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(Circulation. 2003;107:1966.)
© 2003 American Heart Association, Inc.

Clinical Investigation and Reports

Absence of Association Between Infectious Agents and Endothelial Function in Healthy Young Men

Paul Khairy, MD, MSc; Stéphane Rinfret, MD, MSc; Jean-Claude Tardif, MD; Richard Marchand, MD; Stan Shapiro, PhD; James Brophy, MD, PhD; Jocelyn Dupuis, MD, PhD

From the Department of Medicine (P.K., S.R., J.-C.T., R.M., J.D.), Montreal Heart Institute, University of Montreal, and Department of Epidemiology and Biostatistics (P.K., S.S., J.B.), McGill University, Montreal, Quebec, Canada.

Correspondence to Jocelyn Dupuis, MD, PhD, Research Center, Montreal Heart Institute, 5000 Belanger St East, Montreal, Quebec, Canada H1T 1C8. E-mail dupuisj{at}icm.umontreal.ca

	Abstract

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Background— Although several studies have reported correlations between infections and coronary artery disease, associations with endothelial dysfunction, its precursor, have not been established. This study assessed whether infection with Chlamydia pneumoniae (CP), cytomegalovirus (CMV), Epstein-Barr virus (EBV), or Helicobacter pylori (HP) is associated with decreased endothelial function.

Methods and Results— Sixty-five male subjects, aged 20 to 45 years, with no risk factors or known coronary artery disease were enrolled in a seroepidemiological cross-sectional study. Endothelial function was determined by flow-mediated brachial vasodilation. Serum antibodies consisting of anti-CP IgG and IgM, anti-CMV IgG, anti-EBV nuclear antigen, and anti-HP IgG and markers of inflammation including high-sensitivity C-reactive protein were measured. Average age was 29.3±5.5 years. Seroprevalence values were 65.1%, 34.9%, 88.9%, and 14.3% for CP, CMV, EBV, and HP, respectively. Average values for endothelium-dependent and -independent vasodilation were 9.4±4.5% and 12.6±5.0%. Despite adequate statistical power (82% for the primary end point), no association between endothelial function and seropositivity to individual infectious agents, infectious burden, or C-reactive protein was observed in regression analyses controlling for variables including age, blood pressure, and lipid parameters. Moreover, no dose-response trends between serum titers and endothelial function were found.

Conclusions— Lack of association between chronic infection with CP, CMV, EBV, HP, or pathogen burden and endothelial function was observed, suggesting that these agents are not implicated as early etiologic triggers in the genesis of coronary artery disease. These results do not preclude active involvement at later stages of the pathophysiological process, such as acceleration of existing atherosclerosis and acute plaque rupture.

Key Words: endothelium • vasodilation • infection

	Introduction

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Numerous studies have suggested potential associations between coronary artery disease (CAD) and various infectious agents. Cytomegalovirus (CMV) has been associated with atherosclerosis, transplantation vasculopathy, vascular allograft rejection, and restenosis after angioplasty.¹ Ebstein-Barr virus (EBV) has been shown to infect human endothelial cells and has been implicated in coronary aneurysm formation and isolated from cardiac and aortic tissues.² Furthermore, both EBV and CMV have been positively correlated with angiographically determined CAD.³ Although controversial, Helicobacter pylori (HP) has been correlated with various forms of atherosclerosis.^4,5 The body of evidence supporting an association between Chlamydia pneumoniae (CP) and CAD continues to grow at a rapid pace and includes seroepidemiological, histopathologic, and observational studies.^6–10 Small clinical trials have focused on secondary prevention, and larger studies are underway.¹¹

Despite these numerous reports, an association between seropositivity to infectious agents and endothelial dysfunction, an early event in the development of coronary atherosclerosis,¹² has not been conclusively demonstrated. Identifying such an association may contribute to better defining the pathophysiological process and, perhaps, redirecting therapy toward primary prevention. The objective of this study was, therefore, to determine whether seropositivity to CP, CMV, EBV, or HP is associated with decreased endothelial function in young men with no known CAD or risk factors.

	Methods

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Overview of Study Design
A seroepidemiological cross-sectional study was performed at the Montreal Heart Institute between January 1999 and March 2001. After obtaining informed consent, a brief questionnaire was administered on relevant past medical history, blood pressure measurements were taken, and fasting blood samples were drawn. Serum samples were divided into 500- or 1000-µL aliquots, frozen, and maintained at -80°C until dispatched on dry ice to participating laboratories. On the same day as blood sampling, brachial ultrasonography was performed. The institutional review board approved the study.

Population
The study population consisted of male volunteers, 20 to 45 years of age. Inclusion was restricted to men given hormonal variations that limit reproducibility of endothelial function testing in premenopausal women.¹³ Because the primary focus was detection of endothelial dysfunction before development of CAD, patients with already established disease were excluded, as were those older than 45 years of age, given the greater likelihood of subclinical CAD. Subjects with any of the following were likewise excluded: family history of premature CAD (ie, first-degree male or female relative <45 or <55 years of age, respectively), known hypertension or systolic blood pressure >160 mm Hg or diastolic blood pressure >90 mm Hg, dyslipidemia (LDL >5 mmol/L, total cholesterol/HDL >7 mmol/L, or fasting triglycerides >3 mmol/L), diabetes mellitus (known diabetes or fasting blood sugar >7 mmol/L), or cigarette smoking (1 cigarette/d currently or within the previous 5 years).

Endothelial Function
Endothelial function was assessed by brachial artery flow-mediated reactive hyperemia, with reproducibility >98% and a positive predictive value of 95% for coronary endothelial dysfunction.¹⁴ A 10% cutoff value has 91% sensitivity and 95% negative predictive value for functionally significant CAD.¹⁵ All studies were conducted by 2 trained research technicians (who previously performed 240 tests)¹⁶ and were reviewed by an experienced cardiologist (J.C.T.). Arterial diameter was assessed by high-resolution ultrasound with a standard 7.5-MHz linear transducer. A nontortuous segment of the brachial artery above the antecubital fossa was identified and scanned in a longitudinal fashion. Once depth and gain settings were adjusted to optimize images of the lumen to arterial wall interface, baseline scanning was performed with images magnified in a 20- by 20-mm viewing window. A pneumatic blood pressure cuff positioned above the elbow was then inflated to 60 mm Hg above systolic pressure for 5 minutes, after which the cuff was released and the artery imaged continuously for 5 minutes. Mean diameter of the 20-mm brachial artery segment was quantified by means of proprietary software. Frames from 3 consecutive cycles were taken at the R-wave peak, and results were averaged. Percent flow-mediated dilation measured 1 minute after cuff deflation was used as an index of endothelium-dependent vasodilation; percent dilation obtained 3 minutes after administration of nitroglycerin spray (400 µg) represented endothelium-independent dilation.

Laboratory Analyses
C-reactive protein (CRP) levels were quantified by an automated high-sensitivity enzyme immunoassay (Dade Behring).¹⁷ Anti-CP IgG and IgM antibodies were measured at National Microbiology Laboratories of Health Canada by microimmunofluorescence by using TWAR strain AR-39 as antigen (University of Washington Research Foundation).¹⁸ Lipopolysaccharide (LPS)-containing immune complexes were detected by 2 antigen-specific enzyme immunoassays.⁶ In short, for the LPS capture assay, microliter plates were coated with IgG2a mouse monoclonal antibody specific to chlamydia LPS. Sera were diluted 1:100, and alkaline phosphatase-conjugated anti-human IgM was used to detect antibody. Subjects were considered seropositive if anti-CP IgG was 1:64 with IgM <1:8.¹⁰ Sera were screened for CMV IgG antibodies at the Regional Virology Laboratory of Laval Hospital (Quebec, Canada) with an ELISA (Axsym CMV IgG assay, Abbott Labs).¹⁹ Results were expressed in antibody units (AU) per milliliter, with a positive cutoff value >15 AU/mL. Immunoglobulin G antibodies to EBV nuclear antigen were measured at the same laboratory by using immunofluorescence microplate titration by serial dilution. Threshold for seropositivity was defined as 1:10. HP-specific IgG was measured with an ELISA assay (Wampole Laboratories), with cutoff for seropositivity 1.10.²⁰

Statistical Analyses
Sample size requirements were calculated with an independent t test for comparison of means assuming 50% seroprevalence of CP, 2-tailed of 0.05, and flow-mediated endothelial dilation of 8.3±3.5%²¹ in seronegative controls. A total of 62 men were required to obtain a power of 80% to detect a 30% difference in endothelial function. Continuous data were compared with Wilcoxon rank-sum test and expressed as mean±SD or median with interquartile (25th and 75th) range. Discrete data, expressed as percentage, were compared with Fisher’s exact test. Multiple regression models for individual infectious agents and total pathogen burden assessed relationships and trends with endothelial function and markers of inflammation while controlling for potential confounders, baseline imbalances, and known risk factors for endothelial dysfunction. Jackknife residuals and Cook’s D statistics were used to identify potential outliers and influential observations. All analyses were performed with SAS software Version 8. A 2-tailed probability value <0.05 was considered statistically significant.

	Results

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Completeness of Data
A total of 65 men were enrolled in the study. Two subjects were excluded because of misplaced serum samples. Complete information was available for the remaining 63 subjects, with the exception of one missing value for a high-sensitivity CRP, substituted by a standard assay measure. An excellent concordance between both assays has been previously demonstrated, with total imprecision <8%.²²

Baseline Characteristics
Average age was 29.3±5.5 years. Mean lipid values were total cholesterol 4.6±0.9 mmol/L, LDL 2.9±0.8 mmol/L, HDL 1.3±0.3 mmol/L, and triglycerides 1.0±0.5 mmol/L. Endothelium-dependent vasodilation displayed considerable variability, with a mean of 9.3±4.5% and range of 1.1% to 20.0% (Figure 1). Baseline brachial artery diameter was 3.8±0.4 mm, with an average endothelial-independent vasodilation of 12.6±5.0%. Seropositivity to CP, EBV, CMV, and HP was 65.1%, 88.9%, 34.9%, and 14.3%, respectively (Table 1). Baseline characteristics stratified by seropositivity status to CP are summarized in Table 2. Coexistence of infections was noted, with statistically significant pairwise correlations involving the 4 agents (Table 2). As previously reported, an inverse correlation between flow-mediated vascular reactivity and vessel size was noted (r=-0.274, P=0.0294).²³

View larger version (46K): [in this window] [in a new window]   Figure 1. Distribution of endothelial-dependent vasodilation and CRP.

View this table: [in this window] [in a new window]   TABLE 1. Descriptive Analysis of Exposure Variables

View this table: [in this window] [in a new window]   TABLE 2. Distribution of Variables According to Seropositivity to Chlamydia pneumoniae

Markers of Inflammation
Fibrinogen levels were normally distributed (2.7±0.6 g/L), but CRP values were skewed leftwards (Figure 1) with a median of 0.57 mg/L. Fibrinogen and CRP were positively correlated (r=0.465, P<0.0001) but not associated with vascular reactivity. Although seropositivity to CP was associated with increased fibrinogen (r=0.296, P=0.0183), no association between any infectious agent and CRP was observed. Similarly, no association between endothelial function and markers of inflammation (ie, CRP, fibrinogen, leukocytes, and platelets) considered separately or collectively (F_4,49=0.35, P=0.8447) was noted.

Infection and Endothelial Function
In univariate analyses, no correlation between infectious agents and vascular function was observed. On the basis of previously described relationships, the following known potential confounders were included in all multiple regression models: age, blood pressure, LDL, HDL, triglycerides, and baseline brachial artery diameter. Additional variables were considered if they displayed unequal distribution by seropositivity status. Overall, seropositivity to CP, CMV, EBV, or HP was not predictive of endothelial function. Endothelium-dependent flow-mediated vasodilation and parameter estimates are summarized in Table 3. Regression models were recreated with seropositivity to CP and EBV expressed ordinally and CMV continuously. No association between any infectious agent and endothelial function was noted. In addition, no trend between antibody levels and endothelial function was observed (Figure 2). Every possible cutoff value for seropositivity to each agent was retested, and no association with endothelial function was found.

View this table: [in this window] [in a new window]   TABLE 3. Flow-Mediated Vasodilation by Infectious Agent

View larger version (24K): [in this window] [in a new window]   Figure 2. Simple linear regression plot of anti-CP titers with 95% confidence intervals around the slope and mean.

In addition, the total infectious burden (ie, whether subjects were seropositive to 0, 1, 2, 3, or 4 infectious agents), depicted in Figure 3, had no bearing on endothelial function, with a trend in the opposite direction of the hypothesized effect (P=0.2535). All pairwise comparisons (eg, seropositivity to 0 versus 4 agents) were likewise not statistically significant.

View larger version (22K): [in this window] [in a new window]   Figure 3. Total infectious burden and endothelial-dependent vasodilation.

	Discussion

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Seroprevalence rates of CP, EBV, CMV, and HP (65.1%, 88.9%, 34.9%, and 14.3%) were consistent with previous reports in young patient populations.^7,24 Moreover, coexistence of these infections has been well-described.⁸ The endothelial function score of 9.3±4.5% was likewise consistent with values of 8.3±3.5%²¹ and 10.5±0.6%¹⁵ in patients with no risk factors for CAD and negative exercise myocardial perfusion imaging, respectively.

Despite documented associations, evidence implicating infectious agents in CAD pathogenesis is circumstantial. In this young population, despite having similar infection loads as older reported populations, no effect on endothelial function was found. These results are consistent with the lack of increased atherothrombotic risk reported by Ridker and colleagues in apparently healthy older men seropositive to CP²⁵ and CMV.²⁶ Similarly, a recent study in an elderly patient population found no association between infection to CP, HP, and CMV and increased risk of cardiovascular disease.²⁷

Results of this study were robust in that, in this relatively homogeneous population, no correlation or trends were found with total infectious burden or individual antibody titers at predetermined threshold levels and all possible cutoff values. Moreover, effects of gender, smoking, and family history of premature CAD were controlled by restriction. Consistent with these findings, Sharma et al²⁸ reported no significant correlation between CP and flow-mediated vasodilation in patients without CAD, diabetes, hypertension, or dyslipidemia. In a subgroup analysis of 86 patients with no angiographically significant CAD, Prasad et al²⁹ found a significant correlation between total infectious burden to 5 investigated agents (CP, CMV, HP, hepatitis A virus, and herpes simplex virus) and decreased intracoronary endothelium-dependent vasodilation (P=0.03). This apparent discrepancy may be related, in part, to different patient populations, infectious agents studied, and methods of assessing outcome. Interactive effects between conventional risk factors and infectious agents could not be excluded in this older patient population (56±1 years), in whom more than half were hypertensive and smokers and roughly 20% were diabetic. Because subjects with traditional risk factors were excluded from our study, interactions with infections could not be assessed.

Seropositivity to CP or CMV has been positively correlated with CRP in patients with carotid atherosclerosis³⁰ and angiographically demonstrated CAD³¹ and in chronic peritoneal dialysis recipients,⁹ in whom a high prevalence of accelerated atherosclerosis is expected. However, the lack of association observed in this study is consistent with a report documenting no association between CP or CMV with CRP and interleukin-6 in healthy subjects.³² Independent of seropositivity status, CRP may increase as a result of vascular inflammation induced by atherosclerosis, whether or not it contributes to accelerating this process.^33,34 Similarly, both fibrinogen and CRP were found not to be associated with endothelial function. A correlation between markers of inflammation and endothelial dysfunction has likewise not been clearly demonstrated in healthy young subjects, unlike in patients with CAD³⁵ or insulin-dependent diabetes.³⁶

Although results of this study argue against a chronic low-grade infection being responsible for initial injury that induces atherosclerosis, several possible scenarios remain. First, organisms may persist in vascular cells but not contribute to pathological abnormalities.³⁷ Another possible scenario that integrates results of the present study and previous reports is that one or more infectious agent, although not responsible for initial endothelial injury, may accelerate progression of atherosclerosis or promote plaque rupture. Mahony and Coombes³⁸ have proposed an integrated model whereby CP has a contributory rather than causal role, persistently infecting T-cells, macrophages, and endothelial cells and contributing to a sustained inflammatory response. Thus, rather than initiating, infectious agents may promote, sustain, or accelerate atherosclerosis. Alternatively, they may be implicated in the final stages of vessel occlusion. Inflammatory infiltrates found in ruptured plaques suggest an immune component to plaque vulnerability. Infectious agents may act as extrinsic triggers by inciting an inflammatory reaction, activating macrophages and T-lymphocytes within the plaque, or attracting these cells toward the plaque.³⁹ Production of cytokines may promote secretion of metalloproteinases that degrade fibrous capsules, resulting in plaque fissuring. Indeed, CP selectively upregulates 92-kDa gelatinase that actively destroys extracellular matrix.⁴⁰

Limitations
The latency period between seropositivity to CP, CMV, EBV, or HP and measurable effects on endothelial function, if any, is unknown. Duration of infection before endothelial function testing could not be inferred from serological tests, because IgG antibodies reflect infection from birth until sampling.

The volunteer sampling method, in our opinion, is unlikely to have introduced selection bias. The true relationship between exposure and outcome will be biased only if eligible nonparticipants differ with regard to both seropositivity status and other risk factors for endothelial dysfunction. To guard against this theoretical scenario, the study population was narrowly defined with restrictive eligibility criteria and exclusion of subjects with factors known to be associated with endothelial dysfunction. If eligible nonparticipants differ only with respect to outcome, endothelial function tests in participants may differ from those in the targeted population. This is unlikely given endothelial function scores consistent with previous reports. Similarly, if eligible nonparticipants differ only with respect to seropositivity status, the strength of association will retain its validity but may overestimate or underestimate true population seroprevalence rates.

Endothelial function score and standard deviation were higher than anticipated, and seroprevalence rates deviated from an equally distributed pattern. Net effect on power calculations are summarized in Table 4. To detect the prespecified 30% difference in endothelial function, a power of 81.7% was obtained for CP. In contrast, power calculations of 73.1%, 54.3%, and 47.7% were obtained for CMV, EBV, and HP, respectively. Absence of trends between antibody titers and endothelial function and the confidence intervals obtained suggest that the lack of association observed is not simply the result of underpowering. Nevertheless, the purported risk associated with infection may be smaller than for traditional risk and produce changes in endothelial function of a magnitude below the detection threshold determined by the study power.

View this table: [in this window] [in a new window]   TABLE 4. Power Calculations

At the expense of generalizability, a relatively homogeneous population was deliberately selected to increase precision regarding inference about disease etiology and offer some protection against unmeasured variables, such as body mass index, diet, vasoactive substances, and exercise patterns, that may contribute to variability in endothelial function but are less likely associated with seropositivity status.^41,42

Conclusion
In conclusion, this seroepidemiological cross-sectional study demonstrated a lack of association between prior infection to CP, CMV, EBV, or HP and endothelial function. Total infectious burden and high-sensitivity CRP were likewise not correlated with endothelial function. Because endothelial dysfunction is a precursor to CAD, these results suggest that a chronic low-grade infection with these agents is unlikely to be responsible for initiating CAD but do not preclude a role in later stages of the pathophysiological process, such as acceleration of atherosclerosis or plaque rupture.

	Acknowledgments

 
This work was supported in part by a fellowship award (to Dr Khairy) from the Canadian Institutes of Health Research. Drs Dupuis and Tardif are senior scholars from the Fonds de la recherche en santé du Québec. The authors are indebted to Francine Poulin and Marie Gagnon for their excellent technical support and Dr Claire Béliveau for supervising laboratory analyses.

Received December 31, 2002; accepted February 4, 2003.

	References

Top Abstract Introduction Methods Results Discussion References

 

1. Dengler TJ, Raftery MJ, Werle M, et al. Cytomegalovirus infection of vascular cells induces expression of pro-inflammatory adhesion molecules by paracrine action of secreted interleukin-1ß. Transplantation. 2000; 69: 1160–1168.[CrossRef][Medline] [Order article via Infotrieve]
   
2. Jones K, Rivera C, Sgadari C, et al. Infection of human endothelial cells with Epstein-Barr virus. J Exp Med. 1995; 182: 1213–1221.[Abstract/Free Full Text]
   
3. Musiani M, Zerbini ML, Muscari A, et al. Antibody patterns against cytomegalovirus and Epstein-Barr virus in human atherosclerosis. Microbiologica. 1990; 13: 35–41.[Medline] [Order article via Infotrieve]
   
4. Franceschi F, Sepulveda AR, Gasbarrini A, et al. Cross-reactivity of anti-CagA antibodies with vascular wall antigens: possible pathogenic link between Helicobacter pylori infection and atherosclerosis. Circulation. 2002; 106: 430–434.[Abstract/Free Full Text]
   
5. Mayr M, Kiechl S, Willeit J, et al. Infections, immunity, and atherosclerosis: associations of antibodies to Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus with immune reactions to heat-shock protein 60 and carotid or femoral atherosclerosis. Circulation. 2000; 102: 833–839.[Abstract/Free Full Text]
   
6. Leinonen M, Linnanmaki E, Mattila K, et al. Circulating immune complexes containing chlamydial lipopolysaccharide in acute myocardial infarction. Microb Pathog. 1990; 9: 67–73.[CrossRef][Medline] [Order article via Infotrieve]
   
7. Ferrari M, Poli A, Olivieri M, et al. Seroprevalence of Chlamydia pneumoniae antibodies in a young adult population sample living in Verona. Infection. 2000; 28: 38–41.[CrossRef][Medline] [Order article via Infotrieve]
   
8. Gattone M, Iacoviello L, Colombo M, et al. Chlamydia pneumoniae and cytomegalovirus seropositivity, inflammatory markers, and the risk of myocardial infarction at a young age. Am Heart J. 2001; 142: 633–640.[CrossRef][Medline] [Order article via Infotrieve]
   
9. Haubitz M, Brunkhorst R. C-reactive protein and chronic Chlamydia pneumoniae infection long-term predictors for cardiovascular disease and survival in patients on peritoneal dialysis. Nephrol Dial Transplant. 2001; 16: 809–815.[Abstract/Free Full Text]
   
10. Patel P, Mendall MA, Carrington D, et al. Association of Helicobacter pylori and Chlamydia pneumoniae infections with coronary heart disease and cardiovascular risk factors. BMJ. 1995; 311: 711–714.[Abstract/Free Full Text]
    
11. Anderson JL, Muhlestein JB, Carlquist J, et al. Randomized secondary prevention trial of azithromycin in patients with coronary artery disease and serological evidence for Chlamydia pneumoniae infection. Circulation. 1999; 99: 1540–1547.[Abstract/Free Full Text]
    
12. Ross R. Atherosclerosis: an inflammatory disease. N Engl J Med. 1999; 340: 115–126.[Free Full Text]
    
13. Chowienczyk PJ, Watts GF, Cockcroft JR, et al. Sex differences in endothelial function in normal and hypercholesterolaemic subjects. Lancet. 1994; 344: 305–306.[CrossRef][Medline] [Order article via Infotrieve]
    
14. Anderson TJ, Uehata A, Gerhard MD, et al. Close relation of endothelial function in the human coronary and peripheral circulations. J Am Coll Cardiol. 1995; 26: 1235–1241.[Abstract]
    
15. Kuvin JT, Patel AR, Sliney KA, et al. Peripheral vascular endothelial function testing as a noninvasive indicator of coronary artery disease. J Am Coll Cardiol. 2001; 38: 1843–1849.[Abstract/Free Full Text]
    
16. Dupuis J, Tardif JC, Cernacek P, et al. Cholesterol reduction rapidly improves endothelial function after acute coronary syndromes. Circulation. 1999; 99: 3227–3233.[Abstract/Free Full Text]
    
17. Rifai N, Tracy RP, Ridker PM. Clinical efficacy of an automated high-sensitivity C-reactive protein assay. Clin Chem. 1999; 45: 2136–2141.[Abstract/Free Full Text]
    
18. Wang SP, Grayston JT. Microimmunofluorescence serological studies with the TWAR organism. In: Oriel JD, Ridgeway G, Schachter J, et al, eds. Chlamydial Infections. Cambridge: Cambridge University Press; 1986: 329–332.
    
19. Chiu B, Viira E, Tucker W, et al. Chlamydia pneumoniae, cytomegalovirus, and herpes simplex virus in atherosclerosis of the carotid artery. Circulation. 1997; 96: 2144–2148.[Abstract/Free Full Text]
    
20. Evans DJ Jr, Evans DG, Graham DY, et al. A sensitive and specific serologic test for detection of Campylobacter pylori infection. Gastroenterology. 1989; 96: 1004–1008.[Medline] [Order article via Infotrieve]
    
21. Clarkson P, Celermajer DS, Powe AJ, et al. Endothelium-dependent dilatation is impaired in young healthy subjects with a family history of premature coronary disease. Circulation. 1997; 96: 3378–3383.[Abstract/Free Full Text]
    
22. Roberts WL, Schwarz EL, Ayanian S, et al. Performance characteristics of a point of care C-reactive protein assay. Clin Chim Acta. 2001; 314: 255–259.[CrossRef][Medline] [Order article via Infotrieve]
    
23. Celermajer DS, Sorensen KE, Bull C, et al. Endothelium-dependent dilation in the systemic arteries of asymptomatic subjects relates to coronary risk factors and their interaction. J Am Coll Cardiol. 1994; 24: 1468–1474.[Abstract]
    
24. Cohen JI. Epstein-Barr virus infection. N Engl J Med. 2000; 343: 481–492.[Free Full Text]
    
25. Ridker PM, Kundsin RB, Stampfer MJ, et al. Prospective study of Chlamydia pneumoniae IgG seropositivity and risks of future myocardial infarction. Circulation. 1999; 99: 1161–1164.[Abstract/Free Full Text]
    
26. Ridker PM, Hennekens CH, Stampfer MJ, et al. Prospective study of herpes simplex virus, cytomegalovirus, and the risk of future myocardial infarction and stroke. Circulation. 1998; 98: 2796–2799.[Abstract/Free Full Text]
    
27. Haider AW, Wilson PW, Larson MG, et al. The association of seropositivity to Helicobacter pylori, Chlamydia pneumoniae, and cytomegalovirus with risk of cardiovascular disease: a prospective study. J Am Coll Cardiol. 2002; 40: 1408–1413.[Abstract/Free Full Text]
    
28. Sharma N, Rutherford JD, Grayston JT, et al. Association between C-reactive protein, anti-Chlamydia pneumoniae antibodies, and vascular function in healthy adults. Am J Cardiol. 2001; 87: 119–121.[CrossRef][Medline] [Order article via Infotrieve]
    
29. Prasad A, Zhu J, Halcox JP, et al. Predisposition to atherosclerosis by infections: role of endothelial dysfunction. Circulation. 2002; 106: 184–190.[Abstract/Free Full Text]
    
30. Johnston SC, Messina LM, Browner WS, et al. C-reactive protein levels and viable Chlamydia pneumoniae in carotid artery atherosclerosis. Stroke. 2001; 32: 2748–2752.[Abstract/Free Full Text]
    
31. Muhlestein JB, Horne BD, Carlquist JF, et al. Cytomegalovirus seropositivity and C-reactive protein have independent and combined predictive value for mortality in patients with angiographically demonstrated coronary artery disease. Circulation. 2000; 102: 1917–1923.[Abstract/Free Full Text]
    
32. Yudkin JS, Stehouwer CD, Emeis JJ, et al. C-reactive protein in healthy subjects: associations with obesity, insulin resistance, and endothelial dysfunction. Arterioscler Thromb Vasc Biol. 1999; 19: 972–978.[Abstract/Free Full Text]
    
33. Pasceri V, Willerson JT, Yeh ET. Direct proinflammatory effect of C-reactive protein on human endothelial cells. Circulation. 2000; 102: 2165–2168.[Abstract/Free Full Text]
    
34. Ridker PM, Rifai N, Rose L, et al. Comparison of C-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. N Engl J Med. 2002; 347: 1557–1565.[Abstract/Free Full Text]
    
35. Fichtlscherer S, Rosenberger G, Walter DH, et al. Elevated C-reactive protein levels and impaired endothelial vasoreactivity in patients with coronary artery disease. Circulation. 2000; 102: 1000–1006.[Abstract/Free Full Text]
    
36. Schalkwijk CG, Poland DC, van Dijk W, et al. Plasma concentration of C-reactive protein is increased in type I diabetic patients without clinical macroangiopathy and correlates with markers of endothelial dysfunction: evidence for chronic inflammation. Diabetologia. 1999; 42: 351–357.[CrossRef][Medline] [Order article via Infotrieve]
    
37. Jackson LA, Campbell LA, Schmidt RA, et al. Specificity of detection of Chlamydia pneumoniae in cardiovascular atheroma: evaluation of the innocent bystander hypothesis. Am J Pathol. 1997; 150: 1785–1790.[Abstract]
    
38. Mahony JB, Coombes BK. Chlamydia pneumoniae and atherosclerosis: does the evidence support a causal or contributory role? FEMS Microbiol Lett. 2001; 197: 1–9.[CrossRef][Medline] [Order article via Infotrieve]
    
39. Shah PK. Plaque disruption and thrombosis: potential role of inflammation and infection. Cardiol Rev. 2000; 8: 31–39.[CrossRef][Medline] [Order article via Infotrieve]
    
40. Vehmaan-Kreula P, Puolakkainen M, Sarvas M, et al. Chlamydia pneumoniae proteins induce secretion of the 92-kDa gelatinase by human monocyte-derived macrophages. Arterioscler Thromb Vasc Biol. 2001; 21: E1–E8.
    
41. Brook RD, Bard RL, Rubenfire M, et al. Usefulness of visceral obesity (waist/hip ratio) in predicting vascular endothelial function in healthy overweight adults. Am J Cardiol. 2001; 88: 1264–1269.[CrossRef][Medline] [Order article via Infotrieve]
    
42. Abbott RA, Harkness MA, Davies PS. Correlation of habitual physical activity levels with flow-mediated dilation of the brachial artery in 5–10 year old children. Atherosclerosis. 2002; 160: 233–239.[CrossRef][Medline] [Order article via Infotrieve]
    

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				S. Verma, C.-H. Wang, E. Lonn, F. Charbonneau, J. Buithieu, L. M. Title, M. Fung, S. Edworthy, A. C. Robertson, T. J. Anderson, et al. Cross-sectional evaluation of brachial artery flow-mediated vasodilation and C-reactive protein in healthy individuals Eur. Heart J., October 1, 2004; 25(19): 1754 - 1760. [Abstract] [Full Text] [PDF]

				J.-C. Kaski, P. Khairy, S. Rinfret, J.-C. Tardif, R. Marchand, S. Shapiro, J. Brophy, and J. Dupuis Infection, Endothelial Dysfunction, and Atherogenesis * Response Circulation, December 23, 2003; 108 (25): e171 - e172. [Full Text] [PDF]

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