[Therapy of chronic obstructive eustachian tube dysfunction: evolution of applied therapies]

This paper reviews the past and present developments in the treatment of chronic obstructive eustachian tube dysfunction. Alongside tube catheterization and bougie insertion, modern approaches such as laser eustachian tuboplasty and balloon eustachian tuboplasty (BET) are described. In BET, transnasal endoscopic insertion via the pharyngeal ostium places a balloon catheter in the cartilaginous portion of the eustachian tube. This is then dilated to a pressure of 10 bar for 2 min. Up until January 2013, 351 chronic obstructive eustachian tube dysfunction patients had been treated in our department using BET. The average preoperative eustachian tube score was 2.1 (± 1.8 standard deviation, SD); 12 months postoperatively it was 6.1 (± 2.6 SD). Of these patients, 87% expressed satisfaction with the improvement in chronic obstructive dysfunction. These results demonstrate that BET is a safe and effective treatment for improving eustachian tube function and ear ventilation.

[Intratumoral Onyx embolisation in the management of juvenile nasopharyngeal angiofibroma]

Preoperative embolization for the treatment of juvenile nasopharyngeal angiofibroma was successfully accomplished with Onyx by intratumoral puncture for the first time. Extratumoral migration of Onyx particles was not observed, precluding the necessity to inflate the shield balloon. Postinterventional angiography showed complete occlusion of all supporting blood vessels. Transnasal surgery on the following day achieved complete resection of the angiofibroma without complications. Direct intratumoral embolization of juvenile nasopharyngeal angiofibromas appears to be a safe and effective preoperative method without complications. It could represent a new strategy for the treatment of JNA, as is already the case with other highly vascularized head and neck tumors. Moreover, it increases the likelihood of achieving complete resection.

Is there an interaction between interleukin-10 and interleukin-22?

Interleukin(IL)-10 and IL-22 are structurally related cytokines. Their heterodimeric receptors consist of the cytokine-specific chains IL-10R1 and IL-22R1, respectively, and the common chain IL-10R2. This study focused on the question of whether IL-10 modulates IL-22 effects and vice versa. This question is important because IL-10 and IL-22 exert anti- and proinflammatory effects, respectively, and, as we show here, are simultaneously present in both systemic and local inflammation. The revealed lacking concomitance of IL-10R1 and IL-22R1 on identical cells excluded any possible interaction between IL-10 and IL-22 apart from the competition for IL-10R2. To study this competition, monocytes and hepatocytes were chosen. The dependence of the cytokine action on IL-10R2 was verified. Interestingly, no influence of IL-22 on IL-10 effects was observed. The same was true when IL-22 was used in complex with IL-22-binding protein. Similarly, no influence of IL-10 was found on IL-22 action. This missing competition seemed to be due to a lack of binding between IL-10R2 and the native cytokines in the absence of their corresponding R1 chain. However, IL-10R2 interacted with defined IL-10- and IL-22-derived peptides supporting the hypothesis that cytokine binding to its corresponding R1 chain creates a binding site on this cytokine for IL-10R2.

Coherent membrane supports for parallel microsynthesis and screening of bioactive peptides

Since its invention the SPOT-synthesis methodology has become one of the most efficient strategies for the miniaturized assembly of large numbers of peptides. The combination of a facile synthetic method with high throughput solid- and solution-phase screening assays qualifies the SPOT-technique as a valuable tool in biomedical research. Recent developments such as the introduction of novel polymeric surfaces, new linker and cleavage strategies as well as automated robot systems extended the scope of practical chemical reactions that can be accommodated as well as the numbers of compounds obtainable by this technique. Thus, highly complex spatially addressed compound arrays have become accessible. Together with the introduction of novel screening assays, the method is excellently suited to elucidate recognition events on the molecular level.

Interaction of a designed interleukin-10 epitope mimic with an antibody studied by isothermal titration microcalorimetry

The mechanism of recognition of proteins and peptides by antibodies and the factors determining binding affinity and specificity are mediated by essentially the same features. However, additional effects of the usually unfolded and flexible solution structure of peptide ligands have to be considered. In an earlier study we designed and optimized six peptides (pepI to pepVI) mimicking the discontinuous binding site of interleukin-10 for the anti-interleukin-10 monoclonal antibody (mab) CB/RS/1. Three of them were selected for analysis of their solution conformation by circular dichroism measurements. The peptides differ in the content of alpha-helices and in the inducibility of helical secondary structures by trifluoroethanol. These properties, however, do not correlate with the binding affinity. PepVI, a 32-mer cyclic epitope mimic, has the highest affinity to mab CB/RS/1 identified to date. CD difference spectroscopy suggests an increase of the alpha-helix content of pepVI with complex formation. Binding of pepVI to mab CB/RS/1 is characterized by a large negative, favorable binding enthalpy and a smaller unfavorable loss of entropy (DeltaH degrees = -16.4 kcal x mol(-1), TDeltaS degrees = -6.9 kcal x mol(-1)) resulting in DeltaG degrees = -9.5 kcal x mol(-1) at 25 degrees C as determined by isothermal titration calorimetry. Binding of pepVI is enthalpically driven over the entire temperature range studied (10-35 degrees C). Complex formation is not accompanied by proton uptake or release. A negative heat capacity change DeltaC(p) of -0.354 kcal x mol(-1) x K(-1) was determined from the temperature dependence of DeltaH degrees. The selection of protein mimics with the observed thermodynamic properties is promoted by the applied identification and iterative optimization procedure.

Applications of peptide arrays prepared by the SPOT-technology

The growing range of applications for peptide arrays synthesized on coherent membranes by the SPOT-synthesis method proves they have emerged as a powerful proteomics technique to study molecular recognition events and identify biologically active peptides. Several developments, such as the introduction of novel polymeric surfaces, linkers, synthesis/cleavage strategies and detection methods, are facilitating an increasing spectrum of accessible compounds and applications in biological or pharmaceutical research.

Spatially addressed synthesis of amino- and amino-oxy-substituted 1, 3,5-triazine arrays on polymeric membranes

Effective spatially addressed parallel assembly of trisamino- and amino-oxy-1,3,5-triazines was achieved by applying the SPOT-synthesis technique on cellulose and polypropylene membranes. In addition to developing a suitable linker strategy and employing amines and phenolate ions as building blocks, a highly effective microwave-assisted nucleophilic substitution procedure at membrane-bound monochlorotriazines was developed. The 1,3, 5-triazines obtained could be cleaved in parallel from the solid support by TFA vapor to give compounds adsorbed on the membrane surface in a conserved spatially addressed format for analysis and screening. The reaction conditions developed were employed for the synthesis of 8000 cellulose-bound 1,3,5-triazines which were probed in parallel for binding to the anti-transforming growth factor-alpha monoclonal antibody Tab2 in order to identify epitope mimics.

Evidence for conformationally different states of interleukin-10: binding of a neutralizing antibody enhances accessibility of a hidden epitope

We present the mapping of two anti-human interleukin-10 (hIL-10) antibodies (CB/RS/2 and CB/RS/11) which have been described as binding their antigen cooperatively. The epitopes were identified using hIL-10-derived overlapping peptide scans prepared by spot synthesis. To identify residues essential for binding within the two epitopes, each position was replaced by all other L-amino acids. The epitope-derived peptides were further characterized with respect to antibody affinity and their inhibition of the antibody-hIL-10 interaction. One antibody (CB/RS/11) binds to residues which are completely buried in the X-ray structure of IL-10. Accessibility of this hidden epitope is enhanced upon binding of the antibody CB/RS/2, which recognizes a discontinuous epitope located nearby. The recognition of the hidden CB/RS/11 epitope, as well as the cooperative binding behaviour of the two antibodies, provides evidence that IL-10 can adopt a conformational state other than that observed in the crystal structure.

Mutations of the core promoter and response to interferon treatment in chronic replicative hepatitis B

In chronic replicative hepatitis B the significance of mutations in the basic core promoter (BCP), core upstream regulatory sequences (CURS) and negative regulatory element (NRE) for response to interferon (IFN) is unknown. A sequence analysis of the NRE, CURS, BCP, and precore region was performed from sera of 96 patients with chronic replicative hepatitis B (64 hepatitis B e antigen [HBeAg]-positive patients and 32 HBeAg-negative patients) treated with alfa-IFN (IFN-alpha). The overall sustained response (SR) rate to IFN was 30% with no significant difference between HBeAg-positive and HBeAg-negative patients. IFN responsiveness correlated to hepatitis B virus (HBV)-DNA levels, hepatitis B surface antigen (HBsAg) levels, the number of mutations in the complete BCP, especially nucleotide (nt) region 1753 to 1766 and mutations at nt 1762 and 1764. In HBeAg-positive hepatitis, SR to IFN was associated with a high number of mutations in the BCP (P <.04) and nucleotide region 1753 to 1766 (P <.015) as well as mutations at nucleotide 1764 (P <.007). In HBeAg-negative hepatitis, SR to IFN correlated with a low number of mutations in the BCP (P <.04) and nucleotide region 1753 to 1766 (P <.02) and a wild-type sequence at nt 1764 (P <.003). Prediction of IFN response was possible on the basis of nt 1764 in 77% of HBeAg-positive patients and 78% of HBeAg-negative patients. IFN response did not correlate with the occurrence of the 1896 mutation, mutations in the CURS or NRE, disease duration, ethnic origin of the patient, alanine transaminase (ALT) levels and HBV genotype. Our data suggest that HBV genome mutations located within the BCP are determinants of a response to IFN therapy.

Spot synthesis: observations and optimizations

Positionally addressable syntheses of peptides on continuous cellulose membranes (spot synthesis) have often been reported in detail, but important questions dealing with synthesis quality, reproducibility and subsequent binding assays have largely been under-emphasized. In this report we have investigated some of these problems. The most important results were: (i) the signal intensity of ligate binding to cellulose-bound peptides and the affinity of the corresponding soluble peptides show good correlation, illustrated by three different ligate binding assays; (ii) reducing peptide density on the cellulose avoids the 'ring spot' effect, i.e. where less binding is observed in the spot-center compared to the rim. We recommend a peptide density of 10 nmol/cm2 as a reasonable starting point for further optimization; (iii) statistical analysis of binding assay reproducibility with more than 15000 peptides resulted in a mean standard signal deviation of 0.18; and (iv) optimization of side-chain deprotection revealed that a 30-min pretreatment of the cellulose with 90% trifluoroacetic acid followed by the standard deprotection protocol resulted in higher purity of the synthesized products.

Antigen sequence- and library-based mapping of linear and discontinuous protein-protein-interaction sites by spot synthesis

The knowledge (antigen-derived peptide scans)- and library (de novo)-based mapping of linear and discontinuous antibody epitopes as well as protein-protein contact sites in general by spot synthesis now is a well established technique. Due to its automation, this technique also promises great potential for applications in functional genomics. It should help to elucidate the complex network of interacting protein molecules involved in signal transduction events (Adam-klages et al. 1996; Hoffmüller et al. 1999). Although little chemistry is involved in the preparation of peptide scans or libraries and the synthesis procedure is relatively simple, the laboratories of immunologists or molecular biologists are often not equipped to perform spot synthesis. In this case scans or libraries can be purchased from commercial suppliers.

Evidence for conformationally different states of interleukin-10: binding of a neutralizing antibody enhances accessibility of a hidden epitope

We present the mapping of two anti-human interleukin-10 (hIL-10) antibodies (CB/RS/2 and CB/RS/11) which have been described as binding their antigen cooperatively. The epitopes were identified using hIL-10-derived overlapping peptide scans prepared by spot synthesis. To identify residues essential for binding within the two epitopes, each position was replaced by all other L-amino acids. The epitope-derived peptides were further characterized with respect to antibody affinity and their inhibition of the antibody-hIL-10 interaction. One antibody (CB/RS/11) binds to residues which are completely buried in the X-ray structure of IL-10. Accessibility of this hidden epitope is enhanced upon binding of the antibody CB/RS/2, which recognizes a discontinuous epitope located nearby. The recognition of the hidden CB/RS/11 epitope, as well as the cooperative binding behaviour of the two antibodies, provides evidence that IL-10 can adopt a conformational state other than that observed in the crystal structure.

The antigen binding domain of non-idiotypic human anti-F(ab')2 autoantibodies: study of their interaction with IgG hinge region epitopes

In previous studies we described a natural human IgG-anti-F(ab')2 autoantibody family with immunoregulatory properties. Genes coding for the variable regions of the heavy and light chains of the Abs were isolated from a natural Ig gene library and scFv Abs were expressed in E. coli. The scFv Abs bound to F(ab')2 but not to Fab fragments. This points to an epitope located in the hinge region since Fab fragments are lacking most of the hinge. In order to verify our hypothesis, double chain peptides comprising the lower-, middle-, and part of the upper hinge subregion of IgG1-IgG4 were synthesized on cellulose membranes and tested for binding to the Abs. The results show binding of Abs to IgG1 and IgG4 hinge region peptides. In order to identify the key residues of the discontinuous epitopes we carried out complete substitutional analyses in which each amino acid of the wt peptides was substituted by all other amino acids except cysteine. The exchange of proline in the IgG1 or IgG4 middle hinge region abrogated the binding, revealing the importance of this subregion for epitope expression. No binding to the IgG2 or IgG3 hinge was detected. These results indicate that scFv anti-F(ab')2 Abs recognize the hinge region of IgG1 and IgG4 and that the expression of the epitope depends on an intact middle hinge subregion.

A synthetic mimic of a discontinuous binding site on interleukin-10

We synthetically reconstructed a discontinuous binding site on interleukin-10 (IL-10) that recognizes the neutralizing anti-IL-10 antibody CB/RS/1. To design the 32-mer IL-10 mimic, a discontinuous interaction site on IL-10 was mapped, and binding studies with epitope-derived peptides led to specific replacement of several amino acids. Both parts of the interaction site were combined by addition of a linker molecule. Systematic analoging of the combined molecule then led to introduction of several additional substitutions in both regions and the linker. All possible disulfide bridge-containing variants of the 32-mer were tested by binding studies. Parallel syntheses were performed on continuous cellulose membranes by spot synthesis. As a result, a conformationally stabilized IL-10-derived molecule was obtained that both binds to and neutralizes the biological activity of CB/RS/1 in the low nanomolar range. This synthetic approach is a powerful alternative to phage display methods for the design of protein mimics.

Mapping of the interleukin-10/interleukin-10 receptor combining site

The discontinuous interleukin-10(IL-10)/interleukin-10 receptor (IL-10R) combining site was mapped using sets of overlapping peptides derived from both binding partners bound to continuous cellulose membranes. Low affinity binding of single regions of the discontinuous contact sites on IL-10 and IL-10R could be identified due to (1) high peptide density on the membrane support, (2) incubation with high protein concentrations, (3) indirect immunodetection of the ligates after electrotransfer onto polyvinylene difluoride membranes, and (4) use of highly overlapping peptide scans of different length (6-mers and 15-mers). The single binding regions identified for each protein species are separated in the protein sequences, but form continuous areas on the surface of IL-10 (X-ray structure) and IL-10R (computer model). Furthermore, four epitopes of neutralizing anti-IL-10 and anti-IL-10R antibodies were mapped and overlap with these binding regions. Soluble peptides (15- to 19-mers) each spanning one of the three identified IL-10-derived receptor binding regions displayed no significant affinity to IL-10R as expected, whereas a peptide (35-mer) comprising two of these regions had considerably higher binding activity. The data are consistent with a previously published computer model of the IL-10/IL-10R complex. This approach should be generally applicable for the mapping of non-linear protein-protein contact sites.

Mapping protein-protein contact sites using cellulose-bound peptide scans

We have characterized the interaction of two monoclonal antibodies with their respective antigens using cellulose-bound sets of overlapping peptides (peptide scans). Both antibodies CB/RS/5 and CB/MT/1 recognize discontinuous epitopes present in human interleukin-10 (IL-10) and tumor necrosis factor alpha (TNF-alpha). In addition, the interaction between TNF-alpha and its 55-kDa receptor (TNF-R) was investigated by the same approach. Both antibodies, as well as TNF-alpha, interacted with two or more regions of the peptide scans. Antibody-binding competition studies between the native antigens and peptides, covering single parts of the binding regions, enabled us to distinguish between binding to the paratope or other regions of the antibody. The combination of these experimental approaches allowed the identification of short antigen-derived sequences that are separated on the primary sequence but close in space on the surface of IL-10 and TNF-alpha, thus representing putative discontinuous epitopes. In the case of the TNF-R-derived peptide scans, two of the identified regions interact with the structurally similar TNF-beta in the TNF-beta-TNF-R complex. These data indicate that this approach should be generally applicable for mapping nonlinear protein-protein contact sites.

Simultaneous synthesis of peptide libraries on single resin and continuous cellulose membrane supports: examples for the identification of protein, metal and DNA binding peptide mixtures

Peptide libraries were simultaneously synthesized on single supports by double coupling 0.8 equivalents of an equimolar acylating amino acid mixture consisting of 19 amino acids (cysteine omitted) at randomized sites, thus compensating for the different coupling rates of the amino acids. Peptide epitope mixtures, as well as very complex mixtures such as a completely randomized hexapeptide, were prepared and analyzed by HPLC and amino acid analysis. The results obtained indicate that this method can be applied to the synthesis of peptide libraries. Parts of a simultaneously synthesized solution phase combinatorial library XXB1B2XX were successfully used for the detection of the linear epitope HFND of transforming growth factor-alpha (TGF alpha) recognized by the monoclonal antibody Tab2. Furthermore, novel combinatorial peptide libraries XXB1B2XX were prepared on continuous cellulose membrane supports, also allowing the identification of TGF alpha epitope sequences. In addition, peptide mixtures that bound to a double-stranded DNA (15mer) and silver were identified. These preliminary results indicate that cellulose-bound combinatorial peptide libraries can be used for the rapid and inexpensive screening of millions of peptides to identify single molecules that bind any given ligand such as proteins, nucleic acids and metals.