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

Modification of selected host-reactive properties of endotoxin by treatment with sodium deoxycholate

Endotoxin dissociated into subunits by sodium deoxycholate treatment exhibited diminished capacity to kill chick embryos, protect mice against the lethal effects of infection with Salmonella typhi, evoke hemorrhagic necrosis in skin inoculated with epinephrine, prepare for and provoke the dermal Shwartzman reaction, and induce pyrogenic tolerance. Surfactant-treated material which had been allowed to reaggregate displayed activity equivalent to that of untreated material. These findings were consistent with the working hypothesis that a macromolecular complex of critical size is required in order for endotoxin to elicit its characteristic effects in the host.

Hybrid formation between bacterial endotoxins

When endotoxins extracted from enteric bacteria were mixed in the presence of sodium deoxycholate, and the bile salt was subsequently removed by dialysis or by extraction with ethanol, a new type of endotoxin was formed. The latter material was as biologically active as the original endotoxins and possessed a combination of antigenic determinants that were previously unique to each of the individual endotoxins in the mixture. This hybrid formation between endotoxins was detected by immunodiffusion and radioautography and by quantitative precipitation procedures.

Chemical, biological, and structural properties of stable Proteus L forms and their parent bacteria

Proteus L forms were disrupted by osmotic shock, and the sedimentable material present in the homogenate was further fragmented in a Sorvall pressure cell. The pressure cell was also used for disrupting normal Proteus cells. The homogenates obtained were fractionated by differential centrifugation. Purified endotoxins were isolated from the major fractions by phenol extraction. Material extracted with phenol from the membrane fraction of the L forms was about as toxic and pyrogenic on a weight basis as the typical enterobacterial endotoxins isolated from cell walls of normal bacteria. The yield of extract from L forms was about one-third of that from an equal weight of normal bacteria. No differences in the gross chemical composition of the phenol extracts from the L forms and the normal cells could be ascertained. A close serological relationship existed between extracts obtained from two L forms and their respective parent bacteria, but no such relationship was found in the case of the third L form studied and its parent bacterium. Diaminopimelic acid was not detected in the membranes of the L forms, but these membranes contained most of the succinic dehydrogenase of the organisms. Only small amounts of this enzyme were present in the wall fraction of normal bacteria. The data obtained suggest that precursors of the Proteus endotoxins are formed either in the soluble protoplasm of normal cells and L forms or at sites on the membrane from which they are readily liberated into the protoplasm, whereas the final steps of the synthesis of these toxins take place at the cytoplasmic membrane. In normal cells, much endotoxin is transported to and concentrated in the walls.

In vitro assay of endotoxin by the inhibition of macrophage migration

A quantitative in vitro technique was used to compare the ability of different endotoxins to inhibit the migration of macrophages from explants of rabbit spleen cultured in a coagulated plasma medium. The order of potency was different from that observed in chick embryo assays, and in assays with mice, of the same endotoxins. In general, however, the sensitivity of the macrophage inhibition test was comparable to that of other bioassay methods. A highly purified endotoxin from Salmonella enteritidis (Ribi) in a concentration of 0.004 mug/ml regularly inhibited macrophage migration. The in vitro method was used to detect a progressive loss of biological activity in fractions obtained during acid hydrolysis of the purified endotoxin. The selective toxicity of very low concentrations of endotoxin for mammalian macrophages was important in estimating the degree of specificity of the reaction. The pattern of cellular response in explant cultures made it possible to differentiate endotoxic damage from the specific cytotoxic action of antigen associated with delayed hypersensitivity.

Reaction of endotoxin and surfactants. I. Physical and biological properties of endotoxin treated with sodium deoxycholate

Ribi, E. (Rocky Mountain Laboratory, Hamilton, Mont.), R. L. Anacker, R. Brown, W. T. Haskins, B. Malmgren, K. C. Milner, and J. A. Rudbach. Reaction of endotoxin and surfactants. I. Physical and biological properties of endotoxin treated with sodium desoxycholate. J. Bacteriol. 92:1493-1509. 1966.-Endotoxins from three species of gram-negative bacteria were shown to be dissociated by the bile salt sodium deoxycholate (NaD) into nontoxic subunits with molecular weights of about 20,000. When the bile salt was removed by dialysis, the subunits reaggregated in an orderly manner to form a relatively uniform population of biologically active endotoxin particles with average molecular weights of 500,000 to 1,000,000. If a small amount of human plasma was added to the dissociated endotoxin before removal of the NaD, reassociation apparently did not occur and the preparation remained nonpyrogenic. However, the plasma protein could subsequently be removed from the endotoxin subunits, and reaggregation to the toxic form would then occur. The studies on the physical nature of endotoxin performed with biophysical solution techniques were supplemented and confirmed by direct examination of the endotoxin polymers by electron microscopy. The results of these studies were consonant with the theory that the biologically active endotoxic elements are composed of micellar aggregates of linear lipopolysaccharide subunits.

Quantitative studies of the immunoglobulin sequence in the response of the rabbit to a somatic antigen

Employing a sensitive and immunoglobulin-specific assay method based upon antiglobulin augmentation, quantitative and qualitative aspects of the primary and secondary response of the rabbit to Salmonella typhimurium O antigens have been evaluated. These studies examine the validity of the method of assay for detecting and measuring gammaG- and gammaM-antibodies produced in response to whole organisms or its lipopolysaccharide. The results show that during the primary response gammaG-antibodies, not detectable by usual techniques, are produced in a pattern similar to that reported in animals stimulated by other classes of antigens. Moreover, the gammaG response following reinjection is characteristic of a secondary-type response. In contrast, gammaM-antibody levels after both primary and secondary stimulation rose equally to levels between 1 and 4 mg/ml. Despite increased sensitivity of detection and quantitative estimates of the actual molar concentration of each immunoglobulin, the minimal interval between gammaM and gammaG appearance in serum was not less than 1.5 days. The variable degree of augmentation of agglutination by antiglobulin reagent found during the immune response severely limits the quantitative usefulness of the methods developed. However, the data suggest that qualitative changes in anti-O antibodies interpretable as changes in avidity occur regularly during the immune response.

Detoxified bacterial endotoxns. II. Preparation and biological properties of chemically modified crude endotoxins from Salmonella typhimurium

Martin, William J. (University of Utah, Salt Lake City), and Stanley Marcus. Detoxified bacterial endotoxins. II. Preparation and biological properties of chemically modified crude endotoxins from Salmonella typhimurium. J. Bacteriol. 91:1750-1758. 1966.-Chemical modification of a crude endotoxin prepared by the Roschka-Edwards (RE) procedure from a strain of Salmonella typhimurium yielded products which were nontoxic for mice and had reduced fever effects in rabbits. A reduction in rabbit pyrogenicity of approximately 100 times was noted with a potassium periodate-treated RE preparation when compared with the parent RE preparation. Measured in a similar fashion, pyrogenicity of a potassium methylate-treated RE preparation was reduced by a factor of 10 while pyrogenicity of a boron trifluoride RE preparation was unchanged. All of these endotoxoids, including the parent RE preparation, showed little toxicity for mice. Immunogenicity was determined in mice by comparing Boivin, RE, and endotoxoid preparations with a heat-killed, phenol-preserved (HP) vaccine prepared from the same strain of S. typhimurium. Employing a 10 ld(50) challenge, the protective immunogenicity of the respective vaccines was determined by active immunized mouse protection tests. Although two 100 mug immunizing doses of the Boivin, RE, and the respective endotoxoid preparations varied in mouse protection (potassium methylate RE > Boivin > RE > boron trifluoride RE > potassium periodate RE), it was evident that, with the exception of the potassium methylate preparation, the HP vaccine yielded greatest protection against the 10 ld(50) challenge with S. typhimurium. Further mouse protection experiments suggested that the minimal immunogenic dose of the potassium methylate RE vaccine preparation was approximately 50 mug. These data indicated an approximate fivefold difference between the minimal pyrogenic dose (10 mug) and the minimal immunogenic dose (50 mug). These findings further suggest that potassium methylate RE vaccine preparations should be considered in the search for less toxic enteric fever vaccines.

Chemical composition and biological properties of the endotoxin of Brucella abortus

Baker, Phillip J. (University of Wisconsin, Madison), and J. B. Wilson. Chemical composition and biological properties of the endotoxin of Brucella abortus. J. Bacteriol. 90:895-902. 1965.-The ability of endotoxin to induce hypoferremia in mice was used to measure the specific activity of various endotoxin preparations of Escherichia coli and Brucella abortus and to determine the endotoxin content of several strains of B. abortus differing in virulence for guinea pigs. The endotoxin preparations from E. coli possessed greater biological activity than those from B. abortus. The same types of B. abortus endotoxin preparations, whether obtained from strains of high or low virulence, had about the same activity. Although differences in endotoxin content were noted among several strains of B. abortus of different virulence, there appeared to be no correlation between endotoxin content and virulence. Chemical analyses of B. abortus and E. coli endotoxins, based upon nitrogen, phosphorus, fatty acid ester, fatty acid amide, total fatty acids, hexose, and hexosamine content, revealed differences in chemical composition; however, these differences could not be correlated with differences in biological activity. The same types of endotoxin preparations, whether obtained from strains of B. abortus of high or low virulence, were similar in chemical composition and in biological activity. A correlation between the ability of endotoxin to induce hypoferremia and its lethal effects in mice is suggested. In general, endotoxin preparations of high hypoferremic activity had low mouse ld(50) values.

Humoral and cellular aspects of the immune response to the somatic antigen of Salmonella enteritidis

A study was made of the cellular and humoral aspects of the immune response of the rabbit to the somatic polysaccharide of Salmonella enteritidis. The response to a single intravenous injection was characterized by the appearance of elevated titers of bactericidal antibody between 2 and 3 days later. The maximum titer was dose-dependent and occurred between 5 and 7 days, thereafter declining rapidly during the first month. The significant stabilized levels which then persisted for at least 1 year were also dose-dependent. Most of the antibody produced (>99 per cent) was associated with the macroglobulin fraction of serum. Plaque-forming cells (PFC) elaborating antibody specific for this somatic antigen were detected and enumerated by the technique of localized hemolysis in gel employing polysaccharide-coated sheep erythrocytes. Significant numbers of PFC were encountered in the spleen as early as 14 to 18 hours after a single intravenous injection of antigen; after 36 hours the number of PFC rose rapidly and culminated in a maximum population at 5 days, followed by a rapid decline and plateau similar to that for circulating antibody. The spleen was the principal organ involved in the systemic response, but other lymphoid tissues including bone marrow, peripheral blood leucocytes, and thymus contributed significantly. After an interval of 3 months the effect on humoral antibody titers of a second injection of antigen was dependent on the amount of polysaccharide administered; markedly greater titers were now obtained with 0.02 to 0.002 microg, whereas 0.2 to 20 microg resulted in a duplication of the initial humoral response. The cellular response to a second dose of 5 microg was accelerated; larger numbers of PFC appeared more rapidly, attained a maximum population by day 3, and exceeded the primary response by a factor of two. This acceleration in the attainment of maximum numbers of PFC and the increased bactericidal antibody titers following a second injection of limiting amounts of antigen suggest that these somatic polysaccharides may in fact evoke a "secondary" type of response in the rabbit.

EXTRACTION AND PURIFICATION OF ENDOTOXIN FROM ENTEROBACTERIACEAE: A COMPARISON OF SELECTED METHODS AND SOURCES

Fukushi , K. (National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Mont.), R. L. Anacker, W. T. Haskins, M. Landy, K. C. Milner, and E. Ribi . Extraction and purification of endotoxin from Enterobacteriaceae: a comparison of selected methods and sources. J. Bacteriol. 87: 391–400. 1964.—Endotoxins containing only 0.2% N (accounted for by amino sugars) and 2% ester- and amide-linked fatty acids (calculated as palmitic acid) were prepared from Salmonella enteritidis . These products were of high biological potency, and were rapidly destroyed by acid hydrolysis. Equally potent acid-susceptible products were derived from different strains of Escherichia coli and Serratia marcescens . No correlation was evident between potency and content of nitrogen, fatty acids, and hexosamine; however, low values for carbohydrate were invariably associated with reduced endotoxic activity. Factors such as strain, method of cultivation, and extraction procedure markedly affected the chemical composition and activity of primary extracts. Results are given which demonstrate significant advantages in the use of cell walls for the isolation and purification of endotoxins.

Relation of structure to function in bacterial O antigens. II. Fractionation of lipids present in Boivin-type endotoxin of Serratia marcescens

Nowotny, Alois (City of Hope Medical Center, Duarte, Calif.). Relation of structure to function in bacterial O antigens. II. Fractionation of lipids present in Boivin-type endotoxin of Serratia marcescens. J. Bacteriol. 85:427-435, 1963.-Methods for liberation of lipids from their endotoxic O antigen were investigated. In the case of endotoxin isolated from a chromogenic Serratia marcescens, best results were obtained with diluted formic acid. The crude lipid mixture consisted of at least 16 different components, which were analyzed by paper chromatography. Good separation was achieved by silicic acid-impregnated paper. Lipids were stained with metachromatic o-toluidine blue. Solubility of the crude lipid mixture was studied in different organic solvents. Preparative fractionation was developed utilizing various organic solvents on the basis of solubility differences of the lipid components. Pure fractions were obtained by silicic acid column chromatography. Since none of the lipid liberation methods so far developed can produce undegraded lipids free from split products and remnants of cell-wall polysaccharides, their usefulness is limited in comparing the chemical structure of the liberated lipid with that of the lipid intact in the cell wall. The liberation procedures cause changes within the lipid structure itself, which in turn would alter whatever potential ability it might have to elicit certain biological reactions.

Physicochemical changes in endotoxin associated with loss of biological potency

Ribi, Edgar (National Institute of Allergy and Infectious Diseases, Rocky Mountain Laboratory, Hamilton, Mont.), Willard T. Haskins, Kelsey C. Milner, Robert L. Anacker, Daniel B. Ritter, Granville Goode, Robert-John Trapani, and Maurice Landy. Physicochemical changes in endotoxin associated with loss of biological potency. J. Bacteriol. 84:803-814. 1962.-The preparation of endotoxins whose gross chemical composition approached that of refined polysaccharide haptenes raised anew the question of which features of composition and structure are essential for their characteristic host reactivity. Alterations in the physicochemical, immunochemical, and biological properties of Salmonella enteritidis endotoxin subjected to hydrolysis with 0.1 n acetic acid were therefore investigated to relate physical characteristics to biological attributes. As hydrolysis proceeded, the decline in biological potency was paralleled by dissociation of endotoxin into particles of the size of haptenic polysaccharide. The potency still present at various stages of hydrolysis could be accounted for by residual undissociated endotoxin. These findings are consistent with the hypothesis that a macromolecular complex of critical size is one of the major requirements for endotoxin to elicit its characteristic effects in the mammalian host.