A comparative study of biological activities of lipoteichoic acid and lipopolysaccharide

Abstract

Lipoteichoic acids (LTAs) of Gram-positive bacteria and lipopolysaccharide (LPS) are structurally similar and share several biological activities. In this study, the capacity of LTAs for inducing the cell surface expression of adhesion molecules ICAM-1, VCAM-1, and ELAM-1 by HUVEC were investigated and compared to that of LPS. In the presence of serum, LTA from Staphylococcus aureus, Streptococcus sanguis, Streptococcus pyogenes and Streptococcus mutans dose-dependently stimulated adhesion molecule expression above control levels although they were 100-1000 times less potent than LPS. LTA from Streptococcus faecalis and Bacillus subtilis had no effects. Similar to LPS, the activity of the LTAs was dose-dependently inhibited by polymyxin B, whereas unlike LPS, LTA activity decreased in the presence of triethylamine. The LTAs also exhibited reactivity in the Limulus amebocyte lysate (LAL) assay correlating with their ability to induce ICAM-1 expression. However, their LAL reactivity was approximately 3-6 orders of magnitude less than that of LPS. Furthermore, LTA-stimulated ICAM-1 expression was serum-dependent and inhibited by anti-CD14 antibody, 63D3. Thus, LTA shares several properties with LPS including inhibition by polymyxin B, reactivity in the LAL assay, and stimulation of endothelial cells via a CD14-dependent mechanism. These results suggests a possible role for LTAs in the inflammatory response due to infections with Gram-positive bacteria.