Comparison of eleven commercial tests for Chlamydia pneumoniae-specific immunoglobulin G in asymptomatic healthy individuals

Challenges in Chlamydial Serology: Insights from a Belgian and a Dutch Population Cohort

Serology routinely serves as a diagnostic tool to confirm Chlamydia infections in humans. Particularly in delayed settings, such as post-outbreak scenarios where the acute phase of infection has subsided, serology is invaluable. Multiple studies, nonetheless, indicate deficiencies in specificity and sensitivity of current chlamydial antibody detection assays. Incorporation of multiple antigens per target is known to improve the accuracy of chlamydial serological assays. We, therefore, used the recomLine test (Mikrogen diagnostics) on serological samples of two cohorts, as it is the only commercially available test allowing detection of antibodies against three human pathogenic Chlamydia species (C. trachomatis, C. pneumoniae and C. psittaci) using multiple antigens per target. The first cohort (n = 156; samples collected between 2008 and 2022 during a C. trachomatis screening initiative) comprised women from the Netherlands (NL) with past exposure to C. trachomatis, while the second cohort (n = 44; samples collected in 2018 in a health examination survey) consisted of Belgian citizens (BE) with occupational or recreational exposure to chickens, representing a risk population for C. psittaci. The test indicated a statistically equivalent C. pneumoniae seroprevalence in both cohorts (39.10% in NL and 34.09% in BE; p = 0.337). As expected C. trachomatis seroprevalence was significantly higher (p < 0.001) in the Dutch cohort (48.72%), as compared to the Belgian cohort (4.55%). Lastly, C. psittaci seroprevalence did not significantly differ between the two groups (2.27% in BE and 1.92% in NL; p = 0.633), even though a higher prevalence was expected for the Belgian cohort. This prompts us to question whether the Belgian cohort truly constituted a C. psittaci risk population or whether the recomLine test is susceptible to cross-reaction of species-specific antibodies, thereby increasing C. psittaci prevalence in the Dutch cohort. We advocate for the development of affordable, highly sensitive antibody detection assays that can effectively distinguish between chlamydial species, addressing the increasing demand for enhanced serological testing methodologies.

Association of Chlamydophila pneumoniae infection and hypertension during pregnancy - A case control study

BACKGROUND

The association of Chlamydophila pneumoniae infection with essential hypertension is known but its association with hypertension during pregnancy is controversial. Hence, this study aimed to explore the association of C. pneumoniae infection with hypertension during pregnancy. The objectives were to compare the presence of C. pneumoniae DNA in trophoblastic cells of placenta between hypertensive and normotensive pregnant women and to find out the presence of inflammatory marker (HSP-60) and the seropositivity (IgG and IgA) of C. pneumoniae in them.

MATERIALS AND METHODS

The study was conducted at a tertiary-care institute, in South-India between 2018 and 2020. Women with hypertension during pregnancy were study group (75) and normotensive pregnant women were control group (75). IgG and IgA antibodies, HSP-60 against C. pneumoniae were estimated by ELISA from 5 ml of venous blood. C. pneumoniae DNA was extracted from placental tissue after delivery and tested by RT-PCR.

STATISTICAL ANALYSIS

The association between C. pneumoniae DNA, seropositivity and hypertension was determined by student test and univariate regression analysis.

RESULTS

C. pneumoniae DNA was detected in the placenta of 29.3% with hypertension and none in controls and the odds was 6.5 (OR-6.5, CI 95%). HSP-60 was elevated in women with preeclampsia and not in gestational hypertension and controls. IgA was not detected and IgG was positive in 15.2% of women with preeclampsia.

CONCLUSION

There is a significant association between C. pneumoniae infection and hypertension during pregnancy and further studies are required to fulfil the Koch's postulates to prove or disprove it as a causative agent.

The association between serological features of chronic Chlamydia pneumoniae infection and markers of systemic inflammation and nutrition in COPD patients

INTRODUCTION

Chlamydia pneumoniae is an obligatory human pathogen involved in lower and upper airway infections, including pneumonia, bronchitis. Asymptomatic C. pneumoniae carriage is also relatively common. The association of C. pneumoniae infections with the chronic obstructive pulmonary disease (COPD) course is unclear.

OBJECTIVES

The aim of the study was to investigate the association between chronic C. pneumoniae infection and clinical features of COPD, markers of inflammation and metabolic dysfunction.

PATIENTS AND METHODS

The study included 59 patients with stable COPD who had no, or had ≥2 acute exacerbations during last year. The level of IgA and IgG antibody against C. pneumoniae, IL-6, IL-8, resistin, insulin, adiponectin and acyl ghrelin was measured in serum by enzyme-linked immunosorbent assay (ELISA).

RESULTS

No differences in clinical and functional data were observed between COPD patients without serological features of C. pneumoniae infection and chronic C. pneumoniae infection. The level of anti C. pneumoniae IgA significantly correlated with IL-8, IL-6, resistin concentration in group of frequent exacerbators. IgG level correlated negatively with acetyl ghrelin and body mass index (BMI) in patients without frequent exacerbations, in contrast to frequent COPD exacerbation group where significant correlations between IgG level and BMI was demonstrated. Serum IL-6 correlated positively with resistin and insulin and negatively with adiponectin in group of patients with serological features of chronic C. pneumoniae infection only.

CONCLUSIONS

Our study showed that chronic C. pneumoniae infection does not influence the clinical course of COPD in the both study groups. Chronic C. pneumoniae infections might be associated with a distinct COPD phenotype that affects metabolic dysfunction.

Antibody responses of Chlamydophila pneumoniae pneumonia: Why is the diagnosis of C. pneumoniae pneumonia difficult?

The ELNAS Plate Chlamydophila pneumoniae commercial test kit for the detection of anti-C. pneumoniae-specific immunoglobulin M (IgM), IgA and IgG antibodies has become available in Japan recently. To determine the optimum serum collection point for the ELNAS plate in the diagnosis of C. pneumoniae pneumonia, we analyzed the kinetics of the antibody response in patients with laboratory-confirmed C. pneumoniae pneumonia. We enrolled five C. pneumoniae pneumonia cases and collected sera from patients for several months. The kinetics of the IgM and IgG antibody responses were similar among the five patients. Significant increases in IgM and IgG antibody titer between paired sera were observed in all patients. IgM antibodies appeared approximately 2-3 weeks after the onset of illness, reached a peak after 4-5 weeks, and were generally undetectable after 3-5 months. IgG antibodies developed slowly for the first 30 days and reached a plateau approximately 3-4 months after the onset of illness. The kinetics of IgA antibody responses were different among the five patients, and significant increases in IgA antibody titer between paired sera were observed in only two patients. Although the sample size was small, the best serum collection time seemed to be approximately 3-6 weeks after onset of illness when using a single serum sample for the detection of IgM antibodies. Paired sera samples should be obtained at least 4 weeks apart. IgA antibody analysis using ELNAS may not be a useful marker for acute C. pneumoniae pneumonia.

Genetic and infectious profiles influence cerebrospinal fluid IgG abnormality in Japanese multiple sclerosis patients

BACKGROUND

Abnormal intrathecal synthesis of IgG, reflected by cerebrospinal fluid (CSF) oligoclonal IgG bands (OBs) and increased IgG index, is much less frequently observed in Japanese multiple sclerosis (MS) cohorts compared with Western cohorts. We aimed to clarify whether genetic and common infectious backgrounds influence CSF IgG abnormality in Japanese MS patients.

METHODOLOGY

We analyzed HLA-DRB1 alleles, and IgG antibodies against Chlamydia pneumoniae, Helicobacter pylori, Epstein-Barr virus nuclear antigen (EBNA), and varicella zoster virus (VZV) in 94 patients with MS and 367 unrelated healthy controls (HCs). We defined CSF IgG abnormality as the presence of CSF OBs and/or increased IgG index (>0.658).

PRINCIPAL FINDINGS

CSF IgG abnormality was found in 59 of 94 (62.8%) MS patients. CSF IgG abnormality-positive patients had a significantly higher frequency of brain MRI lesions meeting the Barkhof criteria compared with abnormality-negative patients. Compared with HCs, CSF IgG abnormality-positive MS patients showed a significantly higher frequency of DRB1 1501, whereas CSF IgG abnormality-negative patients had a significantly higher frequency of DRB1 0405. CSF IgG abnormality-positive MS patients had a significantly higher frequency of anti-C. pneumoniae IgG antibodies compared with CSF IgG abnormality-negative MS patients, although there was no difference in the frequency of anti-C. pneumoniae IgG antibodies between HCs and total MS patients. Compared with HCs, anti-H. pylori IgG antibodies were detected significantly less frequently in the total MS patients, especially in CSF IgG abnormality-negative MS patients. The frequencies of antibodies against EBNA and VZV did not differ significantly among the groups.

CONCLUSIONS

CSF IgG abnormality is associated with Western MS-like brain MRI features. DRB1 1501 and C. pneumoniae infection confer CSF IgG abnormality, while DRB1 0405 and H. pylori infection are positively and negatively associated with CSF IgG abnormality-negative MS, respectively, suggesting that genetic and environmental factors differentially contribute to MS susceptibility according to the CSF IgG abnormality status.

High seroprevalence of Mycoplasma pneumoniae IgM in acute Q fever by enzyme-linked immunosorbent assay (ELISA)

Q fever is serologically cross-reactive with other intracellular microorganisms. However, studies of the serological status of Mycoplasma pneumoniae and Chlamydophila pneumoniae during Q fever are rare. We conducted a retrospective serological study of M. pneumoniae and C. pneumoniae by enzyme-linked immunosorbent assay (ELISA), a method widely used in clinical practice, in 102 cases of acute Q fever, 39 cases of scrub typhus, and 14 cases of murine typhus. The seropositive (57.8%, 7.7%, and 0%, p<0.001) and seroconversion rates (50.6%, 8.8%, and 0%, p<0.001) of M. pneumoniae IgM, but not M. pneumoniae IgG and C. pneumoniae IgG/IgM, in acute Q fever were significantly higher than in scrub typhus and murine typhus. Another ELISA kit also revealed a high seropositivity (49.5%) and seroconversion rate (33.3%) of M. pneumoniae IgM in acute Q fever. The temporal and age distributions of patients with positive M. pneumoniae IgM were not typical of M. pneumoniae pneumonia. Comparing acute Q fever patients who were positive for M. pneumoniae IgM (59 cases) with those who were negative (43 cases), the demographic characteristics and underlying diseases were not different. In addition, the clinical manifestations associated with atypical pneumonia, including headache (71.2% vs. 81.4%, p=0.255), sore throat (8.5% vs. 16.3%, p=0.351), cough (35.6% vs. 23.3%, p=0.199), and chest x-ray suggesting pneumonia (19.3% vs. 9.5%, p=0.258), were unchanged between the two groups. Clinicians should be aware of the high seroprevalence of M. pneumoniae IgM in acute Q fever, particularly with ELISA kits, which can lead to misdiagnosis, overestimations of the prevalence of M. pneumoniae pneumonia, and underestimations of the true prevalence of Q fever pneumonia.

Recent Chlamydia pneumoniae infection is highly associated with active ankylosing spondylitis in a Chinese cohort

OBJECTIVE

The aim of the present study was to investigate the presence of anti-Chlamydia pneumoniae (Cp) antibodies in patients with ankylosing spondylitis (AS) to determine whether there is an association with AS disease activity.

METHODS

Seventy-nine AS outpatients and 73 normal controls were enrolled in this case-control study. Serum anti-Cp immunoglobulins (CpIg) were detected by enzyme-linked immunosorbent assay (ELISA). Antibodies to Epstein-Barr virus (EBV), cytomegalovirus (CMV), and Chlamydia trachomatis (Ct) were also measured. Clinical and experimental data were collected, and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was determined. Patients with positive Cp IgM or Cp IgA were considered to have had a recent Cp infection.

RESULTS

Cp IgG was detected in the majority of AS patients and also controls (88.8% vs. 91.8%, respectively). The seroprevalence of Cp IgA and Cp IgM was significantly higher in AS patients than in the controls (51.9% vs. 31.5%, p = 0.010 for Cp IgA; 79.7% vs. 20.5%, p < 0.0001 for Cp IgM). Seropositivity of Cp IgM was associated with elevation of the disease activity index, including erythrocyte sedimentation rate (ESR; p = 0.021), C-reactive protein (CRP; p = 0.007) and the BASDAI (p = 0.009). Persistent positive Cp IgM was associated with active disease, while seroreversion of Cp IgM was associated with a reduction in these disease activity indices. There was no correlation between Cp IgM or Cp IgA and symptomatic upper respiratory infections or other clinical manifestations.

CONCLUSIONS

Recent Cp infections occur frequently in AS patients and Cp IgM antibody is correlated with active disease. These findings indicate that Cp infections may be a triggering factor for active AS.

Serological diagnosis of Chlamydia pneumoniae infection: limitations and perspectives

Chlamydia pneumoniae is an obligate intracellular human pathogen responsible for a wide range of acute and chronic human diseases, including pneumonia and other respiratory diseases. Serological methods for the diagnosis of C. pneumoniae infection vary widely, and several authors have reported significant inter- and intra-laboratory variability in diagnostic methods and criteria. Over the past 10 years, numerous studies have focused on the identification of specific antigens for application in serodiagnosis, including the diagnosis of persistent infections. The use of proteomics may enable the development of serological diagnosis kits that offer reliable sensitivity and specificity and might even differentiate between the various stages of infection with this pathogen.

Plasma circulatory markers in male and female patients with coronary artery disease

OBJECTIVE

Inflammatory processes play a role in the pathogenesis of atherosclerosis, and plasma circulatory markers have been associated with cardiovascular risk. There is no single report in which adhesion molecule and circulatory cytokines have been evaluated in a single population set with coronary artery disease (CAD) on the basis of gender. Thus, we evaluated plasma circulatory markers in patients with CAD and in controls that were divided by gender (because functioning of circulatory markers and response toward conventional factors are not identical in men and women) and by conventional risk factors such as smoking and alcohol intake.

METHODS

A total of 192 patients with CAD (148 male and 44 female) and 192 controls with no symptoms of CAD (142 male and 50 female) were enrolled. Detection of concentration to high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, IL-13, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and adhesion molecules (intercellular adhesion molecule [ICAM]-1 and vascular adhesion molecule [VCAM]-1) was performed using enzyme-linked immunosorbent assay kits.

RESULTS

In male patients with CAD, levels of IL-4, IL-6, IL-8, IL-13, ICAM-1, VCAM-1, hsCRP (P < .001), and IFN-gamma (P = .003) were significantly higher compared with controls; however, levels of IL-10 were significantly lower (P < .001). In female patients with CAD, levels of IL-4, hsCRP, VCAM-1 (P = .001), and IL-13 (P = .028) were significantly higher and IL-10 levels were significantly lower (P < .001) compared with controls. In addition, levels of circulatory markers were strongly associated with male smokers and imperceptibly associated with male alcoholics and female smokers and alcoholics.

CONCLUSION

This study compared the plasma circulatory markers between patients with CAD and healthy controls, between patients with CAD who smoke and controls, and between alcoholic patients with CAD and controls divided by gender. Moreover, among circulatory markers studied, higher levels were found for IL-4, IL-13, hsCRP, and VCAM-1, and lower levels were found for IL-10 in male and female patients with CAD compared with healthy controls.

Infectious Risk Factors for Atherosclerotic Vascular Disease in Hemodialysis Patients—Chlamydia pneumoniaebut notHelicobacter pylorior Cytomegalovirus is Associated with Increased C‐Reactive Protein

BACKGROUND

Cardiovascular disease is a major problem in patients with chronic renal failure leading to increased mortality. Several infectious agents have been implicated to be associated with atherosclerosis. We were interested to evaluate whether there is a correlation between a past infection with Chlamydia pneumoniae (Cpn), Helicobacter pylori (Hp) or cytomegalovirus (CMV) and the manifestation of a symptomatic atherosclerotic disease in patients with endstage renal failure.

METHODS AND RESULTS

Patients (n=267) on hemodialysis were investigated. In 101 patients with an apparent atherosclerotic disease (case group) increased IgA levels against Cpn were found (p < or = 0.0001 vs. controls; n=33). Nearly 45% of the case group had a history of myocardial infarction (MI) (p < or = 0.0001). Prior stroke was found in about 30% of patients in the case group (p < or = 0.002). Elevated CRP levels were identified as an independent risk factor for atherosclerosis in all groups. IgA seropositivity against Cpn correlated with elevated CRP values for all atherosclerotic patients (p < or = 0.001), especially in the group of patients with MI (p < or = 0.019) and peripheral vascular disease (p < or = 0.005). There was no correlation between CMV (IgG, IgM) or Hp (IgA, IgG) seropositivity and atherosclerotic disease.

CONCLUSION

IgA seropositivity for Cpn and elevated CRP values but not Hp or CMV was associated with an increased rate of symptomatic atherosclerotic manifestations as MI, stroke, cerebral or peripheral atherosclerosis in patients with endstage renal disease on hemodialysis.

Comparison of the new InoDiag automated fluorescence multiplexed antigen microarray to the reference technique in the serodiagnosis of atypical bacterial pneumonia

The aetiological diagnosis of pneumonia depends largely on culture-, antigen- or PCR-based tests. Atypical agents of pneumonia include Coxiella burnetii, Chlamydophila pneumoniae, Chlamydia psittaci, Legionella pneumophila, Francisella tularensis and Mycoplasma pneumoniae. In these cases, serological tests are commonly used for diagnosis. All of the above species were comparatively screened for by using the InoDiag multiplexed automatic immunofluorescence assay and established reference techniques. The InoDiag assay required 5 microL of serum, took 76 min per serum sample, and required an incubator, a fluorescence reader and interpretation software. In total, 248 single sera from patients were tested, for the diagnosis of pneumonia, and the results obtained with selected serum samples were compared with results obtained with the reference method. It was shown that, for the detection of Coxiella burnetii IgM, the automated assay had a sensitivity and specificity of 100%. For the detection of M. pneumoniae IgM, sensitivity was 100% and specificity was 98%. For the detection of Chlamydophila pneumoniae and Chlamydia psittaci IgG, sensitivity was 81% and specificity was 94%. For the detection of L. pneumoniae IgG, sensitivity was 63% and specificity was 98%. For the detection of F. tularensis IgG and IgM, sensitivity was 100% for both, and specificity was 95% and 100%, respectively. The performance of this serological assay was comparable to that of other assays reported in the literature. This preliminary study shows that the automatic InoDiag assay opens the way to immunofluorescence assay standardization.

High immunoglobulin A seropositivity for combined Chlamydia pneumoniae, Helicobacter pylori infection, and high-sensitivity C-reactive protein in coronary artery disease patients in India can serve as atherosclerotic marker

Atherosclerosis is increasingly recognized as a chronic inflammatory disease. A variety of infectious agents (Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus [CMV]) and inflammatory marker such as high-sensitivity C-reactive protein (hs-CRP) have been found to be associated with atherosclerosis and its consequences. There is a need to know about the type and burden of infection in coronary artery disease (CAD) patients and the level of hs-CRP in India as there is growing evidence that a variety of pathogens are participating in the development and/or acceleration of at least pre-existing atherosclerosis. In addition, there is a need to find the association between these pathogens and conventional risk factors among CAD patients in India, to possibly identify a prognostic marker. In this study 192 patients with incident or prevalent CAD attending the Cardiology Outpatient Department of Safdarjung Hospital, New Delhi, India, were enrolled. In addition, 192 age-and sex-matched controls were also included. Cases and controls differ significantly in seropositivity to C. pneumoniae immunoglobulin IgA (154 vs 76) and IgG (71 vs 48) (P < 0.001, P < 0.015), H. pylori IgA (98 vs 57) and IgG (77 vs 43) (P < 0.001, P < 0.001), CMV IgG (62 vs 38) (P = 0.01) and with hs-CRP (114 vs 60) (P < 0.001), respectively. The level of hs-CRP was higher in CAD patients with IgA seropositivity of C. pneumoniae and H. pylori (5.18 and.65 mg/l) than the IgG of these bacteria (3.73 and 3.36 mg/l), respectively. These findings support an association between specific infectious agents, namely, C. pneumoniae, H. pylori, CMV, and hs-CRP in CAD patients. Association of hs-CRP with IgA specific for C. pneumoniae and H. pylori suggests the role of chronic infection in the development of CAD and may be used as a marker to target the population.

Evaluation and optimization of a commercial enzyme linked immunosorbent assay for detection of Chlamydophila pneumoniae IgA antibodies

BACKGROUND

Serologic diagnosis of Chlamydophila pneumoniae (Cpn) infection routinely involves assays for the presence of IgG and IgM antibodies to Cpn. Although IgA antibodies to Cpn have been found to be of interest in the diagnosis of chronic infections, their significance in serological diagnosis remains unclear. The microimmunofluorescence (MIF) test is the current method for the measurement of Cpn antibodies. While commercial enzyme linked immunosorbent assays (ELISA) have been developed, they have not been fully validated. We therefore evaluated and optimized a commercial ELISA kit, the SeroCP IgA test, for the detection of Cpn IgA antibodies.

METHODS

Serum samples from 94 patients with anti-Cpn IgG titers > or = 256 (study group) and from 100 healthy blood donors (control group) were tested for the presence of IgA antibodies to Cpn, using our in-house MIF test and the SeroCP IgA test. Two graph receiver operating characteristic (TG-ROC) curves were created to optimize the cut off given by the manufacturer.

RESULTS

The MIF and SeroCP IgA tests detected Cpn IgA antibodies in 72% and 89%, respectively, of sera from the study group, and in 9% and 35%, respectively, of sera from the control group. Using the MIF test as the reference method and the cut-off value of the ELISA test specified by the manufacturer for seropositivity and negativity, the two tests correlated in 76% of the samples, with an agreement of K = 0.54. When we applied the optimized cut-off value using TG-ROC analysis, 1.65, we observed better concordance (86%) and agreement (0.72) between the MIF and SeroCP IgA tests.

CONCLUSION

Use of TG-ROC analysis may help standardize and optimize ELISAs, which are simpler, more objective and less time consuming than the MIF test. Standardization and optimization of commercial ELISA kits may result in better performance.

Immunoproteomic identification and serological responses to novel Chlamydia pneumoniae antigens that are associated with persistent C. pneumoniae infections

The controversial discussion about the role of Chlamydia pneumoniae in atherosclerosis cannot be solved without a reliable diagnosis that allows discrimination between past and persistent infections. Using a proteomic approach and immunoblotting with human sera, we identified 31 major C. pneumoniae Ags originating from 27 different C. pneumoniae proteins. More than half of the proteins represent Chlamydia Ags not described previously. Using a comparative analysis of spot reactivity Pmp6, OMP2, GroEL, DnaK, RpoA, EF-Tu, as well as CpB0704 and CpB0837, were found to be immunodominant. The comparison of Ab-response patterns of sera from subjects with and without evidence for persisting C. pneumoniae, determined by multiple PCR analysis of PBMC and vasculatory samples, resulted in differential reactivity for 12 proteins, which is not reflected by reactivity of the sera in the microimmunofluorescence test, the current gold standard for serodiagnosis. Although reactivity of sera from PCR-positive donors was increased toward RpoA, MOMP, YscC, Pmp10, PorB, Pmp21, GroEL, and Cpaf, the reactivity toward YscL, Rho, LCrE, and CpB0837 was decreased, reflecting the altered protein expression of persisting C. pneumoniae in vitro. Our data provide the first evidence of a unique Ab-response pattern associated with persistent C. pneumoniae infections, which is a prerequisite for the serological determination of persistently infected patients.

Endothelial cells are protected against phagocyte-transmitted Chlamydophila pneumoniae infections by laminar shear stress Gueinzius: Shear stress protects from C. pneumoniae infection

The respiratory pathogen Chlamydophila pneumoniae can be detected in atherosclerotic vessels, but the mechanism of dissemination from lung to vasculature remains unknown. Disturbance of vascular shear stress is a risk factor for atherosclerosis. We investigated whether polymorphonuclear neutrophils (PMN) might serve as carriers, transmitting C. pneumoniae to endothelial cells and how this is affected by shear stress. PMN were prepared from blood and incubated with C. pneumoniae. Real-time PCR and Pathfinder staining showed that after 1h, 20% of C. pneumoniae were ingested and started to form inclusions. When infected PMN were co-incubated with HUVEC for 96h, 10% of PMN-ingested C. pneumoniae were transmitted to HUVEC as shown by PCR and confocal microscopy. Infection of HEp-2 cells with C. pneumoniae harvested from HUVEC resulted in C. pneumoniae replication and confirmed that the bacteria remained infective. Exposure to laminar shear stress in a rotating cone-and-plate apparatus did not affect the transmission of C. pneumoniae from PMN to HUVEC, but led to a 75% reduction of inclusion formation. This can explain the focal distribution of C. pneumoniae in the vasculature and links two risk factors of atherosclerosis, i.e. the lack of laminar flow and infection.

Detection of parvovirus B19 and Chlamydophila pneumoniae in a patient with atypical sarcoidosis

We present an elderly female patient with fever, aplastic anemia, arthralgic symptoms and atypical pneumonia. Serological and clinical findings suggested Parvovirus B19 and Chlamydophila pneumoniae infection. These supposed infections delayed the recognition of underlying sarcoidosis which definitive diagnosis was reached through a lung biopsy and histological demonstration of nonnecrotizing granulomas containing giant cells and noncaseating epithelioid cells. The present case highlights the potential difficulty to diagnose sarcoidosis in the presence of unusual infections which may complicate the course of this disease.

Acute respiratory infection due to Chlamydia pneumoniae: current status of diagnostic methods

Reliable diagnosis of respiratory infection due to Chlamydia pneumoniae and investigation of its role in chronic diseases remain difficult because of the absence of well-standardized and commercially available diagnostic tests. In 2001, the US Centers for Disease Control and Prevention published recommendations for standardizing the diagnostic approach. In this review, we discuss the current state of knowledge of C. pneumoniae-associated respiratory infections in the context of epidemiological studies published during the past 5 years, with particular emphasis on the diagnostic strategies used and their impact on results. The single most likely factor underlying wide variations in data is the significant interstudy variation of the choice of diagnostic methods and criteria used. Adoption of a more unified approach, both for choices of diagnostic methods and for validation of new molecular assays, is long overdue and will be critically important for development of a standardized test for clinical laboratories.

Low prevalence of Chlamydia pneumoniae in adults with community-acquired pneumonia

The incidence of community-acquired pneumonia (CAP) due to Chlamydia pneumoniae was determined in a prospective study of 546 adult patients with CAP included in the German CAP Competence Network (CAPNETZ) project. Three different PCR protocols for detection of C. pneumoniae in respiratory specimens were compared by a multicenter, inter-laboratory comparison involving three laboratories. A case was defined as a patient with a respiratory sample positive by PCR in at least two laboratories. CAP was caused by C. pneumoniae in 5/546 cases (0.9%). Antibody testing by microimmunofluorescence was done in 376 of 546 patients. All patients were negative for IgM antibodies. In the five PCR-positive patients, neither specific IgG nor IgA antibodies were found. Patients with CAP caused by C. pneumoniae had a lower median age (36 years) than the general study population (62 years). C. pneumoniae is currently a rare cause of CAP in adult patients in Germany. Analysis of a single serum sample is not useful for diagnosis of acute C. pneumoniae infection in CAP.

Chlamydia pneumoniae and coronary artery disease: controversial results of serological studies

I have read with great interest the article published by Carratelli et al. Briefly they have reported increased levels of inflammatory markers and elevated titers of IgG and IgA of C. pneumoniae by using both ELISA and MIF method. There are several factors which may underly the controversial results of seroepidemiological studies. I have commented on the report of Carratelli et al. regarding some of these factors.

Descripción de inmunógenos de Chlamydia pneumoniae reconocidos por el suero de sujetos con enfermedad arterial periférica

BACKGROUND AND OBJECTIVE

The relationship between antibodies to C. pneumoniae and presence of the bacteria was studied in individuals with peripheral arterial disease.

PATIENTS AND METHOD

An observational analytical, case-control study was performed in 118 patients (68 cases, 50 controls) to investigate immunoglobulin (Ig) G and A against C. pneumoniae in serum, using Western-blot (commercial and no commercial methods), ELISA and MIF; DNA of the bacteria in vascular tissue biopsy specimens was studied by polymerase chain reaction.

RESULTS

Using commercial Western-blot, significant presence of IgG anti-39 kDa and anti-54 kDa was found in cases and was related to MIF results and C. pneumoniae DNA findings; IgA anti-LPS, anti-92 kDa and anti-Hsp60 kDa were also found and related to DNA presence. Using no commercial Western-blot, significant presence of 128.8 and 9.2 kDa bands for IgG was detected in cases and associated with DNA presence; 70.8, 58.9, 47.9, 47.5, 18.4, 12.1, 10.6, 8.1, and 7.6 kDa bands for IgG were found in cases; and DNA was present when 54.6 and 1.1 kDa bands for IgG and 79.4, 50.1, and 18.4 kDa bands for IgA were also detected.

CONCLUSIONS

Using Western-blot, a greater serologic response was found against certain proteins of the bacteria in individuals with peripheral arterial disease. This may reflect an initial stage with presence of DNA and specific IgG. Subsequently, even in absence of the bacteria, an immunomediated disease may develop with presence of IgA and IgG.

Evaluation of serological tests detecting Chlamydophila pneumoniae-specific immunoglobulin M antibody

OBJECT

To evaluate a newly developed enzyme-linked immunosorbent assay (ELISA) (Hitazyme C. pneumoniae) detecting Chlamydophila pneumoniae-specific immunoglobulin M (IgM) antibody, we compared the assay with culturing, immunoblotting and the microimmunofluorescence (MIF) test.

PATIENTS AND METHODS

Two hundred five patients with stable chronic lung diseases without acute respiratory tract infections (ARTIs) and 116 healthy volunteers without ARTIs were enrolled in this study. Nasopharyngeal swab specimens and sera were obtained from all subjects for isolation and serological testing of C. pneumoniae.

RESULTS

C. pneumoniae IgM-positive results were observed in 16.5% of patients with stable chronic lung diseases and in 8.6% of asymptomatic healthy subjects. However, there were no positive cases with cell culture, immunoblot or MIF test. In addition, no cases with a significant increase in IgA or IgG antibody titer for the ELISA kit and MIF test between paired sera were observed in the followed-up groups. IgM-positive cases were more frequent among patients with chronic obstructive pulmonary disease (p=0.1566), collagen disease-associated interstitial lung disease (p<0.0001) and cryptogenic organizing pneumonia (p=0.0199) than among the healthy subjects.

CONCLUSION

Our results indicate that IgM-positive results with the ELISA kit do not always reflect acute C. pneumoniae infections. Further studies are needed, to determine an appropriate cut-off level and the possible causes of the false-positive results in the ELISA kit, such as other underlying conditions.

Prevalence and persistence of Chlamydia pneumoniae antibodies in healthy laboratory personnel in Finland

The rates of Chlamydia pneumoniae seroconversions suggesting acute primary infections or reinfections and the prevalences of antibodies were followed up among healthy laboratory workers. Annual serum samples were collected from 47 persons in Helsinki from 1958 to 1990 and from 40 persons in Oulu from 1994 to 1999. C. pneumoniae species-specific immunoglobulin G (IgG), IgA, and IgM antibodies were measured by microimmunofluorescence (MIF) in 407 sera from Helsinki. The 185 sera collected in Oulu were tested both by MIF and by commercial enzyme immunoassay (EIA). During the follow-up periods of 31 years in Helsinki and 6 years in Oulu, seroconversions were demonstrated by MIF in 45% and 15% of the study groups, respectively. In Helsinki 9% of the persons seroconverted twice during the follow-up period. By MIF, the total incidence rate per 100 person-years at risk was 6.9 in Helsinki and 4.9 in Oulu, and annual incidence rates varied from 0 to 15.4. By EIA, annual incidence rates in Oulu varied from 0 to 10.8. The seroconversions by MIF were usually not confirmed by EIA and vice versa. Prevalence and persistence rates, respectively, of IgA antibodies were higher in EIA (62% and 26%) than in MIF (26% and 17%), whereas the figures for IgG were quite similar. The prevalence of IgG and IgA antibodies was higher in older persons than in younger ones. The presence of antibodies did not offer protection from reinfection.

Impact of serological methodology on assessment of the link between Chlamydia pneumoniae and vascular diseases

We assessed the impact of five serologic tests on the link between Chlamydia pneumoniae and abdominal aortic aneurysms (AAA). The results of the tests were inconsistent. Agreement among the five tests was generally poor. Detection of the link between C. pneumoniae and AAA depends on the serologic methodology chosen.

Comparison of quantitative and semiquantitative enzyme-linked immunosorbent assays for immunoglobulin G against Chlamydophila pneumoniae to a microimmunofluorescence test for use with patients with respiratory tract infections

We previously reported a high degree of variation in the sensitivities of serodiagnostic kits for the detection of Chlamydophila pneumoniae in sera from healthy donors. Since a low predictive value of a test can impair its diagnostic value, we have extended our studies to samples from patients with pneumonia. We focused on the most promising enzyme-linked immunosorbent assays (ELISAs) (SeroCP and SeroCP Quant; Savyon) identified in our previous study and included a new ELISA (sELISA; Medac). The agreement between all ELISAs for immunoglobulin G (IgG) and a reference microimmunofluorescence (MIF) test for IgG (SeroFIA; Savyon) was > or = 90% for a collective of 80 patients. The positive predictive values were all > or = 93%. The negative predictive values ranged from 68 to 83%. False-negative results were obtained only for samples that had low titers in the MIF test. The correlation of the IgG antibody titers determined by the MIF and SeroCP Quant tests was high (r(sp) = 0.9). Since the semiquantitative SeroCP and quantitative SeroCP Quant ELISAs achieved the highest sensitivities, they were evaluated further by using a second batch of sera from 50 patients with predominantly medium and low antibody titers in the MIF test and a control collection of sera from 80 children with negative MIF results. Again, the tests showed a high concordance with the MIF results (96%), and the antibody titers in the SeroCP Quant and MIF tests correlated well (r(sp) = 0.8). The specificities determined with the negative sera were > or = 99% for the SeroCP Quant test and 86% for the SeroCP test. These results show that ELISAs that are fast and objective deliver seroprevalence results, sensitivities, and specificities that are very similar to those of the MIF test.

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.

Prospective study of Chlamydia pneumoniae IgG and IgA seropositivity and risk of incident ischemic stroke

BACKGROUND AND PURPOSE

Chlamydia pneumoniae infection or exposure to C. pneumoniae was implicated as a risk factor for ischemic stroke. Our aim was to evaluate prospectively the association between the presence of antibodies to C. pneumoniae (IgG and IgA) and the risk of incident ischemic stroke among patients with pre-existing vascular disease.

METHODS

Sera were collected from 3,090 coronary heart disease patients enrolled in a secondary prevention trial. We measured baseline antibodies (IgG and IgA) in the sera of patients who developed subsequent ischemic strokes (cases, n = 134) during follow-up (mean 8.2 years), and in 134 age- and gender-matched pairs without subsequent stroke or myocardial infarction.

RESULTS

The crude relative odds (95%CI) of incident ischemic strokes in seropositive patients at baseline (>1.1 relative value units) were 1.29 (95%CI, 0.69-2.47) for IgG and 1.31 (95% CI, 0.69-2.55) for IgA by matched-pair analyses, and 1.42 (95%CI, 0.69-2.98) for IgG and 1.57 (95%CI, 0.76-3.35) for IgA after adjustments for conventional risk factors and the inflammatory marker, soluble intercellular adhesion molecule-1. We explored the possibility that the risk of ischemic stroke may increase in parallel to increasing antibody titers, but did not demonstrate any significant association.

CONCLUSIONS

Serological evidence for prior infection with C. pneumoniae did not emerge as an independent risk factor for incident ischemic stroke among patients at high risk due to pre-existing vascular disease.

Detection of Chlamydia pneumoniae-specific antibodies binding to the VD2 and VD3 regions of the major outer membrane protein

Although Chlamydia pneumoniae is an important human pathogen, the antigens eliciting a specific humoral immune response remain elusive. We scrutinized several recombinant chlamydial surface proteins for species-specific recognition by a panel of human sera previously tested for the presence of anti-C. pneumoniae and anti-C. trachomatis antibodies by microimmunofluorescence and enzyme-linked immunosorbent assay. The 15-kDa cysteine-rich protein (CrpA), porin-b (PorB), 9-kDa outer membrane protein (OMP3), 60-kDa outer membrane protein (OMP2), and four fragments of the major outer membrane protein (MOMP) representing each variable domain (VD) were overexpressed in Escherichia coli, affinity purified, and employed for Western blot analysis. None of the sera tested contained antibodies recognizing PorB and OMP3 of C. pneumoniae. Sera from C. pneumoniae-immune patients cross-reacted with OMP2 of C. trachomatis, and sera from C. trachomatis-immune patients cross-reacted with CrpA of C. pneumoniae, indicating that some of chlamydial surface molecules share antigenic epitopes. In contrast, the VD2, as well as the VD3, regions of the MOMP of C. pneumoniae were only recognized by C. pneumoniae-positive sera, suggesting the existence of species-specific epitopes. The identification of such epitopes of cell surface molecules provides new insights into C. pneumoniae-specific immune responses and may be of value for the improvement of C. pneumoniae-specific diagnostic assay systems based on defined recombinant antigens.

Chlamydia antibody response in healthy volunteers immunized with nonchlamydial antigens: a randomized, double-blind, placebo-controlled study

Serological analysis is often used for the diagnosis of chlamydial infections. However, an increase in Chlamydia antibodies has been reported in patients with parvovirus and Mycoplasma infections. Whether this antibody response is the result of dual infection or nonchlamydial antigen stimulation is unknown. In a randomized study, 48 healthy volunteers either were immunized against yellow fever, polio, diphtheria, and tetanus (the group receiving intervention with nonchlamydial antigen) or received saline injections (the placebo group). The change in antibody levels was compared between the 2 groups. The Chlamydia recombinant lipopolysaccharide enzyme-linked immunosorbent assay (Medac) showed an increase in the antibody titer in the intervention group, compared with that in the control group (for immunoglobulin M, P=.004; for immunoglobulin A, P=.038; and for immunoglobulin G, P=.056), but no differences between study groups was found when the C. pneumoniae enzyme immunoassay (EIA; ThermoLabsystems), the C. pneumoniae EIA (Medac), and the microimmunofluorescence test (MRL) were used. An increase in antibodies to Chlamydia organisms can be measured after exposure to nonchlamydial antigens, depending on the test used.

Characterization of the humoral immune response to Chlamydia outer membrane protein 2 in chlamydial infection

Detection of antibodies to an outer membrane protein 2 (OMP2) by enzyme-linked immunosorbent assay (ELISA) by using either the Chlamydia trachomatis- or the Chlamydia pneumoniae-specific protein was investigated. OMP2 is an immunodominant antigen giving rise to antibody responses in humans infected with different C. trachomatis serovars (A to C and D to K) or with C. pneumoniae, which could be detected by OMP2 ELISA. OMP2 ELISA is not species specific, but antibody titers were usually higher on the homologous protein. The sensitivity of this assay was high but varied according to the "gold standard" applied. Levels of antibody to C. pneumoniae OMP2 as detected by ELISA seem to return to background or near-background values within a shorter period of time compared to antibodies to C. pneumoniae detected by microimmunofluorescence (MIF), making it more likely that positive results in ELISA reflect recent infection. Thus, OMP2 ELISA has distinct advantages over MIF and commercially available ELISAs and might be a useful tool for the serodiagnosis of chlamydial infection.