Biomedical subjects

C H Schneider

Publications and source records attributed to C H Schneider.

At least 19 recordsLinked to original sources

PubMed1995

Basic aspects related to penicillin-allergy skin testing: on the variability of the hapten-paratope interaction.

Ampicillin and benzylpenicillin conjugated to human serum albumin were used as immunogens in order to obtain antihaptenic IgG responses in outbred guinea pigs according to different schedules, all involving complete Freund's adjuvant. The individual responses were characterized by ELISA and by ELISA inhibition using ampicillin, benzylpenicillin, and carbenicillin peptidic conjugates for coating and for inhibition. In several instances, drastically reduced cross-reactivity and even its absence were observed, although the penicillin antigens differ only in the side-chain. The notion that the invariantly present thiazolidine ring will always provide significant binding to antibodies against all penicillins differing only in the side-chain has to be dropped. The experiments were performed in relation to newer findings of clinical penicillin-allergy skin testing which suggest that benzylpenicillin-based reagents alone are not able to detect or predict all reactions against semisynthetic penicillins. The experimental evidence here obtained corroborates this conclusion.

Ampicillin↗

PubMed1993

Synthetic immunogens. The effect of the conformational space on biological and immunological responses to dimeric hormone constructs.

Chimeras of the double chain bis-cystinyl hinge fragment 225-232/225'-232' of the human IgG1 and of peptides related to human little-gastrin were synthesized, whereby the fully bioactive gastrin sequences 2-17 and 5-17 were amide-bond-linked N- and N- or C-terminally, respectively, to the hinge peptide. All the dimeric constructs proved to be efficient immunogens; however, both the configuration of the constructs and the length of the haptenic gastrin molecule were found to drastically affect the specificity of the antibody response and, thus, the type of dominant immune epitope expressed. The different degree of accessibility of the gastrin chains in the dimers is similarly reflected by their binding affinities to gastrin receptors and their bioactivities in vivo. Molecular dynamics simulations of the chimeric compounds clearly revealed that the conformational space of the gastrin peptide chains 2-17 and 5-17 is strongly restricted upon linkage to the hinge peptide. Only in the gastrin-(2-17) construct does sufficient free conformational space seem to be retained, at least for one of the two gastrin chains, in order to allow folding into the bioactive structure. This also agrees with the observation that the dimeric gastrin-(2-17) behaves like a gastrin monomer in terms of receptor binding affinity and biopotency in vivo; but it could additionally explain why an antibody response of gastrin receptor-like specificity could only be induced with this construct. The experimental data may therefore suggest a high degree of parallelism between the mechanism of recognition of the gastrin peptides in the dimeric constructs as hormonal ligands by the gastrin receptors and as haptens by the immune competent cells.

Amino Acid Sequence↗

PubMed1992

Induction and detection of anti-peptide antibody specificity is critically affected by the mode of hapten presentation.

C-Terminal cholecystokinin (CCK)-peptides of increasing chain lengths were all linked at their N-termini to the single surface-exposed cysteine residue 107 of yeast iso-1-cytochrome c by the maleimide/thiol reaction. The resulting CCK/cytochrome 1:1 conjugates with the haptenic peptides in the identical protein environment were used to immunize outbred guinea pigs in order to assess the critical size of CCK peptides required for the expression of a CCK-specific epitope and the induction of antibodies not crossreacting with the homologous gastrin sequence. By using standard ELISA techniques with polystyrene-adsorbed antigen to evaluate the specificity of the antisera, none of the conjugates were found to induce anti-CCK antisera not crossreacting with gastrin. However, when the biotinyl-CCK-antigen was immobilized by polystyrene-adsorbed avidin, i.e. via a procedure which assures maximum accessibility of the bound antigen, we were able to demonstrate that with CCK-12 and particularly CCK-13, linked through their N-termini to the carrier, the critical length for the expression and recognition of a CCK-specific epitope was reached. The related polyclonal antisera did not crossreact with the homologous gastrin in the modified ELISA.

Amino Acid Sequence↗

PubMed1991

Fully synthetic immunogens. Part III. Synthesis of hinge-peptide/gastrin conjugates and their immunological properties.

As core molecule for the multiple attachment of antigenic peptides we have selected the human IgG1 hinge fragment 225-232/225'-232'. Two types of conjugates of this double-chain bis-cystinyl hinge-peptide were prepared i) by linking its C-termini to [NIe15]-human-little-gastrin-[2,17] and ii) by elongating the resulting hinge-peptide/[NIe15]-little-gastrin-[2-17] conjugate at the two N-termini with the human big-gastrin sequence 1-14 to produce the big-gastrin-[1-14]/hinge-peptide/little-gastrin-[2-17] conjugate. For the synthesis of these peptide structures both the route via the preformed double-chain bis-cystinyl peptide and the route via suitably protected monomeric bis-cysteinyl peptides were used. For the latter approach advantage was taken of the previous observation about the preferred oxidation of the bis-cysteinyl hinge-peptide 225-232 to the dimer in parallel alignment. Both synthetic routes led to identical products. Immunization experiments in guinea pigs with the synthetic hybrids led to surprisingly strong immune responses with anti-little-gastrin antibody titers comparable to those induced by the iso-1-cytochrome c/little-gastrin-[2-17] conjugate as carrier-hapten system. These findings show that the two gastrin constructs are fully competent immunogens. Additionally, the gastrin receptor-like specificity of the antibodies indicates that both the synthetic hybrids and the cytochrome c conjugate allow for expression of a little-gastrin-specific conformational epitope similar to the bioactive structure of this hormone. The usefulness of such synthetic hybrids is further confirmed by the observation that the bivalent immunogen, containing both the little-gastrin 2-17 and the big-gastrin 1-14 sequence, is capable of inducing an immune response against both antigenic sequences, although with different efficiency. These results fully confirm our expectations.

Amino Acid Sequence↗

PubMed1990

Anaphylactic properties of monohaptenic dinitrophenylated tripalmitoyl-S-glyceryl-cysteinyl lipopeptides.

Tripalmitoyl-S-glycerylcysteinyl lipopeptides are B-cell and macrophage activating and may be used as low molecular weight immunogens of considerable potency and even as vaccines when conjugated with suitable epitopic structures. Selected lipopeptides carrying single Dnp haptens were found to evoke mild passive cutaneous anaphylaxis in guinea pigs sensitized against Dnp. The reactions were observed after intravenous injection whereas intradermally applied antigen was negative. The anaphylactogenicity seems unrelated to micelle or aggregate formation of the insoluble peptides which require lecithin additions as well as sonication to become solubilized. The dinitrophenylated lipopeptide tripalmitoyl-S-glyceryl-cysteinyl-seryl-lysine produced toxic reactions which were not observed with the lipopeptide devoid of Dnp. Dinitrophenylated tripalmitoyl-S-glycerylcysteiny-1,6-diaminohexane and tripalmitoyl-S-glyceryl-cysteinyl-lysine did not show these toxic reactions.

Animals↗

PubMed1990

On the immunochemical specificity of pyrazolinone and pyrazolidinedione reactions.

Haptenic groups based on the 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one and 1,2-diphenyl-pyrazolidine-3,5-dione structures conjugated to human serum albumin gave antibody responses in rabbits which were compared with those raised against the same haptens conjugated via spacer bridges to the protein carrier. The spacing up to 12.4 A had no marked influence on the antibody specificity evaluated by haptenic inhibition of ELISA. The specificities are more pronounced than those found with e.g. anti-penicilloyl antibodies which seems in line with clinical experience involving e.g. phenylbutazone, sulfinpyrazone, propyphenazone and metamizole. It is argued that such strict specificities may lead to false negative tests in diagnostic procedures in vitro as well as in skin testing.

Animals↗

PubMed1989

Epitope analysis: biotinylated short peptides as inhibitors of anti-peptide antibody.

The interaction of anti-melittin antisera with melittin-coated ELISA plates could be inhibited by biotinylated peptides of the C terminal epitope which is one of three defined antigenic sites on the hexacosapeptide melittin. Non-biotinylated short peptides and peptide derivatives were inactive. It is suggested that biotinylation of epitopic peptides enhances their inhibitory properties in a methodologically useful way.

Amino Acid Sequence↗

PubMed1989

Antigenic structure of the hexacosapeptide melittin: evidence for three determinants, one with a helical conformation.

ELISA-based epitope analysis was performed using rabbit polyclonal antisera against melittin. Antigenic sites were found at the C-terminus, in the middle section and within the N-terminal helix. Antibodies against the helical segment could discriminate between two faces of the amphiphilic helix. The antigenic sites include the bulk of the melittin hexacosapeptide, which is synonymous with a very high epitope density.

Amino Acid Sequence↗

PubMed1988

Potency of hexavalent and decavalent anaphylactogens: affinity enhancement by epitope clusters.

Two deca-L-lysine conjugates, one carrying ten, the other carrying six D-benzylpenicilloyl haptenic groups as epitope models, were used as elicitors of passive cutaneous anaphylaxis in guinea pigs. It was found that equal haptenic doses yielded virtually indistinguishable responses, i.e., the potencies were close to 10:6. Interpretation of these data appears possible by using established immunochemical concepts of preequilibria and equilibria in free solution as starting point. The discussion is simplified due to the fact that the two conjugates being decavalent and hexavalent, respectively, in free solution, are both hexavalent on cell membranes. It was found that the clusters of haptenic groups displayed by the conjugates enhance the affinity for antibody binding and that the haptenic densities are directly related to potencies. Epitope clusters of enhanced affinity interacting with cell-bound antibody may be significant and useful in a number of ways.

Animals↗

PubMed1987

Defined test reagents for the diagnosis of drug-induced allergy. Antibody-dependent skin reactions towards pyrazolinone and pyrazolidinedione derivatives in the guinea pig.

Chemically defined haptenic reagents and haptenic conjugates were synthesized for use in clinical skin testing. One series of reagents was based on the 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one structure, a second series on 1,2-diphenyl-pyrazolidine-3,5-dione. Haptens were connected via flexible spacer molecules which insert considerable distances between haptenic moieties and carriers. The skin test reagents were hexavalent conjugates prepared from the bis-penta-L-lysine carrier 'PAL'. The methodological details exemplify the application of N-hydroxysuccinimide activated ester derivatives for the preparation of peptidic conjugates. Rabbit and guinea-pig antisera against the haptens were obtained by immunization with human serum albumin conjugates. Efficacy and cross-reactivity relationships were assessed by guinea pig PCA and by testing actively immunized guinea pigs. A striking lack of cross-reactivity was found between pyrazolinone and pyrazolidinedione haptenic reagents in all test systems. On the other hand, the elicitation of homologous anaphylaxis was highly effective with the PAL conjugates. The data presented and discussed provide a basis for the evaluation of clinical tests performed in order to define drug-induced allergic reactions. They are relevant for immediate-type skin reactions as well as for serological methods.

Animals↗

PubMed1987

Diagnosis of antibody-mediated drug allergy. Pyrazolinone and pyrazolidinedione cross-reactivity relationships.

Based on the 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one series and on the 1,2-diphenyl-pyrazolidine-3,5-dione series of drugs, haptenic reagents and conjugates were synthesized and evaluated by passive cutaneous anaphylaxis in guinea pigs, and by ELISA tests using rabbit antisera against the haptens. No cross-reactivity between pyrazolinone and pyrazolidinedione haptenic reagents was found in any of the test systems. But also within each series, the animal antibodies showed rather strict specificities upon interaction with related haptens or drugs. These results are somewhat unexpected, because the haptens were used in connection with long and flexible spacer arms. Furthermore, they are not typical for certain other drug allergies. The strict specificity reduces the diagnostic potential of the haptenic reagents when used in serological tests or in skin testing.

Animals↗

PubMed1986

Diagnostic reagents in drug allergy: immunochemical specificity in the 1,2-diphenyl-pyrazolidinedione series.

Chemically defined haptenic reagents and haptenic conjugates were synthesized to be used for skin tests in allergic patients and for serological tests. One series of reagents is based on an open-chain derivative which is formed by reaction of the oxidation product of phenylbutazone, 4-hydroxyphenylbutazone, with amino functions. A second series uses the intact 1,2-diphenyl-pyrazolidine-3,5-dione molecule which is substituted in the 4-position with acetic acid. Both haptens are used in conjunction with spacer molecules which provide considerable distances between haptenic moiety and carriers. The skin test reagents are hexavalent conjugates based on the bis-penta-L-lysine carrier "PAL". Rabbit and guinea-pig antisera against the haptens were obtained by immunizations with human serum albumin conjugates. Data obtained from passive cutaneous anaphylaxis and from ELISA tests show that there is generally only slight cross-reactivity between the two series of haptenic reagents. Also, there is only modest cross-reactivity between intact drugs and haptenic reagents. No measurable crossreactions were noted between 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one derivatives and haptenic reagents of the 1,2-diphenyl-pyrazolidinedione series.

Animals↗

PubMed1986

Studies on monovalent anaphylactogens with carbohydrate auxiliary groups: exclusion of an artefact.

N1-DNCP-N6-lactobionoyl-1,6-hexanediamine is an elicitor of anaphylactic reactions in the guinea pig passively sensitized by antisera raised with a DNCP-bovine gammaglobulin conjugate. If the antisera contained anticarbohydrate antibodies against the carbohydrate residues of the globulin, significantly cross-reacting with the lactobionoyl moiety, anaphylactogenic cell triggering would be by classical hetero-specific bridging which involved the DNCP- and the lactobionoyl residues as ligands. This possibility was excluded by showing that a bis-lactobionoyl conjugate is unable to elicit anaphylactic reactions.

Allergens↗

PubMed1985

Immediate hypersensitivity to drugs and simple chemicals: the efficacy of monovalent elicitors.

Introduction of a reactive monohaptenic chemical into the sensitized organism will not normally result in elicitation of immediate reactions. Rather, the first products of chemical conjugation to suitable carriers in vivo are monohaptenic, conjugates which are inhibitory according to the bridging concept, stating that the initiating event for mast cell and basophil activation is a cross-linking of membrane-bound antibody by dihaptenic or oligohaptenic antigen. Simple calculations and quantitative data are presented to show that built-in inhibition is indeed a powerful barrier to any rapidly occurring allergenic manifestation which depends on the formation of divalent conjugates. If and when such a reaction does nevertheless occur, special requirements have to be invoked. One possibility is that the chemical or drug as such, i.e. without conjugation to a carrier, is an elicitor of anaphylaxis. Such compounds are known in a guinea pig passive cutaneous anaphylaxis model system, but there is evidence that they may also play a role in clinical situations. These monovalent elicitors possess in addition to the haptenic moiety an auxiliary group. The auxiliary group requirements were studied in the guinea pig passive cutaneous anaphylaxis system by using synthetic peptides with an N-terminal 2-carboxy-4,6-dinitrophenyl group as the hapten and phenylalanine and modified phenylalanine at the C-terminus as auxiliary group. The conclusions are that effective auxiliary function depends on the benzene ring and neighboring carboxyl groups in selected positions. Anaphylactogenicity is high when the haptenic and auxiliary groups can act independently, i.e. when separated by a peptide chain of considerable length. Potent anaphylactogens with close linkage of the two groups have, however, also been found. It is unlikely that the passive cutaneous anaphylaxis elicitations observed here are mediated by some form of indirect bridging of membrane-bound antibody.

Animals↗

PubMed1985

Studies on N1-DNCP-N6-lactobionoyl-1,6-hexanediamine--a distinctive monovalent anaphylactogen.

N1-DNCP-N6-lactobionoyl-1,6,hexanediamine, which is a potent anaphylactogen when i.v. injected into anti-DNCP sensitized guinea pigs, was shown to be also anaphylactogenic when administered intradermally into guinea pigs passively sensitized by i.v. injection of anti-DNCP antiserum. The compound, which is monohaptenic conjugate with the DNCP group as haptenic part and the carbohydrate moiety as auxiliary group, was found to be unable to precipitate high-titered anti-DNCP antisera. This precludes formation of simple, functionally oligovalent associates. Since many monohaptenic anaphylactogens with various hydrocarbon chains as auxiliary groups do not induce anaphylaxis when given intradermally, the anaphylaxis, demonstrated after intradermal antigen application, allows a biological distinction between the lactobionoyl and similar conjugates, and the hydrocarbon-bearing anaphylactogens.

Animals↗

PubMed1985

Studies on monovalent anaphylactogens: evidence for a minimal size of the carbohydrate auxiliary group.

N-[6-(DNCP-amino)hexanoyl]-beta-D-glucopyranosylamine was synthesized and was found to be unable to elicit DNCP-specific passive cutaneous anaphylaxis in the guinea pig. This contrasts with the considerable anaphylactogenicity of N1,N5-bis[2-deoxy-beta-D-glucopyranos-2-yl]-N2-[N3-DNCP-beta -alanyl]glutaminamide which likewise carries a single DNCP haptenic group but a larger carbohydrate moiety, comprised of two glucopyranosylamine groups instead of one. It is concluded that monovalent anaphylactogens, carrying in addition to the haptenic part a carbohydrate auxiliary group, generally require carbohydrate moieties larger than a single monosaccharide unit in order to be effective. Metabolic glucuronic acid conjugation will, therefore, not transform an inactive monovalent hapten into an anaphylactogen when only one glucuronic acid residue is attached.

Anaphylaxis↗

PubMed1984

Chain-length dependence for secondary structure formation of homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with a lipophilic C-terminal group.

A solid-state and solution analysis of the homo-oligopeptides from epsilon-tert.-butyloxycarbonyl-L-lysine with p-oxymethylbenzylcholestan-3 beta-yl succinate as C-terminal group, using infrared absorption and circular dichroism, is described. The occurrence of intermolecular beta-structure is seen in the solid state and in solvents of low polarity, e.g. methylene chloride, for peptides of intermediate size (from pentamer to decamer). Conversely, the eicosapeptide exhibits a high percentage of alpha-helical structure both in the solid state and in 2,2,2-trifluoroethanol. The influence of the C-terminal group on the conformational preferences of the epsilon-blocked homo-oligolysines in the solid state and in organic solvents appears negligible.

Chromatography, Thin Layer↗

PubMed1984

Penamaldate assay: improved methodology for the quantitation of penicilloic acids, penicilloyl amides and penicilloyl esters.

Conversion of penicilloic acids or their derivatives with modified alpha-carboxyl function to penamaldic acid derivatives involves formation of strong absorption bands in the UV. The penamaldate absorbances generated in the optical cell by HgCl2 addition can be used for quantitation and detailed accounts on the procedures are given. Methodological improvements allow determinations of penicilloyl derivatives within a range of 3% (+/- 1.5%). Free penicilloic acid determinations fall within a range of 8%. The penamaldate band at 282 nm from penicilloyl derivatives decreases to 95% within 10 min depending on conditions. The band from penicilloic acid at 275 nm decreases to 25%. The decay appears to be complex and measurements fall within a range of 15% even under carefully controlled conditions. The penamaldate stability can be used for characterization and for semiquantitative assessments of penicilloic acid/penicilloyl derivative mixtures.

Dipeptides↗