exists as a homodimer of two non-covalently associated subunits. Inhibition of haemagglutination suggests that the combining site of the recombinant lectin recognizes N-acetyl-galactosamine as the dominant sugar, thus confirming the correct folding of the monosaccharide combining site in the renatured lectin. To the best of our knowledge, this work represents the first reported detailed characterization of a recombinant lectin from apicomplexan parasites, and may contribute to a better understanding of the process of host cell recognition and invasion by these obligate intracellular protozoa.
- [Show abstract] [Hide abstract] ABSTRACT: Toxoplasma gondii is an intracellular protozoan parasite of worldwide distribution. Parasites that habour a complete antigenic profile, that is necessary for the serological diagnosis of human Toxoplasma infections, are provided by in vivo culture methods only. It seems that the host immune pressure is responsible for the expression of a total antigen pattern. Thus, in most laboratories the asexual proliferative stage of the parasite, the tachyzoite, is maintained by successive intraperitoneal passages in highly susceptible animals such as mice. We would like to develop an in vitro method to provide sufficient amounts of high quality parasite antigen suitable for diagnosis of Toxoplasmosis. Using the RAPD-PCR (random amplified polymorphic DNA-PCR) technique, we were able to show that during different culture conditions (in vivo and in vitro culture) the parasites undergo no clonal selection. That means the entire parasite population changes the protein expression pattern due to the in vitro culture conditions. Based on the result described previously the work could be continued as follows. One strategy could be to simulate the host immune pressure during the in vitro cultivation of the tachyzoites. A more convinced approach may be the production of recombinant parasite antigens useful for diagnosis of a Toxoplasma infection in human adults and newborns.
Paul-Ehrlich-InstitutLangen, Hesse, Germany