Chlamydia pneumoniae infection in human monocytes

Chlamydia pneumoniae can infect the central nervous system via the olfactory and trigeminal nerves and contributes to Alzheimer's disease risk

Chlamydia pneumoniae is a respiratory tract pathogen but can also infect the central nervous system (CNS). Recently, the link between C. pneumoniae CNS infection and late-onset dementia has become increasingly evident. In mice, CNS infection has been shown to occur weeks to months after intranasal inoculation. By isolating live C. pneumoniae from tissues and using immunohistochemistry, we show that C. pneumoniae can infect the olfactory and trigeminal nerves, olfactory bulb and brain within 72 h in mice. C. pneumoniae infection also resulted in dysregulation of key pathways involved in Alzheimer’s disease pathogenesis at 7 and 28 days after inoculation. Interestingly, amyloid beta accumulations were also detected adjacent to the C. pneumoniae inclusions in the olfactory system. Furthermore, injury to the nasal epithelium resulted in increased peripheral nerve and olfactory bulb infection, but did not alter general CNS infection. In vitro, C. pneumoniae was able to infect peripheral nerve and CNS glia. In summary, the nerves extending between the nasal cavity and the brain constitute invasion paths by which C. pneumoniae can rapidly invade the CNS likely by surviving in glia and leading to Aβ deposition.

Chronic testicular Chlamydia muridarum infection impairs mouse fertility and offspring development†

With approximately 131 million new genital tract infections occurring each year, Chlamydia is the most common sexually transmitted bacterial pathogen worldwide. Male and female infections occur at similar rates and both cause serious pathological sequelae. Despite this, the impact of chlamydial infection on male fertility has long been debated, and the effects of paternal chlamydial infection on offspring development are unknown. Using a male mouse chronic infection model, we show that chlamydial infection persists in the testes, adversely affecting the testicular environment. Infection increased leukocyte infiltration, disrupted the blood:testis barrier and reduced spermiogenic cell numbers and seminiferous tubule volume. Sperm from infected mice had decreased motility, increased abnormal morphology, decreased zona-binding capacity, and increased DNA damage. Serum anti-sperm antibodies were also increased. When both acutely and chronically infected male mice were bred with healthy female mice, 16.7% of pups displayed developmental abnormalities. Female offspring of chronically infected sires had smaller reproductive tracts than offspring of noninfected sires. The male pups of infected sires displayed delayed testicular development, with abnormalities in sperm vitality, motility, and sperm-oocyte binding evident at sexual maturity. These data suggest that chronic testicular Chlamydia infection can contribute to male infertility, which may have an intergenerational impact on sperm quality.

Mediation of Interleukin-23 and Tumor Necrosis Factor-Driven Reactive Arthritis by Chlamydia-Infected Macrophages in SKG Mice

OBJECTIVE

ZAP-70^W163C BALB/c (SKG) mice develop reactive arthritis (ReA) following infection with Chlamydia muridarum. Since intracellular pathogens enhance their replicative fitness in stressed host cells, we examined how myeloid cells infected with C muridarum drive arthritis.

METHODS

SKG, Il17a-deficient SKG, and BALB/c female mice were infected with C muridarum or C muridarum luciferase in the genitals. C muridarum dissemination was assessed by in vivo imaging or genomic DNA amplification. Macrophages were depleted using clodronate liposomes. Anti-tumor necrosis factor (anti-TNF) and anti-interleukin-23p19 (anti-IL-23p19) were administered after infection or arthritis onset. Gene expression of Hspa5, Tgtp1, Il23a, Il17a, Il12b, and Tnf was compared in SKG mice and BALB/c mice.

RESULTS

One week following infection with C muridarum, macrophages and neutrophils were observed to have infiltrated the uteri of mice and were also shown to have carried C muridarum DNA to the spleen. C muridarum load was higher in SKG mice than in BALB/c mice. Macrophage depletion was shown to reduce C muridarum load and prevent development of arthritis. Compared with BALB/c mice, expression of Il23a and Il17a was increased in the uterine and splenic neutrophils of SKG mice. The presence of anti-IL-23p19 during infection or Il17a deficiency suppressed arthritis. Tnf was overexpressed in the joints of SKG mice within 1 week postinfection, and persisted beyond the first week. TNF inhibition during infection or at arthritis onset suppressed the development of arthritis. Levels of endoplasmic reticulum stress were constitutively increased in the joints of SKG mice but were induced, in conjunction with immunity-related GTPase, by C muridarum infection in the uterus.

CONCLUSION

C muridarum load is higher in SKG mice than in BALB/c mice. Whereas proinflammatory IL-23 produced by neutrophils contributes to the initiation of C muridarum-mediated ReA, macrophage depletion reduces C muridarum dissemination to other tissues, tissue burden, and the development of arthritis. TNF inhibition was also shown to suppress arthritis development. Our data suggest that enhanced bacterial dissemination in macrophages of SKG mice drives the TNF production needed for persistent arthritis.

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.

A platform for studying the transfer of Chlamydia pneumoniae infection between respiratory epithelium and phagocytes

The obligate intracellular bacterium, Chlamydia pneumoniae, has been identified as a risk factor for several chronic inflammatory diseases in addition to respiratory tract infections. The dissemination of C. pneumoniae from respiratory tract to secondary sites of infection occurs via infected monocyte / macrophage line cells, in which C. pneumoniae can persist as an antibiotic-refractory phenotype. To allow more detailed studies on the epithelium-monocyte/macrophage transition of the infection, new in vitro bioassays are needed. To this end, a coculture system with human continuous cell lines was established. Respiratory epithelial HL cells were infected with C. pneumoniae and THP-1 monocytes were added into the cultures at 67 h post infection. After a 5 h coculture, THP-1 cells were collected with a biotinylated HLA antibody and streptavidin-coated magnetic beads and C. pneumoniae genome copy numbers in THP-1 determined by quantitative PCR. The assay was optimized for cell densities, incubation time, THP-1 separation technique and buffer composition, and its robustness was demonstrated by a Z' value of 0.6. The mitogen-activated protein kinase (MAPK) inhibitors: SP600125 (JNK inhibitor), SB203580 (p38 inhibitor) and FR180204 (ERK inhibitor) suppressed the transfer of C. pneumoniae from HL to THP-1 cells, making them suitable positive controls for the assay. Based on analysis of separate steps of the process, the MAPK inhibitors suppress the bacterial entry to THP-1 cells. The transfer of C. pneumoniae from epithelium to phagocytes represents a crucial step in the establishment of persistent infections by this pathogen, and the presented methods enables future studies to block this process by therapeutic means.

Cell-mediated immune response associated with Chlamydia pneumoniae infection in atherosclerotic patients

BACKGROUND

Chlamydia pneumoniae is an obligate intracellular bacterium that activates cell mediated immune responses; several investigations have demonstrated its strong implication in atherosclerosis.

OBJECTIVES

The main objective of our study was to explore the cell-mediated immune response to C. pneumoniae infection in patients with atherosclerosis by evaluating CD14, CD8 and CD4 expression.

METHODS

This investigation involved a total of 27 patients with atherosclerosis and 32 controls, among patients recruited to evaluate the association of C. pneumoniae with atherosclerosis. C. pneumoniae DNA was detected in PBMCs by nested PCR as described in our previous studies. CD4, CD8 and CD14 expression was measured by flow cytometry and data analysis was performed using FlowJo software.

RESULTS

The results revealed an increase in MFI expression of CD4, CD8 and CD14 in Cpn DNA+ subjects among both patients and healthy subject controls (CD4 Cpn DNA⁺ = 829.11 vs. CD4 Cpn DNA^- = 571.14; CD8 Cpn DNA⁺ = 1562 vs. CD8 Cpn DNA^- = 699; CD14 Cpn DNA⁺ = 1513.83 vs. CD14 Cpn DNA^- = 1170.70), with a statistically significant difference (p < 0.05). Furthermore, the comparison of CD4, CD8 and CD14 expression between Cpn DNA+ patients and Cpn DNA+ healthy subject controls showed a statistically significant increase in expression in the former group (p < 0.05).

CONCLUSION

These data provide incentive to further explore the role of C. pneumoniae in stimulating and changing mechanisms of the cell-mediated immune response induced by C. pneumoniae antigens. This may alter immune cell-mediated responses via increased expression of CD4, CD8 and CD14 during inflammation and the development of thrombosis, leading to fatal atherosclerosis.

Influence of different delivery modes on the clinical characteristics of Chlamydia trachomatis pneumonia

We analyzed the effects of delivery methods on Chlamydia trachomatis pneumonia in infants. Three hundred forty-four children hospitalized with Chlamydia trachomatis pneumonia were enrolled. They were divided into the vaginal delivery group and the cesarean delivery group. We compared and analyzed their age of onset, peripheral blood white blood cell count, liver enzymes, chlamydia trachomatis titers, and chest radiograph scores. Seventy-eight (22.7%) were delivered by a cesarean, and 266 (77.3%) were delivered vaginally. There were no statistically significant differences between groups when compared by sex and age (P > 0.05). Copy numbers and white blood cell counts in the peripheral blood of children with Chlamydia trachomatis in respiratory secretions of the vaginal delivery group were significantly higher than those of the cesarean delivery group (P < 0.05). The alanine aminotransferase and aspartate aminotransferase levels between groups were not statistically significant. Comparisons of admission chest radiography scores, discharge radiography scores, and score differences showed no statistical differences (P > 0.05).

CONCLUSION

Infants delivered by cesarean comprise approximately one-fifth of those affected. The Chlamydia trachomatis titers and peripheral blood leukocyte counts of the vaginal delivery group were higher than those of the cesarean delivery group. Age of onset, liver enzymes, pulmonary inflammation, and pneumonia absorption were not different between groups. What is Known: • Chlamydia trachomatis is an important pathogen that causes lower respiratory tract infections in infants. • C. trachomatis is primarily transmitted to infants through the infected mother, resulting in Chlamydia trachomatis pneumonia subsequently. What is New: • Vaginal delivery and cesarean delivery can result in Chlamydia trachomatis pneumonia transmission; however, cesarean delivery accounts for ~ 20% of cases. • C. trachomatis volume in the respiratory tract and the number of peripheral blood leukocytes in infants delivered vaginally were higher than those in infants delivered by cesarean.

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.

M2 Polarization of Human Macrophages Favors Survival of the Intracellular Pathogen Chlamydia pneumoniae

Intracellular pathogens have developed various strategies to escape immunity to enable their survival in host cells, and many bacterial pathogens preferentially reside inside macrophages, using diverse mechanisms to penetrate their defenses and to exploit their high degree of metabolic diversity and plasticity. Here, we characterized the interactions of the intracellular pathogen Chlamydia pneumoniae with polarized human macrophages. Primary human monocytes were pre-differentiated with granulocyte macrophage colony-stimulating factor or macrophage colony-stimulating factor for 7 days to yield M1-like and M2-like macrophages, which were further treated with interferon-γ and lipopolysaccharide or with interleukin-4 for 48 h to obtain fully polarized M1 and M2 macrophages. M1 and M2 cells exhibited distinct morphology with round or spindle-shaped appearance for M1 and M2, respectively, distinct surface marker profiles, as well as different cytokine and chemokine secretion. Macrophage polarization did not influence uptake of C. pneumoniae, since comparable copy numbers of chlamydial DNA were detected in M1 and M2 at 6 h post infection, but an increase in chlamydial DNA over time indicating proliferation was only observed in M2. Accordingly, 72±5% of M2 vs. 48±7% of M1 stained positive for chlamydial lipopolysaccharide, with large perinuclear inclusions in M2 and less clearly bordered inclusions for M1. Viable C. pneumoniae was present in lysates from M2, but not from M1 macrophages. The ability of M1 to restrict chlamydial replication was not observed in M1-like macrophages, since chlamydial load showed an equal increase over time for M1-like and M2-like macrophages. Our findings support the importance of macrophage polarization for the control of intracellular infection, and show that M2 are the preferred survival niche for C. pneumoniae. M1 did not allow for chlamydial proliferation, but failed to completely eliminate chlamydial infection, giving further evidence for the ability of C. pneumoniae to evade cellular defense and to persist in human macrophages.

Human blood monocytes support persistence, but not replication of the intracellular pathogen C. pneumoniae

Background

Intracellular pathogens have devised various mechanisms to subvert the host immune response in order to survive and replicate in host cells. Here, we studied the infection of human blood monocytes with the intracellular pathogen C. pneumoniae and the effect on cytokine and chemokine profiles in comparison to stimulation with LPS.

Results

Monocytes purified from peripheral blood mononuclear cells by negative depletion were infected with C. pneumoniae. While immunofluorescence confirmed the presence of chlamydial lipopolysaccharide (LPS) in the cytoplasm of infected monocytes, real-time PCR did not provide evidence for replication of the intracellular pathogen. Complementary to PCR, C. pneumoniae infection was confirmed by an oligonucleotide DNA microarray for the detection of intracellular pathogens. Raman microspectroscopy revealed different molecular fingerprints for infected and non-infected monocytes, which were mainly due to changes in lipid and fatty acid content. Stimulation of monocytes with C. pneumoniae or with LPS induced similar profiles of tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-6, but higher levels of IL-1β, IL-12p40 and IL-12p70 for C. pneumoniae which were statistically significant. C. pneumoniae also induced release of the chemokines MCP-1, MIP-1α and MIP-1β, and CXCL-8, which correlated with TNF-α secretion.

Conclusion

Infection of human blood monocytes with intracellular pathogens triggers altered cytokine and chemokine pattern as compared to stimulation with extracellular ligands such as LPS. Complementing conventional methods, an oligonucleotide DNA microarray for the detection of intracellular pathogens as well as Raman microspectroscopy provide useful tools to trace monocyte infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-014-0060-1) contains supplementary material, which is available to authorized users.

Comparison of Five PCR Assays for DetectingChlamydophila pneumoniaeDNA

We compared five different polymerase chain reaction (PCR) assays for the detection of Chlamydophila pneumoniae DNA using highly purified elementary bodies (EBs) and peripheral blood mononuclear cells (PBMCs) from healthy blood donors. The primers were as follows; two targeting the 16S rRNA gene, one targeting the ompA gene, one targeting the Pst-I gene, and one targeting the 53 kDa outer membrane protein gene. The 16S rRNA touchdown enzyme time release (TETR) PCR, the ompA nested PCR and the 53 kDa nested PCR were the most sensitive assays and could detect one or more EB per assay. These three PCRs also had the same reproducibility, but the minimal amount of C. pneumoniae that could be reproducibly detected (10 of 10 testing positive) was 20 EBs. In a sample of specimens from healthy blood donors, we found 5 of 77 (6.5%) PBMCs specimens to have C. pneumoniae DNA according to the nested ompA PCR. Specimens with the 16S rRNA TETR and 53 kDa nested assays were found to have C. pneumoniae DNA 7 of 77 (9.1%) and 18 of 77 (23.4%) specimens, respectively. The other two assays failed to detect even a single positive. However, the detection rate decreased with repeated testing of the same samples. Our newly designed 53 kDa nested PCR may be as useful as the other four recommended PCR assays and may be a more useful assay for the detection of C. pneumoniae DNA from PBMCs.

Intracellular survival and persistence of Chlamydia muridarum is determined by macrophage polarization

Macrophages can display a number of distinct phenotypes, known collectively as polarized macrophages. The best defined of these phenotypes are the classically-activated, interferon gamma (IFNγ)/LPS induced (M1) and alternatively-activated, IL-4 induced (M2) macrophages. The goal of this study is to characterize macrophage-Chlamydia interactions in the context of macrophage polarization. Here we use Chlamydia muridarum and murine bone-marrow derived macrophages to show Chlamydia does not induce M2 polarization in macrophages as a survival strategy. Unexpectedly, the infection of macrophages was silent with no upregulation of M1 macrophage-associated genes. We further demonstrate that macrophages polarized prior to infection have a differential capacity to control Chlamydia. M1 macrophages harbor up to 40-fold lower inclusion forming units (IFU) than non-polarized or M2 polarized macrophages. Gene expression analysis showed an increase in 16sRNA in M2 macrophages with no change in M1 macrophages. Suppressed Chlamydia growth in M1 macrophages correlated with the induction of a bacterial gene expression profile typical of persistence as evident by increased Euo expression and decreased Omp1 and Tal expression. Observations of permissive Chlamydia growth in non-polarized and M2 macrophages and persistence in M1 macrophages were supported through electron microscopy. This work supports the importance of IFNγ in the innate immune response to Chlamydia. However, demonstration that the M1 macrophages, despite an antimicrobial signature, fail to eliminate intracellular Chlamydia supports the notion that host–pathogen co-evolution has yielded a pathogen that can evade cellular defenses against this pathogen, and persist for prolonged periods of time in the host.

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.

Doxycycline suppresses Chlamydia pneumoniae-mediated increases in ongoing immunoglobulin E and interleukin-4 responses by peripheral blood mononuclear cells of patients with allergic asthma

OBJECTIVES

Chlamydia pneumoniae, an obligate intracellular bacterium, has been associated with asthma and the induction of immunoglobulin E (IgE) responses. Whereas tetracyclines have anti-chlamydial activity, their effect on human IgE responses to C. pneumoniae has not been studied.

METHODS

Peripheral blood mononuclear cells (PBMCs) from serum IgE+ allergic asthmatic subjects (n = 11) and healthy controls (n = 12) were infected with C. pneumoniae and cultured for 12 days with or without doxycycline (0.01-1.0 mg/L). IgE, interferon (IFN)-γ and interleukin (IL)-4 levels in supernatants were determined on days 1-12 post-infection, and C. pneumoniae DNA copy numbers in PBMC culture were measured on day 2 (quantitative PCR).

RESULTS

C. pneumoniae-infected PBMCs from allergic asthmatic individuals had increased levels of IgE in supernatants compared with uninfected PBMCs (520% on day 10 post-infection, P = 0.008). IgE levels in PBMC cultures from controls were undetectable (<0.3 ng/mL). Increases in C. pneumoniae-induced IgE in asthmatics correlated with those of C. pneumoniae-induced IL-4 (r = 0.98; P < 0.001), but not with IFN-γ. The addition of doxycycline (1.0 mg/L) to the culture strongly suppressed the production of IgE (>70%, P = 0.04) and IL-4 (75%, P = 0.018), but not IFN-γ. The suppressive effect on IL-4 production remained significant even at concentrations of doxycycline that were subinhibitory (0.01 mg/L) for C. pneumoniae. In both asthmatic participants and controls, no significant effect of doxycycline on DNA copy numbers of C. pneumoniae was observed.

CONCLUSIONS

Doxycycline suppressed the C. pneumoniae-induced production of IgE and IL-4, but not IFN-γ, in PBMCs from IgE+ allergic asthmatic subjects. These findings resulted from the immunomodulatory anti-allergic properties of tetracyclines.

A new look at chronicChlamydiainfections and the role of the MHC/HLA in diseases of the CNS

Chlamydia has attracted increased attention as a possible cause of atheromatous plaques, cerebrovascular diseases, multiple sclerosis, Alzheimer’s disease and schizophrenia. The Chlamydia species are obligate intracellular parasites. The unique biphasic life cycle of Chlamydia permits the parasite to persist in cells for years. Acute Chlamydia infections can be recognized serologically in the peripheral blood through observation of rising antibody titers or molecularly using various PCR methods. However, the identification of chronic Chlamydia infection is hampered by many hurdles. This has initiated controversial discussions about the true involvement of Chlamydia, particularly in the CNS. The aspects of the discussion will be inspected as well as the vulnerability of the neuronal MHC to immune reactions.

Jurkat cell proliferation is suppressed by Chlamydia (Chlamydophila) pneumoniae infection accompanied with attenuation of phosphorylation at Thr389 of host cellular p70S6K

Chlamydia (Chlamydophila) pneumoniae infects T lymphocytes and multiplies within them. Our previous studies have indicated that C. pneumoniae infection suppresses proliferation of peripheral blood mononuclear cells stimulated with Staphylococcus-enterotoxin B; however, the mechanism of suppression was unclear. In this study, we explored the molecular mechanism involved in C. pneumoniae infection by using human acute T cell leukemia cell line, Jurkat E6-1. Proliferation of Jurkat cells was suppressed in an m.o.i.-dependent manner by C. pneumoniae infection. The suppression by the infection was particularly evident during the initial 24h of the infection, and down modulation of cyclin D3 protein levels were observed at the same time period by immunoblot analysis. The suppression of the Jurkat cell proliferation and the down modulation of cyclin D3 protein level were only induced by viable C. pneumoniae infection, not by exposure to UV-killed or heat-killed C. pneumoniae. Phosphorylations at Thr308 and Ser473 of AKT were induced by C. pneumoniae infection; however, phosphorylation at Thr389 of the downstream kinase, p70S6K was inhibited by unidentified mechanism associated with C. pneumoniae infection. Taking into account that G1 arrest of the C. pneumoniae infected Jurkat cells were not observed and that p70S6K is one of the most important regulators of protein synthesis, it was suggested that the suppression of Jurkat cell proliferation by C. pneumoniae was at least in part mediated by down modulation of protein synthesis through attenuation of Thr389 phosphorylation of p70S6K.

Chlamydia persistence -- a tool to dissect chlamydia--host interactions

Under stress, chlamydiae can enter a non-infectious but viable state termed persistence. In the absence of a tractable genetic system, persistence induction provides an important experimental tool with which to study these fascinating organisms. This review will discuss examples of: i) persistence studies that have illuminated critical chlamydiae/host interactions; and ii) novel persistence models that will do so in the future.

Analysis of Chlamydia pneumoniae infection in mononuclear cells by reverse transcription-PCR targeted to chlamydial gene transcripts

Chlamydia pneumoniae (C. pneumoniae) is an important etiological agent of respiratory infections including pneumonia. C. pneumoniae DNA can be detected in peripheral blood mononuclear cells indicating that monocytes can assist the spread of infection to other anatomical sites. Persistent infection established at these sites could promote inflammation and enhance pathology. Thus, the mononuclear cells are in a strategic position in the development of persistent infection. To investigate the intracellular replication and fate of C. pneumoniae in mononuclear cells, we have established an in vitro model in the human Mono Mac 6 cell line. In the present study, we analyzed the transcription of 11 C. pneumoniae genes in Mono Mac 6 cells during infection by real-time RT-PCR. Our results suggest that the transcriptional profile of the studied genes in monocytes is different from that seen in epithelial cells. Furthermore, our study shows that genes related to secretion are transcribed, and secreted bacterial proteins are also translated during infection of monocytes, creating novel opportunities for the management of chlamydial infection of monocytes.

Chlamydiales and the innate immune response: friend or foe?

Pathogenicity of Chlamydia and Chlamydia-related bacteria could be partially mediated by an enhanced activation of the innate immune response. The study of this host pathogen interaction has proved challenging due to the restricted in vitro growth of these strict intracellular bacteria and the lack of genetic tools to manipulate their genomes. Despite these difficulties, the interactions of Chlamydiales with the innate immune cells and their effectors have been studied thoroughly. This review aims to point out the role of pattern recognition receptors and signal molecules (cytokines, reactive oxygen species) of the innate immune response in the pathogenesis of chlamydial infection. Besides inducing clearance of the bacteria, some of these effectors may be used by the Chlamydia to establish chronic infections or to spread. Thus, the induced innate immune response seems to be variable depending on the species and/or the serovar, making the pattern more complex. It remains crucial to determine the common players of the innate immune response in order to help define new treatment strategies and to develop effective vaccines. The excellent growth in phagocytic cells of some Chlamydia-related organisms such as Waddlia chondrophila supports their use as model organisms to study conserved features important for interactions between the innate immunity and Chlamydia.

Chlamydia pneumoniae infection suppresses Staphylococcus enterotoxin B-induced proliferation associated with down-expression of CD25 in lymphocytes

Chlamydia pneumoniae (Chlamydophila pneumoniae) infects lymphocytes and modulates their immune functions; this is critical in the development of chronic inflammatory diseases associated with this pathogen. Therefore, to clarify this immune modulation due to C. pneumoniae infection, the effect of this infection on the proliferation of human peripheral blood lymphocytes was examined. Lymphocytes were proliferated by stimulation with Staphylococcus aureus enterotoxin B, and the cell number was increased up to 3 times the unstimulated lymphocyte number. Further, induction of CD25 expression was observed in 55.8% of lymphocytes. Infection with C. pneumoniae suppressed the proliferation of almost half the lymphocytes induced by stimulation with S. aureus enterotoxin B, and CD25 induction was inhibited in 64.7% of lymphocytes. Inhibition of CD25 expression was observed in both infected and uninfected lymphocytes in culture. However, the expression of VLA4 was not affected by C. pneumoniae infection. Furthermore, inhibition was observed only by infection with viable C. pneumoniae and not by the heat-killed bacteria. These results suggest that C. pneumoniae affects lymphocyte function by inhibiting proliferation and CD25 expression in response to immunological stimulation, possibly via humoral mediator(s).

Isolation of Chlamydia pneumoniae from serum samples of the patients with acute coronary syndrome

BACKGROUND

Limited body of evidence suggests that lipopolysaccharide of C. pneumoniae as well as C. pneumoniae-specific immune complexes can be detected and isolated from human serum. The aim of this study was to investigate the presence of viable elementary bodies of C.pneumoniae in serum samples of patients with acute coronary syndrome and healthy volunteers.

MATERIAL AND METHODS

Serum specimens from 26 healthy volunteers and 56 patients with acute coronary syndrome were examined subsequently by serological (C.pneumoniae-specific IgA and IgG), PCR-based and bacteriological methods. Conventional, nested and TaqMan PCR were used to detect C.pneumoniae genetic markers (ompA and 16S rRNA) in DNA from serum specimens extracted with different methods. An alternative protocol which included culturing high-speed serum sediments in HL cells and further C.pneumoniae growth evaluation with immunofluorescence analysis and TaqMan PCR was established. Pellet fraction of PCR-positive serum specimens was also examined by immunoelectron microscopy.

RESULTS

Best efficiency of final PCR product recovery from serum specimens has been shown with specific C. pneumoniae primers using phenol-chloroform DNA extraction protocol. TaqMan PCR analysis revealed that human serum of patients with acute coronary syndrome may contain genetic markers of C. pneumoniae with bacterial load range from 200 to 2000 copies/ml serum. However, reliability and reproducibility of TaqMan PCR were poor for serum specimens with low bacterial copy number (<200 /ml). Combination of bacteriological, immunofluorescence and PCR- based protocols applied for the evaluating HL cells infected with serum sediments revealed that 21.0 % of the patients with acute coronary syndrome have viable forms C.pneumoniae in serum. The detection rate of C.pneumoniae in healthy volunteers was much lower (7.7%). Immunological profile of the patients did not match accurately C.pneumoniae detection rate in serum specimens. Elementary bodies of C.pneumoniae with typical ultrastructural characteristics were also identified in serum sediments using immunoelectron microscopy.

CONCLUSIONS

Viable forms C. pneumoniae with typical electron microscopic structure can be identified and isolated from serum specimens of the patients with acute coronary syndrome and some healthy volunteers. Increased detection rate of C. pneumoniae in serum among the patients with an acute coronary syndrome may contribute towards enhanced pro-inflammatory status in cardiovascular patients and development of secondary complications of atherosclerosis.

Chlamydophila pneumoniae downregulates MHC-class II expression by two cell type-specific mechanisms

Chlamydophila pneumoniae was shown to prevent IFN gamma-inducible upregulation of MHC-class II molecules by secreting chlamydial protease-like activity factor (CPAF) into the cytosol of those host cells which support the complete bacterial replication cycle. CPAF acts by degrading upstream stimulatory factor 1 (USF-1). However, in cells like bone marrow-derived macrophages (BMM), which restrict chlamydial replication, we show that CPAF expression is barely detectable and the expression of USF-1 is induced upon infection with C. pneumoniae. Nevertheless, the infection still reduced base line and prevented IFN gamma-inducible MHC-class II expression. Similar results were obtained with heat-inactivated C. pneumoniae. In contrast, reduction of MHC-class II molecules was not observed in MyD88-deficient BMM. Reduction of IFN gamma-inducible MHC-class II expression by C. pneumoniae in BMM was mediated in part by the MAP-kinase p38. Infection of murine embryonic fibroblasts (MEF) with C. pneumoniae, which allow chlamydial replication, induced the expression of CPAF and decreased USF-1 and MHC-class II expression. Treatment of these cells with heat-inactivated C. pneumoniae reduced USF-1 and MHC-class II expression to a much lower extent. In summary, C. pneumoniae downregulates MHC-class II expression by two cell type-specific mechanisms which are either CPAF-independent and MyD88-dependent like in BMM or CPAF-dependent like in MEFs.

Chlamydia trachomatis antigens in enteroendocrine cells and macrophages of the small bowel in patients with severe irritable bowel syndrome

BACKGROUND

Inflammation and immune activation have repeatedly been suggested as pathogentic factors in irritable bowel syndrome (IBS). The driving force for immune activation in IBS remains unknown. The aim of our study was to find out if the obligate intracellular pathogen Chlamydia could be involved in the pathogenesis of IBS.

METHODS

We studied 65 patients (61 females) with IBS and 42 (29 females) healthy controls in which IBS had been excluded. Full thickness biopsies from the jejunum and mucosa biopsies from the duodenum and the jejunum were stained with a monoclonal antibody to Chlamydia lipopolysaccharide (LPS) and species-specific monoclonal antibodies to C. trachomatis and C. pneumoniae. We used polyclonal antibodies to chromogranin A, CD68, CD11c, and CD117 to identify enteroendocrine cells, macrophages, dendritic, and mast cells, respectively.

RESULTS

Chlamydia LPS was present in 89% of patients with IBS, but in only 14% of healthy controls (p < 0.001) and 79% of LPS-positive biopsies were also positive for C. trachomatis major outer membrane protein (MOMP). Staining for C. pneumoniae was negative in both patients and controls. Chlamydia LPS was detected in enteroendocrine cells of the mucosa in 90% of positive biopsies and in subepithelial macrophages in 69% of biopsies. Biopsies taken at different time points in 19 patients revealed persistence of Chlamydia LPS up to 11 years. The odds ratio for the association of Chlamydia LPS with presence of IBS (43.1; 95% CI: 13.2-140.7) is much higher than any previously described pathogenetic marker in IBS.

CONCLUSIONS

We found C. trachomatis antigens in enteroendocrine cells and macrophages in the small bowel mucosa of patients with IBS. Further studies are required to clarify if the presence of such antigens has a role in the pathogenesis of IBS.

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.

Serum chlamydial lipopolysaccharide as a prognostic factor for a new cardiovascular event

BACKGROUND

Infections caused by Chlamydia pneumoniae are considered to participate in inflammatory processes leading to coronary artery disease. After a primary infection, the bacteria remain dormant intracellularly causing a chronic inflammatory stimulus.

MATERIALS AND METHODS

Blood samples were obtained from 235 patients with acute myocardial infarction (AMI) and 108 patients with unstable angina pectoris (UA). We evaluated the prognostic significance of bacterial and viral antibody titers, serum troponin T, C-reactive protein, and chlamydial lipopolysaccharide (cLPS) concentrations during acute coronary syndrome of patients with AMI and UA for cardiovascular death and new UA and AMI that required hospital care during a 6-year follow-up.

RESULTS

Serum cLPS levels correlated with C-reactive protein and serum troponin T concentrations during acute coronary events. Patients with AMI had significantly higher serum concentration of cLPS compared with patients with UA. Enterovirus antibody titers and cholesterol-lowering therapy at admission of the index event were negatively correlated with cLPS concentration (r = -.198, P = .0003 and r = -.26, P = .019, respectively). The presence of circulating cLPS was associated with a hazard ratio of 2.04 for a new cardiovascular event during the follow-up period (P = .006). The area under the curve in the receiver operating graph was .572.

CONCLUSION

cLPS is evidently liberated from the infected atherosclerotic tissue during an acute coronary event. Our study supports the view that inflammation caused by C. pneumoniae infection is an important but as yet poorly understood factor in the development of atherosclerosis and may play a role in acute vascular events.

Novel Parachlamydia acanthamoebae quantification method based on coculture with amoebae

Parachlamydia acanthamoebae, belonging to the order Chlamydiales, is an obligately intracellular bacterium that infects free-living amoebae and is a potential human pathogen. However, no method exists to accurately quantify viable bacterial numbers. We present a novel quantification method for P. acanthamoebae based on coculture with amoebae. P. acanthamoebae was cultured either with Acanthamoeba spp. or with mammalian epithelial HEp-2 or Vero cells. The infection rate of P. acanthamoebae (amoeba-infectious dose [AID]) was determined by DAPI (4',6-diamidino-2-phenylindole) staining and was confirmed by fluorescent in situ hybridization. AIDs were plotted as logistic sigmoid dilution curves, and P. acanthamoebae numbers, defined as amoeba-infectious units (AIU), were calculated. During culture, amoeba numbers and viabilities did not change, and amoebae did not change from trophozoites to cysts. Eight amoeba strains showed similar levels of P. acanthamoebae growth, and bacterial numbers reached ca. 1,000-fold (10(9) AIU preculture) after 4 days. In contrast, no increase was observed for P. acanthamoebae in either mammalian cell line. However, aberrant structures in epithelial cells, implying possible persistent infection, were seen by transmission electron microscopy. Thus, our method could monitor numbers of P. acanthamoebae bacteria in host cells and may be useful for understanding chlamydiae present in the natural environment as human pathogens.

Chlamydia pneumoniae growth inhibition in cells by the steroid receptor antagonist RU486 (mifepristone)

Since steroids are powerful anti-inflammatory agents and increase susceptibility to a variety of infections, including Chlamydia (Chlamydophila) pneumoniae respiratory tract infections, the effect of the steroid receptor antagonist RU486 (mifepristone) on C. pneumoniae growth in epithelial HEp-2 cells was examined. Treatment of HEp-2 cells with RU486 significantly inhibited the growth of C. pneumoniae in a dose-dependent manner. Electron microscopic studies also revealed that the treatment of infected cells with RU486 resulted in a marked destruction of infecting organisms. The addition of the host cell protein synthesis inhibitor cycloheximide to the infected cells did not alter the inhibition of C. pneumoniae growth by RU486. Pretreatment of C. pneumoniae organisms with RU486 before addition to culture also did not result in any modulation of bacterial growth in the cells. However, the binding of RU486 to C. pneumoniae organisms in cells at 24 h after infection was demonstrated by immune electron microscopy with anti-RU486 antibody. Incubation of cells with anti-RU486 antibody completely diminished the inhibition of C. pneumoniae growth by RU486. These results indicate that RU486 may directly bind to the bacteria within cells and cause the destruction of C. pneumoniae. This novel mode of regulation of C. pneumoniae growth in cells by RU486 might provide a new approach to understanding complicated aspects of C. pneumoniae infection.

Role of Chlamydia pneumoniae in atherosclerosis

Cardiovascular disease, resulting from atherosclerosis, is a leading cause of global morbidity and mortality. Genetic predisposition and classical environmental risk factors explain much of the attributable risk for cardiovascular events in populations, but other risk factors for the development and progression of atherosclerosis, which can be identified and modified, may be important therapeutic targets. Infectious agents, such as Chlamydia pneumoniae, have been proposed as contributory factors in the pathogenesis of atherosclerosis. In the present review, we consider the experimental evidence that has accumulated over the last 20 years evaluating the role of C. pneumoniae in atherosclerosis and suggest areas for future research in this field.

Severity of carotid atherosclerosis unrelated to Chlamydia pneumoniae infection in acute ischemic stroke patients: a clinicopathological study

BACKGROUND

Both clinical and pathological alterations of the carotid arteries were correlated with Chlamydia pneumoniae infection in 67 acute ischemic stroke patients with severe neurological symptoms.

METHODS

In the clinical study, intima-media thickness (IMT) of the common carotid arteries was determined in vivo by B-mode ultrasound measurement and C. pneumoniae-specific IgG and IgA responses were detected. In the pathological study, the absolute wall thickness of the common, internal and external carotid arteries was measured postmortem in specimens obtained at the autopsy of patients who died due to complications of acute stroke. In the atherosclerotic plaques of the autopsy specimens, C. pneumoniae genomic DNA was detected by polymerase chain reaction amplification.

RESULTS

The Spearman's rho correlation coefficient of IMT with the average wall thickness of the common, internal and external carotid arteries was 0.51 (p = 0.002), 0.34 (p = 0.052) and 0.58 (p < 0.001), respectively. Anti-C. pneumoniae IgG and IgA antibodies were detected in 43 (73%) and 29 (49%) patients, but neither antibody marker correlated with IMT (median: 0.91 mm in IgG positives vs. 0.90 mm in IgG negatives, p = 0.86; 0.88 mm in IgA positives vs. 0.90 mm in IgA negatives, p = 0.53). The presence of C. pneumoniae DNA was detected in the carotid plaques of 21 (54%) of the 39 tested patients, independently of either IMT values or the average wall thickness of all carotid arteries.

CONCLUSIONS

In acute ischemic stroke patients, C. pneumoniae infection was frequently detected in the arteriosclerotic plaques of the carotid arteries but it did not correlate with the severity of carotid arteriosclerosis.

Differential effects of Chlamydia pneumoniae infection on cytokine levels in human T lymphocyte- and monocyte-derived cell cultures

Continuous cultures of human lymphocyte- and monocyte-derived cell lines were examined for levels of immunoregulatory cytokines important in resistance to the intracellular opportunistic bacterium Chlamydia pneumoniae (Cp), a ubiquitous pathogen widely disseminated in the population and hypothesized to be involved in chronic inflammatory diseases such as atherosclerosis and neurological diseases like multiple sclerosis and Alzheimer's disease. The results of this study showed that the continuous human T lymphocyte cell line MOLT-4 and the continuous monocytic cell line THP-1 were readily infected by Cp in vitro as shown by immunofluorescence microscopy for Cp lipopolysaccharide (LPS). The 16S rRNA expression determined by real-time RT-PCR increased rapidly after infection of either cell line with these bacteria. The THP-1 cells infected with Cp showed increased levels of the immunoregulatory cytokine IL-12 and also of TNFalpha and IL-10 compared to cultures stimulated with heat-killed Cp (KCp) or Escherichia coli LPS as a control. Stimulation of MOLT-4 cells with KCp or E. coli LPS also induced the Th1 cytokines IFNgamma and IL-12 and the Th2 cytokine IL-10, but infection with viable Cp induced higher Th1 cytokine levels. These results suggest that Cp infection induces a predominant Th1 cytokine profile by T cells, in addition to induction of TNFalpha by monocytes/macrophages. Such effects are likely involved in antibacterial immunity against Cp infection.

Chlamydophila (Chlamydia) pneumoniae Infection of Human Astrocytes and Microglia in Culture Displays an Active, Rather than a Persistent, Phenotype

BACKGROUND

The intracellular pathogen Chlamydia pneumoniae can cause persistent infections during which its morphologic, molecular, and pathogenic characteristics differ importantly from those of active infection. This bacterium was identified within astrocytes and microglia in the brain of late-onset Alzheimer disease patients. We investigated whether infection of these two host cell types displays an active or persistent growth phenotype.

METHODS

The human astrocytoma and microglioma cell lines U-87 MG and CHME-5 (respectively) and the human epithelial cell line HEp-2 were infected by the standard method with C pneumoniae strain AR-39. Cultures were harvested at 24, 48, and 72 hours postinfection and subjected to analysis of inclusion morphology. DNA and RNA were prepared from portions of each infected culture sample and analyzed for relative chromosome accumulation and presence or absence of several specific bacterial mRNAs.

RESULTS

Astrocytes and microglial cells infected in vitro with C pneumoniae displayed inclusions that were indistinguishable from those characteristic of active infection of the standard HEp-2 host cell line. Real time polymerase chain reaction (PCR) showed that the relative accumulation of chlamydial chromosome over time during infection of these two cell lines also was virtually identical to that in actively infected HEp-2 cells. Reverse transcriptase PCR (RT-PCR) analyses showed that mRNA from ftsK, pyk, and other chlamydial genes whose expression is abrogated during persistent infection were easily identifiable in infected CHME-5 and U-87 MG cells.

CONCLUSIONS

In cultured human astrocytes and microglia, C pneumoniae displays an active, not a persistent, growth phenotype. This indicates normal passage through the developmental cycle with its probable concomitant destruction by lysis of some portion of host cells at the termination of that cycle.

Effect of nitric oxide on the growth of Chlamydophila pneumoniae

Chlamydophila pneumoniae is an important human intracellular pathogen; however, the pathogenesis of C. pneumoniae infection is poorly understood and the immune control mechanism versus host cells is not completely known. The role of the nitric oxide (NO) synthase pathway in inhibiting the ability of C. pneumoniae to infect macrophage J774 cells and the ability of NO to damage isolated C. pneumoniae were investigated. Exposure of infected cultures to recombinant murine gamma interferon (MurIFN-gamma) resulted in increased production of NO and reduced viability. Addition of 2-(N,N-diethylamino)-diazenolase-2-oxide before infection of J774 cells or during chlamydial cultivation released NO, both resulting in a reduction in the viability of C. pneumoniae in a dose-dependent way. These results indicate that immune control of chlamydial growth in murine macrophage cells may trigger a mechanism that includes NO release with effects on the multiplication of the microorganism, thus suggesting that NO may play a role in preventing the systemic spread of Chlamydia.

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.

Drosophila melanogaster S2 cells: a model system to study Chlamydia interaction with host cells

Chlamydia spp. are major causes of important human diseases, but dissecting the host-pathogen interactions has been hampered by the lack of bacterial genetics and the difficulty in carrying out forward genetic screens in mammalian hosts. RNA interference (RNAi)-based methodologies for gene inactivation can now be easily carried out in genetically tractable model hosts, such as Drosophila melanogaster, and offer a new approach to identifying host genes required for pathogenesis. We tested whether Chlamydia trachomatis infection of D. melanogaster S2 cells recapitulated critical aspects of mammalian cell infections. As in mammalian cells, C. trachomatis entry was greatly reduced by heparin and cytochalasin D. Inclusions were formed in S2 cells, acquired Golgi-derived sphingolipids, and avoided phagolysosomal fusion. Elementary body (EB) to reticulate body (RB) differentiation was observed, however, no RB to EB development or host cell killing was observed. RNAi-mediated inactivation of Rac, a Rho GTPase recently shown to be required for C. trachomatis entry in mammalian cells, inhibits C. trachomatis infection in S2 cells. We conclude that Drosophila S2 cells faithfully mimic early events in Chlamydia host cell interactions and provides a bona fide system to systematically dissect host functions important in the pathogenesis of obligate intracellular pathogens.

Novel enzyme immunoassay utilizing lipopolysaccharide-binding protein as a capture molecule for the measurement of chlamydial lipopolysaccharide in serum

Chlamydia pneumoniae causes respiratory tract infections. It has a tendency to cause persistent infections, which have been associated with several chronic diseases (e.g., atherosclerosis). At present, there is no reliable method for the diagnosis of chronic C. pneumoniae infection. We developed a novel enzyme immunoassay (EIA) for the quantification of chlamydial lipopolysaccharide (cLPS) in human serum. Serum cLPS was solubilized with detergent and then captured by LPS-binding protein (LBP). LBP-LPS complexes were bound to the solid phase with anti-cLPS monoclonal antibody, and the bound complexes were detected with anti-LBP antibodies. The new method was used to quantify serum cLPS in acute coronary syndrome (ACS) patients (n = 102) and their healthy controls. cLPS was detected in 77.5% of ACS patients and in 52% of controls (P < .001) with geometric mean concentrations of 1.87 and 0.61 microg/mL (P < .001), respectively. The novel cLPS EIA method will provide a potential diagnostic tool for C. pneumoniae infection.

Presence of Chlamydia pneumoniae in patients with and without atherosclerosis

Data published over the past decade show that Chlamydia pneumoniae is likely associated with the development of atherosclerosis. The aim of this study was to ascertain whether C. pneumoniae infections occur more frequently in patients with atherosclerosis than in healthy subjects. A total of 517 persons were studied. Serum samples, leukocytes, and tissue samples were assayed for the presence of C. pneumoniae-specific IgG and IgA antibodies and C. pneumoniae DNA. C. pneumoniae DNA was found in renal, iliac, and brachial vessels, but it was not detected in radial arteries. C. pneumoniae DNA was found most often in directional coronary atherectomy tissue specimens (11/41, 26.8%), but it was also found in the leukocytes of 14.9% (28/188) of patients with atherosclerosis and 24.6% (28/114) of patients without atheroma changes in vessels. Specific IgG and IgA antibodies were present in 63.8 and 49.9% of atheroma patients, respectively. The prevalence of C. pneumoniae antibodies differs significantly in patients with and without atherosclerosis (for IgG, p=0.002, and for IgA, p=0.006). The identification of persons with chlamydial infection of atherosclerotic arteries necessitates the examination of vascular tissues obtained during revascularization procedures. Serological investigation alone cannot identify individuals with vascular chlamydial infections. Detection of C. pneumoniae DNA in peripheral blood mononuclear cells does not seem to be the exclusive marker of persistent vascular infection. A more easily accessible parameter that allows prediction of chlamydial vascular infection is required.

Effects of repeated Chlamydia pneumoniae inoculations on aortic lipid accumulation and inflammatory response in C57BL/6J mice

Chlamydia pneumoniae is a common respiratory tract pathogen, and persistent infections have been associated with atherosclerosis. We studied the effects of repeated chlamydial inoculations on the inflammatory response and on aortic lipid accumulation in C57BL/6J mice. Mice fed a diet supplemented with 0.2% cholesterol were infected three or six times with C. pneumoniae every fourth week. Sera and lungs were analyzed for inflammatory responses, lung tissues were tested for the presence of C. pneumoniae DNA and RNA, and intimal lipid accumulation in the aortic sinus was quantified. High levels of chlamydial heat shock protein 60 (Hsp60) immunoglobulin G2c subclass antibodies were detected in all of the infected mice, and a positive and statistically significant correlation was found between these antibodies and autoantibodies against mouse Hsp60. Both Hsp60 antibody levels correlated with the severity of lung tissue inflammation. The cholesterol supplement in the diet had no effect on serum cholesterol levels. Significantly larger intimal lipid lesions were seen in the mouse group infected six times (6,542 mum(2)) than in the control group (1,376 mum(2); P = 0.034). In conclusion, repeated inoculations increased aortic sinus lipid accumulation in normocholesterolemic mice. The correlation between the antibodies to mouse and chlamydial Hsp60 proteins and their association with lung inflammation further support the theory of the development of an autoimmune response against heat shock proteins after repeated chlamydial infections.

Depletion of resident Chlamydia pneumoniae through leukoreduction by filtration of blood for transfusion

Current studies indicate that a significant percentage of healthy blood donors carry Chlamydia pneumoniae in their blood. Although the clinical significance of such findings is unknown, eradication of such bacteria from blood components may contribute to transfusion safety. Deletion of C. pneumoniae in Red Blood Cell (RBC) units was accomplished through leukoreduction by filtration. The presence of bacteria in RBC units before and after leukoreduction was assessed by real-time PCR using primers specific for C. pneumoniae 16S rRNA. The eluates of filters used for leukoreduction were also assessed by PCR and immunostaining with fluorescein isothiocyanate-conjugated chlamydial monoclonal antibodies specific for C. pneumoniae determination. Nineteen of 30 RBC units tested showed the presence of C. pneumoniae DNA. Leukofiltration resulted in a marked reduction of leukocytes as well as C. pneumoniae in terms of bacterial number and positive rate for the bacteria. The eluates of filters showed trapped bacteria determined by both PCR and immunostaining assays. Thus, leukoreduction with a filter is an effective method to significantly reduce resident C. pneumoniae levels in RBC components but may not be completely sufficient for total eradication of this pathogen.

Successful Treatment of Postvenereal Reactive Arthritis With Synovectomy and 3 Months’ Azithromycin

BACKGROUND

The effects of antibiotic therapy on the course of postvenereal reactive arthritis have not yet been elucidated.

OBJECTIVE

The objective of this study was to observe the clinical course and outcome of synovectomy and 3 months of azithromycin therapy in patients with reactive arthritis and previously diagnosed triggering bacteria.

METHODS

We performed an open, prospective study on 20 (14 male/6 female) patients with postvenereal reactive knee arthritis, aged 36.7 +/- 14.8 years, and with 16.5 +/- 20.4 months' duration of the disease. Detection of bacteria triggers was done by polymerase chain reaction, isolation and identification, and electron microscopy. Synovectomy was performed in all patients at entry into the study. Azithromycin was given at a dose of 500 mg per day for 5 days, and then 500 mg twice a week, during a 3-month period. Patients without remission were treated with combined antibiotic therapy using a macrolide, quinolone, and tetracycline for the next 4 months. Outcome evaluations of therapeutic efficacy and azithromycin safety were done after 1 and 3 months and 2 years of follow up.

RESULTS

Remission, defined by the absence of joint swelling and tenderness, and extraarticular signs, was reached after 3 months in 15 of 20 (75.0%) patients (P = 0.025). Of 5 patients with persistent knee arthritis, remission was achieved with combined antibiotic therapy in 4. Visual analog scale scores (P < 0.01), the number of patients (P = 0.002), and the number of samples (P = 0.01) with a positive finding of bacteria or their DNA were significantly lower after 3 months of therapy. During the azithromycin therapy, there were no significant adverse effects.

CONCLUSIONS

These patients with reactive arthritis did extremely well on the regimen described. In our study group, the number of patients and the number of samples with positive findings of bacteria or their DNA were lower after the antibiotic treatment combined with surgery, although not all bacteria were eradicated. Adverse effects of prolonged azithromycin administration were insignificant. This open treatment approach is recommended but does need a study with controls.

Degradation of Chlamydia pneumoniae by peripheral blood monocytic cells

Chlamydia pneumoniae is a common human respiratory pathogen that has been associated with a variety of chronic diseases, including atherosclerosis. The role of this organism in the pathogenesis of atherosclerosis remains unknown. A key question is how C. pneumoniae is transferred from the site of primary infection to a developing atherosclerotic plaque. It has been suggested that circulating monocytes could be vehicles for dissemination of C. pneumoniae since the organism has been detected in peripheral blood monocytic cells (PBMCs). In this study we focused on survival of C. pneumoniae within PBMCs isolated from the blood of healthy human donors. We found that C. pneumoniae does not grow and multiply in cultured primary monocytes. In C. pneumoniae-infected monocyte-derived macrophages, growth of the organism was very limited, and the majority of the bacteria were eradicated. We also found that the destruction of C. pneumoniae within infected macrophages resulted in a gradual diminution of chlamydial antigens, although some of these antigens could be detected for days after the initial infection. The detected antigens present in infected monocytes and monocyte-derived macrophages represented neither chlamydial inclusions nor intact organisms. The use of {N-[7-(4-nitrobenzo-2-oxa-1,3-diazole)]}-6-aminocaproyl-d-erythro-sphingosine as a vital stain for chlamydiae proved to be a sensitive method for identifying rare C. pneumoniae inclusions and was useful in the detection of even aberrant developmental forms.

Clearance of Chlamydia pneumoniae Infection in H-2 Class I-/- Human Leucocyte Antigen-A2.1 Monochain Transgenic Mice

CD8+ T cells have been suggested to play an important role in protective immunity against pulmonary Chlamydia pneumoniae infection in mice. Moreover, several classical major histocompatibility complex class I - restricted cytotoxic CD8+ T lymphocytes (CTL) specific for C. pneumoniae- derived peptides have been identified. Here, we studied the outcome of C. pneumoniae infection in human leucocyte antigen (HLA)-A2.1 transgenic mice (HHD mice) that are only able to express a classical human class I molecule (HLA-A2.1). C. pneumoniae infection was self-restricted in HHD mice which were able to develop specific immune responses and a protective immunity against a subsequent rechallenge in a manner comparable to wildtype mice. Furthermore, accumulation of functional and C. pneumoniae-specific T cells to the site of infection was detected after challenge. Antigen processing and HLA-A2.1-dependent presentation was studied by immunizing the HHD mice with chlamydial outer protein N (CopN). Isolation of a peptide-specific CTL line from the CopN-immunized mice suggests that the HLA-A2.1 molecule can support the development of CTL response against a chlamydial protein in mice. These findings suggest that the transgenic mouse model can be used for further characterization of the HLA-A2.1-restricted CD8+ T-cell response during C. pneumoniae infection and for identification of CD8 epitopes from chlamydial antigens.

Polymorphonuclear neutrophils improve replication of Chlamydia pneumoniae in vivo upon MyD88-dependent attraction

Chlamydia pneumoniae, an obligate intracellular bacterium, causes pneumonia in humans and mice. In this study, we show that GR1+/CD45+ polymorphonuclear neutrophils (PMN) surprisingly increase the bacterial load of C. pneumoniae in vivo. Upon intranasal infection of wild-type mice, the lung weight is increased; the cytokines TNF, IL-12p40, and IFN-gamma, as well as the chemokines keratinocyte-derived chemokine, MCP-1, and MIP-2 are secreted; and GR1+/CD45+ PMN are recruited into lungs 3 days postinfection. In contrast, in infected MyD88-deficient mice, which lack a key adaptor molecule in the signaling cascade of TLRs and IL-1R family members, the increase of the lung weight is attenuated, and from the analyzed cyto- and chemokines, only IL-12p40 is detectable. Upon infection, almost no influx of inflammatory cells into lungs of MyD88-deficient mice can be observed. Six days postinfection, however, MyD88-deficient mice were able to produce TNF, IFN-gamma, keratinocyte-derived chemokine, and MCP-1 in amounts similar to wild-type mice, but failed to secrete IL-12p40 and MIP-2. At this time point, the infection increased the lung weight to a level similar to wild-type mice. Curiously, the chlamydial burden in MyD88-deficient mice 3 days postinfection is lower than in wild-type mice, a finding that can be reproduced in wild-type mice by depletion of GR1+ cells. In analyzing how PMN influence the chlamydial burden in vivo, we find that PMN are infected and enhance the replication of C. pneumoniae in epithelial cells. Thus, the lower chlamydial burden in MyD88-deficient mice can be explained by the failure to recruit PMN.

Chlamydia pneumoniae infection in HIV-positive patients: prevalence and relationship with lipid profile

OBJECTIVES

The aims of this study were to evaluate the prevalence and impact of Chlamydia pneumoniae infection in HIV-positive patients and to establish the relationship between C. pneumoniae infection and lipid profile.

METHODS

Detection of C. pneumoniae was by polymerase chain reaction (PCR) on Peripheral Blood Mononuclear Cells (PBMCs) collected from 97 HIV-positive patients. Samples were collected after overnight fast in EDTA-treated tubes. On the same day, patients were also tested for routine chemistry, HIV viral load, CD3, CD8 and CD4 cell counts and lipid profile [cholesterol, high-density lipoproteins (HDLs), low-density lipoproteins (LDLs) and triglycerides].

RESULTS

The overall prevalence of C. pneumoniae was 39%. The prevalence of C. pneumoniae was inversely related to the CD4 lymphocyte count (P=0.03). In the naive group, C. pneumoniae-positive patients had both significantly higher HIV load (71 021+/-15 327 vs. 14 753+/-14 924 HIV-1 RNA copies/mL; P=0.03) and lower CD4 cell count (348.0+/-165.4 vs. 541.7+/-294.8; P=0.04) than C. pneumoniae-negative patients. Moreover, treatment-naive patients with C. pneumoniae infection had significantly higher mean levels of cholesterol (185.3+/-56.2 vs. 124.8+/-45.9 mg/dL; P=0.01), triglycerides (117.2+/-74.7 vs. 68+/-27.6 mg/dL; P=0.04) and LDL (122.4+/-60.1 vs. 55.6+/-58 mg/dL; P=0.05) than C. pneumoniae-negative patients.

CONCLUSIONS

These data indicate that, in HIV-positive subjects, C. pneumoniae infection is relatively frequent and is associated with both low CD4 cell count and high HIV load. Furthermore, C. pneumoniae appears to be associated with hyperlipidaemia and might therefore represent a further risk factor for cardiovascolar disease in HIV-positive patients.

Age alterations in extent and severity of experimental intranasal infection with Chlamydophila pneumoniae in BALB/c mice

The intracellular bacterium Chlamydophila ("Chlamydia") pneumoniae is a pathogen for several respiratory diseases and may be a factor in the pathogenesis of chronic diseases of aging including atherosclerosis and Alzheimer's disease. We assessed whether aging is coupled with increased burden of infection in BALB/c mice after intranasal infection by C. pneumoniae. Six- and twenty-month-old BALB/c mice were infected intranasally with 5 x 10(4) inclusion forming units (IFU) or 5 x 10(5) IFU of C. pneumoniae. Lung, brain, and heart tissue were analyzed for infectious C. pneumoniae and for Chlamydophila antigen by immunohistochemistry. At both doses, aging was associated with a decreased proportion of animals that cleared infection from the lung and greater burden of infectious organism within the lung. We observed dose-dependent spread to the heart/ascending aorta in animals infected with C. pneumoniae. In mice given 5 x 10(4) IFU, spread to the heart by day 14 was only observed in old mice. By day 28, all animals inoculated with 5 x 10(4) IFU showed evidence of spread to the heart, although higher C. pneumoniae titers were observed in the hearts from old mice. In mice inoculated with 5 x 10(5) IFU, spread of C. pneumoniae to the heart was evident by day 14, with no discernible age effect. C. pneumoniae was also recovered from the central nervous system (brain and olfactory bulb) of all mice by day 28 postinfection, with higher C. pneumoniae titers in old animals than in young animals. Our results suggest that infection with C. pneumoniae may be more severe in old animals.

Chlamydia pneumoniae enhances cytokine-stimulated human monocyte matrix metalloproteinases through a prostaglandin E2-dependent mechanism

Exposure of human monocytes to Chlamydia pneumoniae resulted in a significant enhancement of matrix metalloproteinase (MMP) 1 and 9 production following stimulation with tumor necrosis factor alpha and granulocyte monocyte-colony stimulating factor. The effect of C. pneumoniae on monocyte MMPs was mediated through the induction of prostaglandin E(2). These findings may have implications for atherosclerotic plaque rupture.

Telithromycin treatment of chronic Chlamydia pneumoniae infection in C57BL/6J mice

Chronic Chlamydia pneumoniae infections have been associated with atherosclerosis, but clear knowledge about how these infections should be treated is lacking. We studied the effect of a new ketolide antibiotic, telithromycin, on chronic C. pneumoniae lung infection. Female C57BL/6J mice on a 0.2% cholesterol diet were inoculated intranasally with C. pneumoniae either two or three times every fourth week. Telithromycin was given to the mice subcutaneously at 75 mg/kg of body weight once daily for 5 or 10 days, starting at 3 days after the last inoculation. Samples were taken at 4 and 12 weeks after the last inoculation. The presence of C. pneumoniae DNA in lung tissue was demonstrated by PCR and the detection of lipid accumulation in the aortic sinus by Oil-Red-O staining. C. pneumoniae DNA positivity and inflammatory reactions in the lung tissue of the mice inoculated twice were significantly affected by treatment after both inoculations or only after the second inoculation at 12 weeks. Intimal lipid accumulation in the aortic sinus was also slightly but significantly less abundant in the mice treated after both inoculations compared to the levels in those treated only after the second inoculation for 10 days (geometric means, 823 and 4,324 microm(2), respectively; P = 0.033). No differences between the infected, untreated controls and the group inoculated three times and treated for 5 days were seen. We conclude that telithromycin is effective in preventing the development of chronic C. pneumoniae infection and intimal lipid accumulation in C56BL/6J mice when the treatment is given after each inoculation.

Production of prostaglandin E2 in monocytes stimulated in vitro by Chlamydia trachomatis, Chlamydophila pneumoniae, and Mycoplasma fermentans

Chlamydia trachomatis (CT) as well as Chlamydophila pneumoniae (CP) cause chronic inflammatory diseases in humans. Persistently infected monocytes are involved in the pathogenesis by inducing mediators of inflammation. An in vitro system of chlamydial persistence in human peripheral blood monocytes (HPBM) was used to investigate prostaglandin E(2) (PGE(2)) production and the expression of the key enzyme for prostaglandin production, cyclooxygenase-2 (COX-2). PGE(2) production was determined by PGE(2)-ELISA of HPBM-culture supernatants. Cox-2 mRNA expression was measured by real-time RT-PCR of total RNA isolated from HPBM. Both, CT and CP, stimulated PGE(2) production of HPBM in vitro. Equivalent numbers of CT per host cell induced a higher PGE(2)-response compared to CP. The amount of synthesized PGE(2) depended on the chlamydial multiplicity of infection (MOI). Even at an MOI of 10 the amount of CT- and CP-induced prostaglandin, respectively, was lower than the amount of prostaglandin induced by E. coli lipopolysaccharide (LPS) at a concentration of 10microg/ml. In contrast to stimulation with LPS, Chlamydia-induced PGE(2) production as well as cox-2 mRNA decreased after day 1 post infection (p.i.). These data indicate that Chlamydia stimulate PGE(2) production in human monocytes. Since Chlamydia are often contaminated by mycoplasma, the influence of mycoplasma on the prostaglandin production was investigated additionally. Mycoplasma fermentans (MF) also stimulated PGE(2) production. The co-infection of mycoplasma and Chlamydia resulted in an additive effect in the production of PGE(2). Thus it is important to use host cells and Chlamydia free of mycoplasma contamination for the analysis of Chlamydia-induced prostaglandin production.

Effect of levofloxacin on the viability of intracellular Chlamydia pneumoniae and modulation of proinflammatory cytokine production by human monocytes

Although antibiotics are known to affect the intracellular growth of Chlamydia pneumoniae in acute infections, their efficacy in therapy for chronic infections, including atherosclerosis, remains debatable. Human monocyte-derived macrophages (MDM) obtained from monocytes of healthy donors were infected with C. pneumoniae AR-39 and treated with levofloxacin (8 microg/mL) immediately after infection (0 hours) or 24 hours after infection. Levofloxacin treatment at 24 hours, but not at 0 hours, resulted in a significant decrease in the number of C. pneumoniae inclusions within the MDM (p < 0.05). Also decreased were concentrations of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 in the extracellular medium (p < 0.01). Viable counts in titrations remained similar to those in untreated controls. In summary, levofloxacin administered to MDM at serum-attainable levels 24 hours after C. pneumoniae infection significantly decreased inclusion counts and proinflammatory cytokine production, but did not eliminate the C. pneumoniae infection.

Infiltration of the brain by pathogens causes Alzheimer's disease

Despite very numerous studies on Alzheimer's disease (AD), especially on amyloid plaques and neurofibrillary tangles, little information has been obtained thus on the causes of the disease. Evidence is described here that implicates firstly herpes simplex virus type 1 (HSV1) as a strong risk factor when it is present in brain of carriers of the type 4 allele of the gene for apolipoprotein E (APOE-4). Indirect support comes from studies indicating the role of APOE in several diverse diseases of known pathogen cause. A second putative risk factor is the bacterium, Chlamydia pneumoniae. This pathogen has been identified and localized in AD brain. Current studies aimed at "proof of principle" address the entry of the organism into the CNS, the neuroinflammatory response to the organism, and the role that the organism plays in triggering AD pathology. An infection-based animal model demonstrates that following intranasal inoculation of BALB/c mice with C. pneumoniae, amyloid plaques/deposits consistent with those observed in the AD brain develop, thus implicating this infection in the etiology of AD.