Chlamydia pneumoniaeSeropositivity Is Associated With Increased Plasma Levels of Soluble Cellular Adhesion Molecules in Community-Dwelling Subjects

Abstract

Background and Purpose— In vitro studies have demonstrated thatChlamydia pneumoniaeinfection of the endothelium increases the expression of adhesion molecules and chemokines, indicating thatC pneumoniaeinfection affects the adhesion and recruitment of leukocytes to the endothelium, which is believed to be involved in the initial steps of atherosclerosis. However, whether chronicC pneumoniaeinfection increases these molecules in vivo has not been elucidated. Methods— The association betweenC pneumoniaeseropositivity and plasma concentrations of soluble adhesion molecules and a chemokine was investigated in 200 community-dwelling residents free from cardiovascular diseases and medication. Plasma levels of IgA and IgG antibodies toC pneumoniaewere measured by enzyme-linked immunosorbent assay. Indices of IgG and IgA antibodies were determined as the ratio to the standardized positive control. The subjects were divided into 3 groups according to the indices of antibodies:C pneumoniaeseronegative (n=57, IgA1.1). Plasma concentrations of soluble forms of intercellular adhesion molecule-1 (ICAM-1), vascular cellular adhesion molecule-1, and monocyte chemoattractant protein-1 were determined by enzyme-linked immunosorbent assay. Results— Plasma concentrations of ICAM-1 (392±118, 398±94, 470±154 ng/mL,P=0.0004) and vascular cellular adhesion molecule-1 (402±146, 419±130, 472±181 ng/mL,P=0.03) were significantly different among theC pneumoniaeseronegative, intermediate, and seropositive groups respectively. However, plasma monocyte chemoattractant protein-1 was not significantly different among the 3 groups. Stepwise regression analysis showed that plasma concentration of ICAM-1 was significantly associated withC pneumoniaeseropositivity, independent of other known risk factors for atherosclerosis and carotid intima-media thickness. Conclusion— These findings indicate thatC pneumoniaeseropositivity is associated with higher plasma concentrations of soluble forms of adhesion molecules in the general population. The increase in circulating adhesion molecules may underlie the mechanisms linkingC pneumoniaeinfection and atherosclerosis in vivo.