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S Miescher

Publications and source records attributed to S Miescher.

At least 19 recordsLinked to original sources
PubMed2000

Mimicry of human IgE epitopes by anti-idiotypic antibodies.

According to Jerne's network hypothesis, the binding site of an anti-idiotypic antibody also represents the internal image of an epitope present on a foreign, or even a self antigen. In recent years, antigen mimicry has been defined at the molecular level for some xeno-antigens. However, until now there has been no demonstration of structural mimicry between a human anti-idiotypic antibody and a self structure. To address this question, we used human IgE as the self structure and a well-defined anti-human IgE mAb (BSW17). We describe the isolation of two anti- idiotypic antibodies specific for the anti-IgE antibody BSW17 from a non-immune human Fab phage display library. Interestingly, these two anti-idiotypic antibodies mimic the same molecular surface region as a previously described IgE peptide mimotope isolated by panning on BSW17, but they cover a much larger epitope on the IgE molecule. Accordingly, immunisation of rabbits with the two anti-idiotypic antibodies induced high-affinity antibodies with the same characteristics as BSW17. Thus, our data demonstrate that it is possible to isolate anti-idiotypic antibodies derived from the human genome without the need for hyperimmunization, and confirm Jerne's hypothesis that both foreign antigens and self structures can be mimicked by our own immunoglobulins.

Amino Acid Sequence↗
PubMed1998

Epitope-specific antibody response to IgE by mimotope immunization.

We have previously described a mouse monoclonal anti-human IgE antibody (BSW17) capable of recognizing receptor-bound IgE without inducing mediator release from human basophils or mast cells. Moreover, immune complexes of IgE and BSW17 are not able to bind to the IgE receptor. An initial attempt to map the precise epitope recognized by this mAb by using Fc epsilon-derived peptides of variable length was unsuccessful. However, by screening random peptide phage display libraries we isolated circular nona- and octapeptides specifically recognized by BSW17. These constrained peptides mimic at least a part of a conformational epitope and are thus called mimotopes. These mimotopes, either phage displayed or synthetically synthesized, did not react with any other anti-human IgE antibody tested, but efficiently inhibited the binding of human IgE to BSW17 only. The use of Rhodol-Green-labeled free cyclic peptide proved that these interactions were not carrier dependent. Immunization of rabbits with phage clones displaying the specific peptides on the surface induced an anti-human IgE response specific for the epitope of BSW17. Therefore, we conclude that such mimotopes or mimotope-derived peptides might be used for vaccination to induce in vivo a beneficial anti-IgE response as a novel immunotherapy.

Amino Acid Sequence↗
PubMed1998

Recombinant human natural autoantibodies against GPIIb/IIIa inhibit binding of autoantibodies from patients with AITP.

Autoimmune thrombocytopenic purpura (AITP) is caused by autoantibodies predominantly against platelet membrane glycoproteins (GP) IIb/IIIa and GPIb/IX. Naturally occurring autoantibodies have been described against a variety of autoantigens; it has been suggested that perturbation of their regulation may be associated with autoimmune diseases. Using a combinatorial Fab phagemid library from an individual immunized with human RhD+ red blood cells, we evaluated the presence of natural anti-GPIIb/IIIa autoantibodies as well as their relation to AITP-associated anti-GPIIb/IIIa autoantibodies. Selection on native GPIIb/IIIa and characterization of positive clones by inhibition studies against murine monoclonal anti-GPIIb/IIIa antibodies and by DNA analysis revealed the presence of two distinct recombinant anti-GPIIb/IIIa autoantibodies, which partially inhibited binding of affinity-purified platelet-associated autoantibodies from 8/12 AITP patients. Our results demonstrated that GPIIb/IIIa-specific Fab directed against conformational epitopes within the GPIIb/IIIa complex may be cloned from the genome of an individual immunized with RhD+ red blood cells, who was not affected by AITP. The partial inhibition of binding of platelet-associated autoantibodies from AITP patients to GPIIb/IIIa by the recombinant anti-GPIIb/IIIa phage clones suggests recognition of closely related antigenic epitopes. These phage clones may represent down-regulated, potentially pathological autoantibodies and could be used as new tools for investigation of AITP.

Amino Acid Sequence↗
PubMed1998

Antigen interaction and heat inactivation expose new epitopes on human IgE.

It is well established that heat-denatured IgE is no longer capable of binding to FcepsilonRI. We have found an antibody that interacts with heat-denatured IgE. Interestingly, this antibody can also be used to detect some serum IgE, but not IgE synthesized de novo in vitro. However, native IgE can be transformed into an IgE that is recognized by this antibody, if antigen is added. Our data indicate that physiological mechanisms exist that biologically inactivate IgE which might still be mistaken for 'functional' IgE by assays based on polyclonal antibodies.

Animals↗
PubMed1998

Sequence and specificity analysis of recombinant human Fab anti-Rh D isolated by phage display.

BACKGROUND AND OBJECTIVES: Hyperimmune anti-Rh D serum is worldwide in short supply. As a first step to develop an alternative source of Rh D antibodies, we describe in this study the isolation and characterization of recombinant anti-Rh D Fab fragments. MATERIALS AND METHODS: Peripheral blood mononuclear cells harvested from a hyperimmunized donor were used to construct two combinatorial Fab libraries. Phages expressing these Fab fragments were selected on whole red blood cells followed by testing of positive clones in an indirect hemagglutination assay. RESULTS: Individual Fab clones are of high affinity and competitively inhibit the binding of a registered anti-D immunoglobulin. The Fab clones are also specific against the partial D phenotypes, Rh33, DIII, DIVa, DIVb, DVa, and DVII. The 13 different but highly homologous clones express preferentially VH3 segments. CONCLUSION: These Fab fragments show potential for the development of a new generation of therapeutic anti-Rh D reagents.

Amino Acid Sequence↗
PubMed1996

Effect of anti-IgE antibodies on Fc epsilonRI-bound IgE.

Anti-IgE mAbs have always been used to trigger mediator release from basophils or mast cells. Now nonanaphylactogenic anti-human IgE Abs are in clinical evaluation as a therapeutic agent against atopic disease. We have found a mAb that is nonanaphylactogenic but recognizes receptor-bound IgE. Interestingly, the Ab prevents the association of IgE with its receptor if immune complexes were formed between IgE and anti-IgE mAb. This explained the phenomenon that addition of anti-IgE Ab to receptor-bound IgE resulted in a decrease of receptor-bound IgE, because IgE dissociating from the receptor was complexed, altering the thermodynamic balance of receptor-bound vs free IgE. Our data show that there are nonanaphylactogenic Abs that do not directly interfere with the receptor binding site on IgE and are capable of preventing the association of IgE with its high affinity receptor. This unique feature would render such an anti-IgE Ab a possible candidate for immunotherapy of atopy.

Anaphylaxis↗
PubMed1996

Anti-IgE in allergic sensitization.

Anti-IgE autoantibodies exist predominantly in the sera of patients with atopic disease. For some time such anti-IgE autoantibodies have been considered a phenomenon that may not be of clinical importance. The cloning of such anti-IgE autoantibodies has eliminated doubts of whether these antibodies exist, but it is still unclear whether such autoantibodies play a pathophysiological role. However, there are ongoing clinical trials that use humanized anti-IgE antibodies for passive immunization of atopic individuals. While this approach may not definitely clarify the role of anti-IgE autoantibodies, it will nevertheless clarify the role of IgE.

Animals↗
PubMed1996

Neuropeptides accentuate interleukin-4 induced human immunoglobuline E synthesis in vitro.

Corticotropin releasing factor, adrenocorticotropic hormone (ACTH) and alpha-melanocyte stimulating hormone either inhibit or enhance in a dose-dependent fashion an interleukin-4 (IL-4) driven human IgE synthesis in vitro. Here, we show that culture conditions strongly influence the earlier observed dose- and donor-dependent effects of adrenocorticotropic hormone. The effect of ACTH on IgE synthesis became only apparent late during culture periods, suggesting an indirect effect via the cellular microenvironment rather than by acting directly at the level of B-cell isotype switching. Thus, we studied other proopiomelanocortin (POMC) derived peptides and neuropeptides known to influence the cellular microenvironment. Indeed, similar modulatory effects on IgE synthesis were also observed by the addition of other proopiomelanocortin-derived peptides such as alpha-, beta-, and gamma-endorphins as well as by the opioid binding pentapeptide Leu-enkephalin. Furthermore the neuropeptide substance P accentuated an IL-4 or an IL-4 and anti-CD40 antibody driven class switch to IgE. In contrast to ACTH, substance P interfered not only with IgE synthesis but also with the synthesis of the other immunoglobulin isotypes. Thus, systemically acting neuroendocrine peptides such as ACTH and locally acting neuropeptides such as the enkephalins and substance P can modulate the magnitude of an IL-4 induced IgE response.

Adrenocorticotropic Hormone↗
PubMed1996

Cross reactive anti-tetanus and anti-melittin Fab fragments by phage display after tetanus toxoid immunisation.

Amino acid sequence homology between tetanus toxoid, a common vaccine and melittin, a bee venom allergen provided us with two antigen models for studying the production of cross reactive antibodies after immunisation. Analysis of the serum of an atopic patient recently boosted with tetanus toxoid revealed the presence of anti-melittin and anti-tetanus antibodies. From this donor a phage display Fab library was constructed five days after vaccination. Screening of this library either with melittin alone or with tetanus toxoid followed by melittin allowed the isolation of Fab fragments specific to melittin but also Fab fragments which cross react with melittin and tetanus toxoid. Amino acid analysis revealed diversity in the heavy and the light Ig chains of the melittin specific and of the cross reactive clones. Interestingly we found that the light chain recognised melittin whereas the heavy chain preferentially bound to tetanus toxoid suggesting that cross reactivity may be due to the different binding specificities of the individual Ig chains.

Amino Acid Sequence↗
PubMed1995

Antigen-specific inhibition of IgE binding to the high-affinity receptor.

Since the beginning of this century, allergen immunotherapy has been widely used to treat allergic disorders. In addition to the long-term clinical efficacy of this therapy, there are immediate beneficial effects as observed in rush immunotherapy for which there is no clear mechanism. We investigated the direct impact of an Ag on its specific IgE in terms of IgE measurability in immunoassays and subsequent binding of IgE to the high-affinity receptor for IgE. As a model we used a chimeric IgE specific for NIP that exhibits similar biologic properties as serum or myeloma IgE. To mimic particulate and soluble allergens we coupled 15 NIP molecules to BSA. Using this "artificial allergen" we could show that the presence of the Ag reduced the IgE measurability in immune assays. Furthermore, IgE binding to the Fc epsilon RI was 60% inhibited in the presence of the Ag shown with an optical biosensor that monitors molecular interactions. In normal basophils passively sensitized with IgE that was preincubated with the Ag, no sulfidoleukotriene release could be induced. Rush immunotherapy may invoke a similar phenomenon, resulting in the short-term alteration of symptoms by blocking or substantially reducing binding of IgE to its high-affinity receptor. Thus, our result may explain some of the short-term beneficial effects observed in rush immunotherapy.

Allergens↗
PubMed1995

IgE-producing hybridomas established after B-cell culture in the CD40 system.

While total IgE synthesis can be easily induced in human PBL or B cells by different stimuli, no systems are known for the induction of allergen-specific IgE in vitro. In this study we investigated whether a specific Ig response could be induced using the CD40 culture system with the final intention to generate B-cell hybridomas secreting IgE of defined specificity. B cells derived from immunized donors normally give rise to many specific hybridomas after cell fusion. However, if cultured in the CD40 system and then immortalized and screened for anti-tetanus specificity, no tetanus-specific clones were found but a large number of IgE-secreting hybridomas had been generated. Also allergen-specific B cells could not be expanded in the CD40 system but long-term cultures yielded again B cells that were efficiently immortalized by cell fusion resulting in stable IgE-secreting hybridomas but of undefined specificity. One of these IgE-producing clones was further characterized and had an IgE production rate of 4.5 micrograms/10(6) cells/24 h. This paper provides two findings. (1) Our cell lines represent a valuable new source of human IgE. (2) Most importantly, our data indicate that the CD40 system is not suitable to expand specific B cells, suggesting that other systems have to be developed for the induction of a significant antigen-specific Ig response.

Allergens↗
PubMed1994

Human anti-IgE antibodies by repertoire cloning.

Anti-IgE antibodies have been detected in sera of patients with an allergic disease where they might play a role in the regulation of (Ig)E-mediated reactions. Using a recombinant phage surface display expression system a combinatorial library of antibody heavy and light chains was constructed from peripheral blood mononuclear cells from an atopic donor immunized with tetanus toxoid. Screening of the library allowed the identification of a large number of phages displaying human monovalent antigen-binding fragments (Phab) against tetanus toxoid and IgE. Surprisingly, we found a high frequency of Phab against particular IgE myelomas that was comparable to the frequency found for Phab against tetanus toxoid. However, most of these Phab were directed to different idiotypic determinants, depending on the IgE myeloma used for the panning procedure. Nevertheless, two clones were found to have anti-isotypic specificity and were shown to react specifically with the CH2 domain of the IgE heavy chain.

Adult↗
PubMed1994

Neuropeptides are potent modulators of human in vitro immunoglobulin E synthesis.

We determined the effect of adrenocorticotropin hormone (ACTH) on the regulation of IgE synthesis. Depending on the concentration, ACTH enhanced or inhibited IgE synthesis in a culture system where IgE synthesis was induced with interleukin-4 (IL-4) and anti-CD40 monoclonal antibody in peripheral blood mononuclear cells. Similar effects on IgE synthesis were observed by adding ACTH-related peptides, e.g. corticotropin-releasing factor (CRF), the inducer of ACTH, or alpha-melanocyte stimulating hormone (alpha-MSH), a cleavage product of ACTH. However, ACTH had no effect on IgG or IgM synthesis in this culture system. ACTH did not act directly on either B or T cells as there was no influence on IgE synthesis in a system using purified B cells alone or co-cultured with T cells. The effect of ACTH on IgE synthesis was mediated by accessory cells. This was shown by priming purified CD14-positive monocytes with ACTH and reconstitution experiments. Therefore, these findings suggest that ACTH and the related peptides CRF and alpha-MSH can influence the microenvironment modulating an IL-4 and anti-CD40 monoclonal antibody driven class switching to IgE via accessory cells.

Adrenocorticotropic Hormone↗
PubMed1994

Inhibition of human IgE synthesis by anti-IgE antibodies requires divalent recognition.

We used a selection of well-characterized murine monoclonal anti-IgE antibodies to investigate their effect on human in vitro IgE synthesis. We found anti-IgE antibodies that either inhibited or enhanced interleukin-4 plus anti-CD40-induced in vitro IgE synthesis in peripheral blood mononuclear cells (PBMC). This differential activity was isotype specific as neither IgM nor IgG synthesis were affected. Interestingly, only coding IgE mRNA was down-regulated, whereas germ-line epsilon RNA expression was not influenced by anti-IgE monoclonal antibody (mAb). On purified B cells all anti-IgE mAb inhibited interleukin-4 plus anti-CD40-induced IgE synthesis, implying a role of non-B cells for the enhancing activity observed in PBMC. Using Fab and F(ab')2 of an inhibitory anti-IgE mAb we could show that divalent recognition was required for inhibition of IgE synthesis.

Antibodies, Anti-Idiotypic↗
PubMed1994

Domain-specific anti-IgE antibodies interfere with IgE binding to Fc epsilon RII.

Human anti-IgE autoantibodies have been identified and implicated in the regulation of IgE-mediated reactions and IgE synthesis. In order to study the potential regulatory role of anti-IgE antibodies on IgE binding to the Fc epsilon RII we used a panel of IgE-specific monoclonal antibodies that were mapped by Western blotting against a series of recombinant epsilon domain peptides. Antibodies specific for all epsilon domains were detected except those against C epsilon H1. Using a competitive inhibition cell-binding assay on Fc epsilon RII + 8866 cells, we identified two major patterns of anti-IgE activity. Antibodies specific for the C epsilon H3 domain removed IgE whereas those specific for the C epsilon H2 domain enhanced IgE binding to the Fc epsilon RII. The anti-C epsilon H2 antibodies, in contrast to the anti-C epsilon H3 antibodies, could not dissociate cell-bound IgE from the Fc epsilon RII. Using preformed immune complexes of IgE and anti-IgE antibodies, it was clear that the anti-C epsilon H2 antibodies bound more IgE to the Fc epsilon RII by addition of immune complexes to the cell surface. Our results suggest that the opposing actions of either inhibition or enhancement of IgE binding by anti-IgE antibodies are related to their epsilon domain specificity.

Animals↗
PubMed1993

A specific feedback by anti-IgE autoantibodies on the cytokine network in allergy.

During recent years we have shown that anti-IgE antibodies can have different biological functions. Depending on their epitope specificity they can be anaphylactogenic or not, they interfere with IgE binding to its receptor or not, and they enhance or inhibit IgE synthesis. Therefore we propose a theoretical model implying that anti-IgE autoantibodies are specific feed back molecules that neutralize IgE induced by the cytokine network. In the normal individual this system would be beneficial, where as the atopic individual, due to differences in its B cell repertoire, will produce the wrong type of anti-IgE antibody. The wrong type of anti-IgE antibody may even aggravate the disease as some of these autoantibodies may induce IgE synthesis or trigger effector cells that in turn generate a Th2 like cytokine pattern.

Antibody Specificity↗