Interaction of Chlamydia pneumoniae and human alveolar macrophages: infection and inflammatory response

Purification, crystallization and preliminary crystallographic analysis of Chlamydophila pneumoniae AP endonuclease IV

Base excision is a crucial DNA repair process mediated by endonuclease IV in nucleotide excision. In Chlamydia pneumoniae, CpendoIV is the exclusive AP endonuclease IV, exhibiting DNA replication error-proofreading capabilities, making it a promising target for anti-chlamydial drug development. Predicting the structure of CpendoIV, molecular docking with DNA was performed, analyzing complex binding sites and protein surface electrostatic potential. Comparative structural studies were conducted with E. coli EndoIV and DNA complex containing AP sites.CpendoIV was cloned, expressed in E. coli, and purified via Ni-NTA chelation and size-exclusion chromatography. Low NaCl concentrations induced aggregation during purification, while high concentrations enhanced purity.CpendoIV recognizes and cleaving AP sites on dsDNA, and Zn2+ influences the activity. Crystallization was achieved under 8% (v/v) Tacsimate pH 5.2, 25% (w/v) polyethylene glycol 3350, and 1.91 Å resolution X-ray diffraction data was obtained at 100 K. This research is significant for provides a deeper understanding of CpendoIV involvement in the base excision repair process, offering insights into Chlamydia pneumoniae.

Respiratory Tract Oncobiome in Lung Carcinogenesis: Where Are We Now?

The importance of microbiota in developing and treating diseases, including lung cancer (LC), is becoming increasingly recognized. Studies have shown differences in microorganism populations in the upper and lower respiratory tracts of patients with lung cancer compared to healthy individuals, indicating a link between dysbiosis and lung cancer. However, it is not only important to identify "which bacteria are present" but also to understand "how" they affect lung carcinogenesis. The interactions between the host and lung microbiota are complex, and our knowledge of this relationship is limited. This review presents research findings on the bacterial lung microbiota and discusses the mechanisms by which lung-dwelling microorganisms may directly or indirectly contribute to the development of lung cancer. These mechanisms include influences on the host immune system regulation and the local immune microenvironment, the regulation of oncogenic signaling pathways in epithelial cells (causing cell cycle disorders, mutagenesis, and DNA damage), and lastly, the MAMPs-mediated path involving the effects of bacteriocins, TLRs signaling induction, and TNF release. A better understanding of lung microbiota's role in lung tumor pathology could lead to identifying new diagnostic and therapeutic biomarkers and developing personalized therapeutic management for lung cancer patients.

Microbial infections as potential risk factors for lung cancer: Investigating the role of human papillomavirus and chlamydia pneumoniae

Background

Lung cancer is the leading cause of cancer morbidity and mortality worldwide. Apart from tobacco smoke and dietary factors, microbial infections have been reported as the third leading cause of cancers globally. Deciphering the association between microbiome and lung cancer will provide potential biomarkers and novel insight in lung cancer progression. In this current study, we performed a meta-analysis to decipher the possible association between C. pneumoniae and human papillomavirus (HPV) and the risk of lung cancer.

Methods

Literature search was conducted in most English and Chinese databases. Data were analyzed using CMA v.3.0 and RevMan v.5.3 software (Cochrane-Mantel-Haenszel method) by random-effects (DerSimonian and Laird) model.

Results

The overall pooled estimates for HPV studies revealed that HPV infections in patients with lung cancer were significantly higher than those in the control group (OR = 2.33, 95% CI = 1.57-3.37, p < 0.001). Base on subgroup analysis, HPV infection rate was significantly higher in Asians (OR = 6.38, 95% CI = 2.33-17.46, p < 0.001), in tissues (OR = 5.04, 95% CI = 2.27-11.19, p < 0.001) and blood samples (OR = 1.40, 95% CI = 1.02-1.93, p = 0.04) of lung cancer patients but non-significantly lower in males (OR = 0.84, 95% CI = 0.57-1.22, p =0.35) and among lung cancer patients at clinical stage I-II (OR = 0.95, 95% CI = 0.61-1.49, p = 0.82). The overall pooled estimates from C. pneumoniae studies revealed that C. pneumoniae infection is a risk factor among lung cancer patients who are IgA seropositive (OR = 1.88, 95% CI = 1.30-2.70, p < 0.001) and IgG seropositive (OR = 1.50, 95% CI = 1.10-2.04, p = 0.010). All seronegative IgA (OR = 0.69, 95% CI = 0.42-1.16, p = 0.16) and IgG (OR = 0.66, 95% CI = 0.42-105, p = 0.08) titers are not associative risk factors to lung cancer.

Conclusions

Immunoglobulin (IgA) and IgG seropositive titers of C. pneumoniae and lungs infected with HPV types 16 and 18 are potential risk factors associated with lung cancer.

The Probable Role of Chlamydia pneumoniae Infection in Acute Stroke

Cardiovascular diseases are the most leading cause of worldwide mortality. According to USA statistics, about 1 of 6 cardiovascular deaths is due to stroke. Stroke is the second most common cause of death and a chief cause of disability due to EU data. Treatment, care providing, rehabilitation costs and with the labor loss, the overall cost in EU due to stroke was estimated about €45 billion in year 2017. Acute stroke due to infectious diseases via several possible mechanisms with various clinical presentations were previously reported in the literature. Chlamydia pneumoniae is an obligate intracellular bacteria and extremely common in adult individuals. Besides it being a major cause of pneumonia in adults, association between atherosclerosis and vascular diseases was demonstrated by several sero-epidemiological studies and by direct detection of organism in atherosclerotic lesions by electron microscopy, immunohistochemistry, polymerase chain reaction. Also, several sero-epidemiological studies have demonstrated a link between Chlamydia pneumoniae infection and acute stroke. In this chapter, we will summarize the data in literature regarding the association between Chlamydia pneumoniae infection and acute stroke and we will try to explain the possible mechanisms that could be responsible in pathophysiology of stroke in these patients.

Links between Infections, Lung Cancer, and the Immune System

Lung cancer is the leading disease of cancer-related deaths worldwide. Since the beginning of the 20th century, various infectious agents associated with lung cancer have been identified. The mechanisms that include systemic inflammatory pathways as effect of microbial persistence in the lung can secondarily promote the development of lung carcinogenesis. Chronic inflammation associated with lung-cancer infections is known to precede tumor development, and it has a strong effect on the response(s) to therapy. In fact, both viral and bacterial infections can activate inflammatory cells and inflammatory signaling pathways. In this review, an overview of critical findings of recent studies investigating associations between each of viral and bacterial pathogens and lung carcinoma is provided, with particular emphasis on how infectious organisms can interfere with oncogenic processes and all the way through immunity. Moreover, a discussion of the direct crosstalk between lung tumor development and inflammatory processes is also presented.

Chronic infection with Chlamydia pneumoniae in asthma: a type-2 low infection related phenotype

Background

Chlamydia pneumoniae and Mycoplasma pneumoniae have been implicated in the pathogenesis of asthma and are responsible for chronic inflammation when host immune system fails to eradicate the bacteria.

Method

We performed a prospective study on 410 patients who underwent a visit at the asthma clinic of CHU of Liege between June 2016 and June 2018 with serology testing for C. pneumoniae and M. pneumoniae.

Results

65% of our asthmatic population had serum IgA and/or IgG towards C. pneumoniae, while only 12.6% had IgM and/or IgG against M. pneumoniae. Compared to seronegative asthmatics, asthmatics with IgA+ and IgG+ against C. pneumoniae were more often male and older with a higher proportion of patients with smoking history. They received higher doses of inhaled corticosteroids (ICS) and displayed lower FEV₁/FVC ratio, higher RV/TLC ratio and lower conductance. They had higher levels of fibrinogen, though in the normal range and had lower sputum eosinophil counts. Patients with IgA− and IgG+ against C. pneumoniae were older and had higher blood monocyte counts and alpha-1-antitrypsin levels as compared to seronegative patients. Patients with IgM and/or IgG towards M. pneumoniae were more often males than seronegative asthmatics. In a subpopulation of 14 neutrophilic asthmatics with Chlamydia pneumoniae IgA + /IgG + treated with macrolides, we found a significant decrease in blood neutrophils and normalization of sputum neutrophil count but no effect on asthma quality of life and exacerbations.

Conclusion

Positive Chlamydia serologic test is more common than positive Mycoplasma serology. Asthmatics with IgA and IgG against C. pneumoniae have more severe disease with increased airway obstruction, higher doses of ICS, more signs of air trapping and less type-2 inflammation.

Chlamydia pneumoniae-induced tumour necrosis factor alpha responses are lower in children with asthma compared with non-asthma

Introduction

Chlamydia pneumoniae respiratory tract infection has been implicated in the pathogenesis of reactive airway disease and asthma. Innate cytokine responses that are protective of infection with intracellular pathogens may be impaired in patients with asthma. Tumour necrosis factor alpha (TNF-α) is a cytokine related to functions of monocytes and may inhibit C. pneumoniae infection. We investigated TNF-α responses in C. pneumoniae-infected peripheral blood mononuclear cells (PBMCs) in patients with asthma and non-asthma, and whether ciprofloxacin, azithromycin or doxycycline affects TNF-α responses.

Methods

PBMC (1.5×10⁶) from paediatric patients with asthma (n=19) and non-asthmatic controls (n=6) were infected or mock infected for 1 hour with or without C. pneumoniae AR-39 at a multiplicity of infection=0.1, and cultured+ciprofloxacin, azithromycin or doxycycline (0.1 ug/mL) for 48 hours. TNF-α levels were measured in supernatants by ELISA.

Results

When PBMC from patients with asthma were infected with C. pneumoniae, levels of TNF-α were significantly lower than in subjects without asthma (48 hours) (5.5±5.6, 38.4±53.7; p=0.0113). However, baseline responses (no infection with C. pneumoniae) were similar in asthma and non-asthma (1.0±1.7, 1.1±1.2; p=0.89). When PBMC frompatiens with asthma were infected with C. pneumoniae+ciprofloxacin, azithromycin or doxycycline, TNF-α levels increased (25%–45%); this affect was not observed in PBMC from patients without asthma.

Conclusions

We identified differences in the quantity of TNF-α produced by C. pneumoniae-infected PBMC in asthma compared with non-asthma.

Chlamydia pneumoniae induces interleukin-12 responses in peripheral blood mononuclear cells in asthma and the role of toll like receptor 2 versus 4: a pilot study

BACKGROUND

Chlamydia pneumoniae causes respiratory infection in adults and children, and has been associated with asthma exacerbations and induction of Immunoglobulin (Ig) E responses. We previously reported that C. pneumoniae enhances T helper (Th) 2 responses of peripheral blood mononuclear cells (PBMC) from asthmatic patients. It is likely that toll like receptor (TLR)-2 and TLR-4 mediate cytokine responses and host defense against C. pneumoniae. Thus, we sought to determine whether engagement of TLR-2 or TLR-4 may induce IL-12 production in our C. pneumoniae model.

METHODS

PBMC (1.5 × 10⁶) from asthmatic patients (N = 10) and non-asthmatic controls (N = 5) were infected or mock-infected for 1 h ± C. pneumoniae TW183 at a multiplicity of infection (MOI) = 1 and MOI = 0.1, and cultured for 48 h ± anti- TLR-2 and TLR-4 antibodies (Abs) (1 mg/mL). Interleukin (IL)-12 (48 h p.i.) and total IgE levels (day 10) were measured in supernatants (ELISA).

RESULTS

High IgE levels were detected in supernatants of C. pneumoniae- infected PBMC from asthmatics on day 10, compared with mock-infected PBMC (p < 0.03). In contrast, IgE was not detected (<0.3 ng/mL) in either C. pneumoniae infected or mock-infected PBMC from non-asthmatics. IL-12 production by C. pneumoniae-infected asthmatic and non-asthmatic PBMC were similar. When anti-TLR4, but not anti-TLR2, was included in culture, IL-12 production by C. pneumoniae- infected asthmatic PBMC decreased.

CONCLUSIONS

C. pneumoniae infection induces IgE production and modulates IL-12 responses in patients with asthma, which may be caused, in part, by differences in TLR-2 and TLR-4 stimulation.

Conservation of extrusion as an exit mechanism for Chlamydia

Chlamydiae exit via membrane-encased extrusion or through lysis of the host cell. Extrusions are novel, pathogen-containing structures that confer infectious advantages to Chlamydia, and are hypothesized to promote cell-to-cell spread, dissemination to distant tissues and facilitate immune evasion. The extrusion phenomenon has been characterized for several Chlamydia trachomatis serovars, but a thorough investigation of extrusion for additional clinically relevant C. trachomatis strains and Chlamydia species has yet to be performed. The key parameters investigated in this study were: (i) the conservation of extrusion across the Chlamydia genus, (ii) the functional requirement for candidate Chlamydia genes in extrusion formation i.e. IncA and CT228 and (iii) extrusion-mediated uptake, and consequent survival of Chlamydia inside macrophages. Inclusion morphology was characterized by live fluorescence microscopy, using an inverted GFP strategy, at early and mid-stages of infection. Enriched extrusions were used to infect bone marrow-derived macrophages, and bacterial viability was measured following macrophage engulfment. Our results demonstrate that extrusion is highly conserved across chlamydiae, including ocular, STD and LGV biovars and divergent Chlamydia species. Consequently, this exit mechanism for Chlamydia may fulfill common advantages important for pathogenesis.

Biophysical and Biochemical Outcomes of Chlamydia pneumoniae Infection Promotes Pro-atherogenic Matrix Microenvironment

Multiple studies support the hypothesis that infectious agents may be involved in the pathogenesis of atherosclerosis. Chlamydia pneumoniae is strongly implicated in atherosclerosis, but the precise role has been underestimated and poorly understood due to the complexity of the disease process. In this work, we test the hypothesis that C. pneumoniae-infected macrophages lodged in the subendothelial matrix contribute to atherogenesis through pro-inflammatory factors and by cell-matrix interactions. To test this hypothesis, we used a 3D infection model with freshly isolated PBMC infected with live C. pneumoniae and chlamydial antigens encapsulated in a collagen matrix, and analyzed the inflammatory responses over 7 days. We observed that infection significantly upregulates the secretion of cytokines TNF-α, IL-1β, IL-8, MCP-1, MMP, oxidative stress, transendothelial permeability, and LDL uptake. We also observed that infected macrophages form clusters, and substantially modify the microstructure and mechanical properties of the extracellular matrix to an atherogenic phenotype. Together, our data demonstrates that C. pneumoniae-infection drives a low-grade, sustained inflammation that may predispose in the transformation to atherosclerotic foci.

Systems Biology Approaches for the Prediction of Possible Role of Chlamydia pneumoniae Proteins in the Etiology of Lung Cancer

Accumulating evidence has recently supported the association of bacterial infection with the growth and development of cancers, particularly in organs that are constantly exposed to bacteria such as the lungs, colon, cervical cancer etc. Our in silico study on the proteome of Chlamydia pneumoniae suggests an unprecedented idea of the etiology of lung cancer and have revealed that the infection of C. pneumoniae is associated with lung cancer development and growth. It is reasonable to assume that C. pneumoniae transports its proteins within host-intracellular organelles during infection, where they may work with host-cell proteome. The current study was performed for the prediction of nuclear targeting protein of C. pneumoniae in the host cell using bioinformatics predictors including ExPASy pI/Mw tool, nuclear localization signal (NLS) mapper, balanced sub cellular localization predictor (BaCeILo), and Hum-mPLoc 2.0. We predicted 47/1112 nuclear-targeting proteins of C. pneumoniae connected with several possible alterations in host replication and transcription during intracellular infection. These nuclear-targeting proteins may direct to competitive interactions of host and C. pneumoniae proteins with the availability of same substrate and may be involved as etiological agents in the growth and development of lung cancer. These novel findings are expected to access in better understanding of lung cancer etiology and identifying molecular targets for therapy.

Interaction of Chlamydiae with human macrophages

The phylum Chlamydiae contains several members that are well-known human pathogens, like Chlamydia trachomatis and C. pneumoniae. Establishing a chronic bacterial infection requires the active evasion of the host immune response. A major arm of the innate immune defence is constituted by macrophages, which fight infections by removing bacteria and triggering an adaptive immune response. However, some pathogenic Chlamydia infect and survive in macrophages at least for a certain period of time. Therefore, macrophages can serve as vehicles for the dissemination of bacterial infections from the primary infection site via the urogenital or respiratory tract to distant sites in the body. The capacity to infect macrophages seems to depend on the chlamydial strain and the source of macrophages. In vitro infections of macrophages with C. trachomatis, C. psittaci and C. pneumoniae reveal low efficiency of infection and progeny formation, as well as failure to develop mature inclusions. In contrast, the emerging pathogen, Simkania negevensis, actively replicates in macrophages. Here we summarize the current knowledge of the intracellular and molecular key mechanisms of C. trachomatis, C. pneumoniae and S. negevensis infections in human macrophages.

Pulmonary Chlamydia muridarum challenge activates lung interstitial macrophages which correlate with IFN-γ production and infection control in mice

Protective immunity to the pathogen Chlamydia is dependent on a robust IFN-γ response generated by innate and adaptive lymphocytes. Here we assess the role of the macrophage in orchestrating a protective response in vivo to the murine pathogen, Chlamydia muridarum. During acute pulmonary and peritoneal infection, resident macrophages in both sites are infected with C. muridarum and adopt an inflammatory phenotype. In the lung, this activation is restricted to interstitial macrophages, which harbor higher levels of C. muridarum 16sRNA than alveolar macrophages. We examined innate and adaptive lymphocyte activation in the peritoneal cavity with macrophage depletion and with adoptive transfer of infected macrophages. These experiments demonstrate macrophage activation correlates with a protective IFN-γ response and effective control of C. muridarum. These studies suggest that a quantitative or qualitative alteration in macrophages may play a key role in the development of Chlamydia-associated diseases.

Exposure to cigarette smoke and Chlamydia pneumoniae infection in mice: Effect on infectious burden, systemic dissemination and cytokine responses: A pilot study

Cigarette smoke exposure has been considered a risk factor for infection with Chlamydia pneumoniae. C. pneumoniae infection is associated with respiratory tract infection and chronic respiratory disease, which is a serious public health concern. To determine whether prior exposure to cigarette smoke worsens C. pneumoniae infection (specifically, increases infectious burden and systemic dissemination) as well as alters cytokine responses in mice, adult female C57BL/6 mice were exposed to either filtered air (FA) or mainstream cigarette smoke (MCS) (15 mg/m(3), total suspended particulates) for 5 days/week for 2 weeks and then infected with C. pneumoniae (10(5) IFU) via intratracheal instillation. Mice were euthanized on Days 7, 14 or 26 post-infection (p.i.). Chlamydial burdens in the lungs and spleen were quantified by quantitative PCR (qPCR) and histologic analyses were performed; cytokine levels (TNFα, IL-4, IFNγ) in bronchoalveolar lavage fluid and serum were assayed by enzyme-linked immunosorbent assay (ELISA). The results indicated that: (1) mice exposed to either FA or MCS had similar chlamydial burdens in the lungs and spleen on Days 14 and 26 p.i.; (2) proximal and distal airway inflammation was observed on Day 14 p.i. in both FA and MCS mice, but persisted in MCS mice until Day 26 p.i.; FA exposed mice demonstrated resolution of distal airway inflammation; and (3) MCS mice displayed higher serum levels of IFNγ and IL-4 on Day 26 p.i. These findings indicate that exposure of mice to MCS (at a concentration equivalent to smoking < 1 pack cigarettes/day) led to greater C. pneumoniae-induced inflammation, as indicated by prolonged inflammatory changes.

Infection of human monocytes by Chlamydia pneumoniae and Chlamydia trachomatis: an in vitro comparative study

Background

An increasing number of studies suggest that chlamydiae can infect immune cells. The altered immune cell function could contribute to the progression of several chronic inflammatory diseases.

The aim of this study was to comparatively evaluate Chlamydia pneumoniae (CP) and Chlamydia trachomatis (CT) interactions with in vitro infected human blood monocytes.

Results

Fresh isolated monocytes were infected with viable CP and CT elementary bodies and infectivity was evaluated by recultivating disrupted monocytes in permissive epithelial cells.

The production of reactive oxygen and nitrogen species was studied in the presence of specific fluorescent probes. Moreover, TNF-α, INF-α, INF-β and INF-γ gene expression was determined.

CT clearance from monocytes was complete at any time points after infection, while CP was able to survive up to 48 hours after infection. When NADPH oxydase or nitric oxide synthase inhibitors were used, CT infectivity in monocytes was restored, even if at low level, and CT recovery’s rate was comparable to CP one.

CT-infected monocytes produced significantly higher levels of reactive species compared with CP-infected monocytes, at very early time points after infection. In the same meanwhile, TNF-α and INF-γ gene expression was significantly increased in CT-infected monocytes.

Conclusions

Our data confirm that CP, but not CT, is able to survive in infected monocytes up to 48 hours post-infection. The delay in reactive species and cytokines production by CP-infected monocytes seems to be crucial for CP survival.

Virulent Coxiella burnetii pathotypes productively infect primary human alveolar macrophages

The intracellular bacterial pathogen Coxiella burnetii is a category B select agent that causes human Q fever. In vivo, C. burnetii targets alveolar macrophages wherein the pathogen replicates in a lysosome-like parasitophorous vacuole (PV). In vitro, C. burnetii infects a variety of cultured cell lines that have collectively been used to model the pathogen's infectious cycle. However, differences in the cellular response to infection have been observed, and virulent C. burnetii isolate infection of host cells has not been well defined. Because alveolar macrophages are routinely implicated in disease, we established primary human alveolar macrophages (hAMs) as an in vitro model of C. burnetii-host cell interactions. C. burnetii pathotypes, including acute disease and endocarditis isolates, replicated in hAMs, albeit with unique PV properties. Each isolate replicated in large, typical PV and small, non-fused vacuoles, and lipid droplets were present in avirulent C. burnetii PV. Interestingly, a subset of small vacuoles harboured single organisms undergoing degradation. Prototypical PV formation and bacterial growth in hAMs required a functional type IV secretion system, indicating C. burnetii secretes effector proteins that control macrophage functions. Avirulent C. burnetii promoted sustained activation of Akt and Erk1/2 pro-survival kinases and short-termphosphorylation of stress-related p38. Avirulent organisms also triggered a robust, early pro-inflammatory response characterized by increased secretion of TNF-α and IL-6, while virulent isolates elicited substantially reduced secretion of these cytokines. A corresponding increase in pro- and mature IL-1β occurred in hAMs infected with avirulent C. burnetii, while little accumulation was observed following infection with virulent isolates. Finally, treatment of hAMs with IFN-γ controlled intracellular replication, supporting a role for this antibacterial insult in the host response to C. burnetii. Collectively, the current results demonstrate the hAM model is a human disease-relevant platform for defining novel innate immune responses to C. burnetii.

Characterization of the activity and expression of arginine decarboxylase in human and animal Chlamydia pathogens

Chlamydia pneumoniae encodes a functional arginine decarboxylase (ArgDC), AaxB, that activates upon self-cleavage and converts l-arginine to agmatine. In contrast, most Chlamydia trachomatis serovars carry a missense or nonsense mutation in aaxB abrogating activity. The G115R missense mutation was not predicted to impact AaxB functionality, making it unclear whether AaxB variations in other Chlamydia species also result in enzyme inactivation. To address the impact of gene polymorphism on functionality, we investigated the activity and production of the Chlamydia AaxB variants. Because ArgDC plays a critical role in the Escherichia coli acid stress response, we studied the ability of these Chlamydia variants to complement an E. coli ArgDC mutant in an acid shock assay. Active AaxB was detected in four additional species: Chlamydia caviae, Chlamydia pecorum, Chlamydia psittaci, and Chlamydia muridarum. Of the C. trachomatis serovars, only E appears to encode active enzyme. To determine when functional enzyme is present during the chlamydial developmental cycle, we utilized an anti-AaxB antibody to detect both uncleaved and cleaved enzyme throughout infection. Uncleaved enzyme production peaked around 20 h postinfection, with optimal cleavage around 44 h. While the role ArgDC plays in Chlamydia survival or virulence is unclear, our data suggest a niche-specific function.

Autophagy restricts Chlamydia trachomatis growth in human macrophages via IFNG-inducible guanylate binding proteins

Interferon γ (IFNG) is a key host response regulator of intracellular pathogen replication, including that of Chlamydia spp The antichlamydial functions of IFNG manifest in a strictly host, cell-type and chlamydial strain dependent manner. It has been recently shown that the IFNG-inducible family of immunity-related GTPases (IRG) proteins plays a key role in the defense against nonhost adapted chlamydia strains in murine epithelial cells. In humans, IFN-inducible guanylate binding proteins (hGBPs) have been shown to potentiate the antichlamydial effect of IFNG; however, how hGBPs regulate this property of IFNG is unknown. In this study, we identified hGBP1/2 as important resistance factors against C. trachomatis infection in IFNG-stimulated human macrophages. Exogenous IFNG reduced chlamydial infectivity by 50 percent in wild-type cells, whereas shRNA hGBP1/2 knockdown macrophages fully supported chlamydial growth in the presence of exogenous IFNG. hGBP1/2 were recruited to bacterial inclusions in human macrophages upon stimulation with IFNG, which triggered rerouting of the typically nonfusogenic bacterial inclusions for lysosomal degradation. Inhibition of lysosomal activity and autophagy impaired the IFNG-mediated elimination of inclusions. Thus, hGBP1/2 are critical effectors of antichlamydial IFNG responses in human macrophages. Through their capacity to remodel classically nonfusogenic chlamydial inclusions and stimulate fusion with autophagosomes, hGBP1/2 disable a major chlamydial virulence mechanism and contribute to IFNG-mediated pathogen clearance.

Chlamydia pneumoniae-specific IgE is prevalent in asthma and is associated with disease severity

Background

Several Chlamydia pneumoniae (Cp) biomarkers have been associated with asthma but Cp-specific IgE (Cp IgE) has not been investigated extensively. Our objective was to investigate Cp IgE in community adult asthma patients.

Methods

(1) Prevalence of Cp IgE (measured by immunoblotting) and Cp DNA (by polymerase chain reaction) in peripheral blood, and biomarker associations with asthma severity. (2) Case-control studies of Cp IgE association with asthma using healthy blood donor (study 1) and non-asthmatic clinic patient (study 2) controls.

Results

Of 66 asthma subjects (mean age 40.9 years, range 5–75, 59% male, 45% ever-smokers) 33 (50%) were Cp IgE positive and 16 (24%) were Cp DNA positive (P = 0.001 for association of Cp IgE and DNA). Cp IgE was detected in 21% of mild intermittent asthma v 79% of severe persistent asthma (test for trend over severity categories, P = 0.002). Cp IgE detection was significantly (P = 0.001) associated with asthma when compared to healthy blood donor controls but not when compared to clinic controls.

Conclusions

Half of this sample of community asthma patients had detectable IgE against C. pneumoniae. Cp IgE was strongly and positively associated with asthma severity and with asthma when healthy blood donor controls were used. These results support the inclusion of Cp IgE as a biomarker in future studies of infectious contributions to asthma pathogenesis.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Chlamydia pneumoniae inhibits activated human T lymphocyte proliferation by the induction of apoptotic and pyroptotic pathways

Chlamydia pneumoniae is an omnipresent obligate intracellular bacterial pathogen that infects numerous host species. C. pneumoniae infections of humans are a common cause of community acquired pneumonia but have also been linked to chronic diseases such as atherosclerosis, Alzheimer's disease, and asthma. Persistent infection and immune avoidance are believed to play important roles in the pathophysiology of C. pneumoniae disease. We found that C. pneumoniae organisms inhibited activated but not nonactivated human T cell proliferation. Inhibition of proliferation was pathogen specific, heat sensitive, and multiplicity of infection dependent and required chlamydial entry but not de novo protein synthesis. Activated CD4(+) and CD8(+) T cells were equally sensitive to C. pneumoniae antiproliferative effectors. The C. pneumoniae antiproliferative effect was linked to T cell death associated with caspase 1, 8, 9, and IL-1β production, indicating that both apoptotic and pyroptotic cellular death pathways were activated after pathogen-T cell interactions. Collectively, these findings are consistent with the conclusion that C. pneumoniae could induce a local T cell immunosuppression and inflammatory response revealing a possible host-pathogen scenario that would support both persistence and inflammation.

Interleukin-13 promotes susceptibility to chlamydial infection of the respiratory and genital tracts

Chlamydiae are intracellular bacteria that commonly cause infections of the respiratory and genital tracts, which are major clinical problems. Infections are also linked to the aetiology of diseases such as asthma, emphysema and heart disease. The clinical management of infection is problematic and antibiotic resistance is emerging. Increased understanding of immune processes that are involved in both clearance and immunopathology of chlamydial infection is critical for the development of improved treatment strategies. Here, we show that IL-13 was produced in the lungs of mice rapidly after Chlamydia muridarum (Cmu) infection and promoted susceptibility to infection. Wild-type (WT) mice had increased disease severity, bacterial load and associated inflammation compared to IL-13 deficient (-/-) mice as early as 3 days post infection (p.i.). Intratracheal instillation of IL-13 enhanced bacterial load in IL-13-/- mice. There were no differences in early IFN-g and IL-10 expression between WT and IL-13-/- mice and depletion of CD4+ T cells did not affect infection in IL-13-/- mice. Collectively, these data demonstrate a lack of CD4+ T cell involvement and a novel role for IL-13 in innate responses to infection. We also showed that IL-13 deficiency increased macrophage uptake of Cmu in vitro and in vivo. Moreover, the depletion of IL-13 during infection of lung epithelial cells in vitro decreased the percentage of infected cells and reduced bacterial growth. Our results suggest that enhanced IL-13 responses in the airways, such as that found in asthmatics, may promote susceptibility to chlamydial lung infection. Importantly the role of IL-13 in regulating infection was not limited to the lung as we showed that IL-13 also promoted susceptibility to Cmu genital tract infection. Collectively our findings demonstrate that innate IL-13 release promotes infection that results in enhanced inflammation and have broad implications for the treatment of chlamydial infections and IL-13-associated diseases.

Chlamydia pneumoniae infection and lung cancer risk: a meta-analysis

Chlamydia pneumoniae (C. pneumoniae) is a common cause of acute respiratory infection and has been hypothesised to cause several chronic diseases, including lung cancer. Numbers studies were conducted to analyse the association between C. pneumoniae infection and risk of lung cancer, but no clear consensus had been found. To assess this relationship more precisely, a meta-analysis was performed. The electronic databases PubMed, Embase, Web of Science and CNKI were searched; Data were extracted and analysed independently by two investigators. Ultimately, 12 studies, involving 2595 lung cancer cases and 2585 controls from four prospective studies and eight retrospective studies were included. Overall, people exposed to C. pneumoniae infection had an odds ratio (OR) of 1.48 (95% confidence interval (CI), 1.32-1.67) for lung cancer risk, relative to those not exposed. C. pneumoniae infection was clearly identified as a risk factor for lung cancer in both prospective studies (OR, 1.16; 95% CI, 1.00-1.36) and retrospective studies (OR, 2.17; 95% CI, 1.79-2.63) and in both IgA ≥ 16 cutoff group (OR, 1.22; 95% CI, 1.06-1.41) and the IgA ≥ 64 cutoff group (OR, 2.35; 95% CI, 1.88-2.93). In conclusion, C. pneumoniae infection is associated with an increased risk for lung cancer, higher titre may be a better predictor of lung cancer risk.

Native properdin binds to Chlamydia pneumoniae and promotes complement activation

Activation of complement represents one means of natural resistance to infection from a wide variety of potential pathogens. Recently, properdin, a positive regulator of the alternative pathway of complement, has been shown to bind to surfaces and promote complement activation. Here we studied whether properdin-mediated complement activation occurs on the surface of Chlamydia pneumoniae, an obligate intracellular Gram-negative bacterium that causes 10 to 20% of community-acquired pneumonia. We have determined for the first time that the physiological P₂, P₃, and P₄ forms of human properdin bind to the surface of Chlamydia pneumoniae directly. The binding of these physiological forms accelerates complement activation on the Chlamydia pneumoniae surface, as measured by C3b and C9 deposition. Finally, properdin-depleted serum could not control Chlamydia pneumoniae infection of HEp-2 cells compared with normal human serum. However, after addition of native properdin, the properdin-depleted serum recovered the ability to control the infection. Altogether, our data suggest that properdin is a pattern recognition molecule that plays a role in resistance to Chlamydia infection.

Chitin particles are multifaceted immune adjuvants

RATIONALE

Chitin is a ubiquitous polysaccharide in fungi, insects, allergens, and parasites that is released at sites of infection. Its role in the generation of tissue inflammation, however, is not fully understood.

OBJECTIVES

We hypothesized that chitin is an important adjuvant for adaptive immunity.

METHODS

Mice were injected with a solution of ovalbumin and chitin.

MEASUREMENTS AND MAIN RESULTS

We used in vivo and ex vivo/in vitro approaches to characterize the ability of chitin fragments to foster adaptive immune responses against ovalbumin and compared these responses to those induced by aluminum hydroxide (alum). In vivo, ovalbumin challenge caused an eosinophil-rich pulmonary inflammatory response, Th2 cytokine elaboration, IgE induction, and mucus metaplasia in mice that had been sensitized with ovalbumin plus chitin or ovalbumin plus alum. Toll-like receptor-2, MyD88, and IL-17A played critical roles in the chitin-induced responses, and MyD88 and IL-17A played critical roles in the alum-induced responses. In vitro, CD4(+) T cells from mice sensitized with ovalbumin plus chitin were incubated with ovalbumin-stimulated bone marrow-derived dendritic cells. In these experiments, CD4(+) T-cell proliferation, IL-5, IL-13, IFN-γ, and IL-17A production were appreciated. Toll-like receptor-2, MyD88, and IL-17A played critical roles in these in vitro adjuvant properties of chitin. TLR-2 was required for cell proliferation, whereas IL-17 and TLR-2 were required for cytokine elaboration. IL-17A also inhibited the generation of adaptive Th1 responses.

CONCLUSIONS

These studies demonstrate that chitin is a potent multifaceted adjuvant that induces adaptive Th2, Th1, and Th17 immune responses. They also demonstrate that the adjuvant properties of chitin are mediated by a pathway(s) that involves and is regulated by TLR-2, MyD88, and IL-17A.

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

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

Chlamydia trachomatis evokes a relative anti-inflammatory response in a free Ca2+ dependent manner in human macrophages

Chlamydia trachomatis infections manifest as unique, chronic inflammatory diseases, indicating a relative compromise in the capacity of early immune responders such as macrophages to resolve the infection. We decided to investigate whether or not the chronic inflammatory manifestations are influenced by a disturbance in the pattern of inflammatory:anti-inflammatory cytokine elaboration early in the infection cycle in macrophages and assess the possible modulatory role of Ca(2+) signals in the process. Although the basal and functional levels of IL-12 and IL-10 are not identical in concentration, chlamydia initiated a significant decline in IL-12. This led to a difference in the ratio of time-course decline in IL-12 compared with IL-10 in a Ca(2+)-poor medium, while there was significant increase in IL-10 in a Ca(2+)-rich medium. Also, when macrophages were infected after treatment with drugs that either facilitated Ca(2+) influx into cells or inhibited efflux from intracellular stores into cytosol, there was a significant enhancement of the elaboration of IL-10 compared with IL-12. The immobilization of cytosolic Ca(2+) by BAPTA-AM resulted in the decline of macrophage IL-12 and IL-10 in both infected and uninfected cases. There was evidence that infectivity and status of chlamydial elementary bodies harvested from macrophages during these experiments were consistent with chronic forms as assessed by HSP-60:MOMP ratio. The implication of these findings is that chlamydia infection of macrophages, together with its capacity to moderate macrophage intracellular Ca(2+) levels, may evoke a net anti-inflammatory response that presumably favors chronic chlamydia infections.

Differences in innate immune responses correlate with differences in murine susceptibility to Chlamydia muridarum pulmonary infection

We investigated the phenotypic basis for genetically determined differences in susceptibility and resistance to Chlamydia muridarum pulmonary infection using BALB/c and C57BL/6 mice. Following C. muridarum intranasal inoculation, the intensity of infection was very different between BALB/c and C57BL/6 beginning as early as 3 days post-infection. Intrapulmonary cytokine patterns also differed at early time-points (days 2 and 4) between these two strains of mice. The early recruitment of neutrophils to lung tissue was greater in BALB/c than in C57BL/6 mice and correlated with a higher number of inclusion forming units (IFU) of C. muridarum. At day 12 post-infection, BALB/c mice continued to demonstrate a greater burden of infection, significantly higher lung cytokine levels for tumour necrosis factor-alpha and interleukin-17 (IL-17) and a significantly lower level for interferon-gamma than did C57BL/6 mice. In vitro, bone-marrow-derived dendritic cells (BMDCs) from BALB/c mice underwent less functional maturation in response to C. muridarum infection than did BMDCs from C57BL/6 mice. The BMDCs of BALB/c mice expressed lower levels of activation markers (CD80, CD86, CD40 and major histocompatibility complex class II) and secreted less IL-12 and more IL-23 than BMDCs from C57BL/6 mice. Overall, the data demonstrate that the differences exhibited by BALB/c and C57BL/6 mice following C. muridarum pulmonary infection are associated with differences in early innate cytokine and cellular responses that are correlated with late differences in T helper type 17 versus type 1 adaptive immune responses.

cIAP-1 controls innate immunity to C. pneumoniae pulmonary infection

The resistance of epithelial cells infected with Chlamydophila pneumoniae for apoptosis has been attributed to the induced expression and increased stability of anti-apoptotic proteins called inhibitor of apoptosis proteins (IAPs). The significance of cellular inhibitor of apoptosis protein-1 (cIAP-1) in C. pneumoniae pulmonary infection and innate immune response was investigated in cIAP-1 knockout (KO) mice using a novel non-invasive intra-tracheal infection method. In contrast to wildtype, cIAP-1 knockout mice failed to clear the infection from their lungs. Wildtype mice responded to infection with a strong inflammatory response in the lung. In contrast, the recruitment of macrophages was reduced in cIAP-1 KO mice compared to wildtype mice. The concentration of Interferon gamma (IFN-γ) was increased whereas that of Tumor Necrosis Factor (TNF-α) was reduced in the lungs of infected cIAP-1 KO mice compared to infected wildtype mice. Ex vivo experiments on mouse peritoneal macrophages and splenocytes revealed that cIAP-1 is required for innate immune responses of these cells. Our findings thus suggest a new immunoregulatory role of cIAP-1 in the course of bacterial infection.

Independent inactivation of arginine decarboxylase genes by nonsense and missense mutations led to pseudogene formation in Chlamydia trachomatis serovar L2 and D strains

BACKGROUND

Chlamydia have reduced genomes that reflect their obligately parasitic lifestyle. Despite their different tissue tropisms, chlamydial strains share a large number of common genes and have few recognized pseudogenes, indicating genomic stability. All of the Chlamydiaceae have homologs of the aaxABC gene cluster that encodes a functional arginine:agmatine exchange system in Chlamydia (Chlamydophila)pneumoniae. However, Chlamydia trachomatis serovar L2 strains have a nonsense mutation in their aaxB genes, and C. trachomatis serovar A and B strains have frameshift mutations in their aaxC homologs, suggesting that relaxed selection may have enabled the evolution of aax pseudogenes. Biochemical experiments were performed to determine whether the aaxABC genes from C. trachomatis strains were transcribed, and mutagenesis was used to identify nucleotide substitutions that prevent protein maturation and activity. Molecular evolution techniques were applied to determine the relaxation of selection and the scope of aax gene inactivation in the Chlamydiales.

RESULTS

The aaxABC genes were co-transcribed in C. trachomatis L2/434, during the mid-late stage of cellular infection. However, a stop codon in the aaxB gene from this strain prevented the heterologous production of an active pyruvoyl-dependent arginine decarboxylase. Replacing that ochre codon with its ancestral tryptophan codon rescued the activity of this self-cleaving enzyme. The aaxB gene from C. trachomatis D/UW-3 was heterologously expressed as a proenzyme that failed to cleave and form the catalytic pyruvoyl cofactor. This inactive protein could be rescued by replacing the arginine-115 codon with an ancestral glycine codon. The aaxC gene from the D/UW-3 strain encoded an active arginine:agmatine antiporter protein, while the L2/434 homolog was unexpectedly inactive. Yet the frequencies of nonsynonymous versus synonymous nucleotide substitutions show no signs of relaxed selection, consistent with the recent inactivation of these genes.

CONCLUSION

The ancestor of the Chlamydiaceae had a functional arginine:agmatine exchange system that is decaying through independent, parallel processes in the C. trachomatis lineage. Differences in arginine metabolism among Chlamydiaceae species may be partly associated with their tissue tropism, possibly due to the protection conferred by a functional arginine-agmatine exchange system against host nitric oxide production and innate immunity. The independent loss of AaxB activity in all sequenced C. trachomatis strains indicates continual gene inactivation and illustrates the difficulty of recognizing recent bacterial pseudogenes from sequence comparison, transcriptional profiling or the analysis of nucleotide substitution rates.

Chronic and repeated Chlamydophila pneumoniae lung infection can result in increasing IL-4 gene expression and thickness of airway subepithelial basement membrane in mice

BACKGROUND/PURPOSE

Chlamydophila pneumoniae infection has been associated with several pulmonary and cardiac diseases. However, it has not been explored for its ability to activate the same immunopathologic mechanisms of asthma, namely, a predominant Th2 immune response and structural changes that are termed airway remodeling. This study evaluated immune responses in the lung and airway pathology of BALB/c mice with chronic and repeated C. pneumoniae infections.

METHODS

Mice were inoculated intranasally with 5 x 10(6) inclusion-forming units of C. pneumoniae TWAR strain, and re-inoculated at 14 and 42 days after the primary inoculation. Cytokine gene expression in bronchoalveolar lavage (BAL) cells was analyzed by RT-PCR on day 70. Airway pathology was also evaluated by morphometric measurements.

RESULTS

A significant increase of interleukin (IL)-4 mRNA was detected in BAL cells in infected mice, and a significant increase in subepithelial basement membrane thickness of the airways was also noted in infected mice as compared with control mice (8.95 +/- 0.28 microm vs. 5.54 +/- 0.22 microm, p < 0.0001). We further analyzed the correlation between IL-4 cytokine expression and the increased subepithelial basement membrane thickness of airways in infected mice. We found that mice with increased IL-4 mRNA expression had significant increases in the thickness of subepithelial basement membrane as compared with mice without increased IL-4 mRNA expression (9.87 +/- 0.51 microm vs. 6.49 +/- 0.52 microm, p < 0.0001).

CONCLUSION

It is believed that our results demonstrated for the first time that chronic and repeated infections with C. pneumoniae increased IL-4 gene expression and thickness of airway subepithelial basement membrane in mice.

Chlamydia pneumoniae induces interleukin-6 and interleukin-10 in human gingival fibroblasts

Chlamydia pneumoniae is an obligate intracellular Gram-negative bacterium with a unique biphasic developmental cycle that can cause persistent infections. In humans, Chlamydia causes airway infection and has been implicated in chronic inflammatory diseases, such as asthma and atherosclerosis. In addition, recent studies demonstrated that patients with severe periodontitis can harbor C. pneumoniae, which can increase the risk for a host inflammatory response with weighty clinical sequelae. Previous studies have established that periodontal pathogenic bacteria (i.e. Gram-negative bacteria) can induce the synthesis and release of cytokines and other inflammatory mediators in human gingival fibroblasts. HGF are resident cells of the periodontium that respond to receptor stimulation by producing a variety of substances including cytokines and growth factors. Our results demonstrate that after 48 hr of incubation with viable C. pneumoniae HGF showed a proliferative response, as seen by both colorimetric MTT assay and direct cell count (30% and 35%, respectively). In addition, HGF incubated with viable or UV light-inactivated C. pneumoniae organisms showed an increase in the levels of IL-6 and IL-10, but not IL-4; on the contrary, HGF infected with heat-killed bacteria did not show a significant production of any of the cytokines considered. In conclusion, the present study suggests that C. pneumoniae may modulate the expression of IL-6 and IL-10 by human gingival fibroblasts. Further studies are warranted to clarify the molecular mechanisms of C. pneumoniae in the regulation of cytokine expression by host cells and to elaborate the relevant clinical implications.

Etiology of asthma exacerbations

Asthma exacerbations are common, and the major morbidity, mortality, and health care costs associated with asthma are related to exacerbations. The majority are related to viral infection, and although progress has been made in identifying the mechanisms of virus-induced asthma exacerbations, there is still much to be learned. Allergen exposure causes some exacerbations and can participate in virus-induced exacerbations, as can other environmental exposures. A role for atypical bacterial infection in exacerbations is also increasingly recognized. Exacerbations are characterized by airway inflammation, which can differ in type depending on whether it is primarily infective or allergic in origin. An increased understanding of the inflammatory pathways might lead to identification of targets for the development of novel prevention or treatment strategies.

Protective or pathogenic immune response to genital chlamydial infection in women--a possible role of cytokine secretion profile of cervical mucosal cells

Little is known about genital mucosal immune response to chlamydial infection in women with or without sequelae (Chlamydia positive women with or without fertility disorders as infertility and multiple spontaneous abortions). Cervical lymphocytes were stimulated with chlamydial EBs and cytokine secretion was determined by ELISA, RT-PCR and ELISPOT assays. Stimulated cervical cells from women with fertility disorders (FD) secrete significantly (P<0.05) higher levels of IL-1beta, IL-6, IL-8 and IL-10 and cells from fertile women secrete significantly higher levels of IL-12 and IFN-gamma compared to other groups. RT-PCR analysis showed similar results for IFN-gamma and IL-12. For IL-10 and IL-4, mRNA expression levels were significantly higher (P<0.05) in cells obtained from women with FD compared to other groups. Results for ELISPOT assay were similar as those of RT-PCR. The results suggest that cytokine secretion profile of cervical cells may decide whether infection does not hamper fertility or will develop fertility disorder.

Role of cervical dendritic cell subsets, co-stimulatory molecules, cytokine secretion profile and beta-estradiol in development of sequalae to Chlamydia trachomatis infection

BACKGROUND

Chlamydia trachomatis infection of the female genital tract can lead to serious sequelae resulting in fertility related disorders. Little is known about the mechanism leading to Chlamydia induced pathology and factors responsible for it. As only some of the women develops reproductive disorders while majority of the women clears infection without any severe sequalae, mucosal immune response in women with or without fertility disorders was studied to identify factors which may lead to final clinical outcome of chlamydial infection.

METHODS

Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) populations in cervical mucosa and peripheral blood were analyzed in controls and Chlamydia positive women with or without fertility disorders with multicoloured flow cytometric analysis. Cervical cytokines (IL-6, IL-8, IL-10, IL-12, TNF-alpha and IFN-gamma), C-reactive protein levels and sex hormone levels in serum were quantified by ELISA.

RESULTS

In cervix of Chlamydia positive women with fertility disorders, significantly high (P < 0.05) numbers of pDCs were present with increased CD80 expression. pDCs correlated significantly with C-reactive protein levels, IL-6 and IFN-gamma levels in women with fertility disorders. In contrast, mDCs showed significant upregulation of CD1a during chlamydial infection and correlated significantly with IL-12 levels in Chlamydia positive fertile women. beta-estradiol levels were significantly higher in women having fertility disorders as compared to fertile women and have significant correlations (r = 0.65; P < 0.05) with pDCs numbers, CD80 expression, IL-6 levels and IFN-gamma levels in these women.

CONCLUSION

These results suggest that development of sequalae in some women can be a result of interplay of many factors including type of dendritic cell, co stimulatory molecule expression, cytokine secretion pattern and hormone levels.

No evidence of involvement of Chlamydia pneumoniae in lung cancer by means of quantitative real-time polymerase chain reaction

Chlamydia pneumoniae, an obligate intracellular pathogen, is well-known as etiological agent of acute respiratory infections; the repeated or prolonged exposure to chlamydial antigens may promote the persistence of C. pneumoniae in the respiratory tract leading to chronic diseases, such as chronic obstructive pulmonary disease and asthma. The predilection of C. pneumoniae to cause respiratory tract infections combined with its persistent nature suggest that it might play a role in lung cancer. The aim of our study is to evaluate the involvement of C. pneumoniae in pathogenesis of lung cancer. We therefore investigated the presence of C. pneumoniae DNA in tumor lung tissues by using real-time PCR assay. Simultaneously, tumor and healthy tissues from the same patient with primary carcinoma lung were analyzed. C. pneumoniae DNA was not detected in a single lung tumor tissue by means of an highly sensitive, and specific real-time PCR assay based on FRET hybridization probes. In conclusion, this study does not support the involvement of C. pneumoniae in the pathogenesis of lung cancer, suggesting that further investigations are needed to clarify other potential causative factors for the development of this malignancy.

Is lipopolysaccharide a factor in infectivity of Chlamydia trachomatis?

Lipopolysaccharide (LPS) is a major surface component of Chlamydia trachomatis, as with all Gram-negative bacteria. The effect of C. trachomatis LPS on C. trachomatis infectivity of human epithelial cells was investigated. C. trachomatis LPS and C. trachomatis LPS antibody significantly reduced infectivity, mostly in a dose-dependent manner. As the structure of LPS in C. trachomatis is simple and consists only of lipid A and 3-deoxy-D-manno-octulosonic acid (Kdo), we investigated whether lipid A or Kdo was inhibitory to chlamydial infectivity. Polymyxin B, as a lipid A inhibitor, and Kdo considerably reduced C. trachomatis infectivity. With all the LPS inhibitors used, there was greater inhibition against serovar E than serovar LGV. These results suggest a role for LPS in chlamydial infectivity. Elucidation of how LPS acts in infectivity and identification of host-cell receptors would help in understanding pathogenicity.

Disparate Innate Immune Responses to Persistent and AcuteChlamydia pneumoniaeInfection in Chronic Obstructive Pulmonary Disease

RATIONALE

Chlamydia pneumoniae (Cpn) infection may play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Few data are available comparing persistent and acute infection of this pathogen in the human respiratory tract.

OBJECTIVES

To study Cpn-induced innate immune responses in lung tissue from patients with COPD and control subjects ex vivo and in vitro.

METHODS

Cpn detection was done by nested polymerase chain reaction, in situ hybridization, and immunohistochemistry ex vivo in unstimulated tissue and in vitro using an acute Cpn infection model. As main endpoints for the assessment of early cellular responses, nuclear factor (NF)-kappaB activation and CXC chemokine ligand (CXCL)-8 expression were evaluated. The role of Toll-like receptors (TLRs) as recognition molecules in Cpn-induced innate responses was tested by blocking experiments.

MEASUREMENTS AND MAIN RESULTS

Fifteen percent of patients with COPD were chronically infected with Cpn in contrast to 0% of control subjects (p < 0.05). There were no differences in CXCL-8 and NF-kappaB expression between infected and noninfected COPD tissue ex vivo. In contrast, acute in vitro infection induced an intense innate immune response including up-regulation of TLR2. Blocking experiments demonstrated the predominant role of TLR2 in induction of the early immune response, whereas no influence on chlamydial infection rates was observed.

CONCLUSIONS

Acute in vitro infection of human lung tissue with Cpn elicited a marked innate response via TLR2, whereas chronic chlamydial infection in patients with COPD was not associated with enhanced cellular activation. These findings suggest different roles of Cpn during acute and chronic stages of pulmonary infection.

Chlamydia pneumoniae infection of brain cells: An in vitro study

Inspired by the suggested associations between neurological diseases and infections, we determined the susceptibility of brain cells to Chlamydia pneumoniae (Cpn). Murine astrocyte (C8D1A), neuronal (NB41A3) and microglial (BV-2) cell lines were inoculated with Cpn. Infection was established by immunofluorescence and real-time PCR at various time points. Productive infection was assessed by transferring medium of infected cells to a detection layer. Finally, apoptosis and necrosis post-infection was determined. Our data demonstrate that the neuronal cell line is highly sensitive to Cpn, produces viable progeny and is prone to die after infection by necrosis. Cpn tropism was similar in an astrocyte cell line, apart from the higher production of extracellular Cpn and less pronounced necrosis. In contrast, the microglial cell line is highly resistant to Cpn as the immunohistochemical signs almost completely disappeared after 24 h. Nevertheless, significant Cpn DNA amounts could be detected, suggesting Cpn persistence. Low viable progeny and hardly any necrotic microglial cells were observed. Further research is warranted to determine whether these cell types show the same sensitivity to Cpn in an in vivo setting.

Platelet activation triggered by Chlamydia pneumoniae is antagonized by 12-lipoxygenase inhibitors but not cyclooxygenase inhibitors

Chlamydia pneumoniae is a respiratory pathogen that has been linked to cardiovascular disease. We have recently shown that C. pneumoniae activates platelets, leading to oxidation of low-density lipoproteins. The aim of the present study was to evaluate the inhibitory effects of different pharmacological agents on platelet aggregation and secretion induced by C. pneumoniae. Platelet interaction with C. pneumoniae was studied by analyzing platelet aggregation and ATP-secretion with Lumi-aggregometry. Platelet aggregation and ATP-secretion induced by C. pneumoniae was markedly inhibited by the NO-donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP), an effect that was counteracted by the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Pre-treatment of platelets with the 12-lipoxygenase (12-LOX) inhibitors cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate (CDC) and 5,6,7-trikydroxyflavone (baicalein) completely blocked the activation, whereas the cyclooxygenase (COX) inhibitors 2-acetyloxybenzoic acid (aspirin) and (8E)-8-[hydroxy-(pyridin-2-ylamino)methylidene]-9-methyl-10,10-dioxo-10$l;(6)thia-9-azabicyclo[4.4.0]deca-1,3,5-trien-7-one (piroxicam) had no inhibitory effects. Opposite to C. pneumoniae-induced activation, platelets stimulated by collagen were inhibited by the COX-inhibitors but were unaffected by the 12-LOX-inhibitors. The platelet activating factor (PAF) antagonist Ginkgolide B blocked the C. pneumoniae-induced platelet activation, whereas the responses to collagen were unaffected. Furthermore, the P2Y1 and P2Y12 purinergic receptor antagonists 2'-deoxy-N6-methyladenosine 3',5'-bisphosphate (MRS2179) and N(6)-(2-methyl-thioethyl)-2-(3,3,3-trifluoropropylthio)-beta,gamma-dichloromethylene-ATP (cangrelor) inhibited the aggregation and secretion caused by C. pneumoniae. It is well-known that the efficacy of COX inhibitors in the prevention and treatment of cardiovascular disease varies between different patients, and that patients with low responses to aspirin have a higher risk to encounter cardiovascular events. The findings in this study showing that platelets stimulated by C. pneumoniae are unaffected by COX inhibitors but sensitive to 12-LOX inhibitors, may thus be of importance in future management of atherosclerosis and thrombosis.

Persistent Chlamydia pneumoniae infection of cardiomyocytes is correlated with fatal myocardial infarction

Acute myocardial infarction (AMI) associated with unfavorable prognosis is likely to be the consequence of a diffuse active chronic inflammatory process that destabilizes the whole coronary tree and myocardium, suggesting a possible common causal agent underlying both conditions. The main objective of this study was to investigate whether Chlamydia pneumoniae (CP) infection occurred beyond the coronary plaques, namely in the myocardium of individuals who died of AMI. The presence of CP cell wall antigen (OMP-2) and CP-HSP60 was investigated in the myocardium and coronary plaques of 10 AMI and 10 age-matched control patients by immunohistochemistry, electron microscopy, and molecular biology. OMP-2 antigens were found in the unaffected myocardium of 9 of 10 AMI patients. Conversely, only 1 of 10 control patients exhibited a positive staining for CP. Moreover, OMP-2 and CP-HSP60 were detected in the whole coronary tree. CP presence was strongly associated with a T-cell inflammatory infiltrate. Our results suggest that CP may underlie both coronary and myocardial vulnerabilities in patients who died of AMI and corroborate the notion that CP may act by reducing cardiac reserves, thus worsening the ischemic burden of myocardium.

Inflammatory responses following Chlamydia pneumoniae infection of glial cells

Recently, infections have been implicated in the pathogenesis of Alzheimer's disease. Apart from the direct effects of pathogens, it can be hypothesized that inflammatory mechanisms, such as the production of pro-inflammatory mediators by resident glia, may result in neurotoxicity. Here, we examined the inflammatory responses in murine microglial cell (MMC) and murine astrocyte cell (MAC) lines following infection with Chlamydia pneumoniae (Cpn), a pathogen that has recently been associated with Alzheimer's disease. Furthermore, we determined whether these inflammatory responses are sufficient to cause neuronal cell death in vitro. MMCs and MACs were infected with Cpn. Subsequently, various chemo- and cytokines were determined in the culture supernatant fluid of infected/control cells at different time points post-infection. Significantly higher levels of monocyte chemoattractant protein 1, interleukin (IL)-6, tumour necrosis factor (TNF)-alpha and IL-1beta were found in supernatant fluids of infected MMCs compared with controls. In contrast, in the supernatant fluid of infected MACs, only monocyte chemoattractant protein 1 and IL-6 displayed significantly higher levels compared with controls. Moreover, neurotoxicity was examined up to 72 h after transferring the conditioned supernatant fluid to a neuronal cell layer. No neuronal cell death was observed when supernatant fluids from infected/mock-treated MACs were transferred. However, when neurones were exposed to conditioned supernatant fluid from infected MMCs, a significant increase in cell death was observed compared with mock. Furthermore, adding neutralizing antibodies against IL-6 and TNF-alpha to that conditioned supernatant fluid prevented neuronal cell death by approximately 50%. In conclusion, these data suggest that Cpn infection results in a pro-inflammatory milieu, particularly by activating MMCs, that ultimately results in neurodegeneration with prominent roles for both IL-6 and TNF-alpha.

Chlamydia pneumoniae infection of microglial cells in vitro: a model of microbial infection for neurological disease

Chlamydia pneumoniae is the aetiological cause of a wide variety of chronic inflammatory diseases and may be associated with neurological disease. Microbiological and immunological aspects of the interaction between C. pneumoniae and the central nervous system (CNS) are not well understood because of the lack of a suitable infection model for neuronal studies. In the present study, an in vitro C. pneumoniae infection model was developed in the established microglial cell line EOC 20. Infection of the cells resulted in obvious induction of proinflammatory cytokines. The infection also selectively induced matrix metalloproteinase-9 (MMP-9) but not MMP-2. Moreover, beta interferon, which is known to modulate CNS disease, inhibited induction of MMP-9 following C. pneumoniae infection. These results support the view that C. pneumoniae infection may be associated with marked alteration of the ability of microglial cells to enhance cytokine production as well as induction of an MMP.

Chlamydia pneumoniae infection after lung transplantation

BACKGROUND

Chlamydia pneumoniae is established as a common agent of acute respiratory tract infection and has been implicated in the pathogenesis of asthma and chronic obstructive pulmonary disease. Airway disease is a prominent cause of morbidity and mortality after lung transplantation. We investigated the role of C pneumoniae as a pulmonary pathogen after lung transplantation.

METHODS

Eighty lung transplant recipients underwent 232 bronchoscopies with bronchoalveolar lavage with or without transbronchial lung biopsy during 1 year for surveillance of rejection and infection, or where clinically indicated.

RESULTS

C pneumoniae was detected using nested polymerase chain reaction in 9 of 36 (25%) recipients studied within 30 days of lung transplantation, 3 of whom remained positive on repeat lavage and died from airway disease in the first year post-operatively. By comparison, all 27 recipients with negative lavage survived >1 year. Lavage was positive for C pneumoniae in 18 of 71 (25%) recipients studied >30 days after lung transplantation, 5 of whom had pneumonia and 8 of whom had bronchiolitis obliterans syndrome. Eleven also had acute pulmonary allograft rejection.

CONCLUSIONS

Persistent infection with C pneumoniae (whether donor-derived, de novo or re-activated) appears deleterious to pulmonary allograft function and is associated with early mortality, rejection and bronchiolitis obliterans syndrome after lung transplantation. A trial of empiric antibiotic therapy for C pneumoniae may therefore be warranted in the attempt to prevent progressive inflammatory airway disease.

Chlamydia pneumoniae infection enhances cellular proliferation and reduces steroid responsiveness of human peripheral blood mononuclear cells via a tumor necrosis factor-alpha-dependent pathway

BACKGROUND

Although epidemiological studies have found an association between Chlamydia pneumoniae infection and severe asthma, the causality and underlying mechanism are largely unknown. We hypothesized that C. pneumoniae infection increases the proliferation and enhances the survival of immune and inflammatory cells, resulting in reduced responsiveness to corticosteroids and suggesting that the underlying mechanism is related to a TNF-alpha-dependent pathway.

METHODS

Human peripheral blood mononuclear cells (PBMCs) were cultured in vitro in the presence or absence of C. pneumoniae infection. Responsiveness to corticosteroids was assayed by adding dexamethasone, and the underlying mechanism was investigated by treating cells with infliximab that is a chimeric anti-TNF-alpha monoclonal antibody. Cellular proliferation and apoptosis was assessed by thymidine uptake and counting apoptotic cells using flow cytometry.

RESULTS

Cellular proliferation was significantly higher in C. pneumoniae-infected PBMCs than in uninfected PBMCs, which is more prominent in Th2-dominant microenvironment. The anti-proliferative and pro-apoptotic effect of corticosteroid were significantly reduced in C. pneumoniae-infected PBMCs compared with uninfected PBMCs. The proliferative effect of C. pneumoniae infection and the reduced response to corticosteroid were effectively reversed by blocking the TNF-alpha pathway at least partially.

CONCLUSION

C. pneumoniae infection enhanced the proliferation and survival of immune and inflammatory cells, resulting in steroid resistance. The reversal of these phenomena by the TNF-alpha inhibitor suggests that TNF-alpha may play an important role in the induction of steroid dependence or resistance. A TNF-alpha inhibitor may therefore be a candidate agent for managing steroid-dependent or -resistant severe asthma.

Fate of Chlamydophila pneumoniae in human monocyte-derived dendritic cells: Long lasting infection

Earlier studies from this group demonstrated that Chlamydophila pneumoniae co-localized with dendritic cells (DC) in temporal artery biopsies from patients with giant cell arteritis (GCA). To investigate the interaction of DC with C. pneumoniae we employed an in vitro cell culture system of human monocyte derived DC. These DC were infected with C. pneumoniae and observed at regular time intervals up to 25 days post infection. Chlamydiae were visualized inside DC by both confocal and electron microscopy. Statistical analysis showed an increase in the number of chlamydial antigen during that period (p < 0.00005, chi2-test). Titration of DC lysates on HEp-2 cells showed that infectious progeny was recovered at various intervals but showed no exponential growth. Additionally, RT-PCR analyses of infected DC identified transcripts from dnaA, ftsK and tal throughout a period of 14 days, indicating viable chlamydiae. Thus, human monocyte-derived DC are susceptible to C. pneumoniae infection. These results indicate that C. pneumoniae-infected DC can play an important role in the transmission of these bacteria in GCA and other chlamydial diseases.

A role for surfactant protein D in innate immunity of the human prostate

OBJECTIVES

Surfactant protein D (SP-D) is a member of the collectin family of proteins, which are involved in host defense mechanisms in the lung. In the present study, we found that SP-D is produced in the human prostate where it may play a role in innate immunity.

METHODS AND RESULTS

Using reverse-transcriptase PCR and Western blot analysis, we demonstrate that SP-D mRNA and protein are present in human prostate tissue. In situ hybridization and immunohistochemistry revealed that SP-D mRNA and protein are localized in epithelial cells of prostate glands. Prostate glands that are surrounded by inflammatory cells produce increased amounts of SP-D protein. We also show that SP-D inhibits the infection of LNCaP and P69SV40T prostate epithelial cells by Chlamydia trachomatis in an in vitro infection assay. Furthermore, using truncated human SP-D mutants, we demonstrate that SP-D binds to Chlamydia trachomatis via its carboxy-terminal lectin domains.

CONCLUSIONS

Our in vitro studies suggest that SP-D protects the prostate from infection by pathogens. SP-D protein levels are increased at sites of inflammation in the prostate, suggesting SP-D may also contribute more generally to inflammatory regulation in the prostate.

Chlamydophila pneumoniae and Mycoplasma pneumoniae: a role in asthma pathogenesis?

The potential role of atypical bacterial infection in the pathogenesis of asthma is a subject of continuing debate. There is an increasing body of literature concerning the association between the atypical bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae and asthma pathogenesis; however, many studies investigating such a link have been uncontrolled and have provided conflicting evidence, in part due to the difficulty in accurately diagnosing infection with these atypical pathogens. This article reviews the evidence for an association between atypical bacterial respiratory pathogens and the pathogenesis of asthma, and discusses the biological mechanisms that could account for such a link. The possible role of antibacterial therapy in the management of asthma and the need for well-designed studies to investigate this is also discussed.