Comparison of five serologic tests for diagnosis of acute infections by Chlamydia pneumoniae

Clinical Analysis of Metagenomic Next-Generation Sequencing Confirmed Chlamydia psittaci Pneumonia: A Case Series and Literature Review

Introduction

Chlamydia psittaci infection is a zoonotic infectious disease, which mainly inhaled through the lungs when exposed to the secretions of poultry that carry pathogenic bacteria. The traditional respiratory specimens or serological antibody testing is slow, and the false-negative rate is high. Metagenomic next-generation sequencing (mNGS) gives a promising rapid diagnosis tool.

Methods

We retrospectively summarized the clinical characteristics of five C. psittaci pneumonia patients diagnosed by mNGS, conducted a literature review summarizing the clinical characteristics of patients with C. psittaci pneumonia reported since 2010.

Results

Five C. psittaci pneumonia patients confirmed by mNGS aged from 36 to 66 years with three males. About 60% of patients had a history of contact with avian or poultry. All patients had a high fever over 38.5 °C, cough, hypodynamia, hypoxemia, and dyspnea on admission. Two patients had invasive ventilator support and extracorporeal membrane oxygenation support. Inflammatory index levels on admission and follow-up were all higher than normal values. Doxycycline or moxifloxacin and their combination therapy were used in patients. Four patients improved and were discharged, and one patient died due to multiple organ failures and disseminated intravascular coagulation. We summarized 19 articles including 69 C. psittaci pneumonia patients and patients in 11 publications were identified by mNGS, and most patients are treated with tetracycline and quinolone with good outcomes.

Conclusion

mNGS is a promising rapid diagnosis tool, which may increase the detection rate and shorten the diagnosis time of C. psittaci pneumonia. Further case-control studies are needed to confirm.

Discovery of Human-Specific Immunodominant Chlamydia trachomatis B Cell Epitopes

Current serological assays for species-specific detection of anti-Chlamydia species antibodies suffer from well-known shortcomings in specificity and ease of use. Due to the high prevalences of both anti-C. trachomatis and anti-C. pneumoniae antibodies in human populations, species-specific serology is unreliable. Therefore, novel specific and simple assays for chlamydial serology are urgently needed. Conventional antigens are problematic due to extensive cross-reactivity within Chlamydia spp. Using accurate B cell epitope prediction and a robust peptide ELISA methodology developed in our laboratory, we identified immunodominant C. trachomatis B cell epitopes by screening performed with sera from C. trachomatis-infected women. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins, in addition to confirming 10 host-independent mouse serum peptide antigens that had been identified previously. This extended set of highly specific C. trachomatis peptide antigens can be used in simple ELISA or multiplexed microarray formats and will provide high specificity and sensitivity to human C. trachomatis serodiagnosis.

Chlamydia species-specific serology is compromised by cross-reactivity of the gold standard microimmunofluorescence (MIF) or commercial enzyme-linked immunosorbent assays (ELISAs). This study was conducted to discover novel C. trachomatis-specific peptide antigens that were recognized only by the antibody response of the natural human host. We evaluated a library of 271 peptide antigens from immunodominant C. trachomatis proteins by reactivity with 125 C. trachomatis antibody-positive sera from women with PCR-confirmed C. trachomatis infection and 17 C. trachomatis antibody-negative sera from low-risk women never diagnosed with C. trachomatis infection. These C. trachomatis peptide antigens had been predicted in silico to contain B cell epitopes but had been nonreactive with mouse hyperimmune sera against C. trachomatis. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins (PmpD, IncE, IncG, CT529, CT618, CT442, TarP, CT143, CT813, CT795, CT223, PmpC, CT875, CT579, LcrE, IncA, CT226, CT694, Hsp60, and pGP3). Using these human sera, we also confirmed 10 C. trachomatis B cell epitopes from 6 immunodominant C. trachomatis proteins (OmpA, PmpD, IncE, IncG, CT529, and CT618) as host species-independent epitopes that had been previously identified by their reactivity with mouse hyperimmune sera against C. trachomatis. ELISA reactivities against these peptides correlated strongly with the C. trachomatis microimmunofluorescence (MIF) text results (Pearson’s correlation coefficient [R] = 0.80; P < 10⁻⁶). These C. trachomatis peptide antigens do not cross-react with antibodies against other Chlamydia species and are therefore suitable for species-specific detection of antibodies against C. trachomatis. This study identified an extended set of peptide antigens for simple C. trachomatis-specific ELISA serology.

IMPORTANCE Current serological assays for species-specific detection of anti-Chlamydia species antibodies suffer from well-known shortcomings in specificity and ease of use. Due to the high prevalences of both anti-C. trachomatis and anti-C. pneumoniae antibodies in human populations, species-specific serology is unreliable. Therefore, novel specific and simple assays for chlamydial serology are urgently needed. Conventional antigens are problematic due to extensive cross-reactivity within Chlamydia spp. Using accurate B cell epitope prediction and a robust peptide ELISA methodology developed in our laboratory, we identified immunodominant C. trachomatis B cell epitopes by screening performed with sera from C. trachomatis-infected women. We discovered 38 novel human host-dependent antigens from 20 immunodominant C. trachomatis proteins, in addition to confirming 10 host-independent mouse serum peptide antigens that had been identified previously. This extended set of highly specific C. trachomatis peptide antigens can be used in simple ELISA or multiplexed microarray formats and will provide high specificity and sensitivity to human C. trachomatis serodiagnosis.

Association of Chlamydia pneumoniae immunoglobulin G antibodies with the risk of lung cancer among non-smoking women in Liaoning, China

The role of Chlamydia pneumoniae in the cause of lung cancer is controversial. In this study, we investigated the association between C. pneumoniae immunoglobulin (Ig) G antibodies and risk of lung cancer among non-smoking women. C. pneumoniae IgG antibody levels were compared between 192 adult Chinese women who met the diagnostic criteria of lung cancer and 90 healthy controls. C. pneumoniae IgG antibodies were tested with the use of an enzyme-linked immunosorbent assay. The prevalence of C. pneumoniae IgG seropositivity was 61.98% of cases and 28.89% of controls (P < 0.05). According to the results of the multiple logistic analysis model, the odds ratios for C. pneumoniae IgG antibody seropositivity, body mass index, and educational levels were 3.919 (P < 0.001), 0.731 (P= 0.274), and 1.646 (P= 0.069), respectively. C. pneumoniae infection may be a risk factor for lung cancer.

Molecular and serological dynamics of Chlamydia pecorum infection in a longitudinal study of prime lamb production

BACKGROUND

Chlamydia pecorum is a globally significant livestock pathogen causing pathology and production losses. The on-farm infection and serological dynamics and the relevance of existing diagnostic tools for diagnosing C. pecorum in livestock remains poorly characterized. In this study, we characterized the antigen and antibody dynamics of this pathogen in a longitudinal study of prime lamb production, utilizing the infection focused C. pecorum-specific 16S rRNA qPCR assay and serology based chlamydial Complement fixation Test (CFT).

METHODS

The study consisted of 76 Border Leicester mixed sex lambs (39 females and 37 males) that were sampled bimonthly from 2-10 months of age in a commercial farm operating in Central NSW, Australia. Blood/plasma was analysed for CFT antibodies, and swabs from conjunctival, rectal and vaginal sites were analysed for C. pecorum shedding using qPCR. We assessed the temporal and overall dynamics of C. pecorum in lambs, including detailed description and comparison of qPCR and CFT, the timing of first detection by either diagnostic method, the lag between infection and antibody response; and the distribution of qPCR load and CFT antibody titre over time.

RESULTS

Over the study period, C. pecorum was highly prevalent (71.0% by qPCR, 92.1% by CFT, 96.0% by both), with 21.1% (16/76) lambs shedding ≥1, 000 qPCR copies/µl (denoted as high shedders). C. pecorum shedding (as evidence of infection) were first observed at two months of age (14.4%) with a significant peak of infection occurring at six months of age (34.2%), whereas seroconversions peaked at eight months of age (81.5%). 52.6% of C. pecorum qPCR and CFT positive lambs became qPCR negative by 10 months of age, indicating clearance of chlamydial infection. Although CFT is utilised for on-farm detection of active infection, we confirm that it lagged behind qPCR detection (average lag 1.7 ± 2.1 months) and that the proportion of qPCR positives simultaneously identified by CFT was low with 2/11 (18.1%), 0/13, 17/25 (68.0%), 5/7 (71.4%) and 1/10 (10.0%) concurrent seroconversions occurring at two, four, six, eight and 10 months of age, respectively.

DISCUSSION

This work reveals rapid rates of C. pecorum infection and widespread exposure during lamb production. The comparison of molecular and serological diagnostic agreement longitudinally, supports the use of qPCR as an important ancillary tool for the detection of active infections in conjunction with chlamydial CFT for routine veterinary diagnostics. Development of rapid Point-of-Care (POC) tools for diagnosing active infection would be valuable for producers and veterinarians.

Management of community-acquired pneumonia in immunocompetent adults: updated Swedish guidelines 2017

Based on expert group work, Swedish recommendations for the management of community-acquired pneumonia in adults are here updated. The management of sepsis-induced hypotension is addressed in detail, including monitoring and parenteral therapy. The importance of respiratory support in cases of acute respiratory failure is emphasized. Treatment with high-flow oxygen and non-invasive ventilation is recommended. The use of statins or steroids in general therapy is not found to be fully supported by evidence. In the management of pleural infection, new data show favourable effects of tissue plasminogen activator and deoxyribonuclease installation. Detailed recommendations for the vaccination of risk groups are afforded.

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.

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.

Chlamydia infection status, genotype, and age-related macular degeneration

PURPOSE

To evaluate whether Chlamydia (C.) infections are associated with age-related macular degeneration (AMD) and to assess if this association is influenced by the complement factor H (CFH) Y402H or the high temperature requirement A serine peptidase 1 (HTRA1) rs11200638 risk genotypes.

METHODS

One hundred ninety-nine AMD patients with early and late forms of the disease and 100 unaffected controls, at least 50 years old were included in the study. Patients in the AMD and control groups were selected based on known CFH Y402H variant genotype status (one third homozygous CC, one third heterozygous CT, and one third wild-type TT). Plasma from all patients and controls was tested for C. pneumoniae, C. trachomatis, and C. psittaci IgG seropositivity using a micro-immunofluorescent assay to establish previous infection status. Assays were conducted blind to risk genotypes and the results analyzed using univariate and multivariate (logistic regression) analysis.

RESULTS

IgG seropositivity to C. pneumoniae was most prevalent (69.2%, n=207), followed by C. trachomatis (7.4%, n=22) and C. psittaci (3.3%, n=10). No association was found between each of the three Chlamydia species IgG seropositivity and AMD status or severity (early/late). There was also no significant association between Chlamydia species IgG seropositivity and AMD status or severity, in patients carrying at least one CFH Y402H risk allele (C) or HTRA1 rs11200638 risk allele (A), with univariate or logistic regression analysis.

CONCLUSIONS

Chlamydia infection status does not appear to be associated with AMD status or severity. The presence of CFH Y402H and HTRA1 rs11200638 risk genotypes does not alter this negative association.

Comparison of real-time PCR and a microimmunofluorescence serological assay for detection of chlamydophila pneumoniae infection in an outbreak investigation

We assessed the performance of a recently validated real-time PCR assay and a commercially available microimmunofluorescence serologic test for the detection of Chlamydophila pneumoniae infection during an outbreak. Evaluation of specimens from 137 individuals suggests that real-time PCR holds greater utility as a diagnostic tool for early C. pneumoniae detection.

The validity of the criteria for primary infection of Chlamydophila pneumoniae in children by measuring ELISA IgM antibodies

As IgM antibody measurement by enzyme-linked immunosorbent assay (ELISA) has become possible for the serological diagnosis of Chlamydophila pneumoniae (C. pn) infection, the HITAZYME-ELISA method has become widely employed in Japan. However, in children, when the diagnostic criterion of primary infection is set at ID ≥1.1, the positive rate is higher than expected, and the potential for inaccurate reflection of the prevalence has been raised. In this study, we performed ROC analysis involving 136 pediatric patients with acute airway symptoms (0-14 years of age), considering a 32-fold or higher micro-immunofluorescence IgM antibody titer against C. pn as positive. Setting the cut-off value for ELISA C. pn IgM antibody ID at 2.0, the specificity was 100%, with no false positivity. The maximum (sensitivity + specificity)/2 was obtained when the cut-off value was set at 1.5. Therefore, IgM ID ≥2.0 was regarded as definitely positive and an IgM ID between 1.5 and 2.0 was regarded as indeterminate as diagnostic criteria for the primary infection. When the prevalence was investigated in 3,108 children (0-15 years of age) with airway symptoms based on these criteria, 542 cases (17.4%) were positive, and the median duration of IgM antibody positivity was five months. Long-term positivity (ten cases) for more than 12 months and recurrent positivity (eight cases) were also observed, but it may be appropriate to set a new criterion of IgM antibody ID ≥2.0 for the diagnosis of primary Chlamydophila pneumoniae infection in children.

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.

Seroprevalence of antibodies to Chlamydophila psittaci in zoo workers in Brazil

To evaluate the prevalence of antibodies to Chlamydophila psittaci 364 serum samples were collected from veterinarians, biologists, animal scientists, veterinary students, animal keepers and others employees in 20 zoos, and from veterinary practitioners in 10 Brazilian states. Subjects ranged from 15 to 64 years of age, with 268 (74%) males and 96 (26%) females. Chlamydial antibodies were determined by the complement fixation test (CFT) and specific anti-C. psittaci IgG antibodies were determined by the microimmunoflurescence (MIF) test. Complement fixation test showed 23.9% (87/364) and MIF test showed 4.7% (17/364) positive serum samples. Titres ranged from 16 to 256 in both assays, demonstrating evidence of recent or current infection. Although chlamydial antibodies were detected in workers of seventeen zoos, MIF test only detected specific C. psittaci antibodies in seven of them. Previous psittacosis infection was suspected in eight workers of two zoos, five of whom reported having pneumonia, while employed at the zoos. However, diagnosis was not established in any of these cases in the past. Results indicated the occurrence of infection and previous contact of Brazilian zoo workers with C. psittaci, as well as the zoonotic potential of psittacosis in this risk population. Other studies are necessary to evaluate the risk factors of infection in this population. This seroepidemiological survey confirmed the need to adopt preventive measures to control avian chlamydiosis and protect the health of zoo workers in the country.

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.

Efficacy of serum procalcitonin in evaluating severity of community-acquired pneumonia in childhood

Microbe-specific diagnosis of community-acquired pneumonia (CAP) in childhood is difficult in clinical practice. Chest radiographs and non-specific inflammatory markers have been used to separate presumably bacterial from viral infection but the results have been inconsistent. The aim of the present study was to evaluate the usefulness of procalcitonin (PCT) in assessing the severity as well as the bacterial or viral aetiology of CAP. Serum PCT was measured by an immunoluminometric assay in 100 patients with CAP; 26 were treated as inpatients and 74 as outpatients. The pulmonary infiltrate was considered to be alveolar in 62 and interstitial in 38 cases, according to the radiological diagnosis. The bacterial and viral aetiology of pneumonia was studied by an extensive serological test panel. No differences were found in PCT concentrations between the 4 aetiological (pneumococcal, atypical bacterial, viral, unknown) and the 3 age (< 2, 2-4 and > or = 5 y) groups. Serum PCT was >0.5 ng/ml in 69%, >1.0 ng/ml in 54% and >2.0 ng/ml in 47% of all patients. PCT was higher in patients that were admitted than as outpatients (medians 17.81 vs 0.72 ng/ml, respectively, p<0.01) and higher in alveolar than in interstitial pneumonia (medians 9.43 vs 0.53 ng/ml, respectively, p<0.01). In conclusion, serum PCT values were found to be related to the severity of CAP in children even though they were not capable, at any level of serum concentration, to differentiate between bacterial and viral aetiology.

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.

Differentiation of bacterial and viral community-acquired pneumonia in children

BACKGROUND

Microbe-specific diagnosis of pediatric community-acquired pneumonia (CAP) and the distinction between typical-bacterial, atypical-bacterial and viral cases are difficult. The aim of the present study was to evaluate the role of four serum non-specific inflammatory markers and their combinations, supplemented by chest radiological findings, in the screening of bacterial etiology of pediatric CAP.

METHODS

Serum procalcitonin (PCT), serum C-reactive protein (CRP), blood erythrocyte sedimentation rate (ESR) and white blood cell (WBC) counts were determined in 101 children with CAP, all confirmed on chest radiograph. Evidence of etiology was achieved in 68 patients (67%) mainly using a serologic test panel including 15 pathogens.

RESULTS

For the combination of CRP > 100 mg/L, WBC count > 15 x 10(9)/L, PCT > 1.0 ng/mL and ESR > 65 mm/h, the likelihood ratio for a positive test result (LR+) was 2.7 in the distinction between pneumococcal and viral CAP and 3.9 between atypical and viral CAP. If there was a higher value in one of these four parameters (CRP > 200 mg/L, WBC count > 22 x 10(9)/L, PCT > 18 ng/mL or ESR > 90 mm/h) LR+ changed to >or=3.4, which means a significant increase from pre-test to post-test disease probability. An alveolar radiological infiltration was associated with higher values in non-specific inflammatory markers when compared with interstitial infiltrates, but there were no significant associations between radiological and etiological findings.

CONCLUSIONS

CRP, WBC count, PCT and ESR or their combinations have a limited role in screening between bacterial and viral pediatric CAP. If all or most of these markers are elevated, bacterial etiology is highly probable, but low values do not rule out bacterial etiology.

Hyponatremia in pediatric community-acquired pneumonia

Studies focusing on serum sodium disorders in children with community-acquired-pneumonia (CAP) are nearly entirely lacking, though clinical experience suggests that at least hyponatremia (HN) might be rather common. We evaluated the incidence of hypo- and hypernatremia, in relation to other clinical, laboratory and etiological findings, in pediatric CAP. Serum sodium concentration was measured in 108 ambulatory and hospitalized children with radiologically confirmed CAP of variable severity. The etiology of CAP was revealed by serology in 97 patients. HN (serum sodium < 135 mmol/l) was present in 49 (45.4%) children, and it was mild (> 130 mmol/l) in 92% of the cases. On admission, hyponatremic patients had higher body temperature (38.96 degrees C vs 38.45 degrees C, P = 0.008), white blood cell count (21,074/microl vs 16,592/microl, P = 0.008), neutrophil percentage (78.93% vs 69.33%, P = 0.0001), serum C-reactive protein (168.27 mg/l vs 104.75 mg/l, P = 0.014), and serum procalcitonin (22.35 ng/ml vs 6.87 ng/ml, P = 0.0001), and lower calculated osmolality (263.39 mosmol/l vs 272.84 mosmol/l, P = 0.0001) than normonatremic ones. No association was found with plasma glucose, type of radiological consolidation or etiology of CAP. HN is common but usually mild in children with CAP. HN seems to be associated with the severity of CAP, assessed by fever, need of hospitalization and serum non-specific inflammatory markers.

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.

Rapid and simple diagnosis of Chlamydophila pneumoniae pneumonia by an immunochromatographic test for detection of immunoglobulin M antibodies

To evaluate a newly developed immunochromatographic test (the MySet test) for the detection of Chlamydophila pneumoniae-specific immunoglobulin M antibodies, the results obtained by the MySet test were compared with those obtained by two serological tests. The sensitivity and specificity of the MySet test were 100% and 92.9%, respectively. The MySet test is rapid and simple to use and is thought to be a useful tool for the selection of appropriate antibiotic therapy.

Frequency of Chlamydia pneumoniae and Mycoplasma pneumoniae infections in children

OBJECTIVE

Chlamydia pneumoniae and Mycoplasma pneumoniae are among the most important pathogens of acute respiratory infections in children between the ages of 5 and 15 years. We aimed to investigate seasonal frequency of respiratory infections caused by C. pneumoniae and M. pneumoniae, frequency of coinfection, clinical findings and to determine relationship between clinical findings and laboratory results.

MATERIAL AND METHODS

Total of 284 patients (ranging 5-15 years of age), admitted to out-patient clinic with symptoms of respiratory tract infections between January 2004 and June 2005, were enrolled in the study. IgA, IgG and IgM antibodies against C. pneumoniae were quantitatively detected in all serum samples by using microimmunofluorescence (MIF). For the M. pneumoniae infection an IgM titer in the ELISA test were analyzed. Nasopharyngeal smear samples were collected for PCR detection.

RESULTS

Mean age was 8 +/- 2.2 (range 5-14) years. Mycoplasma pneumoniae IgM in 86 (30.2%) cases, C. pneumoniae IgM in one (0.3%) case, IgA in six (2.1%) cases and IgG in 10 (3.5%) cases were found positive. In 10 (3.5%) cases, both C. pneumoniae IgG (a titer of >1/216) and M. pneumoniae IgM were found positive concomitantly. The M. pneumoniae IgM in winter was found significantly higher compared to other seasons. Mycoplasma pneumoniae PCR method was performed on a total of 203 samples in 33 (16.2%) of which M. pneumoniae was found positive. The false positive ratio of PCR technique was found 16.2%. In a total of 217 examined samples by PCR method, the DNA of C. pneumoniae was found positive in two patients.

CONCLUSION

Mycoplasma pneumoniae was a common pathogen in respiratory infections. The otherwise C. pneumoniae infections were rarely seen in children. A Comparison of serology diagnostic tests for M. pneumoniae infections was found more sensitive and specific than PCR.

Chlamydia pneumoniae antibody levels before coronary events in the Helsinki Heart Study as measured by different methods

The lack of specific tests for the diagnosis of chronic Chlamydia pneumoniae infection has led to the use of enzyme immunoassay (EIA) instead of the gold standard, that is, microimmunofluorescence (MIF), in the measurement of C. pneumoniae antibodies. We assessed the predictive values of C. pneumoniae antibody levels and seroconversions measured by MIF and EIA for coronary events in the prospective Helsinki Heart Study. Sera from 239 cases with coronary events and 239 controls were available at the baseline and data from 210 cases and 211 controls before and after the event. The agreement between MIF and EIA antibody levels was best in high antibody titers. In conditional logistic regression analysis, only high IgA MIF titers (>/=40) at the baseline predicted future coronary events, and the participants with MIF seroconversion between consecutive sera had a higher (nonsignificant) risk for coronary events than the controls. The difference in the kinetics of EIA and MIF antibodies demonstrated that MIF should remain the gold standard.

Detection of Chlamydophila pneumoniae IgG in paired serum samples: comparison of serological techniques in pneumonia cases

Serological diagnosis of Chamydophila pneumoniae is usually undertaken by complement fixation test (CFT) or by microimmunofluorescence (MIF). A number of commercial methods for detecting C. pneumoniae-specific IgG have been developed. The aim of this study was to compare the performance characteristics of six methods for the diagnosis of pneumonia due to C. pneumoniae, including CFT (in house), MIF (Vircell, Spain), and four ELISAs (Medac, Germany; Savyon, Israel; Serion, Germany; and DRG, Germany). ELISA-Medac, ELISA-Savyon, ELISA-DRG and MIF use C. pneumoniae antigens while ELISA-Serion and CFT use Chlamydophila genus-specific antigen. Acute and convalescent samples from 85 pneumonia patients were studied. Using CFT, cases were initially classified as due to Chlamydophila (43 cases); to other agents (23 cases) (influenza A and B, Mycoplasma pneumoniae, respiratory syncytial virus, adenovirus and Legionella pneumophila); or as negative (19 cases). Cases were considered positive if they showed seroconversion, a significant rise in titer or high titer; and were finally classified as positive if they gave a positive result in at least three assays. Sensitivity values ranged from 87% to 97.8%; and specificity from 84.6% to 97.4%. In conclusion, the assays compared appear to be useful tools for the diagnosis of pneumonia due to Chlamydophila.

Aetiology of community-acquired pneumonia: serological results of a paediatric survey

Serological methods are routinely used in the diagnosis of viral and atypical bacterial respiratory infections. Recently, they have also been applied to typical bacteria, such as Streptococcus pneumoniae. The aim of this study was to determine the aetiology of paediatric community-acquired pneumonia (CAP) in both ambulatory and hospitalized patients, by using antibody assays. During a 15-month prospective surveillance, paired sera were studied for antibodies to 14 microbes in 101 children with symptoms of acute infection and infiltrates compatible with pneumonia on chest radiographs. A potential causative agent was detected in 66 (65%) patients. Evidence of bacterial, viral and mixed viral-bacterial infection was demonstrated in 44%, 42% and 20% of the CAP cases, respectively. The most commonly found agents included Mycoplasma pneumoniae (27%), Pneumococcus (18%) and respiratory syncytial virus (17%). Human metapneumovirus (hMPV) was detected in 5 (5%) children. Pneumococcal infections were evenly distributed among the age groups studied. Our results confirm the role of S. pneumoniae in paediatric CAP at all ages, those of M. pneumoniae at >2 y of age and emphasize the emerging role of hMPV. The high proportion of mixed viral-bacterial infections highlights the need to treat all children with CAP with antibiotics.

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.

Chlamydial antibodies and risk of prostate cancer

OBJECTIVE

We assessed the risk of prostate cancer by exposure to Chlamydia trachomatis.

METHOD

Seven hundred thirty eight cases of prostate cancer and 2,271 matched controls were identified from three serum sample banks in Finland, Norway, and Sweden by linkage to the population based cancer registries.

RESULTS

A statistically significant inverse association (odds ratio, 0.69; 95% confidence interval, 0.51-0.94) was found. It was consistent by different serotypes and there was a consistent dose-response relationship.

CONCLUSION

C. trachomatis infection is not likely to increase the risk of prostate cancer. Whether the inverse relationship is true or due to difficulties in measuring the true exposure in prostatic tissue by serology, confounders or other sources of error remain open.

Chlamydia pneumoniae seropositivity and risk of ischemic stroke: a nested case-control study

Chlamydia pneumoniae has been linked with increased risk of cardiovascular disease, but data on stroke are sparse. We examined whether seropositivity to Chlamydia pneumoniae was associated with the risk of ischemic stroke in a nested case-control study. Data on Chlamydia pneumoniae serology, lifestyle factors, and medical history were obtained at baseline. Verified cases (n = 254) were compared with gender- and age-matched controls (n = 254). Positive IgA (> or = 1:16) or IgG (> or = 1:64) titers were associated with an increased risk of acute ischemic stroke, i.e. adjusted odds ratios (ORs) were 1.54 (95% confidence interval, CI: 0.96-2.47) and 1.28 (95% CI: 0.83-1.95). The adjusted OR was 1.77 (95% CI: 1.04-3.00) when both titers were elevated. The highest point estimates were seen for ischemic stroke due to large-artery atherosclerosis, adjusted OR: 6.32 (95% CI: 0.76-52.61) (IgG (> or = 1:64)). No clear associations were found for other types of ischemic stroke. The strength of the association varied depending on gender and the chosen cut-off values for the antibody titers. These results partly support the hypothesis that serologic evidence of Chlamydia pneumoniae infection may be associated with an increased risk of ischemic stroke. However, the risk may differ according to gender, subtype of ischemic stroke, and cut-off value of antibody titers.

Etiology of community-acquired pneumonia treated in an ambulatory setting

BACKGROUND

Very few studies have addressed the etiology of community-acquired pneumonia (CAP) treated in an ambulatory setting.

METHODS

Patients were recruited from physicians' offices and from Emergency Rooms in Canada. Pneumonia was defined as two or more respiratory symptoms and signs and a new opacity on chest radiograph interpreted by a radiologist as pneumonia. Blood and sputum for culture as well as acute and convalescent serum samples for serology were obtained. Antibodies to Mycoplasma pneumoniae and Chlamydia pneumoniae were determined using enzyme-linked immunosorbent assays.

RESULTS

Five hundred and seven patients were enrolled in the study; 419 (82%) had blood cultures done, seven (1.4%) of which were positive for Streptococcus pneumoniae; 241 (47.5%) had a sputum processed for culture, 31% of which were positive for a potential respiratory pathogen. 437 (86.2%) had both acute and convalescent serum samples obtained, 148 (33.8%) of which gave a positive result. Overall an etiological diagnosis was made in 48.4% of the patients. M. pneumoniae accounted for 15% of the cases, C. pneumoniae 12%, S. pneumoniae 5.9% and Haemophilus influenzae 4.9%.

CONCLUSIONS

Despite considerable effort an etiological diagnosis of CAP treated on an ambulatory basis was made in only half the patients. The most commonly identified pathogens were M. pneumoniae, C. pneumoniae, S. pneumoniae,

Acute hemorrhagic pericarditis in a child with pneumonia due to Chlamydophila pneumoniae

Chlamydophila pneumoniae is mainly responsible for respiratory tract infections but has also been associated with endocarditis and myocarditis. We report a case of pneumonia in a child with hemorrhagic pericardial effusion with a positive result by a new C. pneumoniae TaqMan PCR, suggesting a pericardial inflammation directly induced by C. pneumoniae. C. pneumoniae should be suspected in patients with community-acquired pneumonia and concurrent pericarditis. Empirical treatment with azithromycin seems feasible.

Chlamydia pneumoniae Serology in Donors and Recipients and the Risk of Bronchiolitis Obliterans Syndrome after Lung Transplantation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is a common late complication in lung transplant recipients (LTR). Chlamydia pneumoniae (C. pneumoniae) is a common but difficult to diagnose respiratory pathogen with a propensity to latency.

METHODS

We studied the impact of C. pneumoniae on BOS development using donor-recipient serology obtained before transplantation in a cohort of 76 LTR.

RESULTS

BOS was present in 29.9% patients (mean follow-up 866 days). High donor C. pneumoniae immunoglobulin (Ig)G titers were associated with BOS in the recipient (area under the curve [AUC] 0.71, 95% confidence interval [CI] 0.52-0.91, P=0.027), whereas high recipient titers were inversely associated with BOS (AUC 0.27, 95% CI 0.11-0.44, P=0.018). The risk of developing BOS was 75.0% in the case of a primary seromismatch for C. pneumoniae (D+/R-), whereas a reverse mismatch had a risk of 4.6% (likelihood ratio 9.8, P=0.02). In a multivariate model that included human leukocyte antigen matching, acute rejection and cytomegalovirus pneumonitis, C. pneumoniae IgG donor 32 or greater and C. pneumoniae IgG recipient 32 or greater remained positive and negative independent risk factors, respectively, for BOS in LTR. In the freedom from BOS analysis, BOS occurred more frequently and earlier in C. pneumoniae seropositive donors, and the reverse was true in seronegative recipients.

CONCLUSION

C. pneumoniae serology in donor and recipient is associated with the development of BOS in LTR.

Chlamydia pneumoniae in HIV-infected patients and controls assessed by a novel whole blood interferon-gamma assay, serology and PCR

Chlamydia pneumoniae seropositivity is associated with cardiovascular disease and HIV infection. Cell-mediated immune responses are important for control of C. pneumoniae, and such responses may be impaired in HIV-infected patients. An assay for detection of interferon (IFN)-gamma in whole blood stimulated with C. pneumoniae antigen was developed and studied in HIV-infected patients and uninfected controls. Among 34 HIV-infected patients, none had an IFN-gamma response to C. pneumoniae antigen, compared with five of 32 healthy controls (p < 0.001). Fewer HIV-infected individuals elicited a serum IgG response when tested with a commercial enzyme immunoassay (p 0.009), but this was not so for serum IgA (p 0.12). Additionally, the IFN-gamma and antibody assays showed a trend towards a bivariate response in normal controls. This indicates that cellular and antibody responses against C. pneumoniae may be mutually exclusive, with potential implications for the role of this organism in the genesis of cardiovascular disease in both immunocompetent and HIV-infected populations.

Chlamydia pneumoniae and newly diagnosed asthma: a case-control study in 1 to 6-year-old children

OBJECTIVE

The aim of the study was to evaluate the association between antibodies to Chlamydia pneumoniae and the onset of asthma in children.

METHODOLOGY

In 1996-2000, 122 children aged 1-6 years, who were treated for new asthma as inpatients or outpatients in our hospital, were recruited. For each patient, two controls, matched by age, sex and municipality, were randomly selected from the same population. In 2000, 104 serum samples were available from patients (85%) and 120 from controls (49%) for microimmunofluorescence (MIF) assay for C. pneumoniae and C. trachomatis antibodies, and for enzyme immunoassay (EIA) for C. pneumoniae antibodies.

RESULTS

In EIA, the median IgG concentrations were 20 EIU (EIA units) in the patients, and 16 EIU in the controls. IgG was positive (> 30 EIU) in 37 (36%) patients and in 36 (31%) controls. IgA was positive (> 12 EIU) in four (4%) patients and in eight (7%) controls. In MIF, four (4%) patients and seven (6%) controls were IgG positive, and seven were also IgA positive. IgM antibodies were detected in four children by EIA, and in none by MIF.

CONCLUSION

IgG antibodies to C. pneumoniae, though common in 1 to 6-year-old children as detected by EIA, did not differ between newly diagnosed asthma patients and controls in this case-control study.

Evaluation and optimization of ELISA for detection of anti-Chlamydophila pneumoniae IgG and IgA in patients with coronary heart diseases

We have evaluated and optimized a commercial enzyme-linked immunosorbent assay (ELISA; SeroCP Savyon, Israel), using the commercial microimmunofluorescence test (MIF; Labsystems; Helsinki, Finland) as reference method. This was done for the detection of anti-Chlamydophila pneumoniae IgG and IgA antibodies in patients with coronary heart disease (CHD). After optimization, a good agreement between the ELISA and MIF tests [IgG (P(0.05)=0.0008 and r=0.93) and IgA (P(0.05)=0.00072 and r=0.72)] was found. These ELISA tests proved to be a useful semiquantitative method for seroprevalence studies in CHD patients, with remarkable advantages over MIF test in terms of objective measurement, thus reproducibility, performance and interpretation.

Use of quantitative and objective enzyme immunoassays to investigate the possible association between Chlamydia pneumoniae and Mycoplasma pneumoniae antibodies and asthma

Sera from 150 consecutive patients with established asthma and 150 matched controls were examined for Chlamydia pneumoniae IgG and IgA with commercially available enzyme immunoassays (EIAs) detecting immune response solely to surface proteins of elementary bodies. The assays were also modified to measure combined immune response to surface proteins and family-specific lipopolysaccharide antigen. Mycoplasma pneumoniae IgG and IgA were measured with new commercial EIAs utilising P1-enriched protein fraction as an antigen. No statistically significant differences between the patient groups in terms of prevalence or levels of antibodies to either organism were found with these methods.

The reproducibility of an enzyme-linked immunosorbent assay for detection of Chlamydia pneumoniae-specific antibodies

With use of an enzyme-linked immunosorbent assay (ELISA), Chlamydia pneumoniae immunoglobulins were detected in a consecutive series of patients' sera (n = 122 for IgA and IgG; n = 138 for IgM). When the ELISA tests were repeated, the percentage disagreements were 12%, 16% and 10% for C. pneumoniae IgA, IgG and IgM, respectively. The reproducibility of the ELISA, expressed as kappa values, for IgA, IgG and IgM was 0.73, 0.60 and 0.53, respectively (p < 0.001). It was concluded that the ELISA had good reproducibility for detecting C. pneumoniae IgA, and moderately good reproducibility for detecting C. pneumoniae IgG and IgM.

A prospective study of Chlamydia pneumoniae antibodies in children between 7 months and 8 years of age

To provide insight into the appearance and longitudinal course of Chlamydia pneumoniae antibodies in childhood, C. pneumoniae immunoglobulin G (IgG), IgA and, in selected children, IgM antibodies were measured annually in 199 healthy children, followed prospectively from age 7 months to age 8 y (number of samples 1225) using a commercial enzyme immunoassay kit. IgG antibodies to C. pneumoniae were common throughout the follow-up, and the values declined rapidly after apparent infections during early childhood. Of the 128 identified seroconversions, 94 were probably primary infections and 34 reinfections. IgM antibodies were detected in 28% of the samples that showed a clear increase in IgG. IgA antibodies were scarce before 2 y of age, but their proportion then increased gradually. At the ages of 7 and 8 y, 10% of the children had clearly positive IgG and IgA antibody values. Increases in IgG were not associated with clinical respiratory symptoms. This study shows that C. pneumoniae infections probably occur commonly already at an early age, and that the infections are often asymptomatic. Consecutive high IgG and IgA antibody concentrations at the ages of 7 and 8 y indicate that persistent seropositivity for both antibodies may already develop in young children.

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.

Proinflammatory cytokines, antibodies to Chlamydia pneumoniae and age-associated diseases in Danish centenarians: is there a link?

Plasma levels of tumour necrosis factor (TNF)-alpha levels increase with age. High levels are associated with dementia and atherosclerosis in centenarians. Chlamydia pneumoniae induces the production of proinflammatory cytokines and has been related to the pathogeneses of Alzheimer's disease and cardiovascular diseases. The purpose of this study was to test the hypothesis that circulating levels of TNF-alpha represent a link between C. pneumoniae, high prevalences of dementia and cardiovascular diseases in 126 Danish centenarians. IgA antibody titres against C. pneumoniae were linearly correlated with high plasma levels of TNF-alpha in centenarians. However, both parameters were also correlated with total IgA in the blood and the association between C. pneumoniae IgA and TNF-alpha was not significant when total IgA was included in a multiple linear regression model. Accordingly, the association between C. pneumoniae-specific IgA and TNF-alpha may reflect immune activation rather than a specific antibody response. No associations were found between antibodies to C. pneumoniae and dementia or cardiovascular diseases. Although TNF-alpha is likely to be involved in the pathogenesis of atherosclerosis and dementia, the present study does not support the hypothesis that TNF-alpha represents a link between chronic C. pneumoniae infection and these disorders.

Measurement of Chlamydia pneumoniae-specific immunoglobulin A (IgA) antibodies by the microimmunofluorescence (MIF) method: comparison of seven fluorescein-labeled anti-human IgA conjugates in an in-house MIF test using one commercial MIF and one enzyme immunoassay kit

For the serological diagnosis of acute Chlamydia pneumoniae infection, the microimmunofluorescence (MIF) test is the most commonly used method and also the "gold standard" for the measurement of immunoglobulin G (IgG) and IgM antibodies. The role of IgA antibodies in diagnosis has not been established. Commercially available fluorescein-labeled anti-human IgA conjugates have not been systematically compared to each other, and this situation may cause considerable variations in IgA results. Therefore, we tested 261 serum samples from 122 patients with pneumonia for IgA antibodies by using six alpha-chain-specific anti-IgA conjugates in our in-house MIF test, one commercial MIF test, and one enzyme immunoassay (EIA). Interfering IgG antibodies were removed with Gullsorb reagent before the measurement of IgA antibodies. Altogether, 14 significant IgA antibody increases in serum samples between the acute phase and the convalescent phase were detected by at least one of the conjugates in the MIF test, while no increases were found in the IgA EIA. Only one patient showed a significant IgA antibody increase with all of the fluorescein-labeled conjugates. Five significant titer changes were detected by at least two conjugates, and in nine instances, the titer increase was detected by one conjugate only. The titer agreement indicated by kappa coefficients was very good or good for all of the fluorescein-labeled conjugates and the EIA with low antibody titers but decreased with increasing titers.