Improving the immunostimulatory potency of diethanolamine-containing lipid A mimics

Lipid A is the active principal of gram negative bacterial lipopolysaccharide (LPS) in the activation of Toll-like receptor 4 (TLR4). Given the important role TLR4 plays in innate immunity and the development of adaptive immune responses, ligands that can modulate TLR4-mediated signaling have great therapeutic potential. Recently, we have reported a series of monophosphorylated lipid A mimics as potential ligands of TLR4, in which a diethanolamine moiety is employed to replace the reducing end (d-glucosamine). In this paper, we describe the synthesis of two further diethanolamine-containing lipid A mimics, 3 and 4, in an effort to mimic more closely the di-phosphate nature of natural lipid A. Both mimic 3, with an additional phosphate on the diethanolamine acyclic scaffold, and mimic 4, with a terminal carboxylic acid moiety as a phosphate bioisostere, serve to increase the potency of the immunostimulatory response induced, as measured by the induction of the cytokines TNF-α, IL-6, and IL-1β in the human monocytic cell line THP-1. In addition, mechanistic studies involving the known TLR4 antagonist lipid IVa confirm TLR4 as the target of the diethanolamine-containing lipid A mimics.

Sympathomimetic drug allergy: cross-reactivity study by patch test

INTRODUCTION

Sympathomimetic (alpha-adrenergic) drugs are mainly used because of their vasoconstrictor properties, for nasal congestion, or as mydriatics. Although sympathomimetic drugs are used often, allergic reactions are rare, especially when the drugs are administered systemically. Cross-reactivity may exist among catecholamine derivatives, although reported data on this are contradictory. In this study, we investigate if there is cross-reactivity in patch tests among these drugs.

MATERIAL AND METHODS

Patch tests with 10% phenylephrine and 10% pseudoephedrine in petrolatum, and 10% and 20% ephedrine, 10% phenylpropanolamine, 5% fepradinol, 1% methoxamine, and 10% oxymetazoline, all administered in dimethyl sulfoxide (DMSO), were carried out in 14 patients with a history of allergy to any of these drugs. DMSO was used as the negative control.

RESULTS

All patients except one (patient number five) showed positive patch-test reactions to at least two different drugs. Nine patients (64.3%) were cross-sensitized to three or more different drugs, and 57.1% of patients were sensitized to four or more sympathomimetic drugs. Patients who experienced generalized rashes caused by orally administered pseudoephedrine had a stronger response and more cross-reactivity with other sympathomimetic drugs in patch tests than those who experienced local contact dermatitis.

CONCLUSIONS

We conclude that there is cross-reactivity among the different sympathomimetic drugs tested, especially if the drug is administered systemically.

Regulation of calcium homeostasis in activated human neutrophils--potential targets for anti-inflammatory therapeutic strategies

OBJECTIVES

The objectives of the current study were to: (i) present an integrated model for the restoration of calcium homeostasis in activated human neutrophils based on current knowledge and recent research; and (ii) identify potential targets for the modulation of calcium fluxes in activated neutrophils based on this model and to investigate the effects of intracellular probes which target key processes involved in calcium homeostasis and pro-inflammatory activity in these cells.

DESIGN AND SETTING

Laboratory-based experimental research using purified human neutrophils from healthy, adult human volunteers.

OUTCOME MEASURES

Calcium metabolism and pro-inflammatory activity of neutrophils.

RESULTS

Modulation of calcium fluxes in activated human neutrophils can be achieved by cAMP-dependent upregulation of the activity of the endomembrane Ca(2+)-ATPase which resequesters cytosolic Ca2+. Formoterol, a long-acting beta 2-agonist, elevates intracellular cAMP levels, accelerates Ca2+ restoration in activated neutrophils and downregulates the pro-inflammatory responses of these cells. Alterations in the membrane potential of activated neutrophils may play a role in regulating calcium reuptake into the cells as attenuation of the membrane depolarisation response is associated with accelerated calcium influx.

CONCLUSIONS

Modulation of the activity of the endomembrane Ca(2+)-ATPase in human neutrophils represents an important target for anti-inflammatory

Structural analysis of the lipopolysaccharide from Neisseria meningitidis strain BZ157 galE: localisation of two phosphoethanolamine residues in the inner core oligosaccharide

The structure of the phase-variable lipopolysaccharide (LPS) from the group B Neisseria meningitidis strain BZ157 galE was elucidated. The structural basis for the LPS's variation in reactivity with a monoclonal antibody (MAb) B5 that has specificity for the presence of phosphoethanolamine (PEtn) at the 3-position of the distal heptose residue (HepII) was established. The structure of the O-deacylated LPS was deduced by a combination of monosaccharide analyses, nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. These analyses revealed the presence of a novel inner core oligosaccharide (OS) structure in the MAb B5 reactive (B5+) LPS that contained two PEtn residues simultaneously substituting the 3- and 6-positions of the HepII residue. The determination of this structure has identified a further degree of variability within the inner core OS of meningococcal LPS that could contribute to the interaction of meningococcal strains with their host.

Cross-reactive polyclonal antibodies to the inner core of lipopolysaccharide from Neisseria meningitidis

Sera from mice immunized with native or detergent-extracted outer membrane vesicles derived from lipopolysaccharide (LPS) mutant 44/76(Mu-4) of Neisseria meningitidis were analyzed for antibodies to LPS. The carbohydrate portion of 44/76(Mu-4) LPS consists of the complete inner core, Glc beta 1-->4[GlcNAc alpha 1-->2Hep alpha 1-->3]Hep alpha 1-->5KDO[4-->2 alpha KDO]. Immunoblot analysis revealed that some sera contained antibodies to wild-type LPS which has a fully extended carbohydrate chain of immunotype L3,7, as well as to the homologous LPS. Sera reacted only weakly to LPS from 44/76(Mu-3), which lacks the terminal glucose of the inner core. No binding to more truncated LPS was observed. Consequently, the cross-reactive epitopes are expressed mainly by the complete inner core. Dephosphorylation of wild-type LPS abolished antibody binding to LPS in all but one serum. Thus, at least two specificities of cross-reactive antibodies exist: one is dependent on phosphoethanolamine groups in LPS, and one is not. Detection of these cross-reactive antibodies strongly supports the notion that epitopes expressed by meningococcal LPS inner core are also accessible to antibodies when the carbohydrate chain is fully extended. Also, these inner core epitopes are sufficiently immunogenic to induce antibody levels detectable in polyclonal antibody responses. Meningococci can escape being killed by antibodies to LPS that bind only to a specific LPS variant, by altering the carbohydrate chain length. Cross-reactive antibodies may prevent such escape. Therefore, inner core LPS structures may be important antigens in future vaccines against meningococcal disease.

Genetic linkage analysis to identify a gene required for the addition of phosphoethanolamine to meningococcal lipopolysaccharide

Lipopolysaccharide (LPS) is important for the virulence of Neisseria meningitidis, and is the target of immune responses. We took advantage of a monoclonal antibody (Mab B5) that recognises phosphoethanolamine (PEtn) attached to the inner core of meningococcal LPS to identify genes required for the addition of PEtn to LPS. Insertional mutants that lost Mab B5 reactivity were isolated and characterised, but failed to yield genes directly responsible for PEtn substitution. Subsequent genetic linkage analysis was used to define a region of DNA containing a single intact open reading frame which is sufficient to confer B5 reactivity to a B5 negative meningococcal isolate. The results provide an initial characterisation of the genetic basis of a key, immunodominant epitope of meningococcal LPS.

Conservation and accessibility of an inner core lipopolysaccharide epitope of Neisseria meningitidis

We investigated the conservation and antibody accessibility of inner core epitopes of Neisseria meningitidis lipopolysaccharide (LPS) because of their potential as vaccine candidates. An immunoglobulin G3 murine monoclonal antibody (MAb), designated MAb B5, was obtained by immunizing mice with a galE mutant of N. meningitidis H44/76 (B. 15.P1.7,16 immunotype L3). We have shown that MAb B5 can bind to the core LPS of wild-type encapsulated MC58 (B.15.P1.7,16 immunotype L3) organisms in vitro and ex vivo. An inner core structure recognized by MAb B5 is conserved and accessible in 26 of 34 (76%) of group B and 78 of 112 (70%) of groups A, C, W, X, Y, and Z strains. N. meningitidis strains which possess this epitope are immunotypes in which phosphoethanolamine (PEtn) is linked to the 3-position of the beta-chain heptose (HepII) of the inner core. In contrast, N. meningitidis strains lacking reactivity with MAb B5 have an alternative core structure in which PEtn is linked to an exocyclic position (i.e., position 6 or 7) of HepII (immunotypes L2, L4, and L6) or is absent (immunotype L5). We conclude that MAb B5 defines one or more of the major inner core glycoforms of N. meningitidis LPS. These findings support the possibility that immunogens capable of eliciting functional antibodies specific to inner core structures could be the basis of a vaccine against invasive infections caused by N. meningitidis.

Enantioselective immunoaffinity extraction for simultaneous determination of optically active bufuralol and its metabolites in human plasma by HPLC

A combined method of immunoaffinity extraction with high-performance liquid chromatography has been developed for the enantioselective determination of bufuralol and its metabolites in human plasma. The antibodies having high affinity toward the asymmetric center at the C-1 position of bufuralol and its 1'-oxidized metabolites and low affinity to their antipodes were elicited by immunization of rabbits with immunogens, (1R)- and (1S)-1'-oxobufuralol O-carboxymethyloxime-bovine serum albumin conjugates, respectively. 0.5 ml Of the immunoaffinity adsorbent (7.6 mg.ml-1 for anti-(1S)-antibody and 28.8 mg.ml-1 for anti-(1R)-antibody) prepared by immobilization of an antibody was capable of retaining up to 1 microgram of (R)- and (S)-bufuralol and up to 500 ng of other metabolites. The adsorbates were recovered quantitatively by elution with methanol-10 mM ammonium acetate buffer (pH 5) (95:5, v/v) without any interfering peaks on the high-performance liquid chromatogram. The proposed method was evaluated to be useful for the simultaneous determination of optically active bufuralol and its metabolite in plasma with acceptable recovery and precision.

Diethanolamine-induced occupational asthma, a case report

BACKGROUND

Amino alcohols are low molecular weight chemicals used widely in industrial processes, often as minor constituents. They have been found to cause allergic contact dermatitis. Marked exposure through airways is uncommon in other than occupational settings where chemicals containing amino alcohols may be heated or vaporized, liberating free amino alcohols into the ambient air. A few cases of asthma and allergic rhinitis have been reported, but the amounts inducing the airway reactions have not been defined.

OBJECTIVE

To further characterize ethanolamine-induced asthma and define the concentration inducing the asthmatic reaction, a case of diethanolamine-induced occupational asthma in a patient handling diethanolamine containing cutting fluid is reported.

METHODS

Suspicion of work related asthma was raised by symptoms and peak expiratory flow monitorings at work and at home. Specific bronchial provocation tests with the cutting fluid containing DEA and with DEA aerosol at two different concentration below the American Conference of Governmental Industrial Hygienists threshold limit value of DEA (2.0 mg/m3) were done.

RESULTS

DEA caused asthmatic airway obstruction at two different concentrations below the ACGIH TLV. A slight dose-response relationship was observed. Specific IgE-antibodies against DEA could not be found.

CONCLUSIONS

DEA is able to induce occupational asthma by a sensitization mechanism, the exact pathophysiological mechanism of which is not known.

The influence of the adjuvant Quil A on the epitope specificity of meningococcal lipopolysaccharide anti-carbohydrate antibodies

Rabbits were immunized with immunotype L3,7,9 phosphoethanolamine (PEA) group containing oligosaccharide-tetanus toxoid conjugates both with and without the addition of the adjuvant Quil A. The epitope specificity of the antibodies present in these antisera was analysed in an immunotype L2 and L3,7,9 specific inhibition ELISA using the homologous and heterologous lipopolysaccharide, oligosaccharide and partial dephosphorylated oligosaccharide as inhibitors. Two groups of antisera could be identified. In one group of antisera, at least two antibody populations are present, namely directed against the PEA group containing determinants on immunotype L3,7,9 lipopolysaccharide and against immunotype L2 specific epitopes in which no PEA group is present. In the second group of antisera, one but probably more antibody populations are detected with a similar specificity towards the conserved epitopes of both immunotypes. In general, immunization with the conjugates only resulted in the induction of antibodies against the PEA group containing epitopes on the L3,7,9 lipopolysaccharide (80%). Antibodies directed against the conserved epitopes of both immunotypes are mainly evoked with the conjugates in combination with the adjuvant Quil A (80%). Although these results suggest that the epitope specificity of the antibodies induced depends on the use of Quil A, the influence of genetic factors cannot be excluded. At the moment it is not known whether the differences in epitope specificities are reflected in biological function of these antibodies. However, the induction of antibodies with clearly different epitope specificities after immunization of different rabbits with the same antigen stresses the importance of this kind of analysis when developing a vaccine based on oligosaccharide-protein conjugates.

Preparation, characterization, and immunogenicity of meningococcal immunotype L2 and L3,7,9 phosphoethanolamine group-containing oligosaccharide-protein conjugates

A method was developed for the well-defined coupling of phosphoethanolamine group (PEA)- and carboxylic acid group-containing polysaccharides and oligosaccharides to proteins without the need for extensive modification of the carbohydrate antigens. The carboxylic acid group of the terminal 2-keto-3-deoxyoctulosonic acid moiety was utilized to introduce a thiol function in meningococcal immunotype L2 and L3,7,9 lipopolysaccharide-derived oligosaccharides. The thiol group-containing oligosaccharides were subsequently coupled to bromoacetylated proteins. Immunotype L2 and L3,7,9 PEA group-containing oligosaccharide-tetanus toxoid conjugates were prepared, and their immunogenicities were studied in rabbits. Both the immunotype L2 and immunotype L3,7,9 conjugates evoked high immunoglobulin G (IgG) antibody titers after the first booster injection. These conjugates also displayed an ability to induce long-lasting IgG antibody levels which could be detected until 9 months after one booster injection at week 3. The adjuvant Quil A enhanced the immune response to all the conjugates to a minor extent, which is in contrast with reported adjuvant effects of Quil A on these types of antigens in mice. A conjugate prepared from the dephosphorylated L3,7,9 oligosaccharides evoked a significantly lower IgG response than a similar PEA-containing conjugate, and enzyme-linked immunosorbent assay inhibition studies indicated a different epitope specificity. Furthermore, antisera elicited with the complete bacteria contained antibodies directed against PEA-containing epitopes, which stresses the importance of the presence of unmodified PEA groups in meningococcal lipopolysaccharide-derived oligosaccharide-protein conjugates. The procedure developed offers an elegant solution for the specific coupling of meningococcal PEA-containing oligosaccharides to proteins and may therefore be a very useful tool in the development of a vaccine against group B meningococci.

Characterization of antibodies to the glycosyl-phosphatidylinositol membrane anchors of mammalian proteins

Two polyclonal antisera were raised in rabbits to the phospholipase C-solubilized forms of pig renal dipeptidase (EC 3.4.13.11) and pig aminopeptidase P (EC 3.4.11.9). These antisera were purified and shown to cross-react with other glycosyl-phosphatidylinositol (G-PI)-anchored proteins isolated from pig, human and trypanosomes. The epitopes involved in this cross-reactivity were characterized by Western-blot analysis after mild acid or nitrous acid treatment of the G-PI-anchored proteins and by a competitive e.l.i.s.a. with other G-PI-anchored proteins and individual components of the anchor structure. These studies revealed that the primary epitope for both antisera is the inositol 1.2-(cyclic)monophosphate that is formed on phospholipase C cleavage of the intact G-PI anchor. Other minor epitopes, such as phosphoethanolamine, probably involve side-chain modifications to the core anchor structure that may be species-specific.

Decrease of natural antiphosphorylethanolamine antibodies by injection of C-reactive protein

Natural levels of goat antiphosphorylethanolamine (anti-PE) antibodies decreased after injection of purified human C-reactive protein (CRP). The concentration of anti-CRP antibodies followed a continuous increment from non-detectable levels to a plateau at 80 days after first injection.