Biological activities of synthetic lipid A analogs: pyrogenicity, lethal toxicity, anticomplement activity, and induction of gelation of Limulus amoebocyte lysate

Abstract

Chemically synthesized lipid A analogs were investigated for several endotoxic activities, including pyrogenicity, lethal toxicity, anticomplement activity, and the capacity to gelate Limulus amoebocyte lysate in comparison to natural lipid A. The synthetic preparations contained D-glucosamine or D-glucosamine-p-1,6-D-glucosamine disaccharide substituted by ester-and amide-bound hydroxylated or non-hydroxylated fatty acids and by phosphate groups in different combinations. Some preparations which were insoluble in water were succinylated and thus rendered more soluble. Strong biphasic pyrogenic responses with a maximal increase in body temperature of 1 to 2°C were obtained with 50 pLg/kg doses of 3 disaccharide preparations of 15 tested. With two preparations (50 jig/kg) moderate pyrogenicity with monophasic fever curves and a maximal temperature increase of about 0.6°C was obtained. Lethal toxicity tests were carried out in galactosamine-sensitized mice. Of 15 synthetic preparations, 4 exhibited lethal toxicity under these conditions. The effective doses of the lipid A analogs in both in vivo tests were, however, several hundred times higher than those of bacterial lipid A. For the activities in vivo, hydroxyacyl residues seemed to be important. Anticomplement activity was demonstrable in seven preparations, one of which expressed an activity comparable to that of lipid A. Preparations containing non-hydroxylated fatty acids seemed to be most active in this test. None of the synthetic preparations was found to exhibit gelation activity for Limulus amoebocyte lysate when tested in doses up to 0.4 ,ug, whereas bacterial free lipid A was active in doses of about 2 pg. None of the monosaccharide derivatives exhibited any of these activities.

Immunopharmacological activities of a synthetic counterpart of a biosynthetic lipid A precursor molecule and of its analogs

“…Contrary to expectation, the immunopharmacological activities of these synthetic preparations were far less than those of natural products (lipid A and lipopolysaccharide [LPS]), although some compounds exhibited detectable activities in some assay systems (13). Similar findings have been obtained by other investigators (14,18,28,29) with the notable exception of Yasuda et al (31,32), who have reported definite biological activities of the analogs incorporated in artificial membrane vesicles.…”

Endotoxic induction of prostaglandin release from macrophages by nontoxic lipid A analogs synthesized chemically

“…In this regard, it seemed interesting to test some biological activities of the compounds which resemble the native compound structurally but are biologically nontoxic. The synthetic lipid A analogs used in these experiments were previously found to be almost inactive compared with native LPS or lipid A because the position of fatty acid substitution was incorrect (29,30). Surprisingly, however, some of these compounds, when used to induce prostaglandin synthesis, were found to exhibit activities that nearly equaled that of native LPS.…”

“…Stimulants of prostaglandin release. Lipopolysaccharide (LPS) from Salmonella minnesota R595 (7) and the synthetic lipid A analogs (12)(13)(14) have been described previously (30). The chemical structures of the synthetic preparations used in this study are shown in Fig.…”

“…Among these constituents, the position of fatty acid substitution was especially critical for endotoxic activities (4,16,19). Thus the compounds whose fatty acids were substituted at positions 2, 3, and 4 of a reducing glucosamine residue and positions 2 and 6 of a nonreducing glucosamine residue and which were first synthesized after the old model of lipid A structure were almost inactive compared with natural lipid A (29,30).…”

Chemical composition of the lipopolysaccharide from Edwardsiella tarda.

“…In E. tarda, lipid A has non hydroxylated fatty acids: myristic acid, palmitic acid, 2-tetradecenoic acid and hexadecenoic acid. TANAMOTO et al (1984) showed that preparations containing non-hydroxylated fatty acids were im munosuppressors using an anticomplement activity tests. By elimination of these non-hydroxylated fatty acids, the LPS from E. tarda may improved the immunogen for immunization of eels.…”