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Biomedical subjects

D Heumann

Publications and source records attributed to D Heumann.

At least 37 records · Page 2Linked to original sources
PubMed1997

Similarities and disparities between core-specific and O-side-chain-specific antilipopolysaccharide monoclonal antibodies in models of endotoxemia and bacteremia in mice.

We have previously described cross-reactive antilipopolysaccharide (anti-LPS), or anti-endotoxin, monoclonal antibodies (MAbs) which provide cross-protection in several systems of endotoxin bioactivity. The protective effects of the murine cross-reactive MAb WN1 222-5 (immunoglobulin G2a(kappa) [IgG/2a(kappa)]) and of its chimerized version, SDZ 219-800 [human IgG1(kappa)], have now been evaluated in lethality models against LPS from three different serotypes and in bacterial infection models. We confirmed the protective activity of the two MAbs in D-galactosamine-sensitized mice challenged with LPS of other E. coli serotypes (O18, O127, and O111). The protective effect correlated with the suppression of tumor necrosis factor formation. Furthermore, WN1 222-5 enhanced bacterial clearance of intravenously administered E. coli O111 bacteria, thus protecting mice from death. However, the MAbs were unable to provide protection in a peritonitis model (intraperitoneal inoculation). Our study, therefore, shows that LPS cross-reactive antibodies are capable of mediating cross-protection against LPS and bacteria but that the selected models have a clear influence on the results.

Animals↗
PubMed1996

Streptococcus mitis cell walls and lipopolysaccharide induce lethality in D-galactosamine-sensitized mice by a tumor necrosis factor-dependent pathway.

Purified cells walls of Streptococcus mitis induced tumor necrosis factor in vitro in whole blood of both lipopolysaccharide (LPS)-sensitive OF1 and LPS-resistant C3H/HeJ mice. They were as effective as heat-killed bacteria in inducing death in both strains of mice sensitized with D-galactosamine. Lethality was suppressed by anti-tumor necrosis factor antibodies. The histopathophysiological findings in mice after challenge with LPS or gram-positive cell walls were indistinguishable.

Animals↗
PubMed1995

Do monoclonal antibodies and anticytokines still have a future in infectious diseases?

The continuing high mortality of septic shock has prompted a major effort by the research community to identify novel therapeutic targets. These targets can be conveniently grouped into (1) those derived from microbial components or products; (2) inflammatory mediators; and (3) effector molecules. Many of the experimental, so-called adjunctive agents developed have been monoclonal antibodies or anticytokine molecules of various kinds, and some have progressed into clinical trial. Unfortunately, these trials have failed to show unequivocal survival benefit for patients in shock, prompting a reappraisal of our approach to these agents. In this article, we discuss the possible reasons for these failures: (1) the targets are wrong; (2) the agents are inappropriate; or (3) the trial design is flawed. It would be premature to conclude that adjunctive agents have no future in the therapy of sepsis, but identifying the correct agent, and perhaps more importantly, the correct target population, is going to be more difficult than was at first believed.

Animals↗
PubMed1995

Characterisation of bovine lipopolysaccharide binding protein and the in vivo acute phase response to Pasteurella haemolytica Type A.

Lipopolysaccharide binding protein (LBP) is a liver-derived acute phase protein which is implicated in modulating the host responses to lipopolysaccharide (LPS) from Gram-negative bacteria. LBP interacts with circulatory LPS to form complexes which bind to the CD14 receptor or cells of the monocytic lineage and neutrophils resulting in their activation. This causes the release of mediators and cytokines which are responsible for initiating the acute phase response. LBP-like activity has now been identified in bovine serum and in this study LBP has been purified from acute phase bovine serum using ion exchange chromatography. On sodium dodecyl sulphate polyacrylamide electrophoresis, bovine LBP demonstrated a single band with a molecular mass of 58 kDa. Bovine LBP enhanced the binding of LPS to human monocytes while enzymatic removal of the CD14 receptor abrogated this interaction. Furthermore, bovine LBP increased the sensitivity of monocytes to LPS by at least 100-fold. Depletion of LBP by means of antibodies to bovine LBP inhibited the serum mediated LPS binding to monocytes. Antibodies to rabbit LBP or recombinant human LBP did not cross-react with bovine LBP. Studies on the kinetics of LBP activity in calves during the acute phase response demonstrated a four-fold increase in the serum concentration 36 h after a single intratracheal inoculation of Pasteurella haemolytica A1. The findings of this study indicate that cattle possess a LPS detection mechanism comparable to that described in man and experimental animals in which LBP forms complexes in serum with circulatory LPS enhancing the signal to the immune system to mount a host response. The isolation of LBP will allow further investigations into LBP-mediated responses to LPS in cattle.

Acute-Phase Proteins↗
PubMed1995

Lipopolysaccharide binding protein as a marker of inflammation in synovial fluid of patients with arthritis: correlation with interleukin 6 and C-reactive protein.

OBJECTIVE: To determine levels of lipopolysaccharide binding protein (LBP) in serum and in synovial fluid (SF) of patients presenting with various articular disorders [degenerative arthritis, rheumatoid arthritis (RA), reactive arthritis (ReA)] and to correlate these levels with C-reactive protein (CRP) and interleukin 6 (IL-6), 2 markers of the acute phase response. METHODS: LBP was measured by a radioimmunoassay made up of lipopolysaccharide (LPS) to capture LBP and radiolabelled anti-LBP antibodies to detect LBP. LBP was also measured for its ability to present fluorescein isothiocyanate LPS (FITC-LPS) to human monocytes. CRP was measured by nephelometry and IL-6 bioassay. RESULTS: Levels of LBP in serum and in SF were significantly higher in patients with RA and ReA than in the control group of degenerative arthropathies. In the latter group, LBP values were similar to those found in controls. Serum LBP values correlated positively with SF LBP values. LBP values also correlated with CRP and IL-6 levels measured in SF. Functionally, LBP was found to be active and able to present LPS to monocytes, resulting in tumor necrosis factor-alpha (TNF-alpha) release upon LPS challenge. CONCLUSION: These in vitro data support the observation that LBP could play a major role in local joint disorders. Our results also strengthen the view that LBP may be a new marker of synovial inflammation.

Acute-Phase Proteins↗
PubMed1994

Mode of action of anti-lipopolysaccharide-binding protein antibodies for prevention of endotoxemic shock in mice.

Lipopolysaccharide (LPS)-binding protein (LBP) has been shown to regulate the response of monocytes to LPS in vitro. In a previous study, polyclonal anti-LBP IgGs were found to protect D-galactosamine-sensitized mice against a lethal endotoxemic shock induced by a low challenge of LPS or lipid A when administered simultaneously with endotoxin. In the present study, we investigated the mode of action of these anti-LBP IgGs. In vitro, we demonstrated that they interfere with LPS binding to monocytes or polymorphonuclear cells in different ways: by the mere prevention of binding of LPS to LBP thus preventing the binding of LPS to CD14, or by reacting with LPS-LBP complexes thus mediating their binding to complement or Fc receptors on monocytes and on polymorphonuclear cells. In vivo, we demonstrated that anti-LBP IgGs afforded protection against lethal endotoxemic shock by one of two mechanisms. First, LBP blockade by pretreatment with anti-LBP IgG allowed protection against a low dose of LPS (100 ng). This protection occurred despite LPS levels in blood similar to those in control mice but in the absence of detectable tumor necrosis factor (TNF). This demonstrated that anti-LBP IgG could block the LBP-mediated TNF release upon LPS challenge. In contrast, anti-LBP IgG did not afford protection in mice not sensitized with D-galactosamine and challenged with high-dose LPS (1 mg), confirming that LPS at high concentrations could stimulate cells independently of the LBP pathway. Second, anti-LBP treatment administered simultaneously with LPS challenge protected mice against both low and high doses of LPS. Unlike after pretreatment with anti-LBP IgG, this protection was accompanied by a decrease of circulating LPS, suggesting that anti-LBP IgG in these conditions facilitated clearance of LPS probably by clearing LPS-LBP complexes. These data and the fact that LBP binds to all LPS through lipid A suggest that antibody directed to LBP could be a candidate for therapeutic strategies in endotoxemic shock.

Acute-Phase Proteins↗
PubMed1994

Radioimmunoassay versus flow cytometric assay to quantify LPS-binding protein (LBP) concentrations in human plasma.

LPS-binding protein (LBP) is an acute phase protein present in plasma, that has been shown to play a major role in sensitizing monocytes to LPS. We describe here two assays to quantify LBP in plasma. The first assay made use of monophosphoryl lipid A to capture LBP in human plasma, and LBP was detected by radiolabeled anti-LBP IgG. The second assay measured LBP by flow cytometry, using LBPs ability to present LPS to the CD14 receptor present on monocytes. Both assays had a similar level of sensitivity, that allowed the quantification of LBP in human plasma.

Acute-Phase Proteins↗
PubMed1994

Interferon gamma receptor deficient mice are resistant to endotoxic shock.

Antibody neutralization studies have established interferon gamma (IFN-gamma) as a critical mediator of endotoxic shock. The advent of IFN-gamma receptor negative (IFN gamma R-/-) mutant mice has enabled a more direct assessment of the role of IFN-gamma in endotoxin (lipopolysaccharide [LPS]-induced shock. We report that IFN gamma R-/- mice have an increased resistance to LPS-induced toxicity, this resistance manifesting well before the synthesis and release of LPS-induced IFN-gamma. LPS-induced lymphopenia, thrombocytopenia, and weight loss seen in wild-type mice were attenuated in IFN gamma R-/- mice. IFN gamma R-/- mice tolerated 100-1,000 times more LPS than the minimum lethal dose for wild-type mice in a D-galactosamine (D-GalN)/LPS model. Serum tumor necrosis factor (TNF) levels were 10-fold reduced in mutant mice given LPS or LPS/D-GalN. Bone marrow and splenic macrophages from IFN gamma R-/- mice had a four- to sixfold decreased LPS-binding capacity which correlated with similar reduction in CD14. Serum from mutant mice reduced macrophage LPS binding by a further 50%, although LPS binding protein was only 10% reduced. The expression of TNF receptor I (p55) and II (p75) was identical between wild-type and mutant mice. Thus, depressed TNF synthesis, diminished expression of CD14, and low plasma LPS-binding capacity, in addition to blocked IFN-gamma signaling in the mutant mice, likely to combine to manifest in the resistant phenotype of IFN gamma R-/- mice to endotoxin.

Animals↗
PubMed1994

Pathogenesis and potential strategies for prevention and treatment of septic shock: an update.

Septic shock is mediated by complex interactions of cells, cytokines, and humoral pathways. Clinical therapeutic strategies aimed at inhibiting selected pathways have been efficacious in subsets of patients. Experimental studies focusing on the activities of single cytokines have contributed to the understanding of the complex pathophysiology of septic shock. More precise delineation of the roles of each mechanism contributing to pathogenesis will permit the identification of subsets of patients who might benefit from particular therapeutic strategies and will guide the development of additional approaches to prevention and treatment.

Cytokines↗
PubMed1994

Bactericidal/permeability-increasing protein inhibits induction of macrophage nitric oxide production by lipopolysaccharide.

A recombinant (r) NH2-terminal fragment of bactericidal/permeability-increasing protein, rBPI23, was shown to inhibit murine macrophage nitric oxide (NO) production elicited by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma). Normal mouse plasma amplified NO synthesis (measured as NO2- release) at LPS concentrations of 1-10 ng/mL, and antibody to the plasma LPS-binding protein (LBP) partially inhibited NO2- release in the presence of normal mouse plasma. rBPI23 (1 microgram/mL) effectively inhibited LPS-dependent NO2- release in the presence or absence of normal mouse plasma. Fifty percent inhibition of IFN-gamma/LPS-elicited NO2- production or of binding of fluoresceinated LPS was obtained with approximately 0.2 microgram/mL rBPI23. These results provide a basis for studies of rBPI23 effects on NO synthase activity in murine models of gram-negative sepsis.

Animals↗
PubMed1994

Lipopolysaccharide (LPS)-binding protein in human serum determines the tumor necrosis factor response of monocytes to LPS.

Lipopolysaccharide (LPS)-binding protein (LBP) and CD14 represent key elements in monocyte activation by LPS. The mean concentration of LBP was 18.1 microgram/mL in normal serum and 40-60 micrograms/mL in serum of patients with septic shock, independent of the fact that patients had gram-negative or other infections. Ten percent normal serum presented large concentrations of LPS (in the microgram range) to monocytes. Only when diluted 1:100 was LBP in plasma a limiting factor for monocyte activation, as measured by tumor necrosis factor (TNF) release. When LBP was depleted from serum with anti-LBP antibodies, the resulting serum did not support TNF release of monocytes upon LPS challenge. In conclusion, monocyte activation resulting in TNF secretion was related to LBP, which is abundantly present in normal serum, and elevated two to three times in patients with septic shock.

Acute-Phase Proteins↗
PubMed1994

Gram-positive cell walls stimulate synthesis of tumor necrosis factor alpha and interleukin-6 by human monocytes.

Purified cell walls representing a wide variety in teichoic acid and peptidoglycan structure prepared from eight different gram-positive bacterial species induced the production of tumor necrosis factor alpha (TNF-alpha) and interleukin-6 from human monocytes in the presence of 10% plasma or serum. Significant amounts of cytokines began to be produced at concentrations above 100 ng to 1 microgram of cell walls per ml, with maximal production requiring 10 to 100 micrograms of cell wall material per ml. In the absence of plasma, the cytokine-inducing capacity of cell wall preparations was lower by at least an order of magnitude. The serum-derived cofactor was inactivated by heating at 90 degrees C for 30 min, suggesting that the activity is associated with a protein. On the other hand, replacement of normal with hypogammaglobulinemic plasma, inactivation of complement (at 56 degrees C), and blockade by the monoclonal antibody MY4 of the CD14 receptors on monocytes did not inhibit the production of TNF-alpha induced by whole cell walls. Cell walls also stimulated production of TNF-alpha induced by whole cell walls. Cell walls also stimulated production of TNF-alpha in the presence of polymyxin B, and macrophages derived from the lipopolysaccharide-insensitive cell line of C3He/HeJ mice also produced this cytokine when stimulated by cell walls. Both peptidoglycan and the soluble glycan-teichoic acid component prepared by an enzymatic method from the same wall preparation exhibited a serum-dependent induction of TNF-alpha from monocytes, while stem peptides and disacharride peptides had only poor, if any, activity. Cell walls may contribute to the septic shock induced by gram-positive bacteria.

Antigens, CD↗
PubMed1993

Lipopolysaccharide-binding protein as a major plasma protein responsible for endotoxemic shock.

Because lipopolysaccharide (LPS)-binding protein (LBP) sensitizes monocytes to LPS in vitro, it has been suggested that LBP initiates host defenses against Gram-negative bacteria. The role of LBP in vivo, and particularly in endotoxemic shock, is unknown, however. Therefore an IgG against murine LBP was prepared. It was found to neutralize binding of LPS and subsequent activation of murine macrophages in vitro. This anti-LBP protected mice against the lethal effect of LPS when given at the same time as LPS challenge, but it failed to protect mice when delayed 15 min after LPS challenge. The same preparation was also effective after challenge with lipid A but not after challenge with Staphylococcus aureus enterotoxin. The protection was correlated with a strong decrease of circulating tumor necrosis factor. These data demonstrate that in vivo LBP is a major mediator of the lethal effects of endotoxemia.

Acute-Phase Proteins↗
PubMed1993

IFN-gamma involvement in the severity of gram-negative infections in mice.

The role of IFN-gamma in the regulation of inflammation leading to gram-negative septic shock is still poorly understood. IFN-gamma blockade has been shown to improve the survival of animals challenged with i.v. bolus injections of LPS and gram-negative bacteria. We have investigated a model of focal Escherichia coli infection leading to peritonitis and septic shock. Mice were challenged i.p. with an inoculum near the LD50. The addition of rIFN-gamma together with bacteria increased the mortality and the level of blood TNF-alpha and IL-6. Conversely blockade of IFN-gamma with a neutralizing mAb significantly improved the survival of the mice. This beneficial effect was not associated with a stringent decrease in blood bacterial counts and TNF-alpha and IL-6 levels in survivors. In this model, the protective effect of anti-IFN-gamma mAb contrasted with the ineffectiveness of a neutralizing anti-TNF-alpha mAb. These findings suggest that overproduction of IFN-gamma might have a more detrimental role than overproduction of TNF-alpha during focal gram-negative infections.

Animals↗