Serological diagnosis of Chlamydia pneumoniae infection: limitations and perspectives

Analysis of humoral immune responses to recombinant Chlamydia pneumoniae antigens

OBJECTIVES

Chlamydia pneumoniae is a difficult to diagnose respiratory pathogen. This study was performed to systematically characterize humoral immune responses to selected C. pneumoniae antigens in order to provide novel serodiagnostic perspectives for clinical and epidemiological issues.

METHODS

Based on a literature search, gene library screening, and serological proteome analysis, 15 immunogenic surface-associated, virulence-associated, and hypothetical C. pneumoniae antigens were selected, recombinantly expressed, and lined on a nitrocellulose strip. Specific IgM and IgG reactivity was measured in a total of 172 PCR- and micro-immunofluorescence testing (MIF)-characterized serum samples from patients with respiratory infections. A theoretical model was conceived to approximate a putative course of C. pneumoniae antigen expression and assess the potential of early and late antigens.

RESULTS

While surface antigens performed poorly, the virulence-associated TARP was a reliable antigen for IgM detection, with a sensitivity of 80.0% and a diagnostic specificity of 90.2%. The hypothetical protein YwbM proved powerful for IgG detection with MIF-correlative sensitivities of up to 94.4% and a diagnostic specificity of 95.1%.

CONCLUSIONS

This study provides new insights into antibody profiles to immunogenic proteins in C. pneumoniae infection. The study findings offer antigen candidates for more reliable and standardized serological investigations of C. pneumoniae infections, including studies on seroprevalence and epidemiology.

Multi-peptide ELISAs overcome cross-reactivity and inadequate sensitivity of conventional Chlamydia pneumoniae serology

Cross-reactivity of classical chlamydial antigens compromises Chlamydia (C.) pneumoniae serology. By testing with 185 human antisera, we expanded 18 previously discovered C. pneumoniae-specific B-cell epitopes to 48 peptide antigens from 12 C. pneumoniae immunodominant proteins. For specific detection of antibodies against C. pneumoniae, we developed novel ELISAs with strongly reactive individual peptide antigens and mixtures of these peptides. By comparison to a composite reference standard (CRS) for anti-C. pneumoniae antibody status of human sera, the top-performing CpnMixF12 peptide assay showed 91% sensitivity at 95% specificity, significantly higher than 4 commercial anti-C. pneumoniae IgG ELISAs (36-12% sensitivity at 95% specificity). Human C. pneumoniae (Cpn) and C. trachomatis (Ctr) seroreactivity was 54% biased towards co-positivity in commercial Cpn and Ctr ELISAs, but unbiased in Cpn and Ctr peptide antibody assays, suggesting severe cross-reactivity of commercial ELISAs. Using hyperimmune mouse sera against each of 11 Chlamydia spp., we confirm that commercial Cpn and Ctr ELISA antigens are cross-reactive among all Chlamydia spp., but Cpn and Ctr peptide antigens react only with antisera against the cognate chlamydial species. With simultaneously high specificity and sensitivity, and convenient use for non-specialized laboratories, these ELISAs have the potential to improve serodiagnosis of C. pneumoniae infection.

Atypical and Typical Bacteria in Children with Community Acquired Pneumonia

This study seeks to determine the pathogens in respiratory specimens and blood serum obtained from children who present with community acquired pneumonia (CAP) diagnosed on the basis of clinical and radiological evidence. The study group consisted of 46 hospitalized children aged 1-11 years. The material for research consisted of pharyngeal swabs and samples of blood serum. One hundred and thirty eight pharyngeal swabs were examined for the presence of C. pneumoniae antigen, C. pneumoniae DNA, and for typical pathogens. C. pneumoniae DNA was detected in pharyngeal swabs with nested PCR. Classical microbiological culture was used for detection of typical bacteria. ELISA test were used for detection anti-C. pneumoniae and anti-M. pneumoniae antibodies in the serum. C. pneumoniae DNA was identified in 10.9% of children. Positive culture for typical pathogens was observed in 8.7% of children. Specific anti-C. pneumoniae IgM antibodies were found in 8.7% of children, and IgG and IgA antibodies in 1 child each. Specific anti-M. pneumoniae IgG antibodies were found in 13.1% of children and IgM antibodies in 1 child. We conclude that the underlying bacterial etiology of CAP is rather rarely conclusively confirmed in children. Nonetheless, determining the etiology of CAP is essential for the choice of treatment to optimize the use and effectiveness of antimicrobials and to avoid adverse effect. Due to considerable variations in the power of detection of the type of atypical bacteria causing CAP, the search for the optimum diagnostic methods continues.

Chlamydia pneumoniae sero-prevalence in Moroccan patients with cardiovascular diseases

BACKGROUND

Chlamydia pneumoniae is a pathogen associated with human respiratory tract infection, its viable presence in atherosclerotic plaques is also assumed to play significant function in cardiac diseases. Our study's main objective is to evaluate Chlamydia pneumoniae sero-prevalence in Moroccan patients with cardiovascular diseases using and comparing two serological methods.

METHODS

Two hundred eighteen patients were enrolled; serums were tested by microimmunofluorescence to explore the sero-prevalence. Simultaneously 74 serums were analyzed by both immunoblot and micro-immunofluorescence to evaluate recombinant proteins diagnosis value.

RESULTS

MIF results revealed 81% male and 84.5% female positive cases. The comparative study among 74 patients showed 78% men and 89% women positive cases by immunoblot, whereas MIF showed respectively 80% and 72%, a significant concordance between these methods was revealed. However, this comparison showed also two types of discrepancies, which may be related to difficulties in antigens detection by micro-immunofluorescence resulting from their structure complexity, or the antibodies reactivity with species' common antigens.

CONCLUSIONS

The study revealed a high sero-prevalence of Chlamydia pneumoniae in the studied population, a big interest of recombinant protein was also revealed in the diagnosis accuracy. We suggest therefore using immunoblot for diagnosis confirmation because it provides additional useful information.

Guideline for Antibiotic Use in Adults with Community-acquired Pneumonia

Community-acquired pneumonia is common and important infectious disease in adults. This work represents an update to 2009 treatment guideline for community-acquired pneumonia in Korea. The present clinical practice guideline provides revised recommendations on the appropriate diagnosis, treatment, and prevention of community-acquired pneumonia in adults aged 19 years or older, taking into account the current situation regarding community-acquired pneumonia in Korea. This guideline may help reduce the difference in the level of treatment between medical institutions and medical staff, and enable efficient treatment. It may also reduce antibiotic resistance by preventing antibiotic misuse against acute lower respiratory tract infection in Korea.

The Clinical Significance of FilmArray Respiratory Panel in Diagnosing Community-Acquired Pneumonia

AIM

FilmArray Respiratory Panel (FilmArray RP) test is an emerging diagnostic method in fast detecting multiple respiratory pathogens; the methodology and clinical significance of FilmArray RP in community-acquired pneumonia (CAP) diagnosis were evaluated in this study.

METHODS

Specimens from 74 patients with CAP were analyzed and compared using FilmArray RP, traditional multiple PCR assay, bacterial (or fungal) culture, and serological detection.

RESULTS

FilmArray RP and multiplex PCR showed 100% coincidence rate in detecting coronaviruses 229E, OC43, HKU1, and NL63, human metapneumovirus, influenza A and B, and parainfluenza viruses (PIV1, PIV2, and PIV4). There were 15 viral specimens tested as disagreement positive results. FilmArray RP had higher detection rate in detecting dual viral and Mycoplasma pneumoniae infection. The positive bacteria (or fungi) were found in 25 specimens.

CONCLUSIONS

This study demonstrated the capability of FilmArray RP for simultaneous detection of broad-spectrum respiratory pathogens and potential use in facilitating better patient care.

Relationship Among Chlamydia and Mycoplasma Pneumoniae Seropositivity, IKZF1 Genotype and Chronic Obstructive Pulmonary Disease in A General Japanese Population: The Nagahama Study

Chronic obstructive pulmonary disease (COPD) is a possible risk factor for cardiovascular disease. The association of COPD with the pathogenicity of infection with Chlamydia pneumoniae and Mycoplasma pneumoniae is controversial. We conducted a cross-sectional study to clarify the association between atypical pneumoniae seropositivity and COPD in a general population. We also investigated genetic polymorphisms conferring susceptibility to a pneumonia titer. The study included 9040 Japanese subjects (54 ± 13 years). COPD was defined as a ratio of forced expiratory volume in 1 second to forced vital capacity of less than 70%. Serum levels of IgA and IgG antibodies to C pneumoniae were determined using an enzyme-linked immunoassay, and M pneumoniae seropositivity was assessed by a particle agglutination test. Subjects seropositive for C pneumoniae (26.1%) had a higher prevalence of COPD (seropositive, 5.8%; seronegative, 3.1%; P < 0.001) after adjustment for age, sex, height, weight, and smoking status. The association between M pneumoniae seropositivity (20.4%) and COPD was also significant in covariate-adjusted analysis (P < 0.001). A genome-wide association analysis of the C pneumoniae IgA index identified a susceptible genotype (rs17634369) near the IKZF1 gene, and the seropositive rate of C pneumoniae significantly differed among genotypes (AA, 22.5; AG, 25.3; GG, 29.7%, P < 0.001). On multiple regression analysis, seropositivity for both C pneumoniae (odds ratio = 1.41, P = 0.004) and M pneumoniae (odds ratio = 1.60, P = 0.002) was an independent determinant for COPD, while no direct association was found with the rs17634369 genotype. Seropositivity for both C pneumoniae and M pneumoniae is an independent risk factor for COPD in the general population.

Comparison of serological methods with PCR-based methods for the diagnosis of community-acquired pneumonia caused by atypical bacteria

Background

The diagnosis of community-acquired pneumonia (CAP) caused by Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydophila pneumoniae is traditionally based on cultures and serology, which have special requirements, are time-consuming, and offer delayed results that limit their clinical usefulness of these techniques. We sought to develop a multiplex PCR (mPCR) method to diagnosis these bacterial infections in CAP patients and to compare the diagnostic yields obtained from mPCR of nasopharyngeal aspirates (NPAs), nasopharyngeal swabs (NPSs), and induced sputum (IS) with those obtained with specifc PCR commercial kits, paired serology, and urinary antigen.

Results

A total of 225 persons were included. Of these, 10 patients showed serological evidence of L. pneumophila infection, 30 of M. pneumoniae, and 18 of C. pneumoniae; 20 individuals showed no CAP. The sensitivities were mPCR-NPS = 23.1 %, mPCR-IS = 57.1 %, Seeplex®-IS = 52.4 %, and Speed-oligo®-NPA/NPS = 11.1 %, and the specificities were mPCR-NPS = 97.1 %, mPCR-IS = 77.8 %, Seeplex®-IS = 92.6 %, and Speed-oligo®-NPA/NPS = 96.1 %. The concordance between tests was poor (kappa <0.4), except for the concordance between mPCR and the commercial kit in IS (0.67). In individuals with no evidence of CAP, positive reactions were observed in paired serology and in all PCRs.

Conclusions

All PCRs had good specificity but low sensitivity in nasopharyngeal samples. The sensitivity of mPCR and Seeplex® in IS was approximately 60 %; thus, better diagnostic techniques for these three bacteria are required.

Electronic supplementary material

The online version of this article (doi:10.1186/s12952-016-0047-y) contains supplementary material, which is available to authorized users.

Respiratory Infections

The majority of respiratory tract infections (RTIs) are community acquired and are the single most common cause of physician office visits and among the most common causes of hospitalizations. The morbidity and mortality associated with RTIs are significant and the financial and social burden high due to lost time at work and school. The scope of clinical symptoms can significantly overlap among the respiratory pathogens, and the severity of disease can vary depending on patient age, underlying disease, and immune status, thereby leading to inaccurate presumptions about disease etiology. The rapid and accurate diagnosis of the causative agent of RTIs improves patient care, reduces morbidity and mortality, promotes effective hospital bed utilization and antibiotic stewardship, and reduces length of stay. This chapter focuses on the clinical utility, advantages, and disadvantages of viral and bacterial tests cleared by the Food and Drug Administration (FDA), and new promising technologies for the detection of bacterial agents of pneumonia currently in development or in US FDA clinical trials are briefly reviewed.

Evolution to a chronic disease niche correlates with increased sensitivity to tryptophan availability for the obligate intracellular bacterium Chlamydia pneumoniae

The chlamydiae are obligate intracellular parasites that have evolved specific interactions with their various hosts and host cell types to ensure their successful survival and consequential pathogenesis. The species Chlamydia pneumoniae is ubiquitous, with serological studies showing that most humans are infected at some stage in their lifetime. While most human infections are asymptomatic, C. pneumoniae can cause more-severe respiratory disease and pneumonia and has been linked to chronic diseases such as asthma, atherosclerosis, and even Alzheimer's disease. The widely dispersed animal-adapted C. pneumoniae strains cause an equally wide range of diseases in their hosts. It is emerging that the ability of C. pneumoniae to survive inside its target cells, including evasion of the host's immune attack mechanisms, is linked to the acquisition of key metabolites. Tryptophan and arginine are key checkpoint compounds in this host-parasite battle. Interestingly, the animal strains of C. pneumoniae have a slightly larger genome, enabling them to cope better with metabolite restrictions. It therefore appears that as the evolutionarily more ancient animal strains have evolved to infect humans, they have selectively become more "susceptible" to the levels of key metabolites, such as tryptophan. While this might initially appear to be a weakness, it allows these human C. pneumoniae strains to exquisitely sense host immune attack and respond by rapidly reverting to a persistent phase. During persistence, they reduce their metabolic levels, halting progression of their developmental cycle, waiting until the hostile external conditions have passed before they reemerge.

Immunization with a MOMP-based vaccine protects mice against a pulmonary Chlamydia challenge and identifies a disconnection between infection and pathology

Chlamydia pneumoniae is responsible for up to 20% of community acquired pneumonia and can exacerbate chronic inflammatory diseases. As the majority of infections are either mild or asymptomatic, a vaccine is recognized to have the greatest potential to reduce infection and disease prevalence. Using the C. muridarum mouse model of infection, we immunized animals via the intranasal (IN), sublingual (SL) or transcutaneous (TC) routes, with recombinant chlamydial major outer membrane protein (MOMP) combined with adjuvants CTA1-DD or a combination of cholera toxin/CpG-oligodeoxynucleotide (CT/CpG). Vaccinated animals were challenged IN with C. muridarum and protection against infection and pathology was assessed. SL and TC immunization with MOMP and CT/CpG was the most protective, significantly reducing chlamydial burden in the lungs and preventing weight loss, which was similar to the protection induced by a previous live infection. Unlike a previous infection however, these vaccinations also provided almost complete protection against fibrotic scarring in the lungs. Protection against infection was associated with antigen-specific production of IFNγ, TNFα and IL-17 by splenocytes, however, protection against both infection and pathology required the induction of a similar pro-inflammatory response in the respiratory tract draining lymph nodes. Interestingly, we also identified two contrasting vaccinations capable of preventing infection or pathology individually. Animals IN immunized with MOMP and either adjuvant were protected from infection, but not the pathology. Conversely, animals TC immunized with MOMP and CTA1-DD were protected from pathology, even though the chlamydial burden in this group was equivalent to the unimmunized controls. This suggests that the development of pathology following an IN infection of vaccinated animals was independent of bacterial load and may have been driven instead by the adaptive immune response generated following immunization. This identifies a disconnection between the control of infection and the development of pathology, which may influence the design of future vaccines.

Chronic bronchial infection in COPD. Is there an infective phenotype?

Microorganisms, particularly bacteria, are frequently found in the lower airways of COPD patients, both in stable state and during exacerbations. The host–pathogen relationship in COPD is a complex, dynamic process characterised by frequent changes in pathogens, their strains and loads, and subsequent host immune responses.

Exacerbations are detrimental events in the course of COPD and evidence suggests that 70% may be caused by microorganisms. When considering bacterial exacerbations, recent findings based on molecular typing have demonstrated that the acquisition of new strains of bacteria or antigenic changes in pre-existing strains are the most important triggers for exacerbation onset.

Even in clinically stable COPD patients the presence of microorganisms in their lower airways may cause harmful effects and induce chronic low-grade airway inflammation leading to increased exacerbation frequency, an accelerated decline in lung function and impaired health-related quality of life. Besides intraluminal localisation in the distal airways, bacteria can be found in the bronchial walls and parenchymal lung tissue of COPD patients. Therefore, the isolation of pathogenic bacteria in stable COPD should be considered as a form of chronic infection rather than colonisation. This new approach may have important implications for the management of patients with COPD.

Comparative Seroepidemiologic Analysis of Chlamydophila Pneumoniae Infection using Microimmunofluorescence, Enzyme Immunoassay and Neutralization Test: Implications for Serodiagnosis

A seroepidemiologic study using the microimmunofluorescence (MIF) technique was conducted to determine the prevalence of Chlamydophila pneumoniae IgG antibodies among 205 healthy Singapore university undergraduates using the MRL Diagnostics MIF test kit. The overall seroprevalence was 35.1% with significantly higher seropositivity rates among males than females (48.2 vs. 18.7%, P < 0.001). A comparative study using the Labsystems MIF test kit was conducted on sera from 192 students. Using the MRL MIF test as the reference, the sensitivity and specificity of Labsystems MIF test were 92.6 and 87.9%, respectively. A total of 78 samples comprising 15 MIF-negative and 63 MIF-positive samples were also tested for complement-independent neutralizing antibodies in vitro. All the 78 samples and 11 additional MIF-negative samples were also tested for IgM, IgG and IgA against C. pneumoniae by enzyme immunoassay (EIA) using the Labsystems EIA test kit. None of these 89 samples were seropositive for IgM. The percentages of IgG and IgA seropositivity increased with increasing grades of MIF-positivity. Among the IgG seropositive samples, 69.1% were also positive for IgA, suggesting that a high proportion of infected individuals also had IgA antibodies denoting chronicity. Neutralizing antibodies were detected in 22.2% of MIF-positive sera, but only in 6.7% of MIF-negative sera. 26.4 and 34.2% of samples which were IgG and IgA seropositive respectively also exhibited neutralizing activity. The percentages of MIF-positive sera with neutralizing activity increased with the grade of MIF positivity, i.e. 0% (1+), 7.1% (2+), 18.8% (3+), and 63.6% (4+). High-grade MIF positivity (particularly with MRL MIF kits) may represent a useful serologic marker of predictive value for neutralizing activity.

Pneumonia caused by Mycoplasma pneumoniae and Chlamydophila pneumoniae in children - comparative analysis of clinical picture

PURPOSE

The aim of the study was comparative analysis of clinical picture and prevalence of pneumonia caused by Mycoplasma pneumoniae and Chlamydophila pneumoniae in children.

MATERIAL AND METHODS

The study involved 332 children hospitalized in the 3rd Department of Paediatric, Polish Mother's Memorial Hospital - Research Institute, due to pneumonia caused by Mycoplasma pneumoniae - group I or Chlamydophila pneumonia - group II.

RESULTS

Over 2003-2009 period there were 1870 children hospitalized due to pneumonia, of which in 332 (17.8%) the Mycoplasma pneumoniae and/or Chlamydophila pneumoniae etiology was confirmed. Mycoplasma pneumoniae, Chlamydophila pneumoniae, and mixed infection was diagnosed in 198 (10.6%), 102 (5.5%), and 32 (1.7%) children, respectively. The dominant clinical feature in both groups was cough, observed in 186 (93.9%) and 88 (86.3%) children, respectively. Further, reddening of the throat, rhinitis, shortness of breath, fever, enlarged lymph nodes, skin lesions and dyspepsia were also observed. The frequency of specific clinical features in both groups was similar. Statistical relationship (p≤0.05) was observed only in case of skin lesions. In chest x-ray there was no statistical link as for analyzed changes. Interstitial inflammatory changes were most frequently observed.

CONCLUSIONS

Mycoplasma pneumoniae and Chlamydophila pneumoniae are significant etiological factors in pneumonia in children, and as such they should be taken into consideration in differential diagnosis of pneumonia in children. The clinical picture of pneumonia caused by Mycoplasma pneumoniae and Chlamydophila pneumoniae is hardly specific, with basic labs and chest x-ray of little help in differentiation of infection etiology.