Preparation and host-reactive properties of endotoxin with low content of nitrogen and lipid

Extraction and Electrophoretic Analysis of Bacterial Lipopolysaccharides and Outer Membrane Proteins

Lipopolysaccharides (LPS) (or lipooligosaccharides [LOS], which lack the O-antigen side chains characteristic of LPS), and outer membrane proteins (OMP) are major cell-surface molecules in the outer membrane (OM) of gram-negative bacteria. The LPS is responsible for causing endotoxic shock in infected hosts and, in conjunction with some OMPs, provides protection to the bacterium against host innate immune defenses and attachment to host cells. Electrophoretic analysis can provide valuable information regarding the size, number, and variability of LPS/LOS and OMP components between bacterial strains and mutants, which aids in understanding the basic biology and virulence factors of a particular species. Furthermore, highly purified extracts are normally not required if only electrophoretic analysis is to be done, and various methods have been established for such procedures. Here, we review ameliorated procedures for fast and convenient extraction of LPS/LOS and protein-enriched outer membranes (PEOM) for optimal electrophoretic resolution. Specifically, we will describe the phenol-based micro-method for LPS/LOS extraction, a differential extraction procedure with sodium lauryl sarcosinate for PEOM, and gel preparation for electrophoretic analysis of LPS/LOS samples in detail. Graphic abstract: Workflow for the preparation and analysis of LPS/LOS and PEOM.

Ruminal Lipopolysaccharides Analysis: Uncharted Waters with Promising Signs

Simple Summary

Lipopolysaccharide (LPS) is a component of the outer membranes of Gram-negative bacterial cell wall made of three covalently linked regions: the O-antigen, the core oligosaccharide, and the endotoxin lipid A moiety, which carries the endotoxic activity of LPS. Among Gram-negative bacteria there is significant structural diversity in the lipid A region. Specifically, the number of lipid A acyl chains directly correlates with the ability to induce cytokine production whereas the hexa-acylated forms usually are the most immunostimulant ones, contrary to penta- or tetra- acylated forms that result in weak inflammatory host responses. Ruminal bacteria are predominantly Gram-negative, and their respective LPS presence has been suggested to be associated with ruminal acidosis, a metabolic disorder of cattle with negative effects on health and production. In the rumen, the most predominant phylum is Bacteroidetes which exhibit weak host immunological response compared to widely used Escherichia coli LPS. This review aims to present accumulated knowledge regarding ruminal LPS, pointing out the differences in ruminal LPS compared to widely known LPS, and introduce hypotheses that could contribute to further understanding and planning strategies to tackle ruminal acidosis.

Abstract

The objective of this review is to present the need for the development of a comprehensive ruminal lipopolysaccharide (LPS) extraction, purification and analysis protocol and state hypotheses that could contribute to planning novel strategies against ruminal acidosis. Lipopolysaccharide is an immunostimulatory molecule of Gram-negative bacterial outer membranes and has been reported to contribute to ruminal acidosis in cattle. Bacterial death and lysis are normal processes, and thus LPS is normally present in ruminal fluid. However, ruminal LPS concentration is much greater during subacute ruminal acidosis (SARA). Contrary to the widely known LPSs, ruminal LPS seems to be composed of a variety of LPS chemotypes that may interact with each other resulting in an LPS “mixture”. Hypotheses regarding the influence of each specific ruminal bacterial specie to innate immunity during SARA, and the representativeness of the exclusive use of the Escherichia coli LPS to rumen epithelial tissue challenges, could expand our knowledge regarding SARA. In addition, possible correlation between the monomeric Toll-like Receptor 4 (TRL4) and the antagonistic penta-acylated lipid A of LPS could contribute to novel strategies to tackle this nutrition disorder.

A scalable method for O-antigen purification applied to various Salmonella serovars

The surface lipopolysaccharide of gram-negative bacteria is both a virulence factor and a B cell antigen. Antibodies against O-antigen of lipopolysaccharide may confer protection against infection, and O-antigen conjugates have been designed against multiple pathogens. Here, we describe a simplified methodology for extraction and purification of the O-antigen core portion of Salmonella lipopolysaccharide, suitable for large-scale production. Lipopolysaccharide extraction and delipidation are performed by acetic acid hydrolysis of whole bacterial culture and can take place directly in a bioreactor, without previous isolation and inactivation of bacteria. Further O-antigen core purification consists of rapid filtration and precipitation steps, without using enzymes or hazardous chemicals. The process was successfully applied to various Salmonella enterica serovars (Paratyphi A, Typhimurium, and Enteritidis), obtaining good yields of high-quality material, suitable for conjugate vaccine preparations.

Purification and characterization of lipopolysaccharides

Lipopolysaccharides are the major components on the surface of most Gram-negative bacteria, and recognized by immune cells as a pathogen-associated molecule. They can cause severe diseases like sepsis and therefore known as endotoxins. Lipopolysaccharide consists of lipid A, core oligosaccharide and O-antigen repeats. Lipid A is responsible for the major bioactivity of endotoxin. Because of their specific structure and amphipathic property, purification and analysis of lipopolysaccharides are difficult. In this chapter, we summarize the available approaches for extraction, purification and analysis of lipopolysaccharides.

Subcellular Localization of Salmonella enteritidis Endotoxin in Liver and Spleen of Mice and Rats

Salmonella enteritidis(14)C-endotoxin was recovered predominantly from the nuclear and mitochondrial subcellular fractions of livers and spleens of mice and rats, 3.5 hr and 3 days after intravenous administration. Of the recovered radioactivity, 10 to 20% was present in the liver mitochondrial fraction as high-molecular-weight, biologically active material, suggesting the presence of intact endotoxin. Autoradiographic studies demonstrated nuclear and cytoplasmic labeling in the liver and at least nuclear label in spleen cells. The resistance of rats, as compared to mice, to the induction of amyloidosis does not appear to be based on a difference in subcellular localization of endotoxin within the reticuloendothelial system.

Impact force as a possible cause of mechanical transfer of bacteria to the interior of the cow's teat

Using bacterial endotoxin as a tracer material, it has been shown that a jet of liquid impinging on the end of the teat for 1 min after milk flow had ceased during machine milking could force material past the barrier of the streak canal. Positive results were obtained when the maximum pressure at the centre of the impact area was about 0·25 bar, with a considerably higher frequency of positives at 0·3–0·5 bar. It seems possible that such impact pressures might occur during milking and cause transfer of infective material to the teat sinus. Impact force could arise when milk returned to the teatcup liner as the result of local or general conditions of instability in the milking machine vacuum.

Isolation and characterization of lipopolysaccharides

Lipopolysaccharide (LPS) is the signature glycolipid isolated from almost all Gram-negative bacteria. LPSs are well known for their ability to elicit the release of cytokines from eukaryotic cells including macrophages, neutrophils, and epithelial cells. LPS can be isolated free of contaminating nucleic acids and proteins by various techniques. In this review, we outline approaches for the isolation and preparation of LPSs for structural studies as well as preparation of very highly purified material for biological studies. Methods are also provided for the analysis of the purity and the structural composition of the LPSs. Finally, three methods for the isolation of lipid A are described.

Immunological role of Brucella abortus cell walls

Foster, John W. (University of Georgia, Athens) and Edgar Ribi. Immunological role of Brucella abortus cell walls. J. Bacteriol. 84:258-268. 1962-Cell walls and protoplasm were prepared from organisms disrupted in a refrigerated pressure cell. Cell walls were purified by sedimentation in a linear glycerol gradient. Antigens capable of protecting mice against infection with Brucella abortus and of reacting with antiserum prepared against whole cells were present chiefly in the cell wall; substances lethal to mice and responsible for primary inflammation of rabbit skin were also associated with the cell wall. Limited activity of protoplasm in these biological tests may or may not be due to contamination with cell-wall material. A substance extracted from whole cells with aqueous ether possessed an immunizing potency superior to that of killed whole cells or cell walls.

Influence of the physical state of endotoxic preparations on dermal toxicity

Roberson, Bob S. (University of North Carolina, Chapel Hill) and William J. Cromartie. Influence of the physical state of endotoxic preparations on their dermal toxicity. J. Bacteriol. 84:882-887. 1962.-Studies were performed with various preparations of endotoxin from Escherichia coli to test for a possible relation between the physical state or degree of aggregation of the toxin and dermal toxicity. Endotoxic fractions were prepared by enzymatic and physical dissolution of cell walls, phenol extraction, and ether extraction. A comparison of the toxic effects of the different preparations after a single intradermal injection into rabbits demonstrated that the degree and duration of the inflammatory response was influenced significantly by the physical state of the preparation. In addition, the least active material, the aqueous ether extract, was treated so as to yield three preparations differing only in the degree of aggregation. Dermal titration of these preparations suggests that a departure from an optimal range of particle size results in a diminished capacity of endotoxin to induce the acute and protracted manifestations of dermal response.

Biological properties of parent endotoxins and lipoid fractions, with a kinetic study of acid-hydrolyzed endotoxin

The biological potencies of a number of lipid fractions separated from endotoxins by acid hydrolysis, including the material known as lipid A, were determined in parallel with those of their parent endotoxins, employing bio-assays based on the following dose-related host responses: fever, resistance to infection, tumor damage, primary inflammation of skin, and lethality. Without exception, lipid fractions dispersed by detergents exerted less than 1 per cent of the biological activity of the potent endotoxins from which they were derived. A study was made of the rate at which biologic activities diminished in relation to the release of bound lipid during progressive hydrolysis of Salmonella enteritidis endotoxin with dilute acid. Each of the five assays for endotoxin revealed that biological activity had been reduced to negligible proportions prior to any significant liberation from the endotoxin of water-insoluble firmly bound lipid. The major pharmacological activity of endotoxins, therefore, is acid-labile and cannot be accounted for in isolated lipids. This conclusion is also supported by the finding that lipids with activity similar to that of lipid A could be obtained by non-hydrolytic methods without diminishing the potency of the parent endotoxins.

ORIGIN AND PROPERTIES OF NATURALLY OCCURRING HAPTEN FROM ESCHERICHIA COLI

Anacker, R. L. (National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Mont.), R. A. Finkelstein, W. T. Haskins, M. Landy, K. C. Milner, E. Ribi, and P. W. Stashak. Origin and properties of naturally occurring hapten from Escherichia coli. J. Bacteriol. 88:1705-1720. 1964.-Haptens found in preparations of endotoxin and in fractions of disrupted cells, particularly one termed "native hapten," which appeared to be associated with the protoplasm of cells rather than with cell walls, have been further investigated with a view to establishing their origin and composition as well as their host-reactive properties. For this purpose, cells from a smooth strain of Escherichia coli O111:B4 were either extracted directly or disrupted and separated into cell-wall and protoplasmic fractions. Haptens were obtained by gel filtration of endotoxins, by trichloroacetic acid extraction of protoplasm, and by a mild acid hydrolysis of endotoxin. Several lines of evidence indicated that native hapten originated in the protoplasm rather than by autolysis or degradation of cell-wall endotoxin during procedures employed in disruption. In gel diffusion and quantitative precipitin tests, no hapten was identical with endotoxin, but native hapten was serologically the most complex of the haptens and precipitated the most antibody. Native and acid haptens, on a weight basis, fixed about 1% of the quantity of complement fixed by homologous endotoxin. Haptens did not stimulate the production of antibodies in mice or rabbits and did not elicit endotoxic host reactions. Chemically, native hapten differed from endotoxin and from acid hapten in that it lacked phosphorus, heptose, long-chain fatty acids, and 2-keto-3-deoxyoctonate. These substances did not appear to be determinants of antigenic specificity, but they may provide necessary bonds for assembling hapten-like units into fully antigenic and toxic macromolecules.

TOXIC LYSOLIPOID: ISOLATION FROM PSEUDOMONAS PSEUDOMALLEI

A lipoid of low molecular weight, isolated from the supernatant fluid of cultures of Pseudomonas pseudomallei, killed mice, but not rabbits, in doses comparable to those of the homologous lipopolysaccharide and also lysed sheep erythrocytes. In rabbits this lipoid failed to elicit primary dermal lesions, to prepare the skin for the local Schwartzman reaction, or to induce antibody formation.

NATURE OF THE ENDOTOXIN-INACTIVATING PRINCIPLE IN GUINEA-PIG LIVER

Corwin, L. M. (Walter Reed Army Medical Center, Washington, D.C.), and W. E. Farrar, Jr. Nature of the endotoxin-inactivating principle in guinea-pig liver. J. Bacteriol. 87:832-837. 1964.-Guinea-pig liver preparations inactivate Serratia marcescens endotoxin as assayed in chick embryo. The activity is optimal at pH 6.5 to 7.0 and 8.5 to 9.0. Mitochondria and the supernatant fraction containing microsomes possess activity. Mitochondria are only active at the acid pH optimum. The activity of acetone powder extracts of mitochondria is enhanced by adenosine triphosphate and nicotinamide adenine dinucleotide, whereas the mitochondria themselves are also activated by malate. It was concluded that the enzymes which inactivate endotoxin involve fatty acid activation and oxidation. Such a finding suggests that the lipid moiety of endotoxin is required for toxicity.

Characterization of Brucella abortus and Brucella melitensis native haptens as outer membrane O-type polysaccharides independent from the smooth lipopolysaccharide

Brucella native haptens (NHs) extracted with hot water from smooth (S)-type B. abortus and B. melitensis were purified to high levels of serological activity and compared with the polysaccharide obtained by acid hydrolysis (PS) of the S lipopolysaccharide (S-LPS). By 13C nuclear magnetic resonance analysis, NHs showed the spectrum of a homopolymer of alpha-1,2- or alpha-1,2- plus alpha-1,3-linked 4-formamido-4,6-dideoxy-D-mannose (N-formylperosamine) previously reported for the LPS O chain. However, while PS contained up to 0.6% 3-deoxy-D-manno-2-octulosonate, this LPS-core marker was absent from NH. High performance liquid chromatography and thin-layer chromatography showed heterogeneity in NH purified from whole cells but not in PS. By immunoprecipitation, polysaccharides indistinguishable from NH were demonstrated in extracts obtained with phenol-water, saline at 60 degrees C, and ether-water treatments, and none of these treatments caused S-LPS hydrolysis detectable with antibodies to the O chain and lipid A. Two lines of evidence showed that NH was in the cell surface. First, NH became biotinylated when B. abortus live cells were labelled with biotin-hydrazide, and the examination of cell fractions and electron microscopy sections with streptavidin-peroxidase and streptavidin-coloidal gold, respectively, showed that labelling was extrinsic. Moreover, whereas only traces of NH were found in cytosols, the amount of NH was enriched in cell envelopes and in the outer membrane blebs spontaneously released by brucellae during growth. Interactions between NH and S-LPS were observed in crude cell extracts, and such interactions could be reconstituted by using purified NH and LPS. The results demonstrate that NH is not a hydrolytic product of S-LPS and suggest a model in which LPS-independent O-type polysaccharides (NH) are intertwined with the O chain in the outer membrane of S-type brucellae.

Cell-mediated immune response in gonococcal infections

Peripheral blood lymphocyte (PBL) transformation stimulated by gonococcal and meningococcal antigens was studied in 29 men and 21 women with uncomplicated gonorrhoea. The blastogenic responses of PBLs from these men and women were substantially higher than from normal controls. Cross-reactivity between Neisseria gonorrhoeae and Neisseria meningitidis was manifested by the PBL transformation responses in patients with gonorrhoea to non-purified meningococcal antigen (MGC-I). In both male and female patients the PBLs were stimulated by non-purified gonococcal antigen (GC-I) and by non-purified meningococcal antigen. The extent of the blastogenic response in women was much greater than in men. Partial purification of these antigens by gel chromatography resulted in reduced cross-reactive responses to the semi-purified meningococcal antigen (MGC-II). Female patients demonstrated marked stimulation with the semi-purified gonococcal antigen (GC-II), while male patients showed slight stimulation with GC-II. It is possible that cell-mediated immunity may act to limit the spread of gonococcal infection beyond the genital mucous membranes.

Increased histamine sensitivity in mice after administration of endotoxins

CFW mice given submicrogram doses of endotoxins intravenously became highly susceptible to the lethal effects of 0.5 mg of histamine given intraperitoneally 1 to 2 h later. The histamine-sensitizing effects of the endotoxins were transitory and disappeared within 6 to 8 h. L-Epinephrine administered intravenously immediately after histamine challenge protected mice from death, but aterenol and isoproterenol were ineffective. The histamine-sensitizing effect in endotoxins was precipitated by anti-endotoxin sera with a concomitant eightfold loss in activity. However, dissociation of the immune complex in 0.25 M acetic acid fully restored histamine-sensitizing activity. The transitory nature of the hypersensitivity produced by endotoxin and the high heat resistance of the active material prove that it is different from the histamine-sensitizing effects of pertussigen.

Preparation and properties of a national reference endotoxin

A large pool of refined endotoxin was prepared from Escherichia coli O113 by extraction with hot acqueous phenol. It was characterized chemically and biologically and will be available for a reference standard designated as reference endotoxin EC.

Local immune response in experimental pyelonephritis in the rabbit. II. Lymphocyte stimulation by lipopolysaccharide of infecting organism

The response of circulating and kidney lymphocytes from rabbits with experimental haematogenous pyelonephritis to somatic (O) antigen (lipopolysaccharide) from the infecting organism was evaluated. Lymphocytes were cultured for 3 days in the presence and absence of lipopolysaccharide from the infecting organism, Escherichia coli O75 and a heterologous organism. Circulating lymphocytes showed a significant response to the homologous lipopolysaccharide by day 5 of infection, and kidney lymphocytes responded by day 19 of infection but failed to respond after day 33. The lipid moiety of somatic antigen was required for the stimulation of lymphocytes since antigen preparations in which lipid was low or absent did not activate lymphocytes. B lymphocytes from kidney were stimulated by this antigen whereas both T and B circulating lymphocytes responded. Thus, pyelonephritis in rabbits is associated with the activation of a subpopulation of circulating cells which have specific receptors for the homologous antigen. B lymphocytes that are specifically activated by the homologous or O antigen then localize to the infected site.

Antiviral activity of an ether-extracted nonviable preparation of Brucella abortus

Extraction of living Brucella abortus (strain 456) with aqueous ether yielded a nonviable, insoluble residue (Bru-Pel). When injected into mice, Bru-Pel was an effective, nontoxic interferon stimulus. Mice pretreated with Bru-Pel were protected against challenge with otherwise lethal doses of Semliki Forest virus. Significant protection was afforded when Bru-Pel was given as many as 7 days before virus challenge. Evidence is presented dealing with the complex nature of Bru-Pel and with the possibility that the antiviral activity of Bru-Pel may be associated not only with the production of interferon, but with a general increase in the level of nonspecific resistance in animals.

Interferon induction in mice by lipopolysaccharide from Brucella abortus

Endotoxin or lipopolysaccharide isolated from Brucella abortus (strain 456) produced a typical endotoxin-type interferon response in mice with peak levels of the inhibitor occurring 2 h after intravenous injection of the stimuli. Brucella lipopolysaccharide was a much less effective interferon stimulus than the lipopolysaccharide isolated from Salmonella typhimurium (strain LT-2).

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.

Transfer of antigen from macrophages to lymphocytes. II. Immunological significance of the transfer of lipopolysaccharide

The immunological significance of lipopolysaccharide (LPS) transfer from macrophage into lymphocytes was studied in an in vitro system in which the lymphocytes were incubated during 24–72 hours with macrophages which had previously ingested S. enteriditis LPS (during 1 hour).

Our results show that the in vitro immune response to LPS requires co-operation of lymphocytes with macrophages.

After 24–72 hours of contact of the lymphocytes with macrophages containing ingested antigen, we observed within lymphocyte population a time dependent increase of the number of LPS-binding cells. This result was obtained by means of two different methods: rosettes formation and autoradiography. Autoradiographies performed on thick and thin sections showed that after contact with macrophages which had ingested ¹⁴C-LPS, most rosettes forming cells (RFC) exhibited radioactivity.

All these findings strongly argue in favour of the idea that LPS transfer from macrophages to lymphocytes is highly relevant for specific antibody synthesis by lymphocytes.

Transfer of antigenic macromolecules from macrophages to lymphocytes. I. Autoradiographic and quantitative study of ( 14 C)endotoxin and ( 125 I)haemocyanin transfer

In an in vitro autologous system, studies were carried out on the transfer of either biosynthetically-labelled [¹⁴C]Salmonella enteritidis endotoxin or [¹²⁵I]Maia squinado haemocyanin from macrophages to lymphocytes.

When cultured 1 hour in vitro, lymphocytes adhered to autologous macrophages, forming lymphocyte-macrophage islands (LMI).

Quantitative data obtained from stained thick sections showed that 1.8 per cent of the lymphocytes had adhered to macrophages with ingested [¹⁴C]endotoxin while 0.6 per cent of the lymphocytes adhered to macrophages with ingested [¹²⁵I]haemocyanin. The presence of antigen macromolecules was observed mainly within lymphocytes adhering to macrophages with ingested antigens, i.e. at the level of LMI. On the other hand, autoradiography carried out on the same thick sections, showed that 0.20 per cent of the lymphocyte population in LMI possess silver grains. High resolution autoradiographic pictures of thin sections, showed a peculiar localization of silver grains in LMI lymphocytes: about 80 per cent of the radioactivity was found within lymphocytic nuclei and the remainder either on the cellular membrane or free in the cytoplasm. The disappearance of radioactivity from the LMI-located macrophage membranes (where lymphocytes contain silver grains) as well as the regular inhibition of antigen transfer occurring after pronase treatment of the macrophage which contained ingested antigen, strongly suggest that antigen bound to macrophage membrane was transferred to lymphocytes. As pretreatment of lymphocytes with anti-Ig serum resulted in regular inhibition of antigen transfer, it appears that the Ig receptors of lymphocyte membranes play an important role in the transfer mechanism.

Combined technique, i.e. autoradiography and the peroxidase method for revealing Ig bound to lymphocyte membranes, showed that silver grains occurred only within lymphocytes displaying peroxidase-positive membrane.

Isolation and characterization of a native cell wall complex from Neisseria meningitidis

A cell wall complex has been isolated by gentle methods from both the medium supernatant fluid and whole organisms of Neissieria meningitidis cultures. The two types of preparations have been shown to be essentially identical on the basis of chemical composition, electron microscopy, and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE). Four major components were identified in the complex: group-specific polysaccharide (4 to 10%), protein (45 to 65%), lipopolysaccharide (10 to 25%), and lipid (15 to 30%). The whole complex was found to be immunogenic in rabbits and to elicit production of antibody directed against the protein, the group-specific polysaccharide, and the lipopolysaccharide components. The isolated protein component was also found to be immunogenic in rabbits and to elicit production of serotype-specific antibody. The protein component was found to produce a band pattern in SDS-PAGE that is simple, reproducible, and strain dependent. The lipopolysaccharide component was found to have chemical and biological properties characteristic of bacterial endotoxin. We propose that this complex is representative of the outer trilaminar membrane of the meningococcal cell envelope in its native state.

Biological and chemical characterization of toxic substances from Candida albicans

Whole cells, morphological components, and various extracts of Candida albicans were tested for toxicity by methods involving biological activities ordinarily used to characterize bacterial endotoxin. Fungal preparations exerted several of these activities, but only at much higher dose levels than those required for bacterial products. Both fungal cell walls and intact cells were pyrogenic in rabbits and lethal to actinomycin D-treated mice, but only the former were also lethal to chicken embryos; neither coagulated a hemolysate of horseshoe crabs. Wallfree fungal protoplasm was minimally pyrogenic but negative in the other assays. Bacterial endotoxin was strongly active in all four systems. The toxicity of fungous cell walls was undiminished after exposure to strong alkali, a treatment which destroyed bacterial endotoxin. Extracts obtained with hot phenol-water or potassium hydroxide killed mice but were nonpyrogenic. A defatted and enzyme-digested ethylenediamine extract was both lethal and pyrogenic. Particulate fungal materials but not bacterial endotoxin induced a granulomatous response in prepared mice. These data indicate that contaminating bacterial endotoxin was not responsible for the biological effects of fungal products and suggest that C. albicans may contain at least two different toxic components. Chemical analyses were performed on soluble fractions, but a role in toxicity could not be assigned to any identified component.

Antibody synthesis in kidney, spleen and lymph nodes in acute and healed focal pyelonephritis

Segmental circumscribed pyelonephritis in rabbits was associated with a significant increase in the incorporation of ¹⁴C amino acids into IgG by the infected kidneys and spleen. Specific anti-Esch. coli antibody in the IgG class was synthesized by 8 of 10 kidneys, 5 of 10 spleens, 1 of 6 proximal lymph nodes, 1 of 3 popliteal lymph nodes and by none of the “buffy coat” cells (circulating lymphocytes). Although viable organisms were not present, non-viable antigen persisted for up to 6 months after infection. Persistent circulating antibody may arise from local antibody which is stimulated by the persistence of non-viable antigen at site of infection.

In vitro attachment of radioactive endotoxins to lysosomes

The experiments reported here demonstrate that under certain conditions endotoxin can interact with lysosomes in vitro. After incubation of large granular fraction with (51)Cr-labeled antigen under the conditions required for acid hydrolytic activity, radioactivity was associated with the pellet after centrifugation. This effect can be inhibited by preincubation of the large granular fraction with unlabeled homologous or heterologous endotoxins. High resolution autoradiography showed that (14)C-labeled endotoxin was predominantly attached to the lysosomes contained in the large granular fraction. The mechanism of this interaction and its relationship to the toxic effect of endotoxins on lysosomes are discussed.

Some Structural and Biological Properties of Brucella Endotoxin

Hot phenol-water extraction of smooth Brucella abortus and B. melitensis cells yielded a toxic fraction which was recovered from the phenol phase (fraction 5). Chemically, fractions 5 from both Brucella species were lipid-carbohydrate-protein-2 keto-3-deoxyoctulosonic acid complexes which were stable to heat and resistant to Pronase digestion. Electron micrographs of the Brucella toxins were morphologically indistinguishable from those of enterobacterial endotoxins. Biologically, Brucella toxins were lethal for mice and immunogenic for rabbits. An intravenous injection of Brucella toxin induced severe leukopenia with subsequent leukocytosis in mice. Cross-tolerance experiments with mice demonstrated that pretreatment with B. abortus toxin lessened the hypoferremia produced by challenge with Escherichia coli endotoxin. Furthermore, fractions 5 from B. abortus and B. melitensis were able to form hybrids with E. coli and Salmonella enteritidis endotoxins and also with each other. Although Brucella toxins possess many structural and biological properties in common with endotoxins from the Enterobacteriaceae , some quantitative differences in their biological potencies were observed. Brucella toxins were relatively innocuous in tests for pyrogenicity in rabbits and lethality for chick embryos. In nonspecific protection tests, Brucella toxin had only 1/75 the potency of E. coli endotoxin in protecting mice against challenge with virulent S. typhi . However, on the basis of the data presented and on the work done previously, we concluded that the heat-stable toxins of B. abortus and B. melitensis were endotoxins.

Alteration of physical, chemical, and biological properties of endotoxin by treatment with mild alkali

Treatment with alkali is one of several methods for removing fatty acids from bacterial endotoxins and, in the process, detoxifying the material. Saponification of fatty acid esters is the major detectable chemical change produced by alkali; however, kinetic studies of mild alkaline hydrolysis of endotoxin failed to correlate rates of detoxification with rates of loss of ketodeoxyoctonates, heptose, O-acetyl groups, or fatty acid esters. The alterations occurring during the critical stages of hydrolysis apparently changed the essential chemical conformation of endotoxic particles before cleavage of a significant amount of material took place. The rates of both saponification and detoxification were markedly increased by carrying out the reaction in media of ethyl alcohol or dimethylsulfoxide instead of water.

Immunogenicity of deoxycholate-disrupted endotoxins

A comparison of the immunogenicity of sodium deoxycholate-disrupted lipopolysaccharides from Escherichia coli cell walls revealed that these fragments, which are nonimmunogenic in the rabbit, have some activity in the mouse. This relationship was independent of the route of immunization and sex, but in both species immunogenicity was restored by dilution or dialysis. Adsorption of disrupted lipopolysaccharides onto bentonite particles or administration with methylated bovine serum albumin and Freund's adjuvant did not appreciably augment activity in vivo. It is postulated that in the mouse the requirements for immunogenicity of these lipopolysaccharides are either less stringent with regard to the three-dimensional structure of the antigen, or that a reaggregation to toxic, native lipopolysaccharides may occur in vivo.