FIGURE 6.

Triacylated lipid A-like molecules are LPS antagonists in whole blood. A, whole heparinized human blood was incubated with a fixed amount of E. coli K12 LPS (1 ng/ml). Thirty minutes prior to LPS addition, triacylated compounds were added to blood at different concentrations (dose response ranging from 10 μg/ml up to 1.37 ng/ml, diluted 1:3 in culture media). As controls, OM compounds were added to blood without LPS. Polymyxin B (starting concentration of 10 μg/ml) was used as a classical LPS blocker in this system. IL-6 was measured in conditioned supernatants after 6 h of incubation time by ELISA. Only OM-174-DP, OM-174-MP-EP, OM-174-MP, OM-294-DP, and OM-197-MP-AC showed evidence of LPS antagonism in this assay. This is a representative experiment of three experiments with different blood donors with similar results. B, whole heparinized human blood was incubated with a fixed amount of E. coli K12 LPS (50 ng/ml). Thirty minutes prior to LPS addition, OM-174-DP was added at the concentration of 10 μg/ml. The cytokines IL-1β, IL-8, TNF-α, and IP-10 were measured in conditioned supernatants after 6 h of incubation time by cytometric bead array for IL-1β, IL-8, and TNF-α and by ELISA for IP-10. OM-174-DP also inhibited LPS activation of these cytokines. This is a representative experiment of three experiments with different blood donors with similar results.