A Novel Class of Endotoxin Receptor Agonists with Simplified Structure, Toll-Like Receptor 4-Dependent Immunostimulatory Action, and Adjuvant Activity

Abstract

A series of novel, synthetic compounds containing lipids linked to a phosphate-containing acyclic backbone are shown to have similar biological properties to lipopolysaccharide (LPS). These compounds showed intrinsic agonistic properties when tested for their ability to stimulate tumor necrosis factor-␣ in human whole blood and interleukin-6 in U373 human glioblastoma cells without added LPS coreceptor CD14. The presence of the LPS antagonist E5564 completely blocked responses, suggesting that the novel compounds and LPS share a common mechanism of cell activation. Stereoselectivity of the molecules was observed in vitro; compounds with an R,R,R,R-configuration were strongly agonistic, whereas compounds with an R,S,S,R-configuration were much weaker in their activity on human whole blood and U373 cells. We also tested the effect of the compounds in cells transfected with the LPS receptor Tolllike receptor 4 (TLR4), with similar results, further supporting a shared mechanism with LPS. This was confirmed in vivo where the agonists failed to elicit cytokine responses in C3H/HeJ mice lacking TLR4 signaling. Because LPS-like molecules enhance immune responses, the compounds were mixed with tetanus toxoid and administered to mice in an immunization protocol to test for adjuvant activity. They enhanced the generation of specific antibodies against tetanus toxoid. Our results indicate that these unique compounds behave as agonists of TLR4, resulting in responses similar to those elicited by LPS. They display adjuvant activity in vivo and may be useful for the development of vaccine therapies.

Antagonism of Lipopolysaccharide-Induced Blood Pressure Attenuation and Vascular Contractility

“…22,23,47,48 Eritoran, a second generation analogue of the lipid A component of LPS, prevented the loss of vascular contractility and led to normal vascular contractions after phenylephrine administration ( Figure 3F). Baumgarten et al have demonstrated that the use of Eritoran is beneficial to maintain cardiac function and myocyte contractility during endotoxemia.…”

Neisseria meningitidisLipooligosaccharide Structure-Dependent Activation of the Macrophage CD14/Toll-Like Receptor 4 Pathway

“…For example, synthetic tetra-acylated lipid A (lipid IVa) is an antagonist of LPS activation of human macrophages (9,21) and penta-acylated LPS extracted from Porphyromonas gingivalis containing extended and branched fatty acyl chains has attenuated activity (26). Hawkins et al (11), using synthetic simplified lipid A-like structures, showed that isomers with R,R,R,R-acyl chain configuration were strongly agonistic, whereas similar compounds with R,S,S,R-acyl chain configuration were much weaker in biologic activity.…”

Therapeutic Targeting of Toll-Like Receptors for Infectious and Inflammatory Diseases and Cancer

“…MPL has recently been licensed for use as a vaccine adjuvant (Casella and Mitchell, 2008). TLR4 agonists were also generated during the chemical synthetic program to make E5531 and E5564; some of these compounds, such as E6020 , have good adjuvant activity (Hawkins et al, 2002). Another class of compounds, the aminoalkyl glucosaminide phosphates (AGP), have been developed as immunomodulators that activate TLR4 (Stöver et al, 2004).…”