Biological activities of chemically synthesized Proteus-type lipid A

Lipopolysaccharide heterogeneity: innate host responses to bacterial modification of lipid a structure

The innate host response system is composed of various mechanisms designed to detect and facilitate host responses to microbial components, such as lipopolysaccharides (LPS). To enable this to occur, innate systems contain multiple pattern recognition receptors (i.e., LBP, CD14, and TLRs), which identify certain features within bacterial LPS that are foreign to the host, as well as essential and uniquely specific for bacteria. Innate host identification of unique bacterial components or patterns, therefore, relies on the inability of bacteria to alter these essential or critical components dramatically. Historically, LPS have been viewed as essential outer-membrane molecules containing both a highly variable outer region (O-segment) as well as a relatively conserved inner region (lipid A). However, over the last decade, new evidence has emerged, revealing that increased natural diversity or heterogeneity within specific components of LPS, such as lipid A-resulting in minor to moderate changes in lipid A structure-can produce dramatic host responses. Therefore, examples of natural lipid A heterogeneity, and the mechanisms that control it, represent a novel approach in which bacteria modulate host responses and may thereby confer specific advantages to certain bacterial species under changing environmental host conditions.

Potential virulence factors of Proteus bacilli

The object of this review is the genus Proteus, which contains bacteria considered now to belong to the opportunistic pathogens. Widely distributed in nature (in soil, water, and sewage), Proteus species play a significant ecological role. When present in the niches of higher macroorganisms, these species are able to evoke pathological events in different regions of the human body. The invaders (Proteus mirabilis, P. vulgaris, and P. penneri) have numerous factors including fimbriae, flagella, outer membrane proteins, lipopolysaccharide, capsule antigen, urease, immunoglobulin A proteases, hemolysins, amino acid deaminases, and, finally, the most characteristic attribute of Proteus, swarming growth, enabling them to colonize and survive in higher organisms. All these features and factors are described and commented on in detail. The questions important for future investigation of these facultatively pathogenic microorganisms are also discussed.

Biological activities of lipopolysaccharide isolated from Vibrio cholerae O139, a new epidemic strain for recent cholera in Indian subcontinent

Biological activities of lipopolysaccharide (LPS) isolated from Vibrio cholerae O139, a new causative agent for recent cholera epidemic in Indian subcontinent, were investigated in comparison with those of LPS from O1 V. cholerae. V. cholerae O139 LPS exerted mitogenic activity, lethal toxicity and Shwartzman reaction to the same extent as those observed for O1 V. cholerae LPS, although these activities except for lethal toxicity were obviously lower than those of Salmonella typhimurium LT-2 LPS used as a reference. It was, therefore, suggested that O139 LPS does not contribute to the high infective and pathogenic potentials of the V. cholerae O139 strain as in the case of O1 V. cholerae.

Immunobiological properties of chemically defined lipid A from lipopolysaccharide of Porphyromonas (Bacteroides) gingivalis

Porphyromonas gingivalis 381 lipid A, characterized by beta-(1-6)-linked glucosamine disaccharide 1-phosphate, with one hydroxyacyl group and one acyloxyacl group, i.e., 3-hydroxy-15-methyl-hexadecanoyl and 3-hexadecanoyloxy-15-methylhexadecanoyl groups at the 2 and 2' positions, respectively, was less endotoxically active than the synthetic Escherichia-coli-type lipid A (compound 506), which possesses beta-(1-6)-linked glucosamine disaccharide 1,4'-bisphosphate, with two acyloxyacyl groups at the 2' and 3' positions and two 3-hydroxytetradecanoyl group at the 2 and 3 positions and the synthetic Salmonella-type lipid A (compound 516), which has three acyloxyacyl groups at the 2,2' and 3' positions and one hydroxyacyl group at the 3 position. P. gingivalis lipid A exhibited no or very low endotoxic activities, i.e., lethal toxicity in galactosamine-loaded mice, preparative ability for local Shwartzman reaction, pyrogenicity and Limulus test as compared with compounds 506 and 516. However, polyclonal B-cell activation of BALB/c mouse splenocytes was as strong as that of compound 506. Furthermore, P. gingivalis lipid A had stronger immunoadjuvant and hemagglutinating activities than compound 506. The absence of ester-linked phosphate at the 4' position and ester-linked fatty acids, and the presence and positions of fatty acids possessing considerable lengths of acyl chains are unique features of P. gingivalis lipid A, and they differentiate this lipid A from enterobacterial and other lipids A. The good balance between endotoxic properties and beneficial immunobiological activities of P. gingivalis lipid A may be attributable to these features.

Combined effects of synthetic lipid A analogs or bacterial lipopolysaccharide with glucosaminylmuramyl dipeptide on antitumor activity against Meth A fibrosarcoma in mice

The combined effects of the synthetic glucosaminylmuramyl dipeptide (GMDP) on the antitumor activity of chemically synthesized lipid A analogs, compound A-103 (glucosamine-4-phosphate with (R)-3-tetradecanoyloxytetradecanoyl group at the C-2 and C-3 positions), Escherichia coli-type lipid A (506), Salmonella typhimurium LT-2 lipopolysaccharide (LPS) against Meth A fibrosarcoma in mice were examined. Meth A fibrosarcoma cells (5 x 10(5) were inoculated intradermally into BALB/c mice on day 0, and compound A-103 and/or GMDP was administered intravenously (i.v.) on days 7 and 9. Two i.v. injections of A-103 (50 micrograms) alone or GMDP (10 micrograms) alone induced 42.8 or 51.8% inhibition of the rate of tumor growth, however, A-103 (100 micrograms) with GMDP (10 micrograms) exhibited a high 68.7% inhibition rate 19 days after tumor inoculation. The inhibition of the tumor growth rate by the combination A-103 (100 micrograms) or 506 (50 micrograms) with GMDP (10 micrograms) was stronger than that of A-103 or 506 with MDP (10 micrograms). The combination of LPS (1 or 10 micrograms) with GMDP (10 micrograms) exhibited a higher inhibition rate than that of LPS with MDP, and three or four tumor-free mice out of five mice were observed, suggesting that the combined effect of GMDP is more potent than that of MDP. With the addition of GMDP, A-103 did not enhance the production of tumor necrosis factor (TNF) on the basis of L929 cell lysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological activity of chemically synthesized core sugar linked lipid A analog, heptose-(alpha 1----5)-2-keto-3-deoxyoctonic acid-(alpha 2----6)-2,3-diacyloxyacylglucosamine-4-phosphate

The mitogenicity, lethal toxicity and antitumor activity against Meth A fibrosarcoma and the induction of tumor necrosis factor (TNF) of chemically synthesized compounds designated as A-103, 2,3-diacyloxyacylglucosamine-4-phosphate (GlcN-4-P), and A-503), heptose-(alpha 1----5)-2-keto-3-deoxyoctonic acid (KDO)-linked GlcN-4-P (A-103), were determined. Compound A-103 induced significant incorporation of [3H]thymidine of C57BL/6 mice at 25-100 micrograms/ml, and A-503 showed the highest incorporation of [3H]thymidine at 100 micrograms/ml. The mitogenicity of A-503 exhibited a lower activity than of A-103. Compound A-503 showed no lethality at high doses of 25 and 50 micrograms/mouse in C57BL/6 mice loaded with D-galactosamine, whereas A-103 caused the death of one of three mice at a dose of 50 micrograms/mouse. Although, the two compounds with or without muramyl dipeptide showed weak antitumor activity against Meth A fibrosarcoma in BALB/c mice, but there were no remarkable differences between the compounds on antitumor activity. Peritoneal macrophages, stimulated with A-103 or A-503 caused no production of TNF which induces L929 cell lysis in vitro. These findings indicate that the addition of heptose and KDO to GlcN-4-P seems not to affect mitogenic activity, lethal toxicity, antitumor activity and TNF-production of the GlcN-4-P compound (A-103).

Combined effects of synthetic lipid A analogs and muramyl dipeptide on antitumor activity against Meth A fibrosarcoma in mice

Combined effects of chemically synthesized lipid A analogs, the compound A-171 (acylglucosamine-4-phosphate with (R)-3-hydroxytetradecanoyl and (R)-3-hydroxytetradecanoyloxy]tetradecanoyl group at the C-2 and C-3 positions), or the compound A-172 (with (R)-3-hydroxytetradecanoyloxy]tetradecanoyl and (R)-3-tetradecanoyloxytetradecanoyl group at the C-2 and C-3 positions), and muramyl dipeptide (MDP) on antitumor activity against Meth A fibrosarcoma, were examined. Meth A fibrosarcoma cells (5 X 10(5)) were inoculated intradermally into BALB/c mice on day 0, compound A-172 and/or MDP were administered intravenously (i.v.) on day 7. Although the antitumor activity by single i.v. injection of A-172 (50 micrograms/mouse) with MDP (10 micrograms) was weaker than that of 50 micrograms of synthetic lipid A analogs (506), or 10 micrograms of bacterial lipopolysaccharide (LPS) with MDP, A-172 alone and with MDP exhibited tumor inhibition rates of 49.0 and 70.6%, respectively. When A-171 (50 micrograms) with MDP (10 micrograms) was administered i.v. twice (days 7 and 10) into mice inoculated Meth A fibrosarcoma, two of five mice caused complete tumor regression. Furthermore, L929 cell lysis by the combination of A-171, A-172 with MDP was higher than that by the analogs or MDP alone, suggesting that the lipid A analogs of monosaccharide type as well as LPS are able to enhance the production of tumor necrosis factor in the presence of MDP.

Endotoxic properties of chemically synthesized lipid A analogs. Studies on six inflammatory reactions in vivo, and one reaction in vitro

Biological activities of two groups of synthesized lipid A analogs, the counterpart of biosynthetic precursor, Lehmann's Ia type, 406, and E. coli lipid A type, 506, as well as their non-phosphorylated, and mono-phosphorylated analogs were investigated. The activities employed included four bone marrow cell reactions in mice, mice skin reaction, leukocytes migration in rabbits' cornea, and hemagglutination. Compound 406 and 506 elicited bone marrow reactions in mice and hemagglutination of mouse RBC, although 406 failed to elicit hemorrhage and necrosis also in mice skin. Compound 406 did not elicit corneal reaction in rabbits. The results suggest that for elicitation of this reaction and mice skin reaction, acyloxyacyl structure is required. Cytotoxicity and thromboplastin production of four bone marrow reactions had been reported by us to be endotoxic reactions, since these had not been elicited by peptidoglycan of Lactobacillus and Staphylococcus (1981) and 300 series synthesized analogs (1984) which did not have endotoxic structures. From these results, it seems that these two marrow reactions and hemagglutination require, as does the limulus test, the lipid A part structure as is present in 406.

Structural requirements of lipid A for endotoxicity and other biological activities

For the past ten years, several groups were engaged in synthetic studies of lipid A, namely the lipid portion of bacterial lipopolysaccharides (LPS) that has been assumed to be the bioactive center of LPS, but has not been unanimously approved. Among them, Shiba, Kusumoto, and colleagues, Osaka, Japan have synthesized most energetically and successfully a variety of counterparts of lipid As, biosynthetic lipid A precursors, and their analogs. The endotoxic and related bioactivities of these synthetic compounds were studied by Japanese and German groups, including ours. In 1985, one of the compounds, having an acylation and phosphorylation pattern in beta(1-6)-D-glucosamine disaccharide which was proposed for Escherichia coli F515 lipid A was found to be exhibit full endotoxic and related bioactivities identical to those of the bacterial product. The study was extended by synthesis and examination of bioactivities of variously acylated D-glucosamine di- and monosaccharide phosphates, which correspond to structural components of lipid As, and their analogs or derivatives. Thus, structural requirements have been fairly well elucidated. In this article, first we will review the progress of synthetic and biological studies, with particular emphasis on chemical structure--bioactivities relationships of lipid As, and then we will discuss possible usefulness of some less or nontoxic lipid A-related synthetic compounds in clinical and preventive medicine.

Structural heterogeneity regarding local Shwartzman activity of lipid A

The relation of chemical structure to local Shwartzman activity of lipid A preparations purified by thin-layer chromatography from five bacterial strains was examined. Two lipid A fractions from E. coli F515--Ec-A2 and Ec-A3--exhibited strong activity, similar to that of previous synthetic E. coli-type lipid A (compound 506 or LA-15-PP). The Ec-A3 fraction contained a component that appeared to be structurally identical to compound 506, and the main component of Ec-A2 fraction was structurally similar to compound 506 except that it carried a 3-hydroxytetradecanoyl group at the C-3' position of the backbone in place of a 3-tetradecanoyloxytetradecanoyl group. Free lipid A (12 C) and purified lipid A fractions, Ec-A2 (12 C) and Ec-A3 (12 C), respectively, obtained from bacteria grown at 12 C, exhibited activity comparable to Ec-A2 or Ec-A3. In these preparations, a large part of the 3-dodecanoyloxytetradecanoyl group might be replaced by 3-hexadecenoyloxytetradecanoyl group. Salmonella minnesota R595 free lipid A also contained at least two active lipid A components as seen in E. coli lipid A, but the third component corresponding to the synthetic Salmonella-type lipid A (compound 516 or LA-16-PP) exhibited low activity. A lipid A fraction, Cv-A4 from Chromobacterium violaceum IFO 12614, which was proposed to have two acyloxyacyl groups at the C-2 and C-2' positions with other acyl groups, exhibited weaker activity than the free lipid A or LPS. The purified lipid A fractions from Pseudomonas diminuta JCM 2788 and Pseudomonas vesicularis JCM 1477 contained an unusual backbone with 2,3-diamino-2,3-dideoxy-D-glucose disaccharide phosphomonoester, and these lipid A (Pd-A3 and Pv-A3) exhibited strong activity comparable to the E. coli lipid A. Thus, the present results show that the local Shwartzman reaction can be expressed by partly different lipid A structures in both hydrophilic backbone and fatty acyl residues; when they have the same backbone the potency varies markedly depending on the structure of the acyl residues.

Biological activities of chemically synthesized N-acetylneuraminic acid-(alpha 2----6)-monosaccharide analogs of lipid A

The mitogenicity and lethal toxicity of chemically synthesized lipid A analogs, in which 2,3-acyloxyacylglucosamine-4-phosphate linked to tetraacetyl-N-acetylneuraminic acid (compound A-207) or to N-acetylneuraminic acid (compound A-307), were examined. Although the mitogenic activity of the synthetic compounds was weaker than that of bacterial LPS, doses of 10-50 micrograms/ml of A-207 and 5-10 micrograms/ml of A-307 were capable of increasing incorporation of [3H]thymidine into cultured spleen cells of C57BL/6 mice. Lethal toxicity of A-207 was observed at 10 micrograms/mouse in C57BL/6 mice sensitized with D-galactosamine hydrochloride. However, the attachment of tetraacetyl-N-acetylneuraminic acid or N-acetylneuraminic acid does not appear to enhance the biological activity of acyloxyacylglucosamine-4-phosphate.