HELICOBACTER-PYLORI AND PORPHYROMONAS-GINGIVALIS LIPOPOLYSACCHARIDES ARE POORLY TRANSFERRED TO RECOMBINANT SOLUBLE CD14

Helicobacter pylori and Porphyromonas gingivalis are gram-negative bac teria associated with chronic inflammatory diseases, These bacteria po ssess lipopolysaccharides (LPSs) that are able to activate human monoc ytes to produce tumor necrosis factor alpha but fail to activate human endothelial cells to express E-selectin, With Escherichia coli LPS, t umor necrosis factor alpha activation requires membrane-bound CD14 and E-selectin expression requires soluble CD14 (sCD14). Therefore, the a bility of H. pylori and P. gingivalis LPSs to transfer to and bind sCD 14 was examined by using immobilized recombinant sCD14 and human serum or recombinant LPS-binding protein (LBP), H. pylori and P. gingivalis LPSs were transferred to sCD14 when serum or LBP was present. However , the transfer of these LPSs to CD14 in serum was significantly slower than the transfer of E. coli LPS. Quantitation of the transfer rates by Michaelis-Menten kinetics yielded K-m values of 6 and 0.1 nM for H. pylori and E. coli LPSs, respectively. The amount of P. gingivalis LP S required to obtain half-maximum binding to CD14 was approximately 10 -fold greater than the amount of E. coli LPS required. The slower tran sfer rates displayed by these LPSs fan be explained by the poor bindin g to LBP observed in direct binding assays. These results are consiste nt with the proportionately lower ability of these LPSs to activate mo nocytes compared with E. coli LPS. However, the ability of H. pylori a nd P. gingivalis LPSs to bind LBP and transfer to sCD14 demonstrates t hat the lack of endothelial cell CD14-dependent cell activation by the se LPSs occurs distal to sCD14 binding.