Biological activities of endotoxins detoxified by alkylation

Endotoxin Is Inactivated by Ethylene Oxide, Gamma, Electron Beam, and Steam Sterilization

The effect of sterilization on bacterial endotoxin is receiving greater attention within the medical device industry. Contributing factors to this increased attention include the growing popularity of transferring devices among sterilization modalities and the focus on aspects of microbiological quality other than sterilization. This systematic review examined the effects of sterilization on bacterial endotoxin, with attention drawn to industry standards and regulations to elucidate whether such documents are aligned with published data. In summary, numerous experiments have shown a reduction in pyrogenicity and/or limulus amebocyte lysate reactivity of endotoxin following sterilization, whereas a number of publications and industry standards have claimed (without data or references) that sterilization does not inactivate endotoxin. The results of this review would be useful for device manufacturers when selecting a sterilization modality or deciding whether to test for endotoxin pre- vs poststerilization, as well as for standards developers and regulators in aligning standards and regulations with peer-reviewed data.

Effect of mitotic inducers and retinoic acid blocker on expression of pluripotent genes in ES cells derived from early stage in vitro-produced embryos in buffalo

So far, it has been difficult to generate embryonic stem (ES) cell from early stage preimplantation embryos of buffalo. These ES cells will be more helpful for efficient embryo cloning and generation of body cells as they are more primitive than inner cell mass (ICM)-derived ES cells. The present study was conducted to find the effect of lipopolysaccharide (LPS), melatonin (N-acetyl-5-methoxytryptamine, a pineal gland product), and citral (3,7-dimethyl-2,6-octadienal and a retinoic acid synthesis blocker) on establishment of primary ES cell colonies, the comparative size of the ES cell colonies, and expression of pluripotent genes during extended period of culture in buffalo. Zona-free eight-cell stage in vitro fertilization (IVF) embryos were cultured in ES cell medium supplemented with none (media I as control), LPS (media II), citral melatonin (media III), or melatonin (media IV). The multiplication of blastomere leading to ES cell colony formation and expression of pluripotent genes were assessed up to day 20 of culture. The primary colony formation, the comparative size of the ES cell colonies, and expression of pluripotent genes in these colonies were better in the medium supplemented with melatonin in all days of culture. Within melatonin supplementation, the colony size was comparatively larger on day 8 and day 12 of culture. Further, with this supplementation, the Oct-4 and Nanog expression was comparatively higher on all days of culture. The results indicated that supplementation of melatonin helped in the formation of better primary ES cell colony as well as in the maintenance of pluripotency. The results also indicated that primary colonies developed on day 8 to day 12 of culture may be better for passaging them for establishment of ES cell line from early stage preimplantation IVF embryos of in buffalo.

Lipopolysaccharides of Vibrio cholerae: III. Biological functions

This review presents the salient features of the biological functions including the (i) endotoxic activities, (ii) antigenic properties, (iii) immunological responses to and (iv) phage receptor activities of the Vibrio cholerae lipopolysaccharides (LPS). The biological functions of the capsular polysaccharide (CPS) of V. cholerae have also been discussed briefly as a relevant topic. The roles of LPS and other extracellular polysaccharides in the (i) intestinal adherence and virulence of the vibrios and (ii) the biofilm formation by the organisms have been analysed on the basis of the available data. Every effort has been made to bring out, wherever applicable, the lacunae in our knowledge. The need for the continuous serogroup surveillance and monitoring of the environmental waters and the role of LPS in the designing of newer cholera vaccines has been discussed briefly in conclusion.

Adjuvants--a balance between toxicity and adjuvanticity

Adjuvants have been used to augment the immune response in experimental immunology as well as in practical vaccination for more than 60 years. The chemical nature of adjuvants, their mode of action and the profile of their side effects are highly variable. Some of the side effects can be ascribed to an unintentional stimulation of different mechanisms of the immune system whereas others may reflect general adverse pharmacological reactions. The most common adjuvants for human use today are still aluminium hydroxide, aluminium phosphate and calcium phosphate although oil emulsions, products from bacteria and their synthetic derivatives as well as liposomes have also been tested or used in humans. In recent years monophosphoryl lipid A, ISCOMs with Quil-A and Syntex adjuvant formulation (SAF) containing the threonyl derivative of muramyl dipeptide have been under consideration for use as adjuvants in humans. At present the choice of adjuvants for human vaccination reflects a compromise between a requirement for adjuvanticity and an acceptable low level of side effects.

Biodegradable and biocompatible poly(DL-lactide-co-glycolide) microspheres as an adjuvant for staphylococcal enterotoxin B toxoid which enhances the level of toxin-neutralizing antibodies

Microspheres composed of biocompatible, biodegradable poly(DL-lactide-co-glycolide) (DL-PLG) and staphylococcal enterotoxin B (SEB) toxoid were evaluated as a vaccine delivery system when subcutaneously injected into mice. As measured by circulating immunoglobulin G (IgG) antitoxin titers, the delivery of SEB toxoid via DL-PLG microspheres, 1 to 10 microns in diameter, induced an immune response which was approximately 500 times that seen with nonencapsulated toxoid. The kinetics, magnitude, and duration of the antitoxin response induced with microencapsulated toxoid were similar to those obtained when an equal toxoid dose was administered as an emulsion with complete Freund adjuvant. However, the microspheres did not induce the inflammation and granulomata formation seen with complete Freund adjuvant. The adjuvant activity of the microspheres was not dependent on the superantigenicity of SEB toxin and was equally effective at potentiating circulating IgG antitrinitrophenyl levels in response to microencapsulated trinitrophenyl-keyhole limpet hemocyanin. Empty DL-PLG microspheres were not mitogenic, and SEB toxoid injected as a mixture with empty DL-PLG microspheres was no more effective as an immunogen than toxoid alone. Antigen-containing microspheres 1 to 10 microns in diameter exhibited stronger adjuvant activity than those greater than 10 microns, which correlated with the delivery of the 1- to 10-microns, but not the greater than 10-microns, microspheres into the draining lymph nodes within macrophages. The antibody response induced through immunization with microencapsulated SEB toxoid was protective against the weight loss and splenic V beta 8+ T-cell expansion induced by intravenous toxin administration. These results show that DL-PLG microsphere vaccine delivery systems, which are composed of pharmaceutically acceptable components, possess a strong adjuvant activity for their encapsulated antigens.

Effects of the adjuvants SGP and Quil A on the induction of experimental autoimmune thyroiditis in mice

In the present study, two adjuvants, SGP and Quil A, were assessed for their ability to induce experimental autoimmune thyroiditis (EAT) in mice. SGP (a synthetic copolymer of starch, acrylamide, and sodium acrylate) and Quil A (a plant saponin) were compared with lipopolysaccharide (LPS) and complete Freund's adjuvant (CFA) given together with mouse thyroglobulin (MTg) for their ability to induce EAT in CBA/J mice. Immunization with MTg and LPS, MTg and CFA, or MTg with SGP was effective in inducing anti-MTg antibodies and histologic EAT, while MTg with Quil A was ineffective in inducing either anti-MTg antibodies or EAT. MTg with LPS was able to prime mice for the development of an in vitro spleen cell proliferative response to MTg while MTg with SGP or with Quil A was unable to prime spleen cells to proliferate detectably in response to MTg. MTg with LPS given in vivo primes CBA/J spleen cells for further activation by in vitro culture with MTg to transfer EAT to naive CBA/J recipients. MTg with SGP was also effective in priming CBA/J spleen cells for in vitro activation and transfer of EAT while MTg with Quil A was ineffective. The effective adjuvant activity of SGP and its lack of toxicity relative to LPS should make it a useful agent for further studies in murine models of EAT.

Effects of natural or synthetic microbial adjuvants on induction of autoimmune thyroiditis

Natural and synthetic adjuvants of microbial origin were compared for their capacity to potentiate the induction of experimental autoimmune thyroiditis (EAT) with the autoantigen mouse thyroglobulin (MTg). Regardless of the immunomodulator used, severe thyroiditis was observed only in EAT-susceptible strains of the k haplotype and not in EAT-resistant strains of the d haplotype. Compared to phenol-extracted lipopolysaccharide, a potent adjuvant for enhancing EAT induction, phthalyl-substituted, detoxified lipopolysaccharide, even at doses 15- to 50-fold greater, led to only low anti-mouse thyroglobulin titers and mild thyroid infiltration. The synthetic adjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) and three of its analogs, N-acetylmuramyl-L-alanyl-D-isoglutamine-L-alanyl-D-glycerol mycolate (MDP-L-Ala-Glyc-Myc), N-acetylmuramyl-L-alanyl-D-glutamyl-(decyl)methyl ester [MDP(decyl)methyl], and N-acetylmuramyl-L-alanyl-D-glutamine-alpha n-butyl ester [MDP-(Gln)-OnBu], designated murabutide, were tested in incomplete Freund adjuvant or in saline. In incomplete Freund adjuvant, MDP-L-Ala-Glyc-Myc was inefficient in inducing EAT, murabutide induced very mild involvement, and MDP and, more so, MDP(decyl)methyl were active but to a lesser degree than CFA. When saline was used, low levels of thyroid infiltration were observed in a few of the MDP-treated animals in only one experiment, whereas no lesions were observed when murabutide was used.

Formulation of a potential antipregnancy vaccine based on the beta-subunit of human chorionic gonadotropin (beta-hCG). III. Evaluation of various vehicles and adjuvants

Rabbits were used to test the efficacy of several materials as supplementary adjuvants when administered as part of a vaccine formulation consisting of the beta-subunit of human chorionic gonadotropin linked to tetanus toxoid (beta-hCG-TT) and adsorbed on Al(OH)3. In the amounts used, Corynebacterium parvum, levamisole, thymic factor, and N,N-dioctadecyl-N',N'-bis(2-hydroxyethyl)propanediamine exhibited little adjuvant activity although the latter material elicited marginal increments when incorporated in liposomes. A Salmonella lipopolysaccharide preparation (SPLPS) and a streptococcal preparation (OK-432) each gave approximately 7-fold increments in titer. The SPLPS preparation was pyrogenic at the doses used. OK-432 was nonpyrogenic and did not cause other evident undesirable effects. It may therefore prove to be a useful adjuvant. It gave a nearly flat dose response curve over the range of 0.5 to 4.0 mg per rabbit. Incorporation of beta-hCG-TT on Al(OH)3 in a water-in-oil emulsion caused a moderate increase in titers. Incorporation into liposomes or an oil-in-water emulsion was not effective.

Molecular mechanisms in endotoxin fever

Two important concepts are presented in this review. First, endotoxin fever, like all fevers, is mediated by a host product, leukocytic pyrogen (LP). The mechanism by which LP production is initiated by endotoxin is discussed and evidence is provided which clearly distinguishes the biological and physical differences between LP and endotoxins. The second concept is that many of the molecular and neurochemical mechanisms by which LP causes fever by its action on the hypothalamic thermoregulatory center are also observed when endotoxins are introduced into the central nervous system. Thus, there may be experimental and clinical situations in which endotoxins can directly affect the hypothalamus and initiate fever. Although this bi-modal effect of endotoxin on the production of fever can occur, the importance of LP in mediating endotoxin and other fevers cannot be overstated.

Molecular basis of fever in humans

This review presents several areas of research on the pathogenesis of fever in humans and updates new information concerning the role of fever in host defense mechanisms. Fever is mediated by a polypeptide of phagocytic cell origin called leukocytic pyrogen. Several agents and disease processes are associated with the synthesis and release of leukocytic pyrogen. Although the original studies on leukocytic pyrogen suggested that the neutrophil was the primary source, recent experiments indicate the mononuclear phagocyte to be the major producer of leukocytic pyrogen. The mechanism by which human monocytes are stimulated to produce leukocytic pyrogen is discussed, including the effects of corticosteroids, estrogens and antipyretics on the synthesis of leukocytic pyrogen in vitro. The ability of leukocytic pyrogen to alter the hypothalamic thermoregulatory center by increasing arachidonic acid metabolite levels is the most likely mechanism by which leukocytic pyrogen initiates fever. Antipyretics prevent the synthesis of certain cyclooxygenase metabolites, which accounts for their ability to reduce fever. Studies on the chemical and physical properties of human leukocytic pyrogen are reviewed and form the basis for current experiments on the similarities between leukocytic pyrogen and lymphocyte activating factor. These studies suggest that leukocytic pyrogen, in addition to producing fever, also stimulates non-hypothalamic cells involved in aspects of the acute-phase response. In this regard, leukocytic pyrogen may be an important mechanism for host defenses. Hyperthermia may also be beneficial to the host but is distinct from fever; the role of leukocytic pyrogen as well as hyperthermia as a defense mechanism is discussed.

Biological activities of chemically modified endotoxins from Vibrio cholerae

Lipopolysaccharides from Vibrio cholerae, NIH 41, Ogawa 5321 and Inaba 66/64 were treated with succinic anhydride, phthalic anhydride and dinitrophenyl ethylene diamine, and the resultant derivatives, sodium succinyl lipopolysaccharide, sodium phthalyl lipopolysaccharide, and dinitrohpenyl lipopolysaccharide obtained respectively were investigated for various biological activities. The succinylation and phthalylation of lipopolysaccharide decreased the 3-hydroxy lauric acid, a major ester-linked fatty acid of these bacteria, and as a result of which these modified products exhibited lower toxic activities in chick embryos, mouse and in generalized local Shwartzmann reaction in rabbits than their parent lipopolysaccharides. The dinitrophenylation of lipopolysaccharide increased its toxicity in chick embryos and mice, but dinitrophenyl lipopolysaccharide was completely inactive in Shwartzmann reaction in rabbits. However, despite the loss of these biological activities, these modified derivatives of lipopolysaccharide retained and increased the activities in pyrogenecity and in various immunological properties.

Activity in saline of phthalylated or succinylated derivatives of mycobacterial water-soluble adjuvant

A water-soluble fraction (WSA) of the cell wall can substitute for mycobacterial cells in Freund complete adjuvant. However, when WSA is administered in saline instead of in a water-in-oil emulsion, its adjuvant activity is very weak, and under certain experimental conditions it can even inhibit the humoral immune response. The data reported in the present study show that after treatment by phthalic or succinic anhydride the adjuvant activity of WSA was markedly changed, since high levels of circulating antibodies were produced when these derivatives were administered with an antigen in an aqueous medium. Moreover, the antigenic determinants of WSA were modified and acylated WSA had no tuberculin-like activity.

Failure of endotoxin to increase nonspecific resistance to infection of lipopolysaccharide low-responder mice

In vitro and in vivo responses to lipopolysaccharide (LPS) and various other bacterial immunostimulants were compared in c3H/He low-responder mice. The principal findings were as follows. (i) Their splenic lymphocytes were stimulated by various gram-negative mitogens such as an Escherichia coli peptidoglycan, a detoxified derivative of LPS, and even endotoxins extracted by trichloroacetic acid that are known to contain protein; spleen cells of these mice were also transformed by two other B-cell mitogens extracted from acid-fast organisms. (ii) Their macrophages were refractory to LPS and weakly responsive to a mycobacterial prepartion. (iii) LPS failed to elicit nonspecific resistance in these mice against Klebsiella pneumoniae infection. (iv) Endotoxin extracted by trichloroacetic acid and a mycobacterial preparation that could increase nonspecific resistance to infection in other strains did not protect C3H/He mice against a challenge by K. pneumoniae, although both prepartions could evoke nonspecific responses of B cells in this low-responder subline.