Molecular aspects of endotoxic reactions

Leptospirosis is an invasive infectious and systemic inflammatory disease

Pathogenic Leptospira species are the causative agents of leptospirosis, a world-spreading zoonotic infectious disease. The pathogens possess a powerful invasiveness by invading human body through mucosal/skin barriers, rapid entry into bloodstream to cause septicemia, diffusion from bloodstream into internal organs and tissues to cause aggravation of disease, and discharge from urine through renal tubules to form natural infectious sources. Leptospirosis patients present severe inflammatory symptoms such as high fever, myalgia and lymphadenectasis. Hemorrhage and jaundice are the pathological features of this disease. Previous studies revealed that some outer membrane proteins of Leptospira interrogans, the most important pathogenic Leptospira species, acted as adherence factors to binding to receptor molecules (fibronectin, laminin and collagens) in extracellular matrix of host cells. Collagenase, metallopeptidases and endoflagellum contributed to the invasiveness of L. interrogans. Except for lipopolysaccharide, multiple hemolysins of L. interrogans displayed a powerful ability to induce pro-inflammatory cytokines and hepatocyte apoptosis. vWA and platelet activating factor acetylhydrolase-like proteins from L. interrogans could induce severe pulmonary hemorrhage in mice. L. interrogans utilized cellular endocytic recycling and vesicular transport systems for intracellular migration and transcellular transport. All the research achievements are helpful for further understanding the virulence of pathogenic Leptospira species and pathogenesis of leptospirosis.

Beta-glucans, history, and the present: immunomodulatory aspects and mechanisms of action

The present paper represents a comprehensive up-to-date review of beta -glucans, their chemical and biological properties, and their role in immunological reactions. beta -D-Glucans belong to a group of physiologically active compounds called biological response modifiers and represent highly conserved structural components of cell walls in yeast, fungi, or seaweed. Despite almost 150 years of research, the exact mechanisms of their action remain unclear. The present review starts with the history of glucans. Next, attention is focused on sources and structure, comparing the effects of physicochemical properties, and sources on biological effects. As glucans belong to natural products useful in preventing various diseases, they have been highly sought after throughout human history. Based on extensive recent research, this paper explains the various mechanisms of effects and the ways glucans mediate their effects on defense reactions against infections. Despite the fact that predominately pharmacological effects of glucans are positive, their unfavorable and potentially toxic side effects were not overlooked. In addition, attention was focused on the future research, possible alternatives such as synthetic oligosaccharides, and on clinical applications.

An NMR spectroscopy and molecular mechanics study of the molecular basis for the supramolecular structure of lipopolysaccharides

Lipopolysaccharides from Gram-negative bacteria interact with the mammalian immune system to trigger a cascade of physiological events leading to a shock syndrome which results in the death in over 70% of cases of severe shock. It is known that the supramolecular structures of lipopolysaccharide aggregates are critical contributors to their biological activities. Despite this, the molecular basis for the formation if the regular hexagonal plates and arrays observed in lipopolysaccharide films and suspensions is unknown. Since these structures are two dimensional, it is unlikely that X-ray crystallographic methods will shed much light on their detailed structure. Knowing this structure is important since it is becoming increasingly likely that the insertion of the lipopolysaccharide hydrocarbon chains in the target host cell membrane may be involved in triggering host responses. This work describes the three-dimensional structure of the lipopolysaccharide lipid A moiety. The structure was obtained by a combination of molecular mechanics calculations and nuclear magnetic resonance spectroscopy. This involved calculation of the dihedral angle between the two glucosamine residues of the lipid A molecule from coupling constants and measuring critical interresidue NOE values. The study also takes into account information from X-ray powder diffraction and electron microscopy studies.

Alterations in clinical, hematological and metabolic variables in bovine neonatal endotoxemia

Endotoxemia is an important cause of morbidity and mortality in the neonate. Although many models are used to study the problem, none completely simulates the natural disease. To more clearly define a bovine neonatal endotoxemia model we studied the effects of dose of endotoxin on clinical, hematological and biochemical variables. Thirty-four neonatal calves were administered Escherichia coli endotoxin (LPS) at 0 (0.9% saline solution), 0.2, 2.0 or 20 micrograms/kg, by either IV bolus or infusion over 50 minutes. Variables monitored included mean arterial blood pressure (MAP), leukocyte (WBC) count, plasma glucose and lactate concentrations and clinical status. All LPS-treated calves displayed similar clinical signs within one hour. Dose-dependent differences in response to LPS among groups became evident over time. Substantial dose-dependent changes in attitude, appetite, mucous membrane character, capillary refill time, MAP, plasma glucose and lactate concentrations, and WBC count were noted in LPS-treated calves. Higher doses of LPS induced a more prolonged clinical response and significantly (p < 0.05) greater hypotension, lacticemia and hypoglycemia. While dose altered the response to endotoxin, the method of administration had no overall effect on the variables measured.

Vasopressin: its role in antipyresis and febrile convulsion

When pyrogenic substances are injected intravenously into experimental animals, a sequence of events is set in motion which involves the hypothalamus and perhaps other portions of the diencephalon to produce a febrile response. We now present evidence that the brain produces its own endogenous antipyretic which may serve as a means of controlling the extent of the fever. When arginine vasopressin is perfused through the lateral septal area of the hypothalamus of the sheep, fever is suppressed. Vasopressin alone does not lower normal body temperature when perfused through this region of the brain. In addition, evidence is provided to indicate that vasopressin is released within the lateral septal area during the febrile response. It is concluded that, in fever, arginine vasopressin may be released in the lateral septal area of the brain and serve as an endogenous antipyretic. Results indicate that, following an initial application of vasopressin into the brain itself, a subsequent similar administration of vasopressin produces seizure-like activity. Therefore, it is suggested that this release of arginine vasopressin may contribute to the production of febrile convulsion.

Enzymatic deacylation of the lipid A moiety of Salmonella typhimurium lipopolysaccharides by human neutrophils

Lipid A, the toxic moiety of Gram-negative bacterial lipopolysaccharides (endotoxins), is a glucosamine disaccharide to which fatty acid and phosphate residues are covalently attached. Recent studies of Salmonella lipid A indicate that 3-hydroxytetradecanoic acid (3-OH-14:0) residues are directly linked to the glucosamine backbone and the nonhydroxylated fatty acids (principally dodecanoic and tetradecanoic acids) are esterified to the hydroxyl groups of some of the 3-OH-14:0 molecules. We report here that the granule fraction of human neutrophils contains one or more enzymes that partially deacylate Salmonella typhimurium lipid A by removing the nonhydroxylated fatty acids, leaving almost all of the 3-OH-14:0 residues linked to glucosamine. The available evidence suggests that similar reactions also occur in living neutrophils that ingest lipopolysaccharides by antibody-dependent phagocytosis.

Evaluation of the Limulus test for endotoxemia in neonates with suspected sepsis

A simplified test for endotoxemia was evaluated in parallel with 198 blood cultures from 115 neonates requiring transitional or intensive care. The Limulus assay disclosed endotoxemia in seven of eight patients with gram-negative bacteremia tested on one or two occasions. It was not specific for bacteremia, especially during the first week of life, when 37 of 112 tests from nonbacteremic infants (33%) were positive. In older infants, positive tests were obtained in only ten of 55 without bacteremia (18%) (P less than 0.07), six of whom had necrotizing enterocolitis as the likely source of endotoxemia. Gram-negative bacteremia existed in 5% of infants (two of 39) less than or equal to 7 days with positive tests and in 37% of older infants (six of 16) (P less than 0.01). Endotoxemia appears to be frequent among infants appearing to have sepsis and may contribute to neonatal morbidity. The Limulus assay may be a useful diagnostic test for coliform bacteremia and necrotizing enterocolitis beyond the first week of life.

Nature, type of linkage, quantity, and absolute configuration of (3-hydroxy) fatty acids in lipopolysaccharides from Bacteroides fragilis NCTC 9343 and related strains

The main fatty acids present in lipopolysaccharides from Bacteroides fragilis NCTC 9343 were identified as 13-methyl-tetradecanoic, D-3-hydroxypentadecanoic, D-3-hydroxyhexadecanoic, D-3-hydroxy-15-methyl-hexadecanoic, and D-3-hydroxyheptadecanoic acids. Of these, 13-methyl-tetradecanoic acid is exclusively ester bound, and 3-hydroxy-15-methyl-hexadecanoic acid is exclusively involved in amide linkage. The other 3-hydroxy fatty acids are both ester and amide bound. All 3-hydroxy fatty acids possess the D configuration, and the 3-hydroxyl group of ester-linked 3-hydroxy fatty acids is not substituted. Lipopolysaccharides of related Bacteroides species (B. thetaiotaomicron, B. ovatus, B. distasonis, and B. vulgatus) showed a fatty acid spectrum with both similar and distinct features compared to that of B. fragilis lipopolysaccharides.

Potentiation of tumour growth by endotoxin in serum from syngeneic tumour-bearing mice

The subcutaneous growth of 2 antigenically distinct syngeneic methylcholanthrene-induced murine fibrosarcomas, designated H1 and H7, were significantly augmented by the concomitant administration of E. coli endotoxin (LPS). Amounts as little as 0.2 micrograms i.p. potentiated tumour growth. The weakly antigenic tumour, H1, was more susceptible to provocation by LPS than the more strongly antigenic H7. Maximum provocation of H1 tumour growth occurred when LPS was injected 1 day before the administration of 5000 tumour cells. In contrast, significant anti-tumour resistance resulted if LPS was administered 6 days before the inoculation of tumour cells. Preliminary evidence indicates that low doses of LPS can facilitate the "sneaking through" phenomenon. Enhancement of tumour growth could not be demonstrated with sera or plasma from tumour-bearing mice, unless the samples were contaminated with endotoxin. The results illustrate the importance of excluding endotoxin from solutions used in studies of experimental tumours.

Detection of Pseudomonas aeruginosa antigenemia in granulocytopenic rabbits by radiommunoassay

We assessed the ability of a solid-phase radioimmunoassay, modified to allow antigen detection in serum, to detect circulating antigens in granulocytopenic rabbits with Pseudomonas aeruginosa bacteremia. In vitro experiments with Pseudomonas lipopolysaccharide indicated that treatment of serum-lipopolysaccharide mixtures with heat, chloroform, or heparin improved the sensitivity for detecting lipopolysaccharide 8- to 16-fold. Chloroform treatment permitted antigen detection in serum or plasma of bacteremic rabbits in which antigen could be detected poorly or not at all in untreated specimens. However, chloroform-treated specimens occasionally caused dissolution of plastic tubes, resulting in nonspecific binding of 125I-labeled anti-Pseudomonas immunoglobulin G. Heating sera at 56 degree C for 30 min improved antigen detection both in both in lipopolysaccharide-serum mixtures and in bacteremic rabbits. Antigen was detected in the heated serum or plasma of 20% of 20 culture-positive granulocytopenic rabbits, none of 15 culture-negative granulocytopenic rabbits, and none of 38 normal rabbits. Antigen was detected in none of 15 rabbits with 2 to 300 colony-forming units of P. aeruginosa per ml of blood and in 4 of 5 rabbits with > 10(3) colony-forming units per ml. We conclude that circulating antigens are present in the blood of rabbits with high-level P. aeruginosa bacteremia and that these antigens can be detected by solid-phase radioimmunoassay. Further improvements in assay sensitivity will be required to detect antigens, if present, in animals with lower levels of P. aeruginosa bacteremia.

Endotoxin-induced uveitis in the rat

Experimental studies of ocular inflammation induced by endotoxin have been performed almost exclusively in rabbits. Although the rat has been considered refractory to both the systemic and local effects of endotoxin, the present study has shown that intravitreal injection of endotoxin evoked a characteristic acute inflammatory response which was reproducible and dose-dependent. In addition, a consensual ocular response in the control eye occurred which was less severe but also dose-dependent. Preliminary investigations support the view that consensual responses of this nature may be mediated by a nervous reflex are mechanism. Sequential histological analysis revealed a marked polymorphonuclear cell infiltration of most ocular tissues in the early stages, while mononuclear cells predominated after 3 days. Widespread intravascular microthrombi were also observed, particularly in the ciliary vessels. Recovery, however, was usually complete by 7 days.

Biological and chemical characterization of endotoxin from Capnocytophaga sputigena

An endotoxin was isolated from Capnocytophaga sputigena strain 4 by a modification of the hot phenol-water method. The extraction procedure yielded a lipopolysaccharide which accounted for approximately 1.5% of the dry weight of the cells. The material was composed of 18.6% lipid (as C(15) fatty acid), 46.5% neutral sugar including 9.6% hexose, 18.3% 6-deoxy sugar, 1.0% 2-keto-3-deoxy sugar, and 4.8% heptose. Hexosamine, protein, and phosphorus were found in quantities amounting to 9.0, 2.9, and 2.0% of the dry weight, respectively. No pentose or nucleic acid was detected. Acid hydrolysis resulted in the release of the constituent sugars and the formation of an insoluble precipitate. The lipopolysaccharide was tested for numerous biological activities characteristic of endotoxins. The pyrogenicity was relatively low; the fever index 40 was 17 mug, and 10 mug was required to give the characteristic biphasic fever response. The toxicity of the extract was very low, with a 50% chicken embryo lethal dose of 15.6 mug and a 50% mouse embryo lethal dose of greater than 8 mg. Similarly, the C. sputigena endotoxin had modest effects on leukocytes when compared with endotoxin standards from other organisms. The extract exhibited little or no mitogenicity when tested on mouse spleen lymphocytes. It was not toxic to human peripheral polymorphonuclear leukocytes and caused the release of only a small (13%) portion of lysosomal enzymes. Although the C. sputigena lipopolysaccharide caused significant activation of mouse peritoneal macrophages, the dose required was twice that of an Escherichia coli endotoxic standard. However, the Limulus amoebocyte lysate clotting activity of the lipopolysaccharide was comparable to that of an Serratia marcescens lipopolysaccharide standard, and passive hemagglutination tests revealed that 1 mug of the lipopolysaccharide was capable of sensitizing 1 ml of a 2% sheep erythrocyte suspension for agglutination with an antiserum prepared against C. sputigena whole cells.

Immunotherapy of guinea pig line 10 hepatoma with nonliving BCG cells in aqueous medium

Killed BCG cells suspended in 1.5% carboxymethylcellulose cured guinea pigs with established line 10 tumors in a high percentage of cases. The bacterial preparation of BCG in carboxymethylcellulose displayed a stronger tumor regressive activity and the process of healing was accelerated when endotoxin from a rough (Re) strain of Salmonella typhimurium was added to the BCG bacilli.

Characteristics of lipid A-protein complex from endotoxin of Shigella dysenteriae type 1 (S and R strains)

Mild acetic acid hydrolysis of endotoxin (lipopolysaccharide-protein complex) of Shigella dysenteriae type 1 (S and R forms) yielded a lipid A-protein complex that consisted of amino acids, fatty acids, and sugar and, in terms of chemical composition, displayed no marked differences between the S and R forms. Its protein portion (53 to 56%) consisted of at least 16 amino acids. In the fatty acid portion (14 to 18%), myristic, 3-hydroxymyristic, palmitic, and stearic acids accounted for 50%. The sugar portion (10 to 12%) consisted solely of glucosamine. The remainder was unidentified substances, most of which contained phosphorus. Lipid A-protein complexes derived from both S and R forms were not toxic for mice in doses up to 1,000 microgram/mouse, but their Linulus test activity had increased considerably as compared with the starting lipopolysaccharide-protein complex material: from 10(-6) to 10(-10--10(-12) mg/ml. The lipid A-protein complexes were readily soluble in a water solution of triethylamine, in dimethyl sulfoxide, and in pyridine.

Experimental induction of an immunohaemolytic anaemia in the chicken with Salmonella gallinarum endotoxin

The possibility that the extreme refractoriness of the chicken to injected endotoxin would permit the buildup of sufficient free endotoxin in the circulation to immunologically modify the erythrocytes in vivo and thereby cause them to be eliminated from the circulation was investigated. It was shown that a moderately severe immunohaemolytic anaemia accompanied by a mild spenomegaly could be induced in chickens by single (large) or multiple injections of Salmonella gallinarum endotoxin (SgE). Varying degrees of reticulocytosis, with corresponding decreases in haemoglobin and haematocrit values, were observed from the tenth day after the injection of the SgE. All the injected animals also showed significant immune responses to SgE, peak haemagglutinin titres occurring coincidentally with the peaks of the haemolytic episodes. A similar injection schedule in specifically immune chickens also showed the anaemia appearing much earlier, persisting longer and being much more profound in intensity. It is considered that the in vivo erythrocyte sensitization induced by SgE injection initiates the erythrocytic changes observed and that the underlying mechanism responsible for the subsequent development of the haemolytic anaemia is immunologically mediated.

Bacterial lipopolysaccharides as inducers of disease resistance in tobacco

The cell wall component of Pseudomonas solanacearum that induces disease resistance in tobacco was highly heat stable at neutral or alkaline pH but highly labile at acid pH. Activity was unaffected by nucleases and proteases but destroyed by a mixture of beta-glycosidases. Washing of bacterial cell walls released a lipopolysaccharide (LPS) fraction with high inducer activity. Purified LPS, extracted by a variety of procedures from whole cells, isolated cell walls, and culture filtrates of both smooth and rough forms of P. solanacearum, induced disease resistance in tobacco at concentrations as low as 50 microgram/ml. The LPS from the non-plant pathogens Escherichia coli B, E. coli K, and Serratia marcescens was also active. Cell wall protein, free phospholipid, and nucleic acids were not necessary for activity. Moreover, since LPS from rough forms was active, the O-specific polysaccharide of the LPS was not required for activity. Hydrolysis of the remaining core-lipid A linkage or deacylation of lipid A destroyed inducer activity. When injected into tobacco leaves, purified LPS attached to tobacco mesophyll cell walls and induced ultrastructural changes in the host cell similar to those induced by attachment of whole heat-killed bacteria.

Relationship of structure to function in bacterial endotoxins. IX. Differences in the lipid moiety of endotoxic glycolipids

Chemical, immunochemical, chromatographic, and endotoxic properties of five chromatographically pure glycolipids were compared. The preparations were extracted by chloroform-methanol from three Escherichia coli, one Salmonella minnesota, and one S. typhimurium Re heptoseless mutant strains. The local Shwartzman skin assay, the nonspecific resistance-enhancing effect, and the Limulus assays could not distinguish among the five glycolipids, all five being active in all three assays. Significant differences could be seen when the tumor resistance-enhancing effect of the glycolipids in mice was compared with the nonspecific TA3-Ha murine mammary adenocarcinoma growing in ascites form. Even greater variation was observed in the capacity of the preparations to enhance the nonspecific resistance of mice to virulent S. typhi 0901 infections. The data show that the five glycolipids are quite dissimilar in their biological effects. Similarly, thin-layer chromatography and molecular ratio determinations showed that differences exist in the chemical structure of the glycolipids. Accordingly, we claim that not only the polysaccharide but the lipid moiety as well may vary in various gram-negative endotoxin preparations.

Cerebrospinal fluid endotoxin concentrations in gram-negative bacterial meningitis

The limulus lysate assay was utilized to detect and quantitate endotoxin in cerebrospinal fluid from 232 patients with suspected meningitis. The assay was positive in initial specimens of CSF from all 86 patients with gram-negative bacterial meningitis and was uniformly negative in the remaining 146 patients with a variety of infectious and noninfectious processes. Endotoxin concentrations in initial specimens of CSF from patients with gram-negative meningitis ranged from 4 to 2,000 ng/ml. No correlation between initial CSF levels of endotoxin and initial clinical or laboratory variables of infection was noted. With antibiotic therapy, CSF concentrations of endotoxin fall rapidly to undetectable levels after five days.

Effect of lipopolysaccharide and lipid A on mouse liver pyruvate kinase activity

Several investigators have reported lipid A as the biologically active unit in the lipopolysaccharide (LPS) molecule. To determine if lipid A was responsible for the reported increases in pyruvate kinase, mice were injected with endotoxin from Salmonella typhimurium SR-11, the Re mutant of Salmonella minnesota R 595, and lipid A-bovine serum albumin conjugate. The livers were homogenized and the activity of pyruvate kinase was measured. Similar increases in enzyme were obtained with all three preparations. These data imply that the lipid portion of the LPS molecule was responsible for alterations in host enzyme activity. To further determine if the lipid portion was the active unit, a lipid-degraded endotoxin (endotoxoid) prepared by potassium methylate treatment was inoculated into mice. An initial increase in liver pyruvate kinase activity was observed with all preparations. The marked increase observed at 16 h with the native product and lipid A conjugate was not obtained with the endotoxoid. These experiments extend and confirm previous observations that lipid A is responsible for the effects associated with LPS. Animals tolerant to endotoxin from S. typhimurium SR-11 were challenged with endotoxin from the Re mutant. A significant increase in pyruvate kinase activity was not obtained, suggesting that anti-O antibodies are not important in the development of tolerance.

An endotoxin-induced serum factor that causes necrosis of tumors

In studying "hemorrhagic necrosis" of tumors produced by endotoxin, it was found that the serum of bacillus Calmette--Guerin (BCG)-infected mice treated with endotoxin contains a substance (tumor necrosis factor; TNF) which mimics the tumor necrotic action of endotoxin itself. TNF-positive serum is as effective as endotoxin itself in causing necrosis of the sarcoma Meth A and other transplanted tumors. A variety of tests indicate that TNF is not residual endotoxin, but a factor released from host cells, probably macrophages, by endotoxin. Corynebacteria and Zymosan, which like BCG induce hyperplasia of the reticulo-endothelial system, can substitute for BCG in priming mice for release of TNF by endotoxin. TNF is toxic in vitro for two neoplastic cell lines; it is not toxic for mouse embryo cultures. We propose that TNF mediates endotoxin-induced tumor necrosis, and that it may be responsible for the suppression of transformed cells by activated macrophages.

Chemical structure and biological activity of endotoxins (lipopolysaccharides) and lipid A

Lipopolysaccharides (endotoxins) of gram-negative bacteria consist of two components with distinct physico-chemical character: a heteropolysaccharide and a covalently linked lipid, termed lipid A. Chemically, lipid A is made up of acylated glucosamine disaccharides, which are interlinked by pyrophosphate bridges. Lipid A represents the toxic center of lipopolysaccharides. In rabbits, lipid A also induces pyrogen tolerance as well as pyrogen cross-tolerance. Fever tolerance can be passively transferred with serum from rabbits immunized with lipid A. The protective power of lipid A antiserum, however, is only expressed in amimals which have been pretreated with lipid A or lipopolysaccharide, indicating that other than humoral factors, perhaps cellular, also participate in endotoxin tolerance. Lipid A antiserum also prevents the local Shwartzman reaction in rabbits. The possible potency of lipid A antiserum to prevent other endotoxin effects such as lethal shock is presently investigated.

Potentiation of endotoxin-induced consumptive coagulopathy by lead acetate administration

Since chickens are naturally deficient in several clotting factors normally present in mammalian sera, the ability of lead acetate (PbAc(2)) to sensitize 11-day-old chicks to endotoxin was compared with its ability to sensitize rats. It was found that, although the chicks could tolerate only relatively low doses of PbAc(2), even those doses would produce a greater than 200-fold sensitization to the endotoxin in rats, as compared with little sensitization in the chicks. By using larger doses of PbAc(2), known to maximally sensitize rats to endotoxin, the effect of PbAc(2) sensitization on whole-blood clotting times, platelet counts, plasma factor V and VIII activities, and the appearance of fibrin degradation products was evaluated. It was found that animals treated with lethal doses of endotoxin but no PbAc(2) showed varying degrees of consumptive coagulopathy. On the other hand, the injection of minute quantities of endotoxin into PbAc(2)-sensitized rats invariably resulted in disseminated intravascular coagulation, apparently via a complete activation of the intrinsic pathway. It is concluded that the site of PbAc(2) sensitization to endotoxin is in the blood, and most probably at the level of Hageman factor activation.

Disaggregation of endotoxin by isolated rat liver plasma membranes and lack of product binding

The interaction of bacterial endotoxin with isolated rat liver cell membranes was studied to determine the extent and nature of any binding. Serratia marcescens endotoxin was incubated with isolated rat liver plasma membranes for varying periods of time at 37 C, and this mixture was then centrifuged through a discontinous sucrose density gradient. The membranes banded primarily at the 35 to 45% sucrose interface, whether or not they had been incubated with endotoxin. The endotoxin distributed itself throughout the gradient except when incubated with membranes, in which case it failed to sediment. This membrane-induced alteration in sedimentation could be prevented by heat inactivation of the membranes, and was found to be pH, time, temperature, and concentration dependent. There was neither associated degradation of the endotoxin, as measured by molecular sieve chromatography, nor loss in toxicity, as determined in lead-sensitized rats. These observations are consistent with an enzymatic disaggregation of the endotoxin by membranes and could represent a step in the uptake of the endotoxin by the reticuloendothelial system. No significant binding of this disaggregated endotoxin to the membranes could be detected, either after gradient separation or after repeated washing. This finding strongly suggests that, at least in cells that are active in the uptake of endotoxin, membrane-endotoxin interactions may be relatively transitory in nature, and that firm adherence to such membranes may not be a central feature of endotoxin toxicity.

Degradative effect of phenol on endotoxin and lipopolysaccharide preparations from Serratia marcescens

It has been established that the well-known deproteinizing action of hot 45% aqueous phenol on whole cells or isolated and purified endotoxin of Serratia marcescens 08 is caused by the cleavage of a phenol-sensitive linkage within the lipid moiety. As a result of this degradation, both the lipopolysaccharide and simple protein fragments retained a part of the lipid moiety. Although not proceeding at the same fast rate as the cleavage of the lipid moiety, such phenol treatment also caused a partial hydrolysis of the O-specific side chain and ester-bound fatty acids. Hydrolysis of the O-specific side chain accounted for 5% of the lipopolysaccharide and that of ester-bound fatty acids accounted for 11% of the total fatty acid content after 60 min of treatment. It is suggested that the presence of these degradation products is one of the main causes of the heterogeneity of endotoxin and lipopolysaccharide preparations.

Cardiovascular and metabolic effects of whole or fractionated gram-negative bacterial endotoxin in the unanesthetized Rhesus monkey

Rhesus monkeys were infused with endotoxin lipopolysaccharide (LPS) (10 mg/kg [LPS 10 ] or 2.5 mg/kg [LPS 2.5 ]) or with fractions of LPS containing 6.3% lipid (PS 1 ) or 0.5% lipid (PS 2 ) (2.5 mg/kg). Systemic and regional hemodynamics, leukocyte counts, blood gases, pH, and plasma bradykinin concentration were measured. Monkeys receiving LPS 10 , LPS 2.5 , or PS 1 became hypotensive (mean blood pressure -37 ± 10 mm Hg) and had decreased peripheral vascular resistance (-10% to -24% of the base line), compensated metabolic acidosis, and elevated plasma bradykinin concentrations (14 ± 6 ng/ml) 2 hours after infusion. Vasodilation occurred in coronary, hepatic, and splanchnic vasculature; vasoconstriction occurred in the spleen. Cardiac output was diverted from muscle to viscera. Monkeys receiving PS 2 were normotensive with elevated peripheral vascular resistance (+46%) and no measurable plasma bradykinin concentration. By 6 hours, marked elevation of peripheral vascular resistance developed in monkeys given LPS 10 (+113%) and LPS 2.5 (+57%). Monkeys receiving PS 1 returned to base-line values, but monkeys receiving PS 2 remained unchanged. Leukopenia (-50% to -65%) was persistent only in monkeys receiving LPS or PS 1 . Toxicity of LPS apparently depends on the lipid portions of the molecule. Vasodilation and bradykinin generation are correlated with persistent granulocytopenia. Late toxicity may be independent of early cardiovascular events.

Pyrogenicity and immunogenicity of lipid A complexed with bovine serum albumin or human serum albumin

The lipid A component of bacterial lipopolysaccharides (endotoxins), when complexed to bovine serum albumin (BSA) or human serum albumin (HSA), was shown to be a potent pyrogen. Furthermore, rabbits could be protected against endotoxin fever by immunization with both lipid A.BSA and lipid A.HSA complexes. The results presented in this paper show that lipid A is responsible for the pyrogenic activity of endotoxins and their ability to induce pyrogenic immunity.

Protection Against Meningococcal Challenge Afforded Mice After Immunization with Typhoid-Paratyphoid Vaccine USP

Mice immunized with typhoid-paratyphoid vaccine USP were found to be protected when challenged with serological groups A, B, and C of Neisseria meningitidis . Mice immunized with this vaccine both 14 and 7 days prior to challenge were protected against mean lethal doses (LD 50 ) of 5,220 and 1,151 of groups A and B, respectively, and in two separate experiments they were protected against 3,568 and 268 LD 50 of group C. Mice immunized four or more times on successive days prior to challenge were also protected. They demonstrated tolerance and survived a much larger LD 50 challenge than mice immunized by any other immunization schedule. Mice immunized once or twice anytime within 7 days prior to challenge were not protected and thus failed to exhibit nonspecific resistance. Serum antibody probably was responsible for the protection afforded mice immunized 14 and 7 days prior to challenge. However, this was not demonstrated conclusively.