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Biomedical subjects

A S Cross

Publications and source records attributed to A S Cross.

At least 73 records · Page 4Linked to original sources
PubMed1992

Modulation of blood-brain barrier permeability by tumor necrosis factor and antibody to tumor necrosis factor in the rat.

In an attempt to understand the role of TNF in the central nervous system (CNS) pathophysiologic events associated with bacterial meningitis, we examined the effect of intravenous vs. intracisternal administration of TNF alpha on penetration of circulating 125I-labeled albumin into cerebrospinal fluid (CSF) and CSF white blood cell (WBC) counts in rats. Intracisternal administration of tumor necrosis factor alpha (TNF-alpha) resulted in dose- and time-dependent alterations of the CSF penetration and CSF WBCs, while intravenous administration of TNF-alpha did not induce any changes. These changes by intracisternal TNF were abolished by heat treatment of TNF or coadministration of MAb to TNF-alpha. Mab to TNF-alpha also significantly reduced the CSF penetration of circulating albumin in experimental hematogenous Haemophilus influenzae type b meningitis in infant rats but this salutary effect required both intravenous and intracisternal administration. However, MAb to TNF-alpha failed to affect CSF pleocytosis in experimental hematogenous meningitis. These findings suggest that some of CNS pathophysiologic changes in bacterial meningitis may be a result of the local production of TNF but other host inflammatory responses may also participate in CNS inflammation in hematogenous bacterial meningitis.

Animals↗
PubMed1991

Safety and immunogenicity of Escherichia coli O18 O-specific polysaccharide (O-PS)-toxin A and O-PS-cholera toxin conjugate vaccines in humans.

O-specific polysaccharide (O-PS) isolated from serotype 18 Escherichia coli lipopolysaccharide (LPS) was covalently coupled to either Pseudomonas aeruginosa toxin A (TA) or or cholera toxin (CT). The conjugates were nontoxic and nonpyrogenic. The conjugates were well tolerated on parenteral administration to human volunteers, with only mild, transient local reactions reported. Immunization engendered an IgG antibody response to both the O-PS and carrier protein. Anti-LPS antibody promoted the uptake and killing of an E. coli O18 strain bearing the K1 capsule by human polymorphonuclear leukocytes, which was complement dependent. Antibody to carrier protein neutralized the activity of native TA or CT in cell culture assays. Passively transferred IgG isolated from the serum of immunized donors provided a significant (P less than .01) degree of protection against fatal experimental E. coli O18 sepsis in mice. This study illustrates the potential use of such conjugates as vaccines against E. coli extraintestinal infections.

ADP Ribose Transferases↗
PubMed1991

Production and characterization of a human hyperimmune intravenous immunoglobulin against Pseudomonas aeruginosa and Klebsiella species.

A hyperimmune globulin for intravenous use (H-IVIG) was prepared from the plasma of donors immunized with Pseudomonas aeruginosa and Klebsiella vaccines. H-IVIG preparations contained substantially higher IgG antibody levels to all nine P. aeruginosa vaccine antigens and to 22 of the 24 Klebsiella vaccine antigens than did commercial IVIG. The H-IVIG was more effective at promoting the opsonophagocytic killing of P. aeruginosa and Klebsiella vaccine serotype strains than normal IVIG. The H-IVIG neutralized greater than 20 times more toxin A than commercial IVIG. Only the H-IVIG offered significant protection against Klebsiella K2 sepsis. The H-IVIG provided significantly better protection against six of the eight P. aeruginosa vaccine serotypes than normal IVIG when compared in a murine burn wound sepsis model. The H-IVIG also protected mice against an Enterobacter aerogenes challenge, whereas normal IVIG was ineffective.

Animals↗
PubMed1991

Differential induction of tumor necrosis factor by bacteria expressing rough and smooth lipopolysaccharide phenotypes.

The lipid A portion of the lipopolysaccharide (LPS) molecule of gram-negative bacteria has the ability to turn on the production of tumor necrosis factor (TNF) in macrophage cells. The question addressed in this paper was whether the presence of the polysaccharide moiety on the LPS molecule had any bearing on this ability. The question was asked (i) by using isolated LPS from a series of Salmonella mutants having progressively less polysaccharide attached to the lipid A portion of the molecule and (ii) by using whole bacteria expressing alternatively the smooth or rough LPS phenotype. Isolated LPS and bacteria were examined for their abilities to induce bioactive TNF in the mouse macrophage cell line RAW 264.7. The results indicated that the presence of long- or short-chain polysaccharide moieties had no bearing on the ability of the isolated LPS molecule to induce TNF. However, the presence of long-chain polysaccharides attached to the lipid moiety on the intact smooth bacterium was associated with a decreased ability to induce TNF. To test whether the bacteria were inducing TNF by a cell (bacterium)-to-cell (macrophage) contact mechanism or through a releasable product, the bacteria were removed from direct contact with the macrophage cells by using a Transwell filter insert. Under these conditions the rough bacteria continued to induce TNF, while the smooth bacteria were no longer capable of doing so. When filtrates from the bacteria were examined in the Limulus amebocyte lysate assay, the results showed that the rough bacteria were releasing approximately a log order more Limulus amebocyte lysate activity than the smooth bacteria. The results of this study suggest that rough bacteria may be superior inducers of TNF compared with their smooth counterparts because of a greater propensity to shed their LPS.

Bacteria↗
PubMed1991

Efficacy of antilipopolysaccharide and anti-tumor necrosis factor monoclonal antibodies in a neutropenic rat model of Pseudomonas sepsis.

Monoclonal antibodies (MAb) directed against bacterial lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF) provide partial protection in experimental models of septic shock. To determine if additional benefit accrues from a combination of anti-TNF and anti-LPS MAb in the treatment of septic shock, a neutropenic rat model was developed to study active infection with Pseudomonas aeruginosa 12.4.4. Animals were treated intravenously with an irrelevant MAb (group 1); anti-TNF MAb (group 2); MAb directed against P. aeruginosa 12.4.4 LPS (group 3); or a combination of anti-TNF and anti-LPS MAb (group 4). None of the control animals in group 1 survived the 7-d period of neutropenia (0/16). In contrast, the survival rate was 44% in group 2 (P less than 0.02); 37% in group 3 (P less than 0.05); and 75% in group 4 (P less than 0.0002). The combination of monoclonal antibodies provided greater protection than either MAb given alone (P less than 0.05). Serum TNF levels during infection were significantly greater in groups 1 and 3 (20.1 +/- 3.3 U, mean +/- SE) than in groups 2 and 4 (0.9 +/- 0.8 U, P less than 0.0001). These results indicate that a combination of monoclonal antibodies to LPS and TNF have additive benefit in experimental Pseudomonas aeruginosa sepsis. This immunotherapeutic approach may be of potential utility in the management of serious, gram-negative bacterial infection in neutropenic patients.

Animals↗
PubMed1991

Mobilization of sialidase from intracellular stores to the surface of human neutrophils and its role in stimulated adhesion responses of these cells.

Desialation of cell surfaces has been associated with the initiation or modification of diverse cellular functions. In these studies we have examined the subcellular distribution of sialidase (SE) in human neutrophils as well as the mobilization of this enzyme following neutrophil activation. Separation of subcellular fractions by density gradient centrifugation showed that SE is present not only in neutrophil primary and secondary granule populations, like lysozyme, but also in plasma membrane fractions. Neutrophil activation was associated with a redistribution of SE from secondary granule-enriched fractions to the plasma membrane. Furthermore, SE activity detected on the surface of intact neutrophils with a fluorescent SE substrate increased rapidly after activation with kinetics that matched both the loss of total cell-associated sialic acid and release of free sialic acid from the cells. These activation-dependent events were in each case blocked by incubation of neutrophils with the SE inhibitor, 2-deoxy-N-acetyl-neuraminic acid. Aggregation responses of neutrophils as well as adhesion responses to nylon and plastic surfaces were also inhibited by 2-deoxyNANA. Our findings indicate that the activation-dependent desialation of the neutrophil surface is associated with mobilization of an endogenous SE to the plasma membrane and has a role in stimulated adhesion responses of these cells.

Antigens, CD↗
PubMed1990

Aerobactin and alpha-hemolysin as virulence determinants in Escherichia coli isolated from human blood, urine, and stool.

Because iron acquisition is essential to the survival of invasive strains of Escherichia coli, the frequency of two potential iron acquisition systems, aerobactin and hemolysin production, were compared in E. coli isolated from human blood (n = 95), urine (n = 100), and stool (n = 50). By phenotypic and genotypic methods, the prevalence of hemolysin production was 22% in bacteremic, 38% in urinary, and 22% in fecal isolates of E. coli. Aerobactin production was detected in 76% of blood and in 73% of urinary isolates but in only 52% of fecal isolates (P less than .01). A reciprocal relationship was found in blood isolates between aerobactin and hemolysin; the majority of blood isolates (55%) that lacked aerobactin were hemolytic, whereas only 14% of blood isolates that expressed aerobactin were hemolytic (P less than .0001). Aerobactin may be the principal mechanism of iron acquisition in extraintestinal isolates of E. coli, and hemolysin may serve as an alternative mechanism in the absence of aerobactin genes.

Bacterial Proteins↗
PubMed1990

Efficacy of a monoclonal antibody directed against tumor necrosis factor in protecting neutropenic rats from lethal infection with Pseudomonas aeruginosa.

A monoclonal antibody directed against murine tumor necrosis factor-alpha (TNF) was studied in a neutropenic rat model to determine its efficacy in protecting animals from lethal infection with Pseudomonas aeruginosa. Anti-TNF monoclonal antibody at a dose of 20 mg/kg given intravenously at 0 and 120 h resulted in a 53% survival rate (8/15) compared with no survival in control animals (0/15) (P less than .005). The combination of anti-TNF monoclonal antibody and oral ciprofloxacin at a suboptimal dose of 2.5 mg/kg/day resulted in a 100% survival rate in neutropenic animals (16/16), while ciprofloxacin alone produced only a 67% survival rate (10/15) during the 7-day period of neutropenia (P less than .05). Thus anti-TNF monoclonal antibody alone or in addition to antimicrobial agents improved survival in neutropenic animals after infection with P. aeruginosa.

Agranulocytosis↗
PubMed1990

Bacteria-phagocyte interactions: emerging tactics in an ancient rivalry.

Although phagocytes appear to have a redundancy of both oxidative and non-oxidative killing mechanisms, nevertheless, bacterial pathogens are still able to evade these defenses in vivo and cause lethal infection. As the mechanisms by which phagocytes function have become detailed at the molecular level, both the recognition of specific bacterial virulence determinants and their effects at specific sites in the phagocyte are also being identified. Knowledge of these interactions may permit the use of immunomodulators either to neutralize these virulence determinants or to enhance the bactericidal capabilities of the phagocyte.

Animals↗
PubMed1990

Synthesis and characterization of Escherichia coli O18 O-polysaccharide conjugate vaccines.

Nontoxic, serologically reactive O polysaccharide was derived from Escherichia coli O18 lipopolysaccharide by acid hydrolysis, extraction with organic solvents, and gel filtration chromatography. Oxidized O polysaccharide was covalently coupled to either Pseudomonas aeruginosa toxin A or cholera toxin by using adipic acid dihydrazide as a spacer molecule in the presence of carbodiimide. The resulting conjugates were composed of approximately equal amounts of O polysaccharide and protein and were nontoxic and nonpyrogenic. Both conjugates engendered an immunoglobulin G antibody response in rabbits that recognized native O18 lipopolysaccharide. Such antibody was able to promote the uptake and killing of an E. coli O18 strain bearing the K1 capsule by human polymorphonuclear leukocytes. Immunoglobulin G isolated from the sera of rabbits immunized with either conjugate afforded protection against an E. coli O18 challenge when passively transferred to mice.

ADP Ribose Transferases↗
PubMed1990

Murine hybridoma antibodies enhance bactericidal activity of human cord blood against K1 Escherichia coli strains.

Murine hybridoma antibodies directed against the capsule and O-side chain determinants of the Escherichia coli strain Bort (018ac:K1:H7) were evaluated for their ability to enhance bactericidal activity of cord blood against K1 E. coli strains possessing O antigens common in neonatal E. coli infection, i.e. 018, 07, and 01. The antibodies to the K1 capsule and O-side chain efficiently enhanced cord polymorphonuclear leukocyte-mediated killing of K1 encapsulated E. coli strain possessing a homologous O antigen, but the IgM antibody to the K1 capsule exhibited approximately 10-fold greater activity than did the IgG3 antibody to O-side chain (weight basis). Both antibodies required complement for their opsonic activities. Our findings indicate that antibodies directed against the capsule and O-lipopolysaccharides are able to restore the opsonic activity of cord blood against K1 E. coli, suggesting that these antibodies may be useful in the prevention and therapy of neonatal E. coli infection.

Antibodies, Bacterial↗
PubMed1990

Human monoclonal antibodies to Pseudomonas aeruginosa type-specific lipopolysaccharides, toxin A and Klebsiella capsular polysaccharides.

A number of human monoclonal antibodies (HmAb) recognizing type-specific determinants expressed by the lipopolysaccharide (LPS) of Pseudomonas aeruginosa and by the capsular polysaccharide (CPS) of Klebsiella were generated for potential treatment of nosocomial infections. The goal is to administer these type-specific HmAb prophylactically as a "cocktail" providing broad coverage. Lymphoblastoid cell lines (LCL) secreting HmAb recognizing P. aeruginosa LPS, toxin A or Klebsiella CPS were obtained by Epstein Barr Virus (EBV) transformation of peripheral blood lymphocytes (PBL) from donors immunized with either a polyvalent Klebsiella CPS or P. aeruginosa O-polysaccharide-toxin A conjugate vaccine. LCL secreting antibodies of the desired specificities were fused to a heteromyeloma cell line. Stable clones were selected by limiting dilution. Hybridomas secreting IgM HmAb which recognized P. aeruginosa Habs serotype 3 and 4 and all 7 Fisher immunotypes were isolated. All were able to prevent fatal experimental P. aeruginosa sepsis in mice when passively transferred. In addition, 4 lines secreting IgG HmAb which neutralize the cytotoxic activity of toxin A were characterized. IgM and IgA secreting hybridoma cells with specificity for Klebsiella CPS of 22 different serotypes were also isolated. Preliminary studies indicate that these HmAb are opsonic.

Animals↗
PubMed1990

Escherichia coli and Klebsiella vaccines and immunotherapy.

A polyvalent vaccine has been prepared from the capsular polysaccharide of 24 different serotypes of Klebsiella spp. Nearly 200 volunteers have received this vaccine. It is very well tolerated and elicits both binding (ELISA) and functional antibody to 21 of 24 antigens. Antibodies were also detected against 10 serotypes not included in the vaccine. An immunoglobulin for intravenous use (IVIG) was more protective in mouse lethality assays and enhanced opsonophagocytic killing of bacteria more than standard, nonhyperimmune globulin. A monovalent E. coli conjugate vaccine against O18ac antigen was safe and highly immunogenic in humans. A 12-valent conjugate vaccine elicits good levels of antibody in rabbits, and will soon undergo phase I testing in humans. These vaccines might best be used for inducing antibody in donor plasma that could be made into IVIG for passive administration.

Bacterial Vaccines↗
PubMed1989

Pretreatment with recombinant murine tumor necrosis factor alpha/cachectin and murine interleukin 1 alpha protects mice from lethal bacterial infection.

Tumor necrosis factor/cachectin (TNF/C) is the principal mediator of bacterial endotoxin-induced shock and death. We found that the C3H/HeJ mouse, which is less able to produce TNF/C in response to endotoxin, has a 1,000-fold greater susceptibility to lethal infection with Escherichia coli than the TNF-responsive congenic mouse, C3H/HeN. This surprising finding suggested that this lethal peptide may also be involved in host protection. To test this hypothesis we pretreated the C3H/HeJ mouse with a combination of recombinant murine TNF/C-alpha and IL-1 alpha. This combination protected these mice against an intraperitoneal bacterial challenge of greater than 20 LD50S (nearly 2 x 10(2) CFU) that grew to a level of greater than 10(7) CFU/ml of blood and per gram of liver in untreated mice. This suggests a significant role for these cytokines in host defenses against invasive infections that require bacterial replication within the host. These protective mechanisms may not be important for less virulent organisms. These findings may have important implications for the proposed use of anti-TNF/C agents in the treatment of septic shock.

Animals↗
PubMed1989

Oral ciprofloxacin and a monoclonal antibody to lipopolysaccharide protect leukopenic rats from lethal infection with Pseudomonas aeruginosa.

To study the treatment of infection with Pseudomonas aeruginosa, a leukopenic rat model was developed that closely mimics the pathogenesis of Pseudomonas infection in man. This model achieved approximately 90% mortality within 10 d of infection. Pseudomonas organisms were inconsistently shed from the feces despite gastrointestinal colonization (9 fecal v. 23 cecal cultures positive for challenge strain in 28 rats). Treatment of rats with oral ciprofloxacin at 40 mg/kg afforded complete protection. A suboptimal dose of ciprofloxacin (20 mg/kg), achieving peak levels of 0.31 micrograms/mL in serum and 26.3 micrograms/mL in stool, resulted in survival of 8 (40%) of 20 rats. Intraperitoneal administration of a monoclonal antibody directed at the lipopolysaccharide of the challenge strain of Pseudomonas resulted in survival of 5 rats (26%). The combination of the two increased the survival to 75% (15 of 20, P less than 0.05 compared to either treatment alone). Thus, the combination of suboptimal doses of ciprofloxacin and a monoclonal antibody appears to protect leukopenic rats from lethal infection better than either treatment alone.

Administration, Oral↗
PubMed1989

The human antibody response during natural bacteremic infection with gram-negative bacilli against lipopolysaccharide core determinants.

The class-specific antibody response was measured in sequential serum samples from 17 patients after natural bacteremic infection with gram-negative bacilli. There was a five- to sevenfold mean increase over preexisting antibody in levels of IgG (range, less than 1-to 88-fold), IgA (1- to 83-fold), and IgM (less than 1- to 58-fold) antibody to homologous lipopolysaccharide (LPS) in 16 of these patients. In contrast, there was only a two- to threefold mean increase (range, less than 1- to 78-fold) in about half of the patients who had a detectable antibody response to J5 core determinants and in the third who responded to Re core determinants (range, 1- to 20-fold). All but one of the infective strains of bacteria were smooth on analysis with SDS-PAGE and with rough-specific phages. Humans infected with bacteria that had a rough LPS phenotype, however, did elicit antibody similar to that induced in rabbits after immunization with J5 vaccine. Thus, the human antibody response to natural infection with gram-negative bacilli appears to be directed primarily at homologous, strain-specific epitopes, and the response to the epitopes of LPS core antigens is not against widely shared determinants.

Adolescent↗