Bacterial cell envelopes (ghosts) but not S-layers activate human endothelial cells (HUVECs) through sCD14 and LBP mechanism

Bacterial cell-envelopes (called ghosts) and surface layers (S-layers) are discussed to be used as vaccines and/or adjuvants, consequently it is neces sary to find out which immunomodulatory mediators are induced in human cell s. The present work focuses on the effects of ghosts (Escherichia coli O26: B6), S-layers (Bacillus stearothermophilus) in comparison with LPS and anti biotic-inactivated whole bacteria (E. coli O26:B6) on human umbilical vein endothelial cells (HUVEC) with regard to the release of interleukin 6 (IL-6 ) and the expression of surface E-selectin and the role of lipopolysacchari de binding protein (LBP), soluble CD14 (sCD14) and serum for this activatio n. Endothelial cells responded to ghosts, whole bacteria and LPS with IL-6 rel ease up to 15000 pg/ml and surface E-selectin expression, while in contrast the response to S-layers with IL-6 release up to 500 pg/ml was very weak. Compared to LPS, 10-100-fold higher concentrations of bacterial ghosts and whole bacteria were required to induce the cytokine synthesis and E-selecti n expression. IL-6 release and E-selectin expression of HUVECs were reduced in the absence of serum and equivalent to unstimulated samples. We have al so studied the role of CD14 and LBP for the activation of endothelial cells using antiCD14 and antiLBP antibodies (Ab). AntiCD14 and antiLBP Ab both i nhibited IL-6 release and E-selectin expression in a dose dependent manner after stimulation with ghosts, whole bacteria and LPS but had no effect on S-layers stimulated cells. AntiCD14 Ab inhibited more effectively than anti LBP Ab. These findings suggest that bacterial ghosts but not: S-layers acti vate HUVECs through sCD14 and LBP dependent mechanisms. (C) 1999 Elsevier S cience Ltd. All rights reserved.