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

Are ELISA and PCR Discrepancies in the Identification of Chlamydia pneumoniae Caused by the Presence of "Chlamydia-Related Bacteria"?

Chlamydia are Gram-negative, intracellular pathogens colonizing the epithelial mucosa. They cause primarily atypical pneumonia and have recently been associated with chronic diseases. Diagnostics rely almost exclusively on serological methods; PCR tests are used rarely because in patients with positive ELISA, it is nearly impossible to identify chlamydial DNA. To understand this issue, we elaborated a reliable and sensitive nested PCR method (panNPCR) for identifying all Chlamydiales species, not only in sputa, but also in clotted blood. Sequencing of the PCR product revealed that 41% of positive sputa samples and 66% of positive blood samples were not infected by Chlamydia but with "Chlamydia-related bacteria" such as Rhabdochlamydia sp., Parachlamydia sp., Protochlamydia sp., Neochlamydia sp., Mesochlamydia elodeae and lacustris, Piscichlamydia salmonis, and Estrella lausannensis. Consequently, we propose that there might be more than four human pathogenic Chlamydia species. We did not find any clear correlation between increased levels of antibodies and the presence of their DNA. Chlamydialles DNA was found in sputa samples from individuals positive for IgG or IgA but not in blood samples. Thus, elevated IgG and IgA levels are not reliable markers of chronic infection, and the presence of persistent forms should be proved by panNPCR. Apparently, the differences between ELISA and DNA amplification results have three main methodological reasons. The first one is the threshold occurrence of chlamydial genetic material in sputum and blood. The second one is the fact that a significant part of the samples can have DNA with sequences different from those of other species of the order Chlamydiales. The third one is the high background characteristic for ELISA, the absence of paired sera, and the vague interpretation of the gray zone.

Reliable and Sensitive Nested PCR for the Detection of Chlamydia in Sputum

Chlamydia are Gram-negative, intracellular pathogens colonizing epithelial mucosa. They cause primarily atypical pneumonia and have recently been associated with chronic diseases. Diagnostics relies almost exclusively on serological methods; PCR tests are used rarely because in patients with positive ELISA, it is nearly impossible to identify chlamydial DNA. This paradox is associated with DNA degradation in sputum samples, low abundance, and low sensitivity of PCR systems. In a newly designed and validated “nested” PCR (NPCR) assay, it was possible to amplify DNA of Chlamydia known to infect humans in 31% samples. The reliability of the assay was confirmed by DNA sequencing, and all PCR products belonged exclusively to the Chlamydiales, mainly recognized as Chlamydia pneumoniae. Three samples were related to Ca. Rhabdochlamydia porcellionis and Ca. Renichlamydia lutjani, which infect arthropods. In one case, samples were taken from sick individual, indicating the potential as a human pathogen.

Assessment of evidence for or against contributions of Chlamydia pneumoniae infections to Alzheimer's disease etiology

Alzheimer's disease, the most common form of dementia, was first formally described in 1907 yet its etiology has remained elusive. Recent proposals that Aβ peptide may be part of the brain immune response have revived longstanding contention about the possibility of causal relationships between brain pathogens and Alzheimer's disease. Research has focused on infectious pathogens that may colonize the brain such as herpes simplex type I. Some researchers have proposed the respiratory bacteria Chlamydia pneumoniae may also be implicated in Alzheimer's disease, however this remains controversial. This review aims to provide a balanced overview of the current evidence and its limitations and future approaches that may resolve controversies. We discuss the evidence from in vitro, animal and human studies proposed to implicate Chlamydia pneumoniae in Alzheimer's disease and other neurological conditions, the potential mechanisms by which the bacterium may contribute to pathogenesis and limitations of previous studies that may explain the inconsistencies in the literature.

Alzheimer's disease might depend on enabling pathogens which do not necessarily cross the blood-brain barrier

The development of Alzheimer's Disease (AD) might reflect, in its acquired aspects, a cooperative pathogenesis whereby infectious enablers which do not necessarily cross the blood-brain barrier augment the invasive properties of a less virulent organism, thus enabling it to infect the brain. An example interaction is described which involves Chlamydia species, Human papillomavirus (HPV), microbiota, and yeast, where yeast is a pathogen of low virulence which crosses the blood-brain barrier. The cooperative pathogenesis begins at the mucosal epithelium. Infection by Chlamydia, HPV, or dysbiosis of commensal bacteria disrupts the integrity of the mucosal epithelium, thereby allowing colonizing yeast to penetrate the epithelial barrier and enter into the bloodstream. Chlamydia and enabling commensals promote insulin resistance, which provides yeast with glucose and also sets the stage for accumulation of amyloid beta protein (ABP). Meanwhile, HPV-induced and hyperglycemia-induced immunological changes enable the spread of newly invasive yeast to the brain, where the release of inflammatory cytokines in response to yeast promotes production of ABP. Chlamydia also cross reacts with Candida species, which may stimulate further brain inflammation in response to Candida and may augment production of ABP thereby The yeast's less virulent origins, coupled with immune modulation by enablers, might explain why AD as a model of infectious encephalitis is always slow and insidious rather than occasionally febrile, accompanied by seizures, or marked by signs of meningeal inflammation.

The association of mannose binding lectin genotype and immune response to Chlamydia pneumoniae: The Strong Heart Study

Cardiovascular disease (CVD) is an important contributor to morbidity and mortality in American Indian communities. The Strong Heart Study (SHS) was initiated in response to the need for population based estimates of cardiovascular disease in American Indians. Previous studies within SHS have identified correlations between heart disease and deficiencies in mannose binding lectin (MBL), a motif recognition molecule of the innate immune system. MBL mediates the immune response to invading pathogens including Chlamydia pneumoniae (Cp), which has also been associated with the development and progression of CVD. However, a link between MBL2 genotype and Cp in contributing to heart disease has not been established. To address this, SHS collected baseline Cp antibody titers (IgA and IgG) and MBL2 genotypes for common functional variants from 553 individuals among twelve participating tribes. A single nucleotide polymorphism (SNP) in the promoter, designated X/Y, correlated significantly with increased Cp IgG titer levels, whereas another promoter SNP (H/L) did not significantly influence antibody levels to Cp. Two variants within exon 1 of MBL2, the A and B alleles, also displayed significant association with Cp antibody titers. Some MBL2 genotypes were absent from the population, suggesting linkage disequilibrium may be operating within the SHS cohort. Additional factors, such as increasing age and socioeconomic status, were also associated with increased Cp IgG antibody titers. This study demonstrates that MBL2 genotype associates with immune reactivity to C. pneumoniae in the SHS cohort. Thus, MBL2 may contribute to the progression of cardiovascular disease (CVD) among American Indians indirectly through pathogen interactions in addition to its previously defined roles.

Protein microarray-mediated detection of antienterovirus antibodies in serum

Objective

To utilize prokaryotic gene expression and protein microarray to develop and evaluate a sensitive, accurate protein microarray assay for detecting antienterovirus antibodies in serum samples from patients with hand, foot and mouth disease (HFMD). Enterovirus 71 (EV71) and coxsackievirus A16 (CA16), two common causative agents for HFMD, were used for assay development.

Methods

Serum was collected from patients with HFMD and healthy controls. EV71 and CA16 VP1 and VP3 genes were expressed in transfected Escherichia coli; the resultant VP1 and 3 proteins were used in a microarray assay for human serum EV71 and CA16 immunoglobulin (Ig) M and IgG. To validate the microarray assay, serum samples were tested for EV71 IgM using enzyme-linked immunosorbent assay (ELISA).

Results

Out of 50 patients with HFMD, EV71 IgM and CA16 IgM was detected in 80% and 44% of serum samples, respectively, using protein microarray, and EV71 IgM was detected in 78% of samples using ELISA. Protein microarray and ELISA showed 100% specificity for EV71-IgM detection.

Conclusion

The protein microarray assay developed in the present study shows potential as a sensitive technique for detecting EV71 IgM in serum samples from patients with HFMD.

Laboratory diagnosis of persistent human chlamydial infection

Diagnostic assays for persistent chlamydial infection are much needed to conduct high-quality, large-scale studies investigating the persistent state in vivo, its disease associations and the response to therapy. Yet in most studies the distinction between acute and persistent infection is based on the interpretation of the data obtained by the assays developed to diagnose acute infections or on complex assays available for research only and/or difficult to establish for clinical use. Novel biomarkers for detection of persistent chlamydial infection are urgently needed. Chlamydial whole genome proteome arrays are now available and they can identify chlamydial antigens that are differentially expressed between acute infection and persistent infection. Utilizing these data will lead to the development of novel diagnostic assays. Carefully selected specimens from well-studied patient populations are clearly needed in the process of translating the proteomic data into assays useful for clinical practice. Before such antigens are identified and validated assays become available, we face a challenge of deciding whether the persistent infection truly induced appearance of the proposed marker or do we just base our diagnosis of persistent infection on the presence of the suggested markers. Consequently, we must bear this in mind when interpreting the available data.

High prevalence of Chlamydia pneumoniae infection in an asymptomatic Jordanian population

BACKGROUND/PURPOSE

The bacterium Chlamydia pneumoniae is associated with respiratory diseases and nonrespiratory illnesses like atherosclerosis. This study aims to investigate the seroprevalence of immunoglobulin G (IgG) against C. pneumoniae in an asymptomatic population in Jordan and to analyze the immunity state in relation to age and sex.

METHODS

Serum samples were collected from 588 apparently healthy individuals aged 2-86 years. Using the microimmunofluorescence (MIF) test, seropositivity was defined as an anti-C. pneumoniae IgG titer ≥1:16. Titers from 1:16 to 1:256 were considered indicative for a past infection, whereas 1:512 was considered diagnostic of an acute infection.

RESULTS

The overall prevalence of C. pneumoniae was 54.9%. The mean seropositivity in males was slightly higher than females. The seroprevalence of infection was relatively low in children aged 2-9 years, and steadily increased to reach a plateau of 66.7% at around 30-39 years of age, which remained stable in later years. Recent infection was indicated in 14.3% of study subjects. The seropositivity was highest in males, and more frequent in adults than in children and teenagers.

CONCLUSION

A high seroprevalence of C. pneumoniae in the asymptomatic population suggests that infection with this pathogen is common in Jordan. Higher seropositivity in males compared to females was observed. The primary infection is acquired during the first four decades of life, and in older ages high antibody levels are likely maintained by reinfection or persistent infection.

Chlamydia antibodies and self-reported symptoms of oligo-amenorrhea and hirsutism: a new etiologic factor in polycystic ovary syndrome?

OBJECTIVE

To investigate whether the systemic inflammation induced by chlamydial infections might be associated with symptoms of polycystic ovary syndrome (PCOS).

DESIGN

Nested case-control study.

SETTING

A questionnaire including questions about hirsutism and oligo-amenorrhea was distributed to a representative sample of women (at age 31) from the general population-based Northern Finland Birth Cohort. Those who reported both symptoms were defined as symptomatic (n=81).

PATIENT(S)

A representative sample of women (at age 31) from the general population-based Northern Finland Birth Cohort.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

To test the presence of serum antibodies to Chlamydia pneumoniae (IgG titers ≥32) and Chlamydia trachomatis (IgG titers ≥8) by microimmunofluorescence in symptomatic and control women.

RESULT(S)

Antibodies were investigated in 79 symptomatic and 1427 control women (C. pneumoniae) and in 79 symptomatic and 425 control women (C trachomatis). C. trachomatis antibodies (odds ratio [OR], 2.4; 95% confidence interval [CI], 1.3-4.6) and C. pneumoniae antibodies (OR, 1.5; 95% CI, 1.0-2.4) were more commonly present in symptomatic women, and the simultaneous presence of elevated highly sensitive C-reactive protein levels strengthened this association.

CONCLUSION(S)

Chronic inflammation, which is associated with chlamydial infections, could contribute to the pathogenetic processes that lead to the metabolic and hormonal disorders of PCOS.

Persistent Chlamydia Pneumoniae serology is related to decline in lung function in women but not in men. Effect of persistent Chlamydia pneumoniae infection on lung function

BACKGROUND

Chlamydia pneumoniae (C pn) infection causes an acute inflammation in the respiratory system that may become persistent, but little is known about the long-term respiratory effects of C pn infections.

AIM

To estimate the long term respiratory effects of C pn with change in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) as a main outcome variable.

METHODS

The study comprised of 1109 subjects (500 men and 609 women, mean age 28 ± 6 years) that participated in the Reykjavik Heart Study of the Young. Spirometry and blood samples for measurements of IgG antibodies for C pn were done at inclusion and at the end of the follow-up period (mean follow-up time 27 ± 4 years).

RESULTS

Having IgG against C pn at both examinations was significantly associated to a larger decrease in FEV1 (6 mL/year) and FVC (7 mL/year) in women but not in men. In women the association between C pn and larger FEV1 decline was only found in women that smoked at baseline where having C pn IgG was associated with 10 mL/year decline compared to smokers without C pn IgG. These results were still significant after adjustment for age, smoking and change in body weight.

CONCLUSION

Our results indicate that persistent C pn serology is related to increased decline in lung function in women but not in men. This effect was, however, primarily found in smoking women. This study is a further indication that the pathophysiological process leading to lung impairment may differ between men and women.

Low mannose-binding lectin levels and MBL2 gene polymorphisms associate with Chlamydia pneumoniae antibodies

Objective: Mannose-binding lectin (MBL) has been shown to inhibit infection of host cells by Chlamydia pneumoniae in vitro. We studied if MBL levels and MBL2 polymorphisms associate with the presence of C. pneumoniae antibodies in vivo.

Materials and Methods: Single nucleotide polymorphisms (SNPs) of the MBL2 gene (promoter alleles H/L, X/Y and P/Q; and exon 1 variant alleles B, C and D and wild-type allele A) were genotyped and serum MBL concentrations and C. pneumoniae IgG, IgA and IgM antibodies were analysed in 889 Finnish military recruits.

Results: An MBL level below the median concentration and the MBL2 P/P genotype were significant risk factors of IgG or IgA seroconversions or the presence of IgM antibodies during military service (adjusted odds ratio (OR) 1.5; 95% confidence interval (CI) 1.1—2.1 and OR 1.5; 95% CI 1.0—2.2, respectively). In addition, the promoter Y/Y (OR 1.6; 95% CI 1.1—2.3) and exon 1 variant allele genotypes (OR 1.4; 95% CI 1.0—2.0) were possibly associated with elevated antibodies.

Conclusions: These results suggest, for the first time, that low serum MBL levels and MBL2 polymorphisms may associate with elevated C. pneumoniae antibodies and seroconversions and thus support the previous findings in vitro.

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.

Asthmatic persons are prone to the persistence of Chlamydia pneumoniae antibodies

Acute Chlamydia pneumoniae infection may initiate asthma or worsen asthmatic symptoms. In crowded conditions, such as military service, young men are susceptible to respiratory infections, including C. pneumoniae. We recruited 127 asthmatic and 391 nonasthmatic military conscripts, followed up their respiratory tract infections and the kinetics of serum C. pneumoniae antibodies, and assessed the association between C. pneumoniae and asthma during 6 months of military service in 2 intake groups. During the 6-month period, in the July intake group, IgG antibody prevalence decreased from 60.3% to 43.8% in asthmatic and from 55.6% to 22.6% in nonasthmatic conscripts. In the January intake group, IgG antibody prevalence increased from 38.3% to 48.4% in asthmatic and from 37.2% to 43% in nonasthmatic recruits. IgG and IgA antibodies persisted more often in the asthmatic groups. In conclusion, the prevalence of IgG antibodies showed seasonal variation. Military recruits seem to be most vulnerable to C. pneumoniae infections during the period from January to June. The antibody titer changes were more rapid than previously thought.

Higher incidence of persistent chronic infection of Chlamydia pneumoniae among coronary artery disease patients in India is a cause of concern

Background

There is growing evidence that Chlamydia pneumoniae may be involved in the pathogenesis of atherosclerosis, as several studies have demonstrated the presence of the organism in atherosclerotic lesions. C. pneumoniae infections, which are especially persistent infections, have been difficult to diagnose either by serological methods or isolation of the organism from the tissue. Nucleic Acid Amplification tests (NAATs) has emerged as an important method for detecting C. pneumoniae. Inspite of high prevalence of C. pneumoniae specific antibodies in coronary heart disease patients, direct detection of C. pneumoniae in circulating blood of coronary artery disease (CAD) patients by sensitive nucleic acid amplification tests nested PCR (nPCR), multiplex PCR (mPCR) has not been carried out is required. Further correlation of the presence of C. pneumoniae in blood of CAD patients with C. pneumoniae specific IgA and IgG antibodies, which may indicative of the status of infection with the progression of atherosclerosis. This will help in order to prepare strategies for the antibiotic intervention to avoid the progression towards CAD.

Methods

Venous blood was obtained from 91 CAD patients and 46 healthy controls. Nucleic acid amplification tests viz. nested -, semi-nested – and multiplex PCR were used for detection of C. pneumoniae. ELISA carried out prevalence of C. pneumoniae specific IgG and IgA antibodies.

Results

29.67% (27/91) patients were positive for C. pneumoniae using nested PCR. The sensitivity and specificity of semi-nested and multiplex PCR were 37.03%, 96.96% and 22.22%, 100% with respect to nested PCR. Positive nPCR patients were compared with presence of C. pneumoniae specific IgA, IgA+IgG and IgG antibodies. Among 27 (29.67%) nPCR C. pneumoniae positive CAD patients, 11(12%) were IgA positive, 13(14.2%) were IgA+IgG positive and only1 (1.1%) was IgG positive. A significant presence of C. pneumoniae was detected in heavy smokers, non-alcoholics and with family histories of diabetes and blood pressure group of CAD patients by nPCR.

Conclusion

The results indicate synergistic association of C. pneumoniae infection and development of CAD with other risk factors. We also detected increased positivity for C. pneumoniae IgA than IgG in nPCR positive CAD patients. Positive nPCR findings in conjunction with persisting high C. pneumoniae specific antibody strongly suggest an ongoing infection.

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.