Objective-The relationship between Chlamydia pneumoniae (Cpn) infection and arterial measures of preclinical atherosclerosis has remained controversial. Because atherogenesis begins in early life, we examined whether carotid and aortic intima-media thickness (IMT) and brachial artery endothelial function are associated with Cpn seropositivity in children. Methods and Results-Cpn-specific IgG and IgA antibodies were assessed by enzyme immunoassay in 199 healthy children followed-up annually from 7 to 11 years of age. Carotid (cIMT) and aortic IMT (aIMT), and brachial artery flow-mediated dilatation (FMD) were measured in 137 of the 199 children at the age of 11 years using high-resolution ultrasound. Research into the infectious hypothesis in the pathogenesis of atherosclerosis has focused, in particular, on Chlamydia pneumoniae (Cpn), an obligate intracellular human pathogen responsible for a significant portion of atypical pneumonia. The evidence of Cpn as a causative agent in the development of atherosclerosis is based on seroepidemiological studies, 3 and detection of viable Cpn from the atheromas of coronary, carotid and femoral arteries, and of abdominal aortic aneurysms. 4,5 However, in the available studies in adults, the relation of Cpn infection to endothelial dysfunction and increased intima-media thickness of the common carotid artery (cIMT), 2 measures of subclinical atherosclerosis, has not been conclusively demonstrated.High-resolution ultrasound is a reliable noninvasive method for detecting early functional and structural atherosclerotic changes in the arterial wall. Flow-mediated dilatation (FMD) of the brachial artery is a marker of endothelial function. 6 The carotid artery has been the target in the assessment of early structural vascular changes because it is located superficially on the neck and is thus easily visualized by ultrasound. However, autopsy studies have shown that the earliest morphological alterations in the arterial wall emerge in the abdominal aorta. 7 Therefore, intima-media thickness of the abdominal aorta (aIMT) may provide an even better index of preclinical atherosclerosis than cIMT. Consistent with this idea, we have recently shown that children with increased risk factor load are more efficiently identified by measuring aIMT than cIMT, which shows more overlapping with healthy controls. 8 Numerous cardiovascular risk factors have been related to early functional and structural vascular wall changes already in the first decade of life. 9 -13 In addition, impaired FMD and increased cIMT have been demonstrated in HIV-infected children, 14 and in children with elevated C-reactive protein (CRP) concentrations. 15 Currently, there are no data on the association between exposure to Cpn and markers of subclinical atherosclerosis in childhood. Therefore, we assessed whether the thickness of aortic and carotid intima-media complex, and brachial artery reactivity are related to Cpn seropositivity in otherwise healthy children.
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