Epitope mapping of mAbs to denatured human testicular ACE (CD143)

Angiotensin I-converting enzyme (ACE; CD143) has two homologous enzymatically active domains (N and C) and plays a crucial role in blood pressure regulation and vascular remodeling. A wide spectrum of monoclonal antibodies (mAbs) to different epitopes on the N and C domains of human ACE have been used to study different aspects of ACE biology. In this study, we characterized a set of nine mAbs, developed against the C domain of human ACE, which recognize the denatured forms of ACE and thus are suitable for the detection and quantification of somatic ACE (sACE) and testicular ACE (tACE) using Western blotting and immunohistochemistry on paraffin-embedded human tissues. The epitopes for these mAbs were defined using species cross-reactivity, phage display library screening, Western blotting and ACE mutagenesis. Most of the mAbs recognized common/overlapping region(s) on both somatic and testicular forms of human ACE, whereas mAb 4E10 was relatively specific for the testicular isoform and mAb 5B9 mainly recognized the glycan attached to Asn 731. This set of mAbs is useful for identifying even subtle changes in human ACE conformation because of denaturation. These mAbs are also sensitive tools for the detection of human sACE and tACE in biological fluids and tissues using proteomic approaches. Their high reactivity in paraffin-embedded tissues provides opportunities to study changes in the pattern of ACE expression and glycosylation (particularly with mAb 5B9) in different tissues and cells.

MAP1D, a novel methionine aminopeptidase family member is overexpressed in colon cancer

N-terminal methionine removal is an important cellular process required for proper biological activity, subcellular localization, and eventual degradation of many proteins. The enzymes that catalyze this reaction are called Methionine Aminopeptidases (MAPs). To date, only two MAP family members, MAP1A and MAP2, have been well characterized and studied in mammals. In our studies, we have cloned a full length MAP1D gene. Expression and purification of full length recombinant protein shows that the sequence encodes an enzyme with MAP activity. MAP1D is overexpressed in colon cancer cell lines and in colon tumors as compared to matched normal tissue samples. Downregulation of MAP1D expression by shRNA in HCT-116 colon carcinoma cells reduces anchorage-independant growth in soft agar. These data suggest that MAP1D is a potentially oncogenic, novel member of the MAP gene family that may play an important role in colon tumorigenesis.

Isotope-tagged cross-linking reagents. A new tool in mass spectrometric protein interaction analysis

In protein interaction analysis, one promising method to identify the involved proteins and to characterize interacting sites at the same time is the mass spectrometric analysis of enzymatic hydrolysates of covalently cross-linked complexes. While protein identification can be accomplished by the methodology developed for proteome analysis, the unequivocal detection and characterization of cross-linked sites remained involved without selection criteria for linked peptides in addition to mass. To provide such criteria, we incorporated cross-links with a distinct isotope pattern into the microtubule-destabilizing protein Op18/stathmin (Op18) and into complexes formed by Op18 with tubulin. The deuterium-labeled cross-linking reagents bis(sulfosuccinimidyl)-glutarate-d4, -pimelate-d4, and -sebacate-d4 were prepared together with their undeuterated counterparts and applied as a 1:1 mixture of the respective d0 and d4 isotopomers. The resulting d0/d4 isotope tags allowed a straightforward mass spectrometric detection of peptides carrying the linker even in complex enzymatic protein hydrolysates. In the structure elucidation of the linked peptides by MS/MS, the assignment of the linked amino acids was again greatly facilitated by the d0/d4 tag. By applying two cross-linkers with similar reactivity but different spacer length in parallel, even doublets with very low intensity could be assigned with high confidence in MS and MS/MS spectra. Since in the Op18-tubulin complexes only a limited number of peptides carried the linker, the identification of the involved proteins per se was not impeded, thus accomplishing both protein identification and characterization of interacting sites in the same experiment. This novel methodology allowed us to significantly refine the current view of the complex between Op18 and tubulin corroborating the tubulin "capping" activity of the N-terminal domain of Op18.

Phosphorylation disrupts the central helix in Op18/stathmin and suppresses binding to tubulin

Protein phosphorylation represents a ubiquitous control mechanism in living cells. The structural prerequisites and consequences of this important post-translational modification, however, are poorly understood. Oncoprotein 18/stathmin (Op18) is a globally disordered phosphoprotein that is involved in the regulation of the microtubule (MT) filament system. Here we document that phosphorylation of Ser63, which is located within a helix initiation site in Op18, disrupts the transiently formed amphipathic helix. The phosphoryl group reduces tubulin binding 10-fold and suppresses the MT polymerization inhibition activity of Op18's C-terminal domain. Op18 represents an example where phosphorylation occurs within a regular secondary structural element. Together, our findings have implications for the prediction of phosphorylation sites and give insights into the molecular behavior of a globally disordered protein.

An immunoblotting method for high-resolution isoelectric focusing of protein isoforms on immobilized pH gradients

Post-translational modifications such as phosphorylation and acetylation are important elements for regulating the activity of enzymes or structural proteins. These modifications give rise to isoforms that are often not resolved by separation methods relying on the size of proteins. Here, we optimized an isoelectric focusing (IEF)-immunoblotting method suitable for analyzing protein isoforms in total cell extracts. The separations were carried out in parallel on commercially available immobilized pH gradient slab gels (IPG). The buffer used for separation contained urea, thiourea, dithiothreitol, as well as the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate (CHAPS), and was designed to match those used in two-dimensional polyacrylamide gel electrophoresis (PAGE) separations where efficient solubilization is required. Proteins were transferred to membranes by passive diffusion in the presence of 4 M guanidinium chloride using protocols optimized for several protein classes (tubulin, stathmin, 14-3-3 proteins) some of which required removal of CHAPS prior to transfer. In conjunction with narrow-range pH gradient gels, excellent resolution of isoforms differing by phosphorylation or acetylation was achieved. The usefulness of pI and titration curve calculations for predicting the pI shifts expected for post-translational modifications of proteins with known amino acid composition was demonstrated. Using stathmin--which contains four phosphorylation sites--as an example, the effects on the pI-shifts were well predicted. This sensitive and widely applicable IEF-blotting technology is expected to be especially suited for analyzing protein isoforms first detected by two-dimensional electrophoresis.

PTK787/ZK 222584, a novel and potent inhibitor of vascular endothelial growth factor receptor tyrosine kinases, impairs vascular endothelial growth factor-induced responses and tumor growth after oral administration

PTK787/ZK 222584 (1-[4-chloroanilino]-4-[4-pyridylmethyl] phthalazine succinate) is a potent inhibitor of vascular endothelial growth factor (VEGF) receptor tyrosine kinases, active in the submicromolar range. It also inhibits other class III kinases, such as the platelet-derived growth factor (PDGF) receptor beta tyrosine kinase, c-Kit, and c-Fms, but at higher concentrations. It is not active against kinases from other receptor families, such as epidermal growth factor receptor, fibroblast growth factor receptor-1, c-Met, and Tie-2, or intracellular kinases such as c-Src, c-Abl, and protein kinase C-alpha. PTK787/ZK 222584 inhibits VEGF-induced autophosphorylation of kinase insert domain-containing receptor (KDR), endothelial cell proliferation, migration, and survival in the nanomolar range in cell-based assays. In concentrations up to 1 microM, PTK787/ZK 222584 does not have any cytotoxic or antiproliferative effect on cells that do not express VEGF receptors. After oral dosing (50 mg/kg) to mice, plasma concentrations of PTK787/ZK 222584 remain above 1 microM for more than 8 h. PTK787/ZK 222584 induces dose-dependent inhibition of VEGF and PDGF-induced angiogenesis in a growth factor implant model, as well as a tumor cell-driven angiogenesis model after once-daily oral dosing (25-100 mg/kg). In the same dose range, it also inhibits the growth of several human carcinomas, grown s.c. in nude mice, as well as a murine renal carcinoma and its metastases in a syngeneic, orthotopic model. Histological examination of tumors revealed inhibition of microvessel formation in the interior of the tumor. PTK787/ZK 222584 is very well tolerated and does not impair wound healing. It also does not have any significant effects on circulating blood cells or bone marrow leukocytes as a single agent or impair hematopoetic recovery after concomitant cytotoxic anti-cancer agent challenge. This novel compound has therapeutic potential for the treatment of solid tumors and other diseases where angiogenesis plays an important role.

In vitro modulation of cytokine, cytokine inhibitor, and prostaglandin E release from blood mononuclear cells and synovial fibroblasts by antirheumatic drugs

OBJECTIVE

To assess the effect of various antirheumatic drugs on cytokine, cytokine inhibitor, and prostaglandin E (PGE) production by normal blood mononuclear cells (MNC) and rheumatoid arthritis (RA) synovial fibroblasts in vitro.

METHODS

MNC from healthy donors and RA synovial fibroblasts were preincubated with or without prostaglandin E2 (PGE2), indomethacin, dexamethasone, gold sodium thiomalate (GSTM), methotrexate (MTX), and cyclosporin A (CyA), and then cultured in the absence or presence of interleukin-1 beta (IL-1 beta) or tumor necrosis factor-alpha (TNF-alpha) for 48 h. We characterized cytokines such as IL-1 beta, IL-8, monocyte chemoattractant protein-1 (MCP-1), and cytokine inhibitors such as IL-1 receptor antagonist (IL-1ra) and soluble TNF receptors (sTNFR p55 + p75) as well as PGE in the cell-free culture supernatants.

RESULTS

In MNC and synovial fibroblast cultures dexamethasone, GSTM, and PGE2 most markedly downregulated spontaneous and/or cytokine stimulated production of IL-1 beta, IL-14a, IL-8, and MCP-1, whereas sTNFR shedding was not affected. In contrast, MTX and CyA had only marginal or no effects on mediator release, whereas indomethacin inhibited only PGE production.

CONCLUSION

Among several antirheumatic drugs examined, dexamethasone and GSTM exhibited the most potent inhibitory effects on inflammatory cytokine and cytokine inhibitor production by blood mononuclear cells and synovial fibroblasts. These drugs may exert their antiinflammatory actions by unspecific suppression of monocyte and fibroblast secretory function.

Neoepitope immunoassay: an assay for human interleukin 1 beta based on an antibody induced conformational change

A secondary monoclonal antibody (mAb2) was generated by immunization with immune complexes of human IL-1 beta and a primary monoclonal (mAb1). mAb2 bound to a neoepitope on the IL-1 beta/mAb1-complex with a dissociation constant (Kd) of 26 pM but not to uncomplexed IL-1 beta. As assessed by the binding of labeled IL-1 beta and neutralization of bioactivity, mAb2 enhanced the affinity of IL-1 beta to mAb1; Kd-values were 108 pM in absence and 5.4 pM in presence of mAb2. By analyzing a series of mutants of IL-1 where surface loops had been exchanged with the corresponding loops of human IL-1 receptor antagonist protein, a critical region responsible for mAb2 binding was localized to the C-terminal region. In addition to mAb1/IL-1 beta-complexes, mAb2 bound pro-IL-1 beta/mAb1 complexes as well as pro-IL-1 beta suggesting that mAb2 recognized a conformation of IL-1 beta resembling that of pro-IL-1 beta. Using this pair of mAbs, chemiluminescent and enzyme linked assays with detection limits of 2 pg/ml hIL-1 beta have been established.

High-level expression in insect cells and purification of secreted monomeric single-chain Fv antibodies

We have constructed a recombinant baculovirus encoding an anti-(phenyl-oxazolone) single-chain Fv antibody (anti-phOx-scFv) fused to the baculovirus GP67 secretion signal sequence, 6 liters of Sf9 insect cells were infected with this virus at a multiplicity of infection of one and cultured in a bioreactor for 72 h. The dialyzed supernatant was subjected to cation exchange chromatography at pH 6.0 followed by size exclusion chromatography on a Sephadex G100 superfine matrix. This rapid protocol resulted in the isolation of monomeric scFv with a purity of greater than 98%. The final yield was 32 mg/l (10(9) cells/l). Partial amino-terminal sequencing revealed that the GP67 signal sequence was completely removed upon secretion. The dissociation constant of the scFv monomers is about 1 x 10(-4) M. By competitive ELISA scFv dimers yielded a half maximum inhibitory concentration of 3.4 x 10(-7 M which matches the earlier measured Kd for the anti-phOx-scFv (3.2-5.3 x 10-7 M. Marks et al. (1991) J. Mol. Biol. 222, 581-597: Marks et al. (1992) Bio/Technology 10, 779-783). This method is readily scaled up for the preparation of scFv antibodies in high yield and purity obviating any affinity chromatography and/or refolding steps by exploitation of insect cell expression as an efficient alternative to E. coli expression.

Opposite effects of interleukin-13 and interleukin-12 on the release of inflammatory cytokines, cytokine inhibitors and prostaglandin E from synovial fibroblasts and blood mononuclear cells

We examined the effects of interleukin-12 (IL-12) and interleukin-13 (IL-13) on cytokine, cytokine inhibitor and prostaglandin E (PGE) release from synovial fibroblasts and blood mononuclear cells (MNC). In resting synovial fibroblasts, we found that IL-13 is an inhibitor of IL-8 and PGE release. A significant decrease of PGE synthesis caused by IL-13 was also observed in tumor necrosis factor (TNF)-alpha-stimulated synovial fibroblasts, whereas IL-12 had no regulatory effects on these cells. In resting and cytokine-stimulated MNC, IL-13 markedly inhibited IL-1 beta, IL-8 and monocyte chemoattractant protein-1 (MCP-1) release and potently stimulated interleukin-1 receptor antagonist (IL-1ra) synthesis. In contrast, IL-12 stimulated the production of IL-1 beta and MCP-1 in TNF-alpha-stimulated MNC and inhibited IL-1ra synthesis in cytokine-stimulated cells. These findings identify novel biological actions of IL-12 and IL-13 on connective tissue and on blood mononuclear cells which indicate their regulatory functions as enhancer and suppressor of inflammatory processes, respectively.

Interleukin 1 (IL-1) receptor antagonist, soluble tumor necrosis factor receptors, IL-1 beta, and IL-8--markers of remission in rheumatoid arthritis during treatment with methotrexate

OBJECTIVE

To examine circulating levels of cytokines and cytokine inhibitors and their production by blood mononuclear cells (MNC) in patients with active rheumatoid arthritis (RA) before treatment with methotrexate (MTX) and inactive disease upon treatment as well as healthy control individuals.

METHODS

Interleukin-1 receptor antagonist (IL-1ra), soluble tumor necrosis factor receptors p55 and p75 (sTNFr; p55 and p75), interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF-alpha), interleukin-8 (IL-8), and monocyte chemoattractant protein 1 (MCP-1) were assessed by immunoassays in sera and MNC culture supernatants of 27 patients with RA with active disease before and 14 patients with inactive disease during MTX treatment, and 10 healthy controls.

RESULTS

Levels of circulating IL-1ra, sTNFr p55 and p75 were higher in patients with active RA compared to those with inactive disease or controls. At the cellular level, resting MNC of patients with active RA released more IL-1 beta and IL-8, but less IL-1ra, and showed a lower ratio of IL-1ra:IL-1 beta than MNC of patients without inflammatory symptoms or healthy controls. In addition, unstimulated and in vitro lipopolysaccharide stimulated MNC cultures of patients with inactive RA released higher amounts of sTNFr p75 than MNC of patients with active RA.

CONCLUSION

Circulating levels of IL-1ra and sTNFr as well as IL-1 beta, IL-8, and sTNFr p75 release from MNC and the ratio of IL-1ra:IL-1 beta production by these cells serve as markers to assess complete disease remission in patients with RA during MTX treatment.

Differential effects of prednisolone and indomethacin on zymosan-induced inflammation in a modified murine tissue-chamber model

A tissue-chamber model of inflammation in mice has been modified and used to investigate the kinetics of zymosan-induced inflammatory mediators such as tumour necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta) and prostaglandin E2 (PGE2). In addition, the influx of polymorphonuclear leukocytes (PMN) into the chamber fluid and the granuloma surrounding the chamber was measured by myeloperoxidase (MPO) activity using a new microtitre plate assay. TNF alpha and IL-1 beta reached a peak concentrations at 3 and 6 h respectively after zymosan injection. Intermediate high concentrations of IL-1 beta were observed until the end of the experiment at 72 h, but TNF alpha concentrations decreased from 24 h to biologically insignificant values. In contrast, exudate PGE2 and MPO activity increased up to 24 h after zymosan injection and remained high until 72 h. At 6 h after zymosan challenge, oral pre-treatment with prednisolone (3 to 30 mg/kg) dose-dependently reduced TNF alpha, IL-1 beta and PGE2 concentrations while indomethacin (0.3 to 3 mg/kg) significantly attenuated PGE2, slightly enhanced TNF alpha and had no effect on IL-1 beta concentrations in the exudate. Both drugs had similar potencies against exudate and tissue MPO activities. Prednisolone inhibited IL-1 beta at 72 h post-zymosan. Indomethacin was more potent than prednisolone against PGE2 (ID50 of< 0.3 versus 0.6 mg/kg). The data obtained confirm the usefulness and reliability of this model in evaluating the effects of anti-inflammatory agents on inflammatory mediators induced by zymosan.

Methotrexate action in rheumatoid arthritis: stimulation of cytokine inhibitor and inhibition of chemokine production by peripheral blood mononuclear cells

This open label study examines whether methotrexate (MTX) treatment modulates ex vivo synthesis of interleukin-1 receptor antagonist (IL-1ra), soluble tumour necrosis factor receptors (sTNFR p55 and p75), interleukin-1 beta (IL-1 beta), tumour necrosis factor alpha (TNF-alpha), interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) by peripheral blood mononuclear cells (PBMC) and whether changes reflect clinical response. Significant stimulation of IL-1ra and sTNFR p75 as well as inhibition of IL-8 production of PBMC were associated with clinical improvement observed in patients treated with MTX. When defining the characteristics of patients at study entry retrospectively in responders and non-responders, a significantly lower ratio of IL-1ra:IL-1 beta production before and its increase upon treatment was associated with clinical response in 13 patients compared to five patients not responding to MTX. In addition, clinical improvement was associated with decreased synthesis of IL-1 beta, TNF-alpha and IL-8 induced by bacterial lipopolysaccharide, IL-1 alpha and IL-1 beta in PBMC in vitro. These findings suggest that MTX therapy reverses the inflammatory type of rheumatoid arthritis (RA) blood mononuclear cells by stimulating cytokine inhibitor production while inhibiting inflammatory cytokine release at the same time. This may explain the powerful anti-inflammatory properties of low-dose MTX as observed in most RA patients. Pretreatment determination of the IL-1ra:IL-1 beta ratio in PBMC may be predictive with regard to a favourable therapeutic response and therefore may be useful for the selection of RA patients to be treated with MTX.

Cytokine immunotrapping: an assay to study the kinetics of production and consumption or degradation of human interferon-gamma

With the aim of determining the rate of cytokine production, we have investigated immunoassay conditions which prevent consumption/degradation. These assays, termed cytokine immunotrapping assays (CITA), are based on early capturing of cytokines secreted during cell culture by immobilised or soluble mAbs and a recently described chemiluminescent immunoassay. Here we describe assay conditions using IFN-gamma as a prototype cytokine. For production of IFN-gamma, PBMC, purified CD4+ or CD8+ T cells, or diluted whole blood were cultured with different T cell stimulating agents. Polystyrene macrobeads precoated with an anti-IFN-gamma mAb were put in culture and after a defined incubation period, a dimethyl acridinium ester (DMAE)-labelled second anti-IFN-gamma mAb and sodium azide were added into the culture for additional 24 h. The beads were washed and chemiluminescence signals determined in a luminometer. Trapping experiments were also performed with the beads or the soluble mAbs alone. Irrespective of the configuration, IFN-gamma concentrations measured in trapping conditions were always higher (3-20-fold) than in conventional cultures. By using the best trapping combination, i.e. both bead-mAb1 and DMAE-mAb2 added at the start of culture (single step), it was possible to detect IFN-gamma production as early as 2 h. Also, IFN-gamma secreted by less than 500 PBMC or whole blood cells could be detected within 24 h. When purified CD4+ or CD8+ cells were used instead of PBMC, a reduction of the trapping effect was observed. Conversely, addition of monocytes to purified T cells increased the trapping factor suggesting that a substantial amount of IFN-gamma was consumed or degraded both by CD14+ cells as well as T cells in culture. Preliminary results show that this assay is also suitable for the early detection of IL-1 and IL-4 which are known to be more tightly regulated. Thus, the new principle described here is expected to be useful in clinical settings where both the time and amounts of material are limited to investigate the role of cytokines in particular disease.

Sandwich immunoassay for the hapten angiotensin II. A novel assay principle based on antibodies against immune complexes

Immunoassays for haptens such as short peptides or drugs are usually based on the principle of competition for a limited number of binding sites on antibody molecules. Owing to the small size of these antigens it has been thought that two specific antibodies cannot simultaneously bind a hapten. However, antisera containing so called anti-metatypic antibodies have been reported (Voss et al. (1988) Mol. Immunol. 25, 751-759) that bind to hapten-mAb complexes in a reaction where conformational changes on the primary antibody are important. Here, we report on monoclonal antibody pairs able to form ternary complexes with the octapeptide angiotensin II. The first mAb (mAb1) is conventional and binds angiotensin II with high affinity (Kd 10(-11) M). The secondary (anti-metatypic) mAbs (mAbs2s) recognize the immune complex consisting of angiotensin II bound to mAb1, but only poorly recognize mAb1 alone. An immunization technique involving tolerization with uncomplexed mAb1 was used to generate mAb2s. None of the mAbs2s were able to bind angiotensin II by themselves but all efficiently bound the complex of angiotensin II and mAb1. All mAb2s stabilized the angiotensin II-mAb1 complex and one mAb2 distinctly improved the specificity of the assay for angiotensin II. By either labelling mAb1 and immobilizing mAb2 (or vice versa) two-site immunometric assays with detection limits of 1 pg/ml angiotensin II have been established. The kinetics of the complex formation was investigated by fiber optic biospecific interaction analysis (FOBIA), a system allowing real time observation of binding events on the surface of a glass fiber. The association rate towards the liganded conformation of mAb1 was higher than towards the free mAb1. By contrast, the mAb2s dissociated at similar rates from complexed and uncomplexed mAb1.

Interleukin-10 differentially regulates cytokine inhibitor and chemokine release from blood mononuclear cells and fibroblasts

In this study we have examined the effects of interleukin-10 (IL-10) on blood mononuclear cells (MNC) and on skin as well as on synovial fibroblasts. In unstimulated MNC, we found that IL-10 is a potent stimulator of interleukin-1 receptor antagonist (IL-1ra) and monocyte chemoattractant protein-1 (MCP-1) production and an inhibitor of IL-8 release. In cells exposed to IL-1 beta, it also moderately stimulated IL-1ra production and release of soluble tumor necrosis factor receptor p75 (sTNF-R p75) and inhibited IL-8 and MCP-1 production. In addition, we have evidence that the biological effects of IL-10 are not restricted to hematopoietic cells. IL-10 stimulated sTNF-R p55 dose-dependently and inhibited MCP-1 release from IL-1 beta-activated fibroblasts, whereas IL-8 production was not affected. Taken together, these findings identify novel biological actions of IL-10 on blood mononuclear and connective tissue cells which support its regulatory functions as a suppressor of inflammatory processes.

Quantitation of interferon-induced Mx protein in whole blood lysates by an immunochemiluminescent assay: elimination of protease activity of cell lysates in toto

Due to the rapidly expanding usage of interferons and its costliness of therapy, it is important to evaluate the clinical efficacy of the various interferons. Directly assaying circulating interferon is technically quite difficult. Here, we present an alternate method to evaluate interferon therapy by assaying a unique protein, called Mx protein, which is a 78 kDa cytoplasmic protein selectively induced by type-1 interferon in human leukocytes. The current assay is a two-site chemiluminescent immunoassay, designed to detect Mx protein in whole blood lysates. Since the Mx protein once solubilized, is highly susceptible to proteolysis in whole blood lysates, we have devised a new procedure both to maximize its solubility and virtually eliminate its proteolytic degradation. A mouse monoclonal antibody conjugated to the derivatized-paramagnetic particles and an acridinium ester-labeled antibody serve as the solid phase capture and detector antibodies, respectively. This assay is applicable to both manual and automated modes with a detection limit of Mx protein at 20 ng/ml whole blood. Availability of a reliable assay for Mx protein should facilitate the clinical evaluation of many of the newly constructed type-1 interferons.

Structure-function analysis of angiotensin I-converting enzyme using monoclonal antibodies. Selective inhibition of the amino-terminal active site

Angiotensin I-converting enzyme (ACE; kininase II) contains two very similar domains (the NH2- and COOH-terminal domains (N and C domains, respectively)), each bearing an active site. These active sites hydrolyze the same peptides, but do not have the same catalytic properties and substrate specificities. In an attempt to develop domain-specific immunological probes, two series of monoclonal antibodies (mAbs), 19 clones in all, were produced and tested against human ACE. These mAbs recognized at least nine different epitopes within three antigenic regions of the ACE molecule. Testing on wild-type recombinant ACE and several mutants with only one intact domain showed that these epitopes were all located in the N domain. None of the mAbs recognized the C domain. This particular specificity and analysis of results obtained with several polyclonal antibodies to human ACE suggest that ACE immunogenicity is determined mainly by the N domain. Two mAbs (3A5 and i2H5) recognizing epitopes from different antigenic regions of ACE inhibited the enzymatic activity of the N (but not of the C) domain. mAb 3A5 had the same inhibitory potency toward hippuryl-His-Leu, benzyloxycarbonyl-Phe-His-Leu, and angiotensin I hydrolysis, with 50% inhibition achieved at a mAb/ACE molar ratio of 6. mAb i2H5 was roughly three times more effective than mAb 3A5 inhibiting the hydrolysis of benzyloxycarbonyl-Phe-His-Leu and the natural substrates angiotensin I and bradykinin (50% inhibition at a molar ratio of 1-2), but was less effective in inhibiting hippuryl-His-Leu cleavage (50% inhibition at a molar ratio of 22-25), indicating that this substrate interacts with a specific subsite. mAb i2H5 almost completely inhibited the hydrolysis of the luteinizing hormone-releasing hormone by the isolated N domain. Both the primary carboxyl- and amino-terminal cleavages of this peptide were suppressed. This antibody suppressed the primary amino-terminal cleavage of the luteinizing hormone-releasing hormone by wild-type ACE by > 90%, indicating that this particular ACE function is mediated mainly by the N domain active site. These data provide evidence for structural differences between the two homologous domains of ACE despite their high degree of sequence homology and show that monoclonal antibodies are able to distinguish between the two active sites in ACE.

Chemiluminescent and enzyme-linked immuno assays for sensitive detection of human IFN-gamma

We have produced and characterized 4 mAbs to human IFN-gamma and established sensitive, non-radioactive immuno-assays. The first two assays use microtiter plates as the solid phase and enzymes or chemiluminescence (acridinium ester) for development. The use of chemiluminescence instead of peroxidase increased the sensitivity of the assay by a factor of about 75. The third and the fourth assays utilize polystyrene beads as the solid phase and enzymes or acridinium ester for development. The use of beads also increased the sensitivity of detection. The most sensitive IFN-gamma detection was achieved by the combination of bead with acridinium ester. In this configuration we were able to detect about 0.2 pg/ml IFN-gamma (1/250th of a unit). These chemiluminescent immunoassays (CLIA) appear to be more sensitive than existing ELISAs or radioimmunoassays and may find new application areas.

Photoaffinity labeling for evaluation of uridinyl analogs as specific inhibitors of rat liver microsomal UDP-glucuronosyltransferases

The UDP-glucuronosyltransferases (UGT) involved in glucuronidation of endogenous and exogenous toxic compounds transfer the glucuronic acid residue from UDP-glucuronic acid (UDP-GlcUA), to various acceptor groups. A series of compounds that contain N-acyl phenylaminoalcohol derivatives linked to uridine or isopropylideneuridine were tested as UGT inhibitors. The potency of these inhibitors was determined by studying their effect on the photoaffinity labeling of rat liver microsomal UGTs by two photoaffinity probes, [beta-32P]5-azido-UDP-glucuronic acid (5N3UDP-GlcUA) and [beta-32P]5-azido-UDP-glucose (5N3UDP-Glc) and on the enzymatic formation of the two glucuronide conjugates (3-O- and carboxyl-specific) of lithocholic acid. All but one of the compounds tested proved to have an inhibitory effect on UGTs, both in the photoaffinity labeling system and in the enzymatic glucuronidation assay. In the photoaffinity labeling system, the inhibitors containing the isopropylidene moiety were less effective than their unprotected derivatives; however, the protected forms were, with one exception, more potent inhibitors of enzymatic activity. The photoaffinity labeling of UGTs with [beta-32P]5N3UDP-Glc was more susceptible to inhibition by all derivatives than that with [beta-32P]5N3UDP-GlcUA. The effect of one inhibitor, PP50B, on the two enzymatic activities involved in LA glucuronidation was extensively tested. A double-reciprocal plot suggested a competitive inhibition for UDP-GlcUA with an apparent Ki of 35 microM for LA 3-O-glucuronide formation and 94 microM for the carboxyl-linked glucuronide of the same substrate.

Monoclonal antibody based enzyme-linked and chemiluminescent assays for the human interleukin-1 receptor antagonist. Application to measure hIL-1ra levels in monocyte cultures and synovial fluids

Interleukin-1 receptor antagonist (IL-1ra) has the potential to counteract at least part of the biological effects of interleukin-1. The outcome of an inflammatory reaction may therefore be determined by the balance between IL-1 and IL-1ra, rather than by IL-1 alone. We have developed an immunoassay to address this issue as well as to assess the effects of anti-inflammatory agents on the expression of IL-1 and IL-1ra in vitro or in body fluids. Recombinant human IL-1ra was expressed in an E. coli system, purified to homogeneity, and used to derive monoclonal antibodies in mice as well as polyclonal antibodies in rabbits. A sandwich ELISA was constructed with F(ab')2 fragments of a high affinity monoclonal antibody and the rabbit serum as a source of secondary antibody. The assay required no sample treatment to avoid interference by rheumatoid factor. The measuring range was 0.020-2 ng/ml. By labelling a second monoclonal antibody with an acridinium ester, a chemiluminescence assay with a wider measuring range (0.050-15 ng/ml) was generated. In accord with published data, we found that IL-1ra was secreted by human monocytes stimulated with LPS, Zymosan, IL-1 alpha, or human IgG. After an induction phase of ca. 4 hours and depending on the stimulus, IL-1ra accumulated linearly for periods up to 96 h. IL-1ra levels in synovial fluids of 19 patients suffering from various inflammatory joint diseases were compared with the cytokine levels of IL-1 beta, IL-6, IL-8, and TNF-alpha. Highest positive correlations were found with IL-8 and IL-1 beta. In normal blood donors IL-1ra serum levels were 150-800 pg/ml (Median: 387 pg/ml). Owing to its sensitivity and large measuring range the newly developed assays appear to be suitable for measuring IL-1ra in cell cultures as well as in biological fluids.

Production of interleukin-1 receptor antagonist, inflammatory chemotactic proteins, and prostaglandin E by rheumatoid and osteoarthritic synoviocytes--regulation by IFN-gamma and IL-4

This study analyzes the effects of the T cell cytokines IL-4 and IFN-gamma on the spontaneous and stimulated production of IL-8, MCP-1, IL-1 receptor antagonist (IL-1ra), and PGE by synoviocytes from rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Cells from both sources constitutively released IL-8 and MCP-1, but no IL-1ra or PGE. Stimulation with IL-1 beta or TNF-alpha massively increased chemokine production and induced the generation of PGE and low amounts of IL-1ra. The constitutive or cytokine-stimulated release of IL-8 was inhibited by IFN-gamma, but not by IL-4. The constitutive or IL-1 beta-stimulated release of MCP-1, by contrast, was markedly enhanced by IL-4 and IFN-gamma. Both cytokines, however, had only borderline effects on the release stimulated by TNF-alpha. The yield of IL-1ra was strongly enhanced by IFN-gamma in all cases, whereas the effect of IL-4 was pronounced only in IL-1 beta-stimulated OA synoviocytes. IL-4, on the other hand, markedly decreased the release of PGE, which was less susceptible to IFN-gamma. The observed effects on chemokines, IL-1ra expression, and PGE release by synoviocytes suggest that IFN-gamma and IL-4 are important regulatory elements in the inflamed synovium and may exert anti-inflammatory effects.

Production of interleukin-1 receptor antagonist, inflammatory chemotactic proteins, and prostaglandin E by rheumatoid and osteoarthritic synoviocytes--regulation by IFN-gamma and IL-4

This study analyzes the effects of the T cell cytokines IL-4 and IFN-gamma on the spontaneous and stimulated production of IL-8, MCP-1, IL-1 receptor antagonist (IL-1ra), and PGE by synoviocytes from rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Cells from both sources constitutively released IL-8 and MCP-1, but no IL-1ra or PGE. Stimulation with IL-1 beta or TNF-alpha massively increased chemokine production and induced the generation of PGE and low amounts of IL-1ra. The constitutive or cytokine-stimulated release of IL-8 was inhibited by IFN-gamma, but not by IL-4. The constitutive or IL-1 beta-stimulated release of MCP-1, by contrast, was markedly enhanced by IL-4 and IFN-gamma. Both cytokines, however, had only borderline effects on the release stimulated by TNF-alpha. The yield of IL-1ra was strongly enhanced by IFN-gamma in all cases, whereas the effect of IL-4 was pronounced only in IL-1 beta-stimulated OA synoviocytes. IL-4, on the other hand, markedly decreased the release of PGE, which was less susceptible to IFN-gamma. The observed effects on chemokines, IL-1ra expression, and PGE release by synoviocytes suggest that IFN-gamma and IL-4 are important regulatory elements in the inflamed synovium and may exert anti-inflammatory effects.

Acridinium ester labelled cytokines: receptor binding studies with human interleukin-1 alpha, interleukin-1 beta and interferon-gamma

As a consequence of environmental protection and legal restrictions, increasing efforts are made to avoid radioactivity. One alternative is the labelling of ligands with chemiluminescent acridinium esters such as 2,6-dimethyl-4-(N-succinimidyloxy-carbonyl)phenyl 10-methylacridinium-9-carboxylate methosulphate (DMAE-NHS). When exposed to hydrogen peroxide in a basic solution, the DMAE-moiety decays with emission of a short-lasting chemiluminescent flash. With the goal of replacing the radioactive label in protein ligands with a DMAE label, and of increasing the efficiency by using microtitre plate technology for DMAE detection, we compared the receptor binding properties of iodinated interleukin-1 alpha (125I-IL-1 alpha), interleukin-1 beta (125I-IL-1 beta) and interferon-gamma (125I-IFN-gamma) with the corresponding DMAE-labelled ligands. The luminescence signal was assessed in a single-tube luminometer and in the prototype of a chemiluminescent microtitre plate reader. Derivatization of the three proteins with DMAE-N-hydroxy-succinimide resulted in photon yields of up to 100,000 counts per femtomole. As shown by Scatchard analysis, no significant loss of receptor binding affinity was observed, which might have been expected as a consequence of the chemical modification of the proteins. The use of DMAE labelling of proteins has the following advantages as compared to iodination: (i) the coupling reaction and binding assay can be performed in a normal laboratory, (ii) since there is no radiolysis, the DMAE-labelled proteins remain stable, (iii) the detection sensitivity may be improved as a consequence of higher specific activity of the DMAE label.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutralization of interleukin-1 beta activity in vivo with a monoclonal antibody alleviates collagen-induced arthritis in DBA/1 mice and prevents the associated acute-phase response

Interleukin-1 (IL-1) has been implicated in the development and progression of a variety of acute and chronic inflammatory diseases. Due to its pro-inflammatory and tissue-degrading activities, IL-1 is regarded as a major mediator of chronic inflammatory joint diseases, including rheumatoid arthritis in man, adjuvant arthritis in rats and collagen-induced arthritis in mice. However, conclusive experimental evidence for the crucial role of IL-1 in the development of joint destruction has not been presented as yet. In the present study, we investigated the effect of a neutralizing monoclonal mouse antibody against mouse IL-1 beta (IgG1 isotype) on the development and progression of collagen-induced arthritis in DBA/1 mice. The antibody was injected intraperitoneally 3 times a week, either from day 3 or from day 21 after primary immunization, to day 60. In the positive control group an arthritis incidence of 80% was observed after 60 days. The injection of a control antibody of the same isotype did not influence the incidence of arthritis, whereas injection of anti-IL-1 beta from day 21 reduced the arthritis incidence to about 30%. Injection of anti-IL-1 beta starting at day 3 totally prevented both the development of arthritis and the associated increase of the acute phase protein serum amyloid P (SAP). Anti-collagen antibody titers, which increased significantly after immunization, were not influenced by the injection of anti-IL-1 beta antibodies, in spite of the suppressive effect on arthritis development.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and characterization of a new class of inhibitors of membrane-associated UDP-glycosyltransferases

A new class of compounds designed to inhibit membrane-associated glycosyltransferases were synthesized and their biological activities were characterized in liver microsomes and human lymphoma cell lines. These inhibitors are composed of N-acyl phenylaminoalcohol derivatives linked to uridine via different spacers. One inhibitor, termed PP36 (5'-[[N-(2-decanoylamino-3-hydroxy-3-phenylpropyloxycarbonyl )-glycyl[amino]-5'-deoxyuridine) competitively inhibited the enzyme glucosyl phosphoryldolichol synthase (Glc-P-Dol synthase) in rat liver microsomes. In rat and human liver microsomes incubated with PP36 and photolabeled with [beta-32P]5-azido-UDP-Glc, Glc-P-Dol synthase was the only protein observed to have decreased photoincorporation. Two other inhibitors, PP37 (5'-O-[[(2-decanoylamino-3-hydroxy-3-phenyl- propyloxycarbonyl)amino]sulfonyl]uridine and PP55 (5'-O-[[(2-decanoylamino-3- phenylpropyloxycarbonyl)amino]sulfonyl]uridine), were also shown to be competitive inhibitors of Glc-P-Dol synthase activity and photolabeling. Activities of glycosyltransferases involved in glycosphingolipid biosynthesis were little affected by these compounds. Analysis of the effects of PP36, PP37, and PP55 on the incorporation of [3H] leucine and [14C]galactose into glycoprotein and glycolipid fractions from two human cell lines indicated the following: PP36 reduced incorporation into both fractions, PP37 was ineffective, and PP55 only decreased incorporation into glycolipids.

Interleukin-1 (IL-1) production in a mouse tissue chamber model of inflammation. II. Identification of (tissue) macrophages as the IL-1 producing cells and the effect of anti-inflammatory drugs

We have used our newly described mouse tissue chamber model [1], to investigate the process of IL-1 production in more detail. The inflammatory reaction in the tissue surrounding the implanted chambers was investigated histologically and by using the polymerase chain reaction (PCR). The inflammatory response included influx of leucocytes into the granuloma surrounding the tissue chamber, expression of IL-1 beta on macrophages present in the inflamed tissue and an increase in the mRNA coding for IL-1 beta and IL-6 proteins in the granuloma. The effects of three anti-inflammatory or immunosuppressive drugs, prednisolone, indomethacin and cyclosporin A, on IL-1 beta and PGE2 production in zymosan and Bordetella-pertussis-vaccine (BPV)-challenged tissue chambers were also examined. Oral treatment with prednisolone and cyclosporin A of zymosan-challenged animals showed a dose-dependent reduction of IL-1 beta concentrations, but no effect of indomethacin. Both prednisolone and indomethacin dose-dependently reduced PGE2 concentrations to control levels, while cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.). In drug-treated BPV-challenged animals, prednisolone and cyclosporin A also showed a dose-dependent reduction of IL-1 beta, while indomethacin was again ineffective. Prednisolone and indomethacin also dose-dependently reduced the PGE2 concentrations to control levels, whereas cyclosporin A was effective only at the highest dose tested (100 mg/kg/day p.o.). This model will be useful for investigating the mechanisms controlling the production of IL-1 beta from the mRNA level to the secretion of mature biologically active protein [1], and in the search for new drugs which could selectively interfere with this process.

Interleukin-1 (IL-1) production in a mouse tissue chamber model of inflammation. I. Development and initial characterisation of the model

A simple and reliable animal model to quantify interleukin-1 (IL-1) production at a site of inflammation has been developed and characterised. This model involves the subcutaneous implantation of sterile Teflon chambers (30 mm x 10 mm diameter) into the backs of mice. After 14 days, a straw coloured transudate fluid was present in the lumen of the implanted chamber which was withdrawn for the determination of baseline measurements of various inflammatory parameters. A localised chronic inflammatory response was then induced in the chambers by injection of 1% zymosan or Bordetella pertussis vaccine (BPV) (in presensitised animals). The local inflammatory reaction in the chamber, over a 30 day time course, was characterised by leucocyte infiltration, and marked increases in protein, prostaglandin E2, IL-1 and IL-6 concentrations in the chamber fluid. A rapid increase in plasma concentrations of the acute-phase reactant serum amyloid P (SAP) also occurred. This model allows repeated samples to be obtained from the same animal for the assessment of inflammatory parameters and may be useful for investigating the mechanisms controlling the production of IL-1 during the inflammatory response in vivo.

Pharmacokinetics and immunomodulatory effects on monocytes during prolonged therapy with liposomal muramyltripeptide

The macrophage activator muramyl tripeptide-phosphatidyl ethanolamine (MTP-PE) was infused in liposomal form in 14 metastatic cancer patients (4 mg i.v. during 30 min twice weekly for 12 weeks). Clinical, pharmacokinetic and immunological parameters were studied before and 0.5, 2, 4, 24 and 72h after start of drug infusion in week 1, 4, 8 and 12. No tumor regressions were seen. Tumors progressed in 11 patients, in 4 of them within 2 months; 3 patients had stable disease. The intensity and frequency of side effects (fever and nausea) diminished from week 1 to 12. The rate of disappearance of total and free MTP-PE from blood was rapid and mean serum concentration-time curves remained unchanged throughout 12 study weeks. MTP-PE caused a marked increase of serum TNFa, IL-1 receptor antagonist (IL-1ra) and IL-6 in week 1, but not thereafter. In contrast, MTP-PE caused a persistent, 2-fold increase in serum neopterin and young forms of granulocytes (bands) during week 1 to 12. Before therapy, monocyte tumor cytotoxicity and in-vitro monocyte derived TNFa, IL-1 beta and IL-6 production were low in 9 patients (group L, < 15%) and high in 5 patients (group H, > 40%). Monocyte cytotoxicity and in-vitro cytokine production was transiently enhanced in week 1 in group L, it declined under therapy in group H. In conclusion, MTP-PE induced marked initial immunomodulation; the extent of the ex vivo monocyte cytokine and tumor cytotoxic response was dependent on pre-therapy cell activity. A decrease of the cytokine and IL-1ra response during prolonged therapy contrasted with a persistent increase of neopterin and juvenile blood granulocytes. The long lasting biologic effects may be relevant to direct future clinical studies with liposomal MTP-PE in an adjuvant setting.

Lipopolysaccharide induces human interleukin-1 receptor antagonist and interleukin-1 production in the same cell

A new member of the interleukin-1 (IL-1) family has recently been described. Human IL-1 receptor antagonist (IL-1ra) is structurally related to IL-1 alpha and IL-1 beta but binds to IL-1 receptors on various target cells without demonstrable agonist activity. Understanding the mechanisms of regulation of IL-1ra production may clarify the biology of this unique cytokine as well as elucidate its possible role as a natural anti-inflammatory protein. The effects of lipopolysaccharide (LPS) on IL-1 alpha, IL-1 beta and IL-1ra production was studied at a single-cell level by use of cytokine-specific antibodies and indirect immunofluorescence technique. The peak synthesis of IL-1ra and IL-1 alpha/beta occurred in peripheral blood monocytes obtained from healthy blood donors within 4 and 6 h of cell stimulation, respectively. By double-staining procedure all IL-1ra-positive cells were also IL-1 alpha and/or beta positive. Thus, endotoxin induced simultaneous synthesis of the IL-1 gene family in the same cells. Only monocytes contributed to the production of IL-1 alpha, beta and IL-1ra during the 96 h of cell culture. The maximum number of IL-1ra-producing monocytes was 48 +/- 16% as compared to peak production of IL-1 alpha and beta which occurred in 75 +/- 9% and 80 +/- 12% (p < 0.001), respectively, of all peripheral blood monocytes. The incidence of IL-1 alpha- and beta-containing cells was not only significantly higher but also occurred for a longer time period, 72 h as compared to 24 h for IL-1ra localized in the Golgi organelle. However, IL-1ra-containing cells with a diffuse cytoplasmic appearance were also evident (20%-30%) at a later stage, 12 to 72 h after stimulation. Blocking IL-1 surface receptors by addition of exogenous recombinant IL-1 beta before stimulation could not inhibit the diffuse cytosolic localization. This indicates that the "late" staining pattern did not reflect IL-1ra being secreted and internalized after binding to extracellular receptors. Thus, perhaps IL-1ra modulates IL-1 effector mechanisms by receptor interactions both inside and outside the cell.

Simultaneous determination of sugar incorporation into glycosphingolipids and glycoproteins

We assessed inhibitors of glycosylation by simultaneous determination of [14C]Gal incorporated into glycosphingolipids and glycoproteins as well as of [3H]Leu incorporated into proteins of intact cells. After metabolic labeling in 96-well plates in the presence or absence of a test substance, cells were collected on glass-fiber filters. The lipid components were extracted from the filter and radioactivities of both extract and filter determined. The reliability of the procedure was tested with different drugs. Using the glucocerebroside synthetase inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP; 5 microM), glycolipid biosynthesis was shown to be reduced to 50% in the murine T-cell EL-4 6.1 line, whereas glycosylation of proteins was not disturbed. With 0.5 microM tunicamycin, the glycosylation of proteins was 50% of that in the control. The procedure was also able to detect various specific effects: the inhibition of protein glycosylation with D-glucosamine and castanospermine, the inhibition of glycosphingolipid biosynthesis with L-cycloserine, and a slight enhancement of glycosphingolipid biosynthesis with conduritol B epoxide and castanospermine. Within a series of N-acyl homologs of PDMP the inhibitory potency increased with chain length. In contrast, these homologs were equipotent by enzymatic in vitro assays.

A whole blood immunoassay for the interferon-inducible human Mx protein

Mx protein, an intracellular protein induced by type I interferons (IFNs), is useful as a marker for the IFN-induced state. It is detectable, for example, in leukocytes of patients undergoing IFN-alpha treatment as well as in patients suffering from viral or autoimmune diseases. For immunizations and standardizations, recombinant human MxA protein was expressed in Escherichia coli and purified from inclusion bodies by several steps of chromatography. Two monoclonal antibodies against nonoverlapping epitopes and specific for human Mx protein were selected to establish a simple two-site immunometric enzyme assay. In addition, a monoclonal antibody also reacting with Mx proteins of other species was identified. Prior to assay, whole blood samples were lysed with a nonionic detergent. The sample was incubated on wells coated with a first monoclonal antibody (1304.5.32) together with a second biotinylated monoclonal (1302.34.16), which, after washing, was revealed by an avidin-alkaline phosphatase system. Limit of detection was 5 ng/ml. In two-thirds of normal blood samples (n = 87), Mx protein levels were below 5 ng/ml; 25 samples (29%) had Mx levels between 5 and 50 ng/ml; and 4 samples (5%) were above 50 ng/ml. No Mx was found in plasma, and the mononuclear cell fraction accounted for the bulk of Mx in blood. In vitro, as determined by flow cytometry, monocytes and lymphocytes accumulated Mx protein for 24 h with similar kinetics and remained at plateau levels for more than 70 h. Monocytes contained around eight times more Mx than lymphocytes. The immunoassay was also suitable for detecting Mx after IFN induction in heparinized blood.

Direct chemiluminescence immunoassay (CLIA) for muramyl tripeptide phosphatidyl-ethanolamine in plasma

A competitive chemiluminescent immunoassay for quantitation of muramyl tripeptide phosphatidyl-ethanolamine (MTP-PE) in plasma has been developed. The assay is based on the use of an acridinium ester-labelled analogue of muramyl tripeptide and a rabbit antiserum. It includes an overnight incubation and a separation with a second antibody covalently coupled to paramagnetic particles. The sensitivity of detection is 0.012 nmol/l, the assay working range is 0.1-5 nmol/l, and the inter-assay CVs are less than or equal to 10%. Using up to 6000-fold sample dilutions, a wide working range (0.1-30,000 nmol/l) is obtained. Rat plasma samples were collected during and one day after intravenous infusion of MTP-PE. Following infusion, the concentrations in plasma declined multiphasically. Half-life time was 0.37 h +/- 0.03 (mean +/- SD, alpha phase) and 1.76 h +/- 0.08 (mean +/- SD, beta phase), clearance and volume of distribution were 0.09 +/- 0.02 l/h x kg (mean +/- SD) and 0.06 +/- 0.01 l/kg (mean +/- SD) respectively. The use of an acridinium ester as a chemiluminescent (CL) label overcomes the problems associated with reagents of limited shelf-life.

Immunoblotting in the clinical laboratory

Since its introduction in 1979 protein blotting has become a routine tool in research laboratories. In the clinical laboratory its potential is becoming recognised for applications in fields such as infectious and autoimmune diseases, allergy and others. In this article we would like to outline the basic principles of protein blotting, to illustrate these with some examples related to clinical applications and to point out differences between these and classical methods.

Chromogenic labeling of milk oligosaccharides: purification by affinity chromatography and structure determination

Oligosaccharides from human milk were derivatized with 4'-N,N-dimethylamino-4-amino-azobenzene (DAAB) by reductive amination and purified by affinity chromatography on immobilized antibodies followed by resolution of the retained antigenic molecules by adsorption chromatography on HPLC. The visibility to the naked eye and the favorable handling properties of the DAAB-oligosaccharides (desalting, quantification) offered distinctive advantages over underivatized oligosaccharides. Analysis by MS and NMR identified the two major antigens as the Lewis a active pentasaccharide and the Lewis b active hexasaccharide, respectively. Further derivation of DAAB-oligosaccharides by palmitoylamidoacetaldehyde generated glycolipid-like compounds suitable for immunological detection by in situ overlay techniques after separation by thin-layer chromatography.

Receptor analogs and monoclonal antibodies that inhibit adherence of Bordetella pertussis to human ciliated respiratory epithelial cells

The adherence of Bordetella pertussis to human respiratory cilia is critical to the pathogenesis of whooping cough. To explore the development of agents that could interrupt adherence, the structure of the receptor on the ciliary surface was investigated. Using an in vitro adherence assay to human ciliated epithelial cells, galactose, lactose, and complex carbohydrates containing lactose eliminated adherence when preincubated with the bacteria. 10(-2) M galactose eluted adherent bacteria from cilia. B. pertussis and its two purified adhesins bound specifically to natural lactose-containing glycolipids in a TLC assay. mAbs to eukaryotic glycoconjugates with specificity for substituted galactose-glucose moieties blocked adherence when preincubated with ciliated cells. The carbohydrates that serve as receptors for B. pertussis on human cilia are galactose-glucose-containing glycolipids. Receptor analogs and anti-receptor antibodies effectively block adherence of B. pertussis to cilia and thus should be considered candidates for therapeutic intervention against disease.

Enhanced antiproliferative action of interferon targeted by bispecific monoclonal antibodies

It has previously been shown that interferon (IFN) can be coupled covalently to tumor-specific monoclonal antibodies (mAb) and that the in vitro antiviral and antiproliferative action of these IFN-mAb conjugates is superior to that of uncoupled IFN. We now report a different mode of IFN delivery, i.e., via bispecific mAbs, avoiding chemical coupling of IFN. Bispecific mAbs were prepared by cross-linking two mAbs with SPDP, mAb1 being specific for an idiotype of a hybridoma cell-surface immunoglobulin and mAb2 specific for an IFN. Alternatively, Fab' fractions of mAb1 and mAb2 were coupled by disulfide formation to produce F(ab')2. Binding capacity and specificity of both arms of the mAb conjugates were first demonstrated by a solid-phase radioimmunoassay using idiotype-positive mAb as test antigen and 125I-labeled hybrid IFN-alpha B/D. Secondly, hybridomas either idiotype positive or negative were incubated with bispecific mAbs (mAb1-mAb2 or Fab'1-Fab'2) and 125I-labeled IFN at 4 degrees C. After washing away unbound reagents, the uptake of radioactivity into cells was determined. Additionally, the antiproliferative action of cold or labeled IFN targeted via different modes was assessed by an [3H]TdR incorporation method. Results showed that bispecific mAbs could specifically deliver IFN to the target cells and also inhibit their growth in vitro. Furthermore, targeting IFN by any of the three methods, IFN-mAb, mAb1-mAb2, or Fab'1-Fab'2, enhanced its in vitro antiproliferative potency compared to IFN alone.

Serological activity against galactosyl-alpha(1-3)galactose in sera from patients with several kinetoplastida infections

Using rabbit erythrocyte-derived neutral glycosphingolipids enriched for a defined ceramide pentasaccharide as antigens, we have detected elevated anti-galactosyl-alpha(1-3)galactose (anti-G alpha G) antibody values in patients with American cutaneous leishmaniasis (ACL), chronic Chagas' disease, and Trypanosoma rangeli infections compared with normal subjects or with patients suffering from any of 15 other infectious diseases. The specificity of the G alpha G antibodies was determined by inhibition enzyme-linked immunosorbent assays, which revealed that several alpha-galactosyl- but not beta-galactosyl-bearing sugars blocked absorption of G alpha G antibodies to the specific antigen used. G alpha G antibodies were mainly distributed between immunoglobulin classes G and M in three Kinetoplastida infections studied, with a lower increase in reactivity detected in immunoglobulin A. Absorption of highly reactive G alpha G antibodies with purified murine laminin and nidogen, two basement membrane proteins, almost abolished G alpha G reactivity, suggesting the identity of anti-G alpha G with laminin and nidogen antibodies previously reported as elevated in Kinetoplastida infections. In ACL, G alpha G antibodies were detected in 71% of patients having skin lesions with a clinical evolution time of 0.5 month. This percentage increased with the time of evolution of skin lesions, reaching 93% in lesions older than 3 months, and tended to decrease inversely to the induration diameter in the skin leishmanin test. It is proposed that similar epitopes may exist on kinetoplast protozoa and that the determination of G alpha G antibodies may be a highly sensitive assay for the detection of humoral responses to Kinetoplastida infections.

Circulating antibodies to mouse laminin in Chagas disease, American cutaneous leishmaniasis, and normal individuals recognize terminal galactosyl(alpha 1-3)-galactose epitopes

Sera from patients with American cutaneous leishmaniasis and Chagas disease and from monkeys infected with either Trypanosoma cruzi or Trypanosoma rhodesiense show, in RIAs, strong binding to mouse laminin. A distinct although weaker binding activity is also detected in normal human sera. The antibodies recognize a common carbohydrate epitope present on mouse laminin, which was assigned to a terminal galactosyl(alpha 1-3)-galactose group. Distinct crossreactions were observed with some other basement membrane proteins, rabbit glycosphingolipids, defucosylated human B blood group substance and components produced by some human tumor cells. Only little activity was, however, found on laminin obtained from human placenta. The data indicate that the antibodies arising in infectious diseases are stimulated by similar carbohydrate epitopes present on the surface of parasites. Tissue-specific occurrence of such epitopes may exist and explain the involvement of distinct tissues in autoimmune disorders.

Chromogenic labeling of monosaccharides using 4'-N,N-dimethylamino-4-aminoazobenzene

Twenty-three monosaccharides, e.g., D- or L-pentoses, D- or L-hexoses, heptose, 2- or 6-deoxyhexoses, 2-deoxy-2-aminohexoses, hexuronic acids, and N-acetylmuramic acid, were coupled to the azo dye 4'-N,N-dimethylamino-4-aminoazobenzene by reductive amination using sodium cyanoborohydride as reducing agent and in the presence of pentaerythritol. The structure of the colored glycamines was established by mass spectrometry. The average yield of the reaction was more than 80%. The sugar derivatives were separated either by silica-gel thin-layer chromatography or by high-performance liquid chromatography. Spectrophotometric quantitation was performed in the visible range at the picomole level. The method was applied to the determination of the sugar composition of the glycosphingolipid globotetraosyl ceramide and the human milk oligosaccharide lacto-N-fucopentaose I.

Glycosphingolipid-blotting: an immunological detection procedure after separation by thin layer chromatography

A method for detecting glycosphingolipids (GSL) in situ after thin layer chromatography is described. The separated GSL are transferred by diffusion to nitrocellulose. The replica is incubated with poly- or monoclonal antibodies and bound antibodies are detected with second antibodies coupled to peroxidase. Advantages of the procedure are its speed, the non-radioactive detection method, and its suitability for screening applications. In addition, small scale affinity purification of antibodies from the replicas is possible. The presence of Forssman antigen in mouse tissues and the reaction of monoclonal antibodies with human GSL is demonstrated.

Monoclonal antibodies in analysis of cathepsin G-digested proteolytic fragments of human plasma fibronectin

Proteolytic fragments of fibronectin, obtained by digestion with cathepsin G, were transferred electrophoretically from sodium dodecyl sulphate (NaDodSO4) polyacrylamide gels to nitrocellulose sheets and used as antigens for monoclonal antibodies. All 9 monoclonal antibodies tested reacted with undenatured intact fibronectin or its fragments applied directly to nitrocellulose sheets. Two of the clones did not react with the NaDodSO4-treated transferred material suggesting reactivity with conformational determinants. Distinct fragments of fibronectin could be detected by several of the antibodies. None of the monoclonal or the polyclonal antibodies used reacted with the Mr = 40,000 or Mr = 30,000 gelatin-binding fragments of fibronectin. However, one of the monoclonal antibodies reacted specifically with their precursor Mr = 64,000 fragment, but apparently with its gelatin-nonbinding segment. The apparent non-immunogenicity of the gelatin-binding domain is conspicuous, suggesting that it may be highly conserved in evolution. The present method, combination of controlled proteolytic cleavage with electrophoretic transfer, provides an effective means for characterization of monoclonal antibodies raised against proteins.

Monoclonal antibodies against eucaryotic ribosomes. Use to characterize a ribosomal protein not previously identified and antigenically related to the acidic phosphoproteins P1/P2

Mice were immunized against chick ribosomes with the use of various protocols and immunogen preparations. Hybridomas were prepared, clones screened, and specific antibodies identified by reversible protein staining followed by immunoperoxidase staining on nitrocellulose blots. Clones were obtained which secreted specific antibodies against ribosomal proteins S6, L7, L18a, P1/P2, and also against ribosomal RNA. Antibodies were typed by means of a dot-binding assay with typing antibodies immobilized on a solid support of nitrocellulose, and also characterized by their species cross-reactivities. The common determinant on proteins P1 and P2 cross-reacted with proteins of similar molecular weight in all eucaryotes tested, and with a determinant in a previously uncharacterized 38,000-dalton protein of the large ribosomal subunit. We designate this protein P0. The determinant of P0 was also present in a protein of similar molecular weight in all eucaryotes tested. Unlike P1 and P2, P0 was not removable from ribosomes by an ethanol-NH4Cl washing procedure. No evidence for a precursor-product relationship between P0 and P1/P2 was found. P0, P1, and P2 were found in active polysomes and in the nucleolus. The molecular weights of the nucleolar forms were not identical with those of the cytoplasmic forms, suggesting some processing during ribosomal assembly and/or transport.

The phosphorylation of ribosomal protein S6 in rat tissues following cycloheximide injection, in diabetes, and after denervation of diaphragm. A simple immunological determination of the extent of S6 phosphorylation on protein blots

The extent of phosphorylation of S6 was measured in a variety of cells, organs, and tissues using a simplified procedure. Ribosomal proteins were separated by electrophoresis on a one-dimensional urea-sodium dodecyl sulfate gel. They were transferred electrophoretically to nitrocellulose, and S6 was specifically stained by means of its reaction with a monoclonal antibody. The mobility of the stained protein was shown to be a measure of the extent of its phosphorylation. Using this method, we found that cycloheximide injection of rats gives rise to the phosphorylation of S6 in a variety of organs and tissues: diaphragm, heart and skeletal muscle liver and kidney, but not brain. Diabetes induced with alloxan did not result in the phosphorylation of S6 in any of the tissues examined, and subsequent insulin injection resulted in a slight increase in the phosphorylation of S6 in liver. Insulin injection in normal rats also caused the phosphorylation of liver S6. Unilateral denervation of rat diaphragm resulted in phosphorylation of S6 in the denervated portion but not in the innervated portion of the diaphragm.

Ribosomal protein S6 from Xenopus laevis ovaries. Isolation, phosphorylation in vivo and cross-reaction with heterologous anti-S6 antibodies

Ribosomal protein S6 from Xenopus laevis ovaries was prepared by ion-exchange chromatography on phosphocellulose and gel filtration on Sephadex G-75. The protein was identified as S6 from its position on two-dimensional polyacrylamide gels and from its immunological cross-reaction with monoclonal antibody raised against chicken liver S6, and from the fact that it is the major phosphorylated protein of the small subunit. When oocytes were incubated with [32P]orthophosphate in the presence of progesterone, 32P incorporation of 40-S ribosomal proteins was stimulated about 10-fold over controls without hormone. The bulk of the 32P radioactivity was incorporated into protein S6.