Detection of Chlamydia pneumoniae in peripheral blood mononuclear cells: correlation with inflammation and atherosclerosis in haemodialysis patients

Chlamydophila pneumoniae infection and cardiovascular disease

Atherosclerosis is a multifactorial vascular inflammatory process; however, the inciting cause for inflammation remains unclear. Two decades ago, Chlamydophila pneumoniae (formerly Chlamydia pneumoniae) infection was proposed as a putative etiologic agent. We performed a PubMed search using the keywords Chlamydia and atherosclerosis in a Boolean query to identify published studies on C. pneumoniae and its role in atherogenesis, and to understand research interest in this topic. We found 1,652 published articles on this topic between 1991 and 2011. We analyzed relevant published studies and found various serological, molecular, and animal modeling studies in the early period. Encouraged by positive results from these studies, more than a dozen antibiotic clinical-trials were subsequently conducted, which did not find clinical benefits of anti-Chlamydophila drug therapy. While many researchers believe that the organism is still important, negative clinical trials had a similar impact on overall research interest. With many novel mechanisms identified for atherogenesis, there is a need for newer paradigms in Chlamydophila-atherosclerosis research.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Inflammatory syndrome in patients on hemodialysis

Mortality is markedly elevated in hemodialysis (HD) patients. Between 30 and 50% of prevalent patients have elevated serum levels of inflammatory markers such as C-reactive protein and IL-6. The presence of inflammation, chronic or episodic, has been found to be associated with increased mortality risk. The causes of inflammation are multifactorial and include patient-related factors, such as underlying disease, comorbidity, oxidative stress, infections, obesity, and genetic or immunologic factors, or on the other side, HD-related factors, mainly depending on the membrane biocompatibility and dialysate quality. The adequate knowledge of these causes and their prevention or treatment if possible may contribute to improving the inflammatory state of patients who are on HD and possibly their mortality.

Cardiovascular Biomarkers in CKD: Pathophysiology and Implications for Clinical Management of Cardiac Disease

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with all forms of chronic kidney disease (CKD). The underlying pathological state is caused by a complex interplay of traditional and nontraditional risk factors that results in atherosclerosis, arteriosclerosis, and altered cardiac morphological characteristics. This multifactorial disease introduces new challenges in predicting and treating patients with CVD sufficiently early in the course of CKD to positively alter patient outcome. Asymptomatic individuals with progressive CVD are a group of patients that deserve focused attention because early detection and intervention may provide the best opportunity for improved outcome. However, identifying CVD in asymptomatic patients with CKD or end-stage renal disease remains a significant hurdle in the management of these patients. Recently, a number of cardiovascular biomarkers were identified as predictors of patient outcome in individuals with CVD and, with additional research, may be used to guide the early diagnosis of and therapy for CVD in patients with CKD. This review examines the pathophysiological characteristics and potential clinical role of these novel cardiovascular biomarkers in risk stratification, risk monitoring, and selection of preventive therapies for patients with CKD.

Association between seroprevalence of anti-chlamydial antibodies and long-term cardiovascular mortality in chronic hemodialysis patients

Chlamydial infection has been suspected in the pathogenesis of ischemic heart disease. However, it remains undetermined if persistent chlamydial infection is related to cardiovascular mortality in regular hemodialysis (HD) patients. We measured Chlamydia pneumoniae (Cp) antibody seropositivity in 154 HD subjects (age 59 +/- 11 years, time on HD 13 +/- 7 years, male/female = 101/53), and prospectively examined an association between Cp antibody status and cardiovascular death for 56 months of follow-up. Seropositivity for Cp IgA and IgG antibodies at the entry of the study was 50.6 and 60.8%, respectively. There was no significant difference in age, time on HD, serum albumin, C-reactive protein (CRP) and interleukin-6 (IL-6) between those positive and negative for IgA antibodies. During follow-up over 56 months, 31 patients (20.1%) expired, 16 (55.2%) of them of cardiovascular causes. Serological IgA and IgG antibody positivity did not influence mortality, while multiple Cox proportional hazards analysis revealed that diabetes, ischemic changes on electrocardiogram, log-transformed CRP and intact parathyroid hormone were independent determinants of cardiovascular death. These observations suggest that serological Cp antibody status does not affect long-term cardiovascular mortality in chronic HD patients.

Serum and peripheral blood mononuclear cells infectious burden: Correlation to inflammation and atherosclerosis in haemodialysis patients

BACKGROUND

Infectious agents may be implicated in the inflammatory atherosclerotic process. Not only specific microorganisms but also the infectious burden, defined as the number of pathogens to which a patient is exposed, has been associated with atherosclerosis. In the present study, the infectious burden, determined directly (by identification of viable pathogens in peripheral blood mononuclear cells (PBMC)) and indirectly (by serum antibodies detection) is correlated to the inflammatory and atherosclerotic status in haemodialysis (HD) patients, a population at high risk for cardiovascular disease.

METHODS

The viable forms of four microorganisms (Chlamydia pneumoniae, herpes virus 1 and 2 and cytomegalovirus) were identified in patients PBMC by cell cultures and subsequent polymerase chain reaction. Serum IgG against the above pathogens and Helicobacter pylori were also determined. Inflammation was assessed by measurement of C-reactive protein (CRP), serum amyloid A (SAA), three pro- and one anti-inflammatory cytokines and four adhesion molecules. Atherosclerosis was defined by a scoring system using medical history data.

RESULTS

The number of viable pathogens identified in PBMC in the 122 HD patients included in the study were zero in 22.1% of them, one in 33.6%, two in 43.4% and three in one patient. The number of IgG antibodies determined was one in 6.6% of patients, two in 32%, three in 48.4% and four in 13.1%. Seropositivity was not significantly different between patients with or without the respective viable pathogen identified in PBMC. Atherosclerosis was present in 40.2% of patients, and CRP, SAA and interleukin-6 were all increased in these patients. Neither inflammatory indexes nor atherosclerosis were significantly different in patients with a higher number of viable pathogens detected in PBMC or in those with a higher antibodies number.

CONCLUSIONS

The direct infectious burden determination (the number of viable pathogens in PBMC) does not coincide with the serum (by IgG detection) infectious burden. Although inflammation correlates to atherosclerosis, neither PBMC nor the serum infectious burden is associated with these two entities in the inflamed and atherosclerotic HD patients.

The pattern of inflammation and a potential new clinical meaning and usefulness of C-reactive protein in end-stage renal failure patients

Inflammatory indexes are frequently elevated in end-stage renal failure (ESRF) patients. It seems that the pattern of inflammation is particular in this population. In the presence of a higher than normal microinflammatory background (CRP, C-reactive protein, values between 0.1 and 10-15 mg/l) that varies with time, waves of 'true' inflammation (CRP > 10-15 mg/l), mainly due to infections, are added periodically. To accurately assess the average microinflammation in these patients, multiple CRP measurements are required. As recent experimental studies showed that inflammation and particularly elevated CRP levels may be risk factors and not just a risk index for atherosclerosis, in this case, the characteristic inflammation pattern might be of importance in the evolution of this disease in ESRF patients. The causes of the inflammatory state in ESRF patients are multiple: renal insufficiency per se and its complications, coexisting diseases, established atherosclerosis, the consequences of renal replacement treatment, and frequent infections are potentially the main ones. The fluctuating inflammatory pattern is probably due to destabilization or changes in time of the above-mentioned parameters. Thus, the clinical meaning of the average microinflammation in these patients, as assessed by CRP measurements, seems to be that of an index indicative of the grade of their health aggravation by the multiple factors implicated in the inflammation formation. CRP is a sensitive, but not specific, risk index of the overall morbidity and mortality in these patients. The manipulation of the inflammation in ESRF patients should include follow-up and treatment of all the factors that contribute to this state and probably medications such as the statins. If inflammation and CRP in particular definitely prove to be risk factors for atherosclerosis, intensification of this treatment will be necessary.

Repetitive measurements of Chlamydia pneumoniae DNA in peripheral blood mononuclear cells in healthy control subjects and dialysis patients: a prospective study

Infection with Chlamydia pneumoniae has been suggested to play a role in the development and maintenance of atherosclerosis. However, the course of C. pneumoniae infection is not clarified. Thus, both the persistence of C. pneumoniae DNA in blood and the tendency to recurrence have not been studied. We determined the prevalence of C. pneumoniae DNA in the white cells of the peripheral blood in 98 dialysis patients and in 52 healthy subjects. Blood samples were collected approximately 6 times from each subject during a period of 1 y with an interval of approximately 2 months and analysed with a polymerase chain reaction. C. pneumoniae DNA was detectable in 47 out of 150 subjects at least once during a y. Reinfection was a rare phenomenon and the presence of C. pneumoniae DNA in blood was of less than 2 months' duration in almost all patients. There was a significant association between the presence of C. pneumoniae DNA during 1 y and the presence of atherosclerosis in the legs of dialysis patients (OR=3.50, p=0.03). Additionally, a significant association was found between the presence of C. pneumoniae DNA and an abnormal electrocardiogram (ECG) (OR=3.16, p=0.01). These findings may support the hypothesis of an association between infection with C. pneumoniae and the presence or development of atherosclerosis.

Detection of Chlamydophila pneumoniae in dendritic cells in atherosclerotic lesions

Dendritic cells (DCs) populate atherosclerotic lesions and might be involved in the regulation of immune reactions in atherosclerosis. The present work was undertaken to examine a possible association of DCs with Chlamydophila pneumoniae in human atherosclerotic plaques obtained by endarterectomy. C. pneumoniae was identified in 17 of 60 (28%) atherosclerotic plaques by a combination of immunohistochemistry and polymerase chain reaction (PCR). Double immunohistochemistry identified the presence of C. pneumoniae within S100(+) DCs that were localised predominantly in the deep layer of the intima under the necrotic core. Quantitative analysis showed that there were no differences in the numbers of DCs between C. pneumoniae(+) and C. pneumoniae(-) groups of atherosclerotic specimens. There were also no differences in the expression of Lag-antigen and HLA-DR by DCs between the groups of specimens. Markers of DC activation CD80 and CD86 were absent from both groups of specimens. Flow cytometry analysis of the effects of C. pneumoniae infection on immature monocyte-derived DCs in vitro showed no changes in the expression of CD1a, MHC class II, CD80 and CD86. The results of this study demonstrate that C. pneumoniae might infect DCs within the atherosclerotic intima but whether the presence of C. pneumoniae in DCs affects the intensity of immune reactions in atherosclerosis needs further clarification.

Chlamydia pneumoniae and Atherosclerosis: No Way-Out or Long Way?

Recently, Chlamydia pneumoniae is the microorganism frequently implicated in the infection-based inflammatory atherogenous hypothesis. Although in vitro experimental data and initial sero-epidemiologic, pathology-based studies and antibiotic trials supported this interesting hypothesis, later data are conflicting. Some confounding factors are the causes of uncertainty; lacking of standard methods for C. pneumoniae detection, co-existence of other atherosclerotic risk factors and anti-inflammatory effects of antibiotics used in clinical trials seem to be the principal ones. Standardization of methodology used, antibiotic trials with a different orientation-design and a vaccine preparation that eventually will be tested in clinical trials with a long follow-up, should provide a definite answer regarding the probability C. pneumoniae to be a main, a secondary or an irrelevant factor to atherosclerosis. Studies linking C. pneumoniae to inflammation and accelerated atherosclerosis in renal failure patients are accumulated but limitations are similar to the above mentioned.

Chlamydial infection and progression of carotid atherosclerosis in patients on regular haemodialysis

BACKGROUND

Recent findings have suggested a possible contribution of chlamydial infection to the pathogenesis of atherosclerosis in the general population. However, the role that chlamydial antibody status plays in atherosclerosis generation in haemodialysis (HD) patients remains uncertain.

METHODS

We measured carotid artery intima medial thickness (IMT) over 4 years in 100 HD subjects (age: 58+/-10 years; time on HD: 13+/-7 years; male/female: 67/33) and examined potential associations between Chlamydia pneumoniae (Cp) antibody seropositivity and changes in carotid artery IMT.

RESULTS

During 4 years, carotid artery IMT increased significantly from 0.62+/-0.13 to 0.73+/-0.12 mm (P< 0.01). IMT progression was significantly and positively correlated with age (r = 0.37, P<0.01), log-transformed C-reactive protein (CRP; r = 0.33, P<0.01) and log-transformed interleukin-6 (IL-6; r = 0.22, P<0.04), but inversely correlated with blood creatinine (r = -0.36, P<0.01) and albumin (r = -0.24, P<0.02). IMT increases were more prominent in patients positive for IgA antibodies (0.039+/- 0.022 mm/year, n = 52) compared with those without IgA antibodies (0.025+/-0.032 mm/year, n = 48) (P<0.01). IgA seropositivity did not accelerate IMT progression in patients with increased CRP (>0.11 mg/dl, n = 53), but significantly increased IMT to a greater extent in IgA-positive subjects than in IgA-negative subjects having lower CRP (</=0.11 mg/dl, n = 47) (0.017+/-0.024 vs 0.034+/- 0.021 mm/year; P = 0.01). Multivariate regression analysis revealed that serum creatinine, log-transformed CRP and IgA Cp seropositivity were independent risk factors for IMT progression (P<0.01). In contrast, IgG Cp antibody did not affect IMT progression or carotid plaque formation.

CONCLUSIONS

IMT progression is associated with inflammation and malnutrition. In addition, persistent chlamydial infection may be associated with IMT progression, but only in HD patients having low blood CRP.

Pretransplantation levels of C-reactive protein predict all-cause and cardiovascular mortality, but not graft outcome, in kidney transplant recipients

BACKGROUND

Chronic inflammation, the common pathway that leads to cardiovascular disease and chronic allograft nephropathy after transplantation, is prevalent in patients with end-stage renal failure. We set out to investigate the hypothesis that enhanced pretransplantation C-reactive protein (CRP) levels and Chlamydia seropositivity, both markers of an altered immune response, would predict graft failure and mortality in patients receiving renal replacement therapy.

METHODS

A retrospective study of 115 patients, based on CRP levels in pretransplantation serum (group 1, 0 to 5 mg/L; group 2, 5 to 10 mg/L; group 3, >10 mg/L), were investigated for the following end points: transplant rejection, graft failure, and all-cause and cardiovascular mortality.

RESULTS

There were no correlations between CRP levels or Chlamydia seropositivity with respect to rejection rates or graft failure. Furthermore, there was no relationship between Chlamydia seropositivity and survival. All-cause and cardiovascular mortality were significantly greater in patients with CRP levels greater than 10 mg/L and 5 to 10 mg/L compared with those with CRP levels less than 5 mg/L. All-cause mortality rates were 5% in the 0-to-5-mg/L group, 20% in the 5-to-10-mg/L group, and 44% in the greater-than-10-mg/L group. With regard to cardiovascular mortality, death rates were 0% in the 0-to-5-mg/L group, 10% in the 5-to-10-mg/L group, and 22% in the greater-than-10-mg/L group. Univariate analysis of cardiovascular mortality and covariates showed a significant relationship with age (relative risk [RR], 1.07; P < 0.05), diabetes (RR, 5.6; P < 0.05), aspirin intake (RR, 0.2; P < 0.05), antihypertensive therapy (RR, 0.02; P < 0.05), and CRP level (RR, 11; P < 0.05), but CRP level remained the only significant predictor (RR, 1.19; P < 0.05) on multivariate analysis.

CONCLUSION

Pretransplantation CRP level is independently associated with all-cause and cardiovascular mortality in our cohort of transplant recipients and may be a useful predictive marker in the follow-up of posttransplantation patients.