Opsonophagocytosis of Chlamydia pneumoniae by Human Monocytes and Neutrophils.

The human respiratory tract pathogen Chlamydia pneumoniae, which causes mild to severe infections, has been associated with the development of chronic inflammatory diseases. To understand the biology of C. pneumoniae infections, several studies have investigated the interaction between C. pneumoniae and professional phagocytes. However, these studies have been conducted under nonopsonizing conditions, making the role of opsonization in C. pneumoniae infections elusive. Thus, we analyzed complement and antibody opsonization of C. pneumoniae and evaluated how opsonization affects chlamydial infectivity and phagocytosis in human monocytes and neutrophils. We demonstrated that IgG antibodies and activation products of complement C3 and C4 are deposited on the surface of C. pneumoniae elementary bodies when incubated in human serum. Complement activation limits C. pneumoniae infectivity in vitro and has the potential to induce bacterial lysis by the formation of the membrane attack complex. Coculture of C. pneumoniae and freshly isolated human leukocytes showed that complement opsonization is superior to IgG opsonization for efficient opsonophagocytosis of C. pneumoniae in monocytes and neutrophils. Neutrophil-mediated phagocytosis of C. pneumoniae was crucially dependent on opsonization, while monocytes retained minor phagocytic potential under nonopsonizing conditions. Complement opsonization significantly enhanced the intracellular neutralization of C. pneumoniae in peripheral blood mononuclear cells and neutrophils and almost abrogated the infectious potential of C. pneumoniae In conclusion, we demonstrated that complements limit C. pneumoniae infection in vitro by interfering with C. pneumoniae entry into permissive cells by direct complement-induced lysis and by tagging bacteria for efficient phagocytosis in both monocytes and neutrophils.

Assaying Chlamydia pneumoniae Persistence in Monocyte-Derived Macrophages Identifies Dibenzocyclooctadiene Lignans as Phenotypic Switchers.

Antibiotic-tolerant persister bacteria involve frequent treatment failures, relapsing infections and the need for extended antibiotic treatment. The virulence of an intracellular human pathogen C. pneumoniae is tightly linked to its propensity for persistence and means for its chemosensitization are urgently needed. In the current work, persistence of C. pneumoniae clinical isolate CV6 was studied in THP-1 macrophages using quantitative PCR and quantitative culture. A dibenzocyclooctadiene lignan schisandrin reverted C. pneumoniae persistence and promoted productive infection. The concomitant administration of schisandrin and azithromycin resulted in significantly improved bacterial eradication compared to sole azithromycin treatment. In addition, the closely related lignan schisandrin C was superior to azithromycin in eradicating the C. pneumoniae infection from the macrophages. The observed chemosensitization of C. pneumoniae was associated with the suppression of cellular glutathione pools by the lignans, implying to a previously unknown aspect of chlamydia-host interactions. These data indicate that schisandrin lignans induce a phenotypic switch in C. pneumoniae, promoting the productive and antibiotic-susceptible phenotype instead of persistence. By this means, these medicinal plant -derived compounds show potential as adjuvant therapies for intracellular bacteria resuscitation.

M. pneumoniae and C. pneumoniae are no relevant pathogens in critically ill patients with hospital-acquired respiratory tract infections.

PURPOSE: To assess the incidence of Mycoplasma pneumoniae and Chlamydia pneumoniae in the pathogenesis of hospital-acquired respiratory tract infections (RTIs) in critically ill patients. METHODS: This is a retrospective cohort study of all ICU-patients ≥ 18 years with RTI who underwent conventional culture techniques and PCR testing for both M. pneumoniae and C. pneumoniae from respiratory tract specimens (bronchoalveolar lavage or tracheobronchial aspirates) between January 2013 to May 2017 at the Jena University Hospital. RESULTS: In total, 314 patients were included in the analysis. Of these, 210 (66.9%) patients were diagnosed with HAP, 65 (20.7%) with VAP and 39 (12.4%) with VAT. Overall, 73 (30.7%) patients were on mechanical ventilation on the day of microbiological examination. PCR-testing for M. pneumoniae was positive in two patients (0.6%) and for C. pneumoniae in zero patients. CONCLUSIONS: Our study shows that the incidence of M. pneumoniae and C. pneumoniae in the pathogenesis of hospital-acquired RTIs in critically ill patients is negligible. The results support the recommendations of the guidelines not to perform empiric therapy covering these pathogens.

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 exploits adipocyte lipid chaperone FABP4 to facilitate fat mobilization and intracellular growth in murine adipocytes.

Fatty acid-binding protein 4 (FABP4), a cytosolic lipid chaperone predominantly expressed in adipocytes and macrophages, modulates lipid fluxes, trafficking, signaling, and metabolism. Recent studies have demonstrated that FABP4 regulates metabolic and inflammatory pathways, and in mouse models its inhibition can improve type 2 diabetes mellitus and atherosclerosis. However, the role of FABP4 in bacterial infection, metabolic crosstalk between host and pathogen, and bacterial pathogenesis have not been studied. As an obligate intracellular pathogen, Chlamydia pneumoniae needs to obtain nutrients such as ATP and lipids from host cells. Here, we show that C. pneumoniae successfully infects and proliferates in murine adipocytes by inducing hormone sensitive lipase (HSL)-mediated lipolysis. Chemical inhibition or genetic manipulation of HSL significantly abrogated the intracellular growth of C. pneumoniae in adipocytes. Liberated free fatty acids were utilized to generate ATP via ß-oxidation, which C. pneumoniae usurped for its replication. Strikingly, chemical inhibition or genetic silencing of FABP4 significantly abrogated C. pneumoniae infection-induced lipolysis and mobilization of liberated FFAs, resulting in reduced bacterial growth in adipocytes. Collectively, these results demonstrate that C. pneumoniae exploits host FABP4 to facilitate fat mobilization and intracellular replication in adipocytes. This work uncovers a novel strategy used by intracellular pathogens for acquiring energy via hijacking of the host lipid metabolism pathway.

Chlamydia pneumoniae infection promotes monocyte transendothelial migration by increasing vascular endothelial cell permeability via the tyrosine phosphorylation of VE-cadherin.

Migration of monocytes into the subendothelial layer of the intima is one of the critical events in early atherosclerosis. Chlamydia pneumoniae (C. pneumoniae) infection has been shown to promote monocyte transendothelial migration (TEM). However, the exact mechanisms have not yet been fully clarified. In this study, we tested the hypothesis that C. pneumoniae infection increases vascular endothelial cell (VEC) permeability and subsequent monocyte TEM through stimulating the tyrosine phosphorylation of vascular endothelial-cadherin (VE-cadherin). Here, we demonstrated that C. pneumoniae infection promoted monocyte TEM in a TEM assay possibly by increasing the permeability of a VEC line EA.hy926 cell as assessed by measuring the passage of FITC-BSA across a VEC monolayer. Subsequently, Western blot analysis showed that C. pneumoniae infection induced VE-cadherin internalization. Our further data revealed that Src-mediated VE-cadherin phosphorylation at Tyr658 was involved in C. pneumoniae infection-induced internalization of VE-cadherin, VEC hyperpermeability and monocyte TEM. Taken together, our data indicate that C. pneumoniae infection promotes monocyte TEM by increasing VEC permeability via the tyrosine phosphorylation and internalization of VE-cadherin in VECs.

The novel chlamydial adhesin CPn0473 mediates the lipid raft-dependent uptake of Chlamydia pneumoniae.

Chlamydiae are Gram-negative, obligate intracellular pathogens that pose a serious threat to public health worldwide. Chlamydial surface molecules are essential for host cell invasion. The first interaction with the host cell is thereby accomplished by the Outer membrane complex protein B (OmcB) binding to heparan sulfate moieties on the host cell surface, followed by the interaction of the chlamydial polymorphic membrane proteins (Pmps) with host cell receptors. Specifically, the interaction of the Pmp21 adhesin and invasin with its human interaction partner, the epidermal growth factor receptor, results in receptor activation, down-stream signalling and finally internalization of the bacteria. Blocking both, the OmcB and Pmp21 adhesion pathways, did not completely abolish infection, suggesting the presence of additional factors relevant for host cell invasion. Here, we show that the novel surface protein CPn0473 of Chlamydia pneumoniae contributes to the binding and invasion of infectious chlamydial particles. CPn0473 is expressed late in the infection cycle and located on the infectious chlamydial cell surface. Soluble recombinant CPn0473 as well as rCPn0473-coupled fluorescent latex beads adhere to human epithelial HEp-2 cells. Interestingly, in classical infection blocking experiments pretreatment of HEp-2 cells with rCPn0473 does not attenuate adhesion but promotes dose-dependently internalization by C. pneumoniae suggesting an unusual mode of action for this adhesin. This CPn0473-dependent promotion of infection by C. pneumoniae depends on two different domains within the protein and requires intact lipid rafts. Thus, inhibition of the interaction of CPn0473 with the host cell could provide a way to reduce the virulence of C. pneumoniae.

The impact of pathogen burden on leukocyte telomere length in the Multi-Ethnic Study of Atherosclerosis.

Several infections have been linked to telomere shortening and in some cases these associations have varied by sex. We assessed the association between seropositivity to four persistent pathogens (cytomegalovirus (CMV), herpes simplex virus-1, Helicobacter pylori, Chlamydia pneumoniae), and total pathogen burden on leukocyte telomere length in a diverse US sample. Data came from the Multi-Ethnic Study of Atherosclerosis, a population-based cohort study. We utilized cross-sectional survey data, and biological samples from participants tested for pathogens and telomere length (N = 163). Linear regression was used to examine the association between seropositivity for individual pathogens as well as total pathogen burden and telomere length, adjusting for various confounders. CMV seropositivity and increased total pathogen burden level were significantly associated with shorter telomere length among females (ß = -0·1204 (standard error (s.e.) 0·06), P = 0·044) and (ß = -0·1057 (s.e. = 0·05), P = 0·033), respectively. There was no statistically significant association among males. Our findings suggest that prevention or treatment of persistent pathogens, in particular CMV, may play an important role in reducing telomere shortening over the life course among women. Future research is needed to confirm these novel findings in larger longitudinal samples.

Comparative genomic analysis of human Chlamydia pneumoniae isolates from respiratory, brain and cardiac tissues.

Chlamydia pneumoniae is an obligate intracellular bacterium implicated in a wide range of human diseases including atherosclerosis and Alzheimer's disease. Efforts to understand the relationships between C. pneumoniae detected in these diseases have been hindered by the availability of sequence data for non-respiratory strains. In this study, we sequenced the whole genomes for C. pneumoniae isolates from atherosclerosis and Alzheimer's disease, and compared these to previously published C. pneumoniae genomes. Phylogenetic analyses of these new C. pneumoniae strains indicate two sub-groups within human C. pneumoniae, and suggest that both recombination and mutation events have driven the evolution of human C. pneumoniae. Further fine-detailed analyses of these new C. pneumoniae sequences show several genetically variable loci. This suggests that similar strains of C. pneumoniae are found in the brain, lungs and cardiovascular system and that only minor genetic differences may contribute to the adaptation of particular strains in human disease.

Role of Chlamydia in Multiple Sclerosis.

Chlamydia and antibodies to them were detected by serological, molecular biological, and culture methods in the sera and cerebrospinal fluid of patients with multiple sclerosis and in the reference groups of subjects without neurological diseases. Correlations between the agent presence in the biological fluids of patients and clinical characteristics of the disease were analyzed. C. pneumoniae were more incident in the biological liquids of patients with multiple sclerosis than in healthy volunteers. On the other hand, the incidence of the agent in the patients was not high and its presence did not correlate with the clinical manifestations. C. trachomatis was equally rare in the patients and volunteers. The studies indicated the existence of a group of patients infected by C. pneumoniae in the cohort of patients with multiple sclerosis, but the impact of this agent for the disease course remains unclear.

Distinct gene signatures in aortic tissue from ApoE-/- mice exposed to pathogens or Western diet.

BACKGROUND: Atherosclerosis is a progressive disease characterized by inflammation and accumulation of lipids in vascular tissue. Porphyromonas gingivalis (Pg) and Chlamydia pneumoniae (Cp) are associated with inflammatory atherosclerosis in humans. Similar to endogenous mediators arising from excessive dietary lipids, these Gram-negative pathogens are pro-atherogenic in animal models, although the specific inflammatory/atherogenic pathways induced by these stimuli are not well defined. In this study, we identified gene expression profiles that characterize P. gingivalis, C. pneumoniae, and Western diet (WD) at acute and chronic time points in aortas of Apolipoprotein E (ApoE-/-) mice. RESULTS: At the chronic time point, we observed that P. gingivalis was associated with a high number of unique differentially expressed genes compared to C. pneumoniae or WD. For the top 500 differentially expressed genes unique to each group, we observed a high percentage (76%) that exhibited decreased expression in P. gingivalis-treated mice in contrast to a high percentage (96%) that exhibited increased expression in WD mice. C. pneumoniae treatment resulted in approximately equal numbers of genes that exhibited increased and decreased expression. Gene Set Enrichment Analysis (GSEA) revealed distinct stimuli-associated phenotypes, including decreased expression of mitochondrion, glucose metabolism, and PPAR pathways in response to P. gingivalis but increased expression of mitochondrion, lipid metabolism, carbohydrate and amino acid metabolism, and PPAR pathways in response to C. pneumoniae; WD was associated with increased expression of immune and inflammatory pathways. DAVID analysis of gene clusters identified by two-way ANOVA at acute and chronic time points revealed a set of core genes that exhibited altered expression during the natural progression of atherosclerosis in ApoE-/- mice; these changes were enhanced in P. gingivalis-treated mice but attenuated in C. pneumoniae-treated mice. Notable differences in the expression of genes associated with unstable plaques were also observed among the three pro-atherogenic stimuli. CONCLUSIONS: Despite the common outcome of P. gingivalis, C. pneumoniae, and WD on the induction of vascular inflammation and atherosclerosis, distinct gene signatures and pathways unique to each pro-atherogenic stimulus were identified. Our results suggest that pathogen exposure results in dysregulated cellular responses that may impact plaque progression and regression pathways.

Chlamydia pneumoniae harness host NLRP3 inflammasome-mediated caspase-1 activation for optimal intracellular growth in murine macrophages.

Chlamydia pneumoniae is an obligate intracellular pathogen that replicates within a vacuole and acquires host cell nutrients. We show that C. pneumoniae utilizes host innate immune signaling NLRP3/ASC/caspase-1 inflammasome for intracellular growth. Bone marrow-derived macrophages (BMMs) secreted mature interleukin-1ß upon infection with C. pneumoniae depending on the NLRP3 inflammasome activation. Intracellular growth of C. pneumoniae was severely impaired in BMMs from Nlrp3(-/-), Asc(-/-), and Casp1(-/-) mice but not wild type or Nlrc4(-/-) mice. Furthermore defective NLRP3 inflammasome components led to accumulation of lipid droplets inside the infected BMMs, suggesting that uptake and/or utilization of lipids is disturbed in the absence of NLRP3 inflammasome activation. These results suggest C. pneumoniae has evolved to harness both host innate immune response and NLRP3 inflammasome activation, for the acquisition of essential nutrients necessary for intracellular growth. This unique property of C. pneumoniae may shed a new light on how C. pneumoniae increase the risk of atherosclerosis and metabolic syndrome.

Chlamydia pneumoniae and oxidative stress in cardiovascular disease: state of the art and prevention strategies.

Chlamydia pneumoniae, a pathogenic bacteria responsible for respiratory tract infections, is known as the most implicated infectious agent in atherosclerotic cardiovascular diseases (CVDs). Accumulating evidence suggests that C. pneumoniae-induced oxidative stress may play a critical role in the pathogenesis of CVDs. Indeed, the overproduction of reactive oxygen species (ROS) within macrophages, endothelial cells, platelets and vascular smooth muscle cells (VSMCs) after C. pneumoniae exposure, has been shown to cause low density lipoprotein oxidation, foam cell formation, endothelial dysfunction, platelet adhesion and aggregation, and VSMC proliferation and migration, all responsible for the typical pathological changes of atherosclerotic plaque. The aim of this review is to improve our insight into C. pneumoniae-induced oxidative stress in order to suggest potential strategies for CVD prevention. Several antioxidants, acting on multi-enzymatic targets related to ROS production induced by C. pneumoniae, have been discussed. A future strategy for the prevention of C. pneumoniae-associated CVDs will be to target chlamydial HSP60, involved in oxidative stress.

The effect of proatherogenic pathogens on adipose tissue transcriptome and fatty acid distribution in apolipoprotein E-deficient mice.

BACKGROUND: Chronic infections have been demonstrated to maintain low-grade systemic inflammation and associate with atherosclerosis. We studied the inflammation- and lipid homeostasis-related effects of Aggregatibacter actinomycetemcomitans (Aa) and Chlamydia pneumoniae (Cpn) infections on the epididymal and inguinal adipose tissue (AT) transcriptomes and fatty acid distribution in apolipoprotein (apo) E-deficient mice. Chow-fed apoE-deficient mice were exposed to 1) chronic intranasal infection with C. pneumoniae (Cpn group), 2) recurrent intravenous infection with A. actinomycetemcomitans (Aa group), 3) a combination of both types of infection (Cpn + Aa group), or 4) infection with the vehicle (control group). Epididymal and inguinal AT gene expression was analyzed using an Illumina Mouse WG-6 v2.0 platform and quantitative PCR (QPCR). Microarray data were analyzed using Gene Ontology enrichment analysis. AT fatty acid analysis was performed using gas-liquid chromatography. RESULTS: The transcriptomics data revealed significant enrichment in inflammation-associated biological pathways in both AT depots derived from the Aa and Cpn + Aa treated mice compared with the control group. The proportion of saturated fatty acids was higher in the inguinal AT in Aa (p = 0.027) and Cpn + Aa (p = 0.009) groups and in the epididymal AT in Aa group (p = 0.003). The proportion of polyunsaturated fatty acids was significantly lower among all Aa-infected groups in both depots. Chronic Cpn infection displayed only minor effects on transcriptomics and fatty acids of the AT depots. CONCLUSIONS: Systemic infection with A. actinomycetemcomitans activates inflammation-related biological pathways and modulates cellular lipid homeostasis. The adverse changes in adipose tissues during chronic infection may promote atherosclerosis.

Molecular cartography in acute Chlamydia pneumoniae infections--a non-targeted metabolomics approach.

Infections with Chlamydia pneumoniae cause several respiratory diseases, such as community-acquired pneumonia, bronchitis or sinusitis. Here, we present an integrated non-targeted metabolomics analysis applying ultra-high-resolution mass spectrometry and ultra-performance liquid chromatography mass spectrometry to determine metabolite alterations in C. pneumoniae-infected HEp-2 cells. Most important permutations are elaborated using uni- and multivariate statistical analysis, logD retention time regression and mass defect-based network analysis. Classes of metabolites showing high variations upon infection are lipids, carbohydrates and amino acids. Moreover, we observed several non-annotated compounds as predominantly abundant after infection, which are promising biomarker candidates for drug-target and diagnostic research.

Could past Chlamydial vascular infection promote the dissemination of Chlamydia pneumoniae to the brain?

Chlamydia pneumoniae, a pathogen responsible for respiratory tract infections, has been associated with atherosclerosis which, along with hypertension, hyperlipidemia, cardiovascular and/or cerebrovascular ischemia and stroke, is a risk factor for chronic neurological disorders. Several studies have demonstrated the ability of C. pneumoniae to disseminate from lungs to arteries through peripheral blood mononuclear cells. Once inside the vascular tissue, C. pneumoniae infection may disseminate via peripheral monocytes to the brain over the intact blood-brain barrier, and contribute to the development of chronic neurological disorders. The aim of our study was to evaluate whether past C. pneumoniae vascular infection may promote the dissemination of this microorganism to the brain, therefore we investigated the presence of C. pneumoniae in post-mortem brain tissue specimens of patients with past chlamydial vascular infection. Seventy six post-mortem brain tissue specimens from 19 patients with past chlamydial vascular infection were investigated for the presence of C. pneumoniae by immunohistochemistry, polymerase chain reaction, in situ polymerase chain reaction and in situ reverse transcription polymerase chain reaction. As control, 28 brain tissue specimens were taken from 7 age and sex matched subjects without chlamydial infection. C. pneumoniae was detected in 16 (84.2%) out of 19 patients with chlamydial vascular infection whereas it was not detected in control subjects (p= 0.0002). In conclusion, the main result of our study is the evidence that a chlamydial vascular infection can disseminate to the brain. It will be important for current and future researches to perform large-scale prospective studies on cardiovascular patients with chlamydial vascular infection in order to evaluate the long-term pathological alterations of the brain.

Chlamydia pneumoniae infection in atherosclerotic lesion development through oxidative stress: a brief overview.

Chlamydia pneumoniae, an obligate intracellular pathogen, is known as a leading cause of respiratory tract infections and, in the last two decades, has been widely associated with atherosclerosis by seroepidemiological studies, and direct detection of the microorganism within atheroma. C. pneumoniae is presumed to play a role in atherosclerosis for its ability to disseminate via peripheral blood mononuclear cells, to replicate and persist within vascular cells, and for its pro-inflammatory and angiogenic effects. Once inside the vascular tissue, C. pneumoniae infection has been shown to induce the production of reactive oxygen species in all the cells involved in atherosclerotic process such as macrophages, platelets, endothelial cells, and vascular smooth muscle cells, leading to oxidative stress. The aim of this review is to summarize the data linking C. pneumoniae-induced oxidative stress to atherosclerotic lesion development.

Dual-color bioluminescent assay using infected HepG2 cells sheds new light on Chlamydia pneumoniae and human cytomegalovirus effects on human cholesterol 7α-hydroxylase (CYP7A1) transcription.

Chlamydia pneumoniae and human cytomegalovirus (HCMV) are intracellular pathogens able to infect hepatocytes, causing an increase in serum triglycerides and cholesterol levels due to the production of inflammatory cytokines. We investigated whether these pathogens could interfere with cholesterol metabolism by affecting activity of hepatic cholesterol 7α-hydroxylase (CYP7A1) promoter. CYP7A1 is the rate-limiting enzyme responsible for conversion of cholesterol to bile acids, which represents the main route of cholesterol catabolism. A straightforward dual-reporter bioluminescent assay was developed to simultaneously monitor CYP7A1 transcriptional regulation and cell viability in infected human hepatoblastoma HepG2 cells. C. pneumoniae and HCMV infection significantly decreased CYP7A1 promoter activity in a dose-dependent manner, with maximal inhibitions of 33±10% and 32±4%, respectively, at a multiplicity of infection of 1. To support in vitro experiments, serum cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides and glucose levels were also measured in Balb/c mice infected with C. pneumoniae. Serum cholesterol and triglycerides also increased in infected mice compared with controls. Although further investigation is required, this work presents the first experimental evidence that C. pneumoniae and HCMV inhibit CYP7A1 gene transcription in the cultured human hepatoblastoma cell line.

[Role of Chlamydia trachomatis and Chlamydophila pneumoniae in damage of eye posterior segment structures].

AIM: Study the ability of Chlamydia trachomatis and Chlamydophila pneumoniae to damage structures of eye posterior segment, features of development of such infectious process, its morphological and clinical characteristics. MATERIALS AND METHODS: 6 rabbits with confirmed absence of C. trachomatis, C. pneumoniae were used in the study. 3 animals were infected with C. trachomatis culture and 3 animals--with C. pneumoniae culture. Subconjunctival and intravitreal mode of infectious agent introduction were used, as well as instillation of its culture into conjunctival sac. Microbiological diagnostics included microscopy with direct immunofluorescence, culture method and determination of antibody titers. Infectious process was studied by using ophthalmologic methods and histological examination. Observation period was 4 months. RESULTS: In all the animals a development of infectious process at early stages after the infection was confirmed. Conjunctivitis symptoms, inflammatory exudation into vitreous humor, chorioretinal inflammation loci, disorders in transparency of optical media and detachment of retina were clinical manifestations. In 2 animals infected with C. trachomatis severe panuveitis was noted. In 4 animals infectious process assumed subclinical characteristics (infection with both C. trachomatis or C. pneumoniae). In pathomorphologic studies data on the ability of C. trachomatis and C. pneumoniae to cause damage to cells of retina, pigment epithelium and choroid were obtained. CONCLUSION: C. trachomatis and C. pneumoniae may play a significant role in pathology of vitreous humor, retina, pigment epithelium and choroid.

Deficiency of XIAP leads to sensitization for Chlamydophila pneumoniae pulmonary infection and dysregulation of innate immune response in mice.

Obligate intracellular Chlamydophila pneumoniae induce apoptosis resistance in host cells to escape eradication by immune effector cells. Apoptosis resistance depends on the increased expression and stabilization of cellular inhibitor of apoptosis proteins (cIAPs) and X-linked inhibitor of apoptosis protein (XIAP). Here we investigated the role of XIAP in experimental pulmonary infection of mice with C. pneumoniae. XIAP knock out (KO) mice were sensitized for C. pneumoniae infection compared with wild type mice. XIAP was involved in lipopolysaccharide (LPS)-induced production of nitric oxide (NO) and endotoxin shock. Hyper-secretion of tumor necrosis factor-alpha and lower NO in LPS-treated KO mouse macrophages revealed its regulatory role in inflammatory responses. Unexpectedly, activating stimuli like LPS, tumor necrosis factor-alpha, or interferon-gamma very efficiently induced apoptotic cell death in KO macrophages but not in wild type macrophages. Cell survival transcription factor nuclear factor kappaB (NF-kappaB) p65 levels were reduced in lungs and pulmonary macrophages of infected KO mice. Furthermore, a reduced CD8 T cell population and their increased sensitivity for concanavalin A and chlamydial HSP60 stimulation revealed a defect in CD8 T cells in XIAP KO mice. These data demonstrated a role of XIAP for the integrity of both innate and cellular immune responses during C. pneumoniae infection.