Antibodies to chlamydial lipopolysaccharides in unstable angina pectoris

Chlamydia Pneumoniae Infection in Patients with Acute Coronary Syndrome: A Clinical and Serological 1-Year Follow-Up

The role of Chlamydia pneumoniae infection in pathogenesis and prognostic stratification of patients with acute coronary syndromes is still unclear. However, a limitation of many studies is the evaluation of the long-term prognostic role of a sample obtained during the acute phase, whereas the assessment of the temporal trend of antibody titers could be more useful. One-hundred and fourteen consecutive patients with acute coronary syndromes (71 with acute myocardial infarction and 43 with unstable angina) were studied. Blood samples were obtained immediately after hospital admission and 1, 3, 6 and 12 months after the acute event. The microimmunofluorescence test was used to detect C. pneumoniae specific antibodies. The incidence of new coronary events (death, myocardial infarction, recurrent angina) was recorded during the 1-year follow-up period. No significant difference was found between patients with (n = 35) or without (n = 79) new coronary events (N.C.E.) regarding baseline and serial values of C. pneumoniae antibodies. The rate of high titers at any time of follow-up was also similar in the two groups: IgG ≥1:512 were present in 52%, 64%, 55% and 32% of N.C.E.+ patients, and in 48%, 54%, 52% and 36% of N.C.E.- patients at 1, 3, 6 and 12 months respectively; IgA ≥ 1:256 were present in 26%, 23%, 30% and 23% of N.C.E.+ patients and in 20%, 30%, 25% and 19% of N.C.E.- patients at 1, 3, 6 and 12 months respectively. Our data indicate that elevated titers of C. pneumoniae antibodies, even with a serial 1-year evaluation, are not a predictor of future coronary events in patients with acute myocardial infarction or unstable angina.

The acute phase reactant response to respiratory infection with Chlamydia pneumoniae: implications for the pathogenesis of atherosclerosis

The acute phase response to Chlamydia pneumoniae infection was analyzed over a 72 h period post-infection in C57BL/6J mice. A single intra-nasal inoculation stimulated statistically significant increases in the plasma levels of IL-2, IL-5, IL-6, IL-10, IL-12, GM-CSF, IFN-gamma, and serum amyloid A but not TNF-alpha, IL-1beta, IL-4 and serum amyloid P. There was also a decrease in the activity of the HDL protective enzyme paraoxonase as well as a reduced ability of HDL to prevent oxidation of palmitoyl-2-arachidonyl-sn-glycerol-3-phosphocholine by hydroperoxyoctadecadienoic acid at 48 and 72 h post-infection. To determine whether the C. pneumoniae induced acute phase response had any effect on atherosclerotic plaque stability, we measured the frequency of intra-plaque hemorrhage as a marker of plaque disruption in the innominate arteries of apolipoprotein E deficient mice at 29-30 weeks and 1.5-2.0 years of age. There was an increased frequency of intra-plaque hemorrhage only in the older mice infected with the live organism (8/14) as compared to mice treated with killed C. pneumoniae (2/11) or sham inoculated with PBS (2/12). These results suggest that acute phase reactant proteins produced in response to pulmonary infection with C. pneumoniae may contribute to the progression and destabilization of atherosclerotic lesions.

C-reactive protein: the harbinger of cardiovascular diseases

Coronary heart disease remains the major cause of mortality and morbidity in the United States and other western countries despite major advances in its treatment. During the last decades, many markers of coronary artery disease have been found which help predict future risk of cardiovascular events. High-sensitivity C-reactive protein has been studied extensively and was seen to be associated with a higher risk of cardiovascular events in patients with acute coronary syndromes and/or peripheral artery disease. Discussed in this review is the latest literature about this marker and its association with cardiovascular disease, as well as the latest therapeutic options available.

Endotoxin-induced effects on platelets and monocytes in an in vivo model of inflammation

AIMS

Chronic inflammation is a major contributing factor to atherosclerosis and various markers of inflammation, fibrinolysis and coagulation are upregulated in patients with established atherosclerotic disease. The aim of this study was to investigate the direct and short-term effects of inflammation on platelet and monocyte activation with an in vivo model of endotoxemia in healthy volunteers.

METHODS AND RESULTS

In this study, 13 healthy male subjects with a mean age of 29.5+/-5.4 years received intravenous administration of lipopolysaccharide (LPS; 20 IU/kg IV). The kinetics of CD40-ligand and CD62P expression on platelets, tissue-factor binding on monocytes and platelet-monocyte aggregates were measured by whole blood flow cytometry at baseline and at 1, 2, 4, 6 and 24 hours after LPS administration. Plasma levels of soluble CD40-ligand were measured with an ELISA over the same time course. Platelet-monocyte aggregates, tissue-factor binding on monocytes and surface expression of platelet CD40L significantly increased in experimental endotoxemia in vivo, reaching peak values 1 hour after LPS administration. All values returned to baseline after 24 hours. Surface expression of CD62P on platelets and plasma levels of sCD40L did not change significantly in response to LPS.

CONCLUSIONS

In vivo administration of endotoxin leads to an activation of platelets and monocytes with an upregulation of proatherogenic CD40L on platelets. These findings underpin the role of inflammation in early atherogenesis through platelet and monocyte activation in an in vivo model.

Enhanced expression of platelet CD40-ligand by in vitro lipopolysaccharide-challenge in patients with ventricular fibrillation complicating acute myocardial infarction

BACKGROUND

Acute myocardial infarction can be complicated by ventricular arrhythmias due to electrophysiological changes in the ischemic myocardium, but the exact predisposing factors causing ventricular fibrillation during myocardial infarction still remain unclear. A role of inflammatory stimulation on platelets as a potential risk factor for ventricular fibrillation during acute myocardial infarction has not been described yet.

METHODS AND RESULTS

Whole blood samples of 21 patients with a history of acute myocardial infarction (AMI) and ventricular fibrillation (VF) were incubated with lipopolysaccharide (LPS). As a control group, we studied 19 patients without VF during AMI. CD40-ligand and CD62P expression on platelets and tissue factor binding on monocytes were measured by flow cytometry. Platelet-monocyte aggregates were measured by CD41 expression on platelets adherent to monocytes. Soluble CD40-ligand plasma levels were measured with an ELISA. Without LPS, no significant difference between the patient groups concerning CD40L expression on platelets was observed, but plasma levels of soluble CD40L were significantly higher in patients with a history of AMI with VF. After LPS stimulation, patients with a history of VF showed a significantly increased expression of CD40L in comparison to the patients without ventricular fibrillation, based on a significantly higher increase of CD40L expression. CD62P expression on platelets was significantly increased in patients with a history of VF.

CONCLUSIONS

Patients with a history of VF complicating AMI show an enhanced expression of CD40L on platelets after in vitro lipopolysaccharide-challenge with an enhanced platelet activation.

A randomized trial in patients undergoing percutaneous coronary angioplasty: roxithromycin does not reduce clinical restenosis but angioplasty increases antibody concentrations against Chlamydia pneumoniae

BACKGROUND

Elevated antibodies against Chlamydia pneumoniae have been associated with coronary artery disease. In patients undergoing percutaneous coronary angioplasty, we therefore investigated the effect of roxithromycin on symptomatic restenosis and determined antichlamydial antibodies as well as inflammatory and immunological parameters.

METHODS

A total of 327 patients undergoing coronary angioplasty were randomized to roxithromycin or placebo and followed-up for 1 year. Antibodies were determined by microimmunofluorescence and enzyme-linked immunosorbent assay; C-reactive protein, interleukin-10, tumor necrosis factor-alpha (TNF-alpha), and eotaxin were determined by enzyme-linked immunosorbent assay.

RESULTS

Although the frequency of restenosis was not affected by roxithromycin (25 restenoses vs 32 in the control group), antichlamydial antibodies increased during follow-up (anti-CP IgG +12 +/- 2%, P < .001). Concentrations of TNF-alpha and eotaxin increased as well (TNF-alpha +9 +/- 1% and eotaxin +10 +/- 2%) and correlated with antichlamydial antibody concentrations (TNF-alpha, r = 0.23, P = .02; eotaxin, r = 0.32, P = .002).

CONCLUSIONS

Treatment with roxithromycin was not associated with a reduction of symptomatic restenoses. During follow-up, a marked increase in antichlamydial antibodies, TNF-alpha, and eotaxin was observed, suggesting that angioplasty-induced plaque rupture induces a specific immunological response without activation of inflammatory mechanisms as represented by C-reactive protein. Whether this mechanism occurs in all plaque ruptures remains to be determined.

Coagulation activation and expression of CD40 ligand on platelets upon in vitro lipopolysaccharide-challenge in patients with unstable angina

BACKGROUND

Elevated markers of inflammation and coagulation are found in patients with coronary heart disease. A role of inflammatory stimulation on coagulation time and expression of CD40 ligand on platelets in acute coronary syndromes has not been described yet.

METHODS AND RESULTS

Whole blood samples of 9 patients with coronary heart disease and stable angina, 10 patients with unstable angina, 7 patients with acute myocardial infarction and 7 patients without coronary heart disease were incubated with lipopolysaccharide (LPS). Coagulation time was measured in arterial and coronary blood with the ReoRox(R), a viscometric whole blood coagulometer. CD40L and CD62P expression on platelets and platelet-monocyte aggregates were measured by flow cytometry. Without LPS, patients with unstable angina showed a significantly decreased coagulation time in arterial and coronary blood compared to patients without coronary heart disease. After incubation with LPS, in patients with unstable angina, a significantly decreased coagulation time in coronary blood was observed compared to patients with stable angina or patients without coronary heart disease. CD40L expression on platelets in patients with unstable angina was significantly higher in arterial and coronary blood compared to patients with stable angina. No significant differences between the patient groups were observed concerning CD62P expression on platelets, tissue factor binding on monocytes, platelet-monocyte aggregates and plasma levels of platelet factor 4.

CONCLUSIONS

Patients with unstable angina show an enhanced coagulation activation and an upregulation of CD40L on platelets. This may be of importance in the understanding of coronary plaque rupture and formation of coronary thrombosis.

Infección previa por Chlamydia pneumoniae y pronóstico a largo plazo en pacientes con síndrome coronario agudo sin elevación del segmento ST

BACKGROUND AND OBJECTIVE

Contradictory data exists from case-control studies and in patients with stable coronary artery disease on the association of prior exposure to Chlamydia pneumoniae and cardiovascular events. We underwent a prospective study to investigate the prognostic value of C. pneumoniae seropositivity in patients with acute coronary syndromes.

PATIENTS AND METHOD

In a prospective cohort of 259 consecutive patients (194 men and 65 women), mean age 65 (10 years) with non-ST elevation acute coronary syndromes, we measured serum levels of IgG antibodies directed against C. pneumoniae.

RESULTS

After a mean follow-up of 28 (25, 29) months, the incidence of cardiovascular death or myocardial infarction was of 15% in seropositive patients versus 13% in seronegatives at IgG titers (1:64 (p=0.58); of 14% versus 14% at IgG titers > or = 1:128 (p=0.96); and of 14% versus 15% at IgG titers (1:256 (p=0.82). The relative risks (RR, 95% CI) of these major cardiac events adjusted for possible confounding factors were 1.11 (0.52-2.40); 1.01 (0.52-1.96); and 0.94 (0.48-1.87) respectively.

CONCLUSIONS

Chlamydia pneumoniae IgG seropositivity is not associated with a higher incidence of death or myocardial infarction in patients with non-ST segment elevation acute coronary syndromes.

Importance of methodology in determination of Chlamydia pneumoniae seropositivity in healthy subjects and in patients with coronary atherosclerosis

Enzyme immunoassays (EIAs) for the detection of Chlamydia pneumoniae antibodies were compared to the microimmunofluorescence (MIF) test, the reference method. Furthermore, we assessed the hypothesis that a possible relationship between Chlamydia pneumoniae immunoglobulin G (IgG) antibodies and coronary artery disease is dependent on the type of EIA. Sera from 112 healthy men (mean age, 50.1 years) were tested for antibodies against Chlamydia pneumoniae by five commercial test kits: Focus Chlamydia MIF IgG test, Labsystems Chlamydia pneumoniae IgG EIA (LS EIA), R-Biopharm Elegance Chlamydia pneumoniae IgG EIA (RB EIA), Medac Chlamydia pneumoniae IgG sandwich enzyme-linked immunosorbent assay ELISA (MCp sELISA) and Medac Chlamydia IgG recombinant enzyme-linked immunosorbent assay ELISA (MC rELISA). Sera from 106 consecutive male patients (mean age, 63.6 years) undergoing diagnostic coronary angiography were also examined using the Focus MIF, LS EIA, MCp sELISA, and MC rELISA techniques. The agreement between LS EIA (65 to 83% [controls-patients]) or MC rELISA (49 to 61%) and Focus MIF (78 to 83%) was average to fair (kappa = 0.597 and 0.234, respectively). MCp sELISA and RB EIA showed good agreement with MIF (kappa = 0.686 and 0.665, respectively), with 80 to 89 and 79% of individuals reacting positively. A significant difference in seroprevalence between patients and healthy subjects was observed with the LS EIA, while seropositivities in the two study groups appeared equal when the Focus MIF assay was applied. The MC rELISA and MCp sELISA gave statistically significant differences in antibody seroprevalence in patients with two-vessel disease or when the patient group combined individuals with a two- or a three-vessel disease, respectively. The concordance between MIF and other commonly used serological assays for C. pneumoniae IgG antibody detection is good to fair. The choice of serological assay has important implications for C. pneumoniae antibody seroprevalence, as well as for the relationship between C. pneumoniae seropositivity and coronary artery disease.