Chlamydia trachomatis infection modulates trophoblast cytokine/chemokine production

Associations of Chlamydia trachomatis serology with fertility-related and pregnancy adverse outcomes in women: a systematic review and meta-analysis of observational studies

BACKGROUND

Chlamydia trachomatis (CT) infection has an increased risk for fertility-related and pregnancy adverse outcomes partly due to mechanisms related to a pro-inflammatory response to CT-, or cHSP60-induced delayed hypersensitivity. This study aimed to assess the evidence on the association between CT serology and adverse outcomes.

METHODS

PubMed/Medline, Embase and Web of Science databases were searched for observational studies on the association of CT-specific antibodies (e. g. IgG, IgA, IgM, etc.) with infertility, tubal factor infertility (TFIF), ectopic pregnancy (EP), spontaneous abortion (SA), or preterm labor (PL) that were published from database inception to 31 August 2022. Pooled adjusted odds ratios or relative risks with corresponding 95% confidence intervals were calculated using a random effects model. This study was registered with PROSPERO (CRD42022368366).

FINDINGS

We identified 128 studies that met the inclusion criteria, comprising 87 case-control, 34 cross-sectional and 7 cohort studies, for a total of 167 records involving 128,625 women participants included into the meta-analyses. Based on the adjusted estimates, it was found that CT-specific IgG was significantly associated with TFIF (pooled adjusted OR = 2.09, 95% CI 1.33-3.27, I2 = 63.8%) or EP (pooled adjusted OR = 3.00, 95% CI 1.66-5.40, I2 = 93.0%). Analyses of the unadjusted estimates indicated significant associations between CT-specific IgG and infertility, TFIF, EP or SA (four pooled unadjusted ORs ranging between 1.60 and 5.14, I2 ranging between 40% and 83%); IgA and infertility, TFIF, EP (three pooled unadjusted ORs ranging between 3.64 and 4.91, I2 ranging between 0% and 74%); IgM and TFIF (pooled unadjusted OR = 5.70, 95% CI 1.58-20.56, I2 = 56%); or cHSP60 and TFIF (pooled unadjusted OR = 7.83, 95% CI 5.42-11.31, I2 = 49%).

INTERPRETATION

A broad range of CT-specific antibodies have been studied in association with fertility-related and pregnancy adverse outcomes. However, our study identified a low- or moderate-quality evidence for an association of CT serology with the outcomes. There are substantial research gaps in relation to the clinical implications of CT serological biomarkers.

FUNDING

The work was supported by the Chinese Academy of Medical Sciences Initiative for Innovative Medicine (2016-I2M-3-021).

Cyclophilin A as a Pro-Inflammatory Factor Exhibits Embryotoxic and Teratogenic Effects during Fetal Organogenesis

The precise balance of Th1, Th2, and Th17 cytokines is a key factor in successful pregnancy and normal embryonic development. However, to date, not all humoral factors that regulate and influence physiological pregnancy have been completely studied. Our data here pointed out cyclophilin A (CypA) as the adverse pro-inflammatory factor negatively affecting fetal development and associated with pregnancy complications. In different mouse models in vivo, we demonstrated dramatic embryotoxicity and teratogenicity of increased CypA levels during pregnancy. Using generated transgenic models, we showed that CypA overexpression in fetal tissues induced the death of all transgenic fetuses and complete miscarriage. Administration of recombinant human CypA in a high dose to pregnant females during fetal organogenesis (6.5-11.5 dpc) exhibited teratogenic effects, causing severe defects in the brain and bone development that could lead to malformations and postnatal behavioral and cognitive disorders in the offspring. Embryotoxic and teratogenic effects could be mediated by CypA-induced up-regulation of M1 macrophage polarization via activation of the STAT1/3 signaling pathways. Here, we propose secreted CypA as a novel marker of complicated pregnancy and a therapeutic target for the correction of pregnancy complications.

Chlamydia trachomatis antigen induces TLR4-TAB1-mediated inflammation, but not cell death, in maternal decidua cells

BACKGROUND

During gestation, the decidua is an essential layer of the maternal-fetal interface, providing immune support and maintaining inflammatory homeostasis. Although Chlamydia (C.) trachomatis is associated with adverse pregnancy outcomes the pathogenic effects on maternal decidua contributing to adverse events are not understood. This study examined how C. trachomatis antigen affects cell signaling, cell death, and inflammation in the decidua.

METHODS

Primary decidua cells (pDECs) from term, not-in-labor, fetal membrane-decidua were cultured using the following conditions: (1) control - standard cell culture conditions, (2) 100 ng/ml or (3) 200 ng/ml of C. trachomatis antigen to model decidual cell infection in vitro. Differential expression of Toll-like receptor (TLR) 4 (receptor for C. trachomatis antigen), signaling pathway markers phosphorylated TGF-Beta Activated Kinase 1 (PTAB1), TAB1, phosphorylated p38 mitogen-activated protein kinases (Pp38 MAPK), and p38 MAPK (western blot), decidual cell apoptosis and necrosis (flow cytometry), and inflammation (ELISA for cytokines) were determined in cells exposed to C. trachomatis antigen. T-test was used to assess statistical significance (p < 0.05).

RESULTS

C. trachomatis antigen significantly induced expression of TLR4 (p = 0.03) and activation of TAB1 (p = 0.02) compared to controls. However, it did not induce p38 MAPK activation. In addition, pDECs maintained their stromal cell morphology when exposed to C. trachomatis antigen showing no signs of apoptosis and/or necrosis but did induce pro-inflammatory cytokine interleukin (IL)-6 (100 ng/ml: p = 0.02 and 200 ng/ml: p = 0.03), in pDECs compared to controls.

CONCLUSION

Prenatal C. trachomatis infection can produce antigens that induce TLR4-TAB1 signaling and IL-6 inflammation independent of Pp38 MAPK and apoptosis and necrosis. This suggests that C. trachomatis can imbalance decidual inflammatory homeostasis, potentially contributing to adverse events during pregnancy.

Aberrant gene expression of superoxide dismutases in Chlamydia trachomatis-infected recurrent spontaneous aborters

Study aimed to characterize the expression of antioxidant genes SOD1 and SOD2 in Chlamydia trachomatis-induced recurrent spontaneous aborters and further determine their role by in silico analysis. First void urine was collected from 130 non-pregnant women with history of recurrent spontaneous abortion (RSA) (Group I) and 130 non-pregnant women (Group II; control) attending Obstetrics and Gynecology Department, SJH, New Delhi, India. C. trachomatis detection was performed by conventional PCR in urine. Gene expression of SOD1 and SOD2 was performed by quantitative real-time PCR. Further, its interacting partners were studied by in silico analysis. 22 patients were positive for C. trachomatis in Group I. Significant upregulation was observed for SOD2 gene in C. trachomatis-infected RSA patients while SOD1 was found to be downregulated. Increased concentration of oxidative stress biomarkers 8-hydroxyguanosine and 8-isoprostane was found in C. trachomatis-infected RSA patients. Protein–protein interaction (PPI) of SOD proteins and its interacting partners viz.; CCS, GPX1, GPX2, GPX3, GPX4, GPX5, GPX7, GPX8, CAT, PRDX1, TXN, SIRT3, FOXO3, and AKT1 were found to be involved in MAPK, p53 and foxo signaling pathways. Molecular pathways involved in association with SODs indicate reactive oxygen species (ROS) detoxification, apoptotic pathways and cell cycle regulation. Overall data revealed alleviated levels of SOD2 gene and decreased expression of SOD1 gene in response to C. trachomatis-infection leading to production of oxidative stress and RSA.

Sexually transmitted infections and risk of hypertensive disorders of pregnancy

Hypertensive disorders of pregnancy (HDP) result in maternal morbidity and mortality but are rarely examined in perinatal studies of sexually transmitted infections. We examined associations between common sexually transmitted infections and HDP among 38,026 singleton pregnancies. Log-binomial regression calculated relative risk (RRs) and 95% confidence intervals (CIs) for associations with gestational hypertension, preeclampsia with severe features, mild preeclampsia, and superimposed preeclampsia. All models were adjusted for insurance type, maternal age, race/ethnicity, and education. Additional adjustments resulted in similar effect estimates. Chlamydia was associated with preeclampsia with severe features (RR_adj. 1.4, 95% CI 1.1, 1.9). Effect estimates differed when we examined first prenatal visit diagnosis only (RR_adj. 1.3, 95% CI 0.9, 1.9) and persistent or recurrent infection (RR_adj. 2.0, 95% CI 1.1, 3.4). For chlamydia (RR_adj. 2.0, 95% CI 1.3, 2.9) and gonorrhea (RR_adj. 3.0, 95% CI 1.1, 12.2), women without a documented treatment were more likely to have preeclampsia with severe features. Among a diverse perinatal population, sexually transmitted infections may be associated with preeclampsia with severe features. With the striking increasing rates of sexually transmitted infections, there is a need to revisit the burden in pregnant women and determine if there is a link between infections and hypertensive disorders of pregnancy.

Presence of Chlamydia trachomatis DNA in the amniotic fluid in women with preterm prelabor rupture of membranes

OBJECTIVE

The primary aim of this study was to assess the rate and load of amniotic fluid Chlamydia trachomatis DNA and their associations with intra-amniotic infection and intra-uterine inflammatory complications in women with preterm prelabor rupture of membranes (PPROM). The secondary aim was to assess the short-term morbidity of newborns from PPROM pregnancies complicated by amniotic fluid C. trachomatis DNA.

METHODS

A retrospective study of 788 women with singleton pregnancies complicated by PPROM between 24 + 0 and 36 + 6 weeks of gestation was performed. Transabdominal amniocenteses were performed at the time of admission. C. trachomatis DNA in the amniotic fluid was assessed by real-time polymerase chain reaction using a commercial AmpliSens® C. trachomatis/Ureaplasma/Mycoplasma hominis-FRT kit, and the level of Ct DNA was quantified.

RESULTS

Amniotic fluid C. trachomatis DNA complicated 2% (16/788) of the PPROM pregnancies and was present in very low loads (median 57 copies DNA/mL). In addition to amniotic fluid C. trachomatis DNA, other bacteria were detected in 62% (10/16) of the C. trachomatis DNA-complicated PPROM pregnancies. Amniotic fluid C. trachomatis DNA was associated with intra-amniotic infection, histologic chorioamnionitis (HCA), and funisitis in 31%, 47%, and 33%, respectively. The presence of C. trachomatis DNA accompanied by Ureaplasma species in the amniotic fluid was associated with a higher rate of HCA than the presence of amniotic fluid C. trachomatis DNA alone. The composite neonatal morbidity in newborns from PPROM pregnancies with amniotic fluid C. trachomatis DNA was 31%.

CONCLUSION

The presence of C. trachomatis DNA in the amniotic fluid is a relatively rare condition in PPROM. Amniotic fluid C. trachomatis DNA in PPROM is not related to intensive intra-amniotic and intr-auterine inflammatory responses or adverse short-term neonatal outcomes.

Non-invasive Embryo Assessment: Altered Individual Protein Profile in Spent Culture Media from Embryos Transferred at Day 5

In order to improve ART outcome, non-invasive embryo assessment is gaining more and more attention. Therefore, the aim of this study is to determine the consecutive implantation potential via the secretome between blastocysts with or without implantation and to analyse possible interactions between these differentially expressed proteins. In this prospective study, 69 spent culture media from blastocysts transferred at day 5 were collected from patients undergoing IVF/ICSI treatment in a single IVF centre between April 2015 and November 2018 after informed consent and analysed individually. Exclusion criteria were the absence of informed consent, PCOS, endometriosis and maternal age > 42 years. Dependent on the treatment outcome, media were subsequently divided into two groups: from embryos who implanted successfully (n = 37) and from embryos without implantation (n = 32). Ninety-two proteins were measured simultaneously using the proximity extension assay (PEA) technology with the Olink® CVD III panel employing oligonucleotide-labelled antibodies. Statistical analysis was performed using the Kolmogorov-Smirnov test, Student's t test, the Mann-Whitney U test and Fisher's exact test. Media from implanted blastocysts showed significantly higher expression of EPHB4, ALCAM, CSTB, BMH, TIMP4, CCL24, SELE, FAS, JAM-A, PON3, PDGF-A, vWF and PECAM-1 compared with media from blastocysts without subsequent implantation. The highest relative expression change could be demonstrated for PECAM-1 and TIMP4. PECAM-1, SELE and vWF were co-expressed. Especially EPHB 4, SELE, ALCAM, MCP-1, CCL24, FAS, JAM-A and PDGF-A have already been described in early embryonic development and metabolism. Therefore, these proteins together with PECAM-1 indicate possible biomarkers for non-invasive embryo assessment in the future. However, due to the innovative methodology, defining a threshold for the use as biomarkers remains to be assessed.

The role of CXC chemokine ligand 16 in physiological and pathological pregnancies

The survival and development of a semi-allogeneic fetus during pregnancy require the involvement of a series of cytokines and immune cells. Chemokines are a type of special cytokine those were originally described as having a role in leukocyte trafficking. CXC chemokine ligand (CXCL) 16 is a member of the chemokine family, and CXC chemokine receptor (CXCR) 6 is its sole receptor. Emerging evidence has shown that CXCL16/CXCR6 is expressed at the maternal-fetal interface, by cell types that include trophoblast cells, decidual stroma cells, and decidual immune cells (eg, monocytes, γδT cells, and natural killer T (NKT) cells). The regulation of expression of CXCL16 is quite complex, and this process involves a multitude of factors. CXCL16 exerts a critical role in the establishment of a successful pregnancy through a series of molecular interactions at the maternal-fetal interface. However, an abnormal expression of CXCL16 is associated with certain pathological states associated with pregnancy, including recurrent miscarriage, pre-eclampsia, and gestational diabetes mellitus (GDM). In the present review, the expression and pleiotropic roles of CXCL16 under conditions of physiological and pathological pregnancy are systematically discussed.

Proinflammatory response of canine trophoblasts to Brucella canis infection

Brucella canis infection is an important cause of late-term abortion in pregnant bitches. The pathophysiological mechanisms leading to B. canis-induced abortion are unknown, but heavily infected trophoblasts are consistently observed. As trophoblasts responses to other pathogens contribute to placental inflammation leading to abortion, the aim of the present study was to characterize the cytokine response of canine trophoblasts to B. canis infection. To achieve this, trophoblasts isolated from term placenta of healthy female dogs were infected with B. canis, culture supernatants were harvested for cytokine determinations, and the load of intracellular viable B. canis was determined at different times post-infection. Additionally, cytokine responses were assessed in non-infected trophoblasts stimulated with conditioned media (CM) from B. canis-infected canine monocytes and neutrophils. Finally, cytokine response and bacteria replication were assessed in canine placental explants infected ex vivo. B. canis successfully infected and replicated in primary canine trophoblasts, eliciting an increase in IL-8 and RANTES (CCL5) secretion. Moreover, the stimulation of trophoblasts with CM from B. canis-infected monocytes and neutrophils induced a significant increase in IL-8, IL-6 and RANTES secretion. B. canis replication was confirmed in infected placental explants and the infection elicited an increased secretion of TNF-α, IL-8, IL-6 and RANTES. This study shows that canine trophoblasts produce proinflammatory cytokines in response to B. canis infection and/or to stimulation with factors produced by infected monocytes and neutrophils. These cytokines may contribute to placental inflammation leading to abortion in B. canis-infected pregnant bitches.

Chlamydia trachomatis regulates innate immune barrier integrity and mediates cytokine and antimicrobial responses in human uterine ECC-1 epithelial cells

PROBLEM

Chlamydia trachomatis infection is the most common sexually transmitted bacterial infection worldwide and known to increase the risk for HIV acquisition. Few studies have investigated how infection of epithelial cells compromises barrier integrity and antimicrobial response.

METHOD OF STUDY

ECC-1 cells, a human uterine epithelial cell line, were treated with live and heat-killed C. trachomatis. Epithelial barrier integrity measured as transepithelial resistance (TER), chemokines antimicrobial levels, and antimicrobial mRNA expression was measured by ELISA and Real-time RT-PCR.

RESULTS

Epithelial barrier integrity was compromised when cells were infected with live, but not with heat-killed, C. trachomatis. IL-8 secretion by ECC-1 cells increased in response to live and heat-killed C. trachomatis, while MCP-1, HBD2 and trappin2/elafin secretion decreased with live C. trachomatis.

CONCLUSION

Live C. trachomatis suppresses ECC-1 innate immune responses by compromising the barrier integrity, inhibiting secretion of MCP-1, HBD2, and trappin-2/elafin. Differential responses between live and heat-killed Chlamydia indicate which immune responses are dependent on ECC-1 infection rather than the extracellular presence of Chlamydia.

Differential expression of circulating Th1/ Th2/ Th17 cytokines in serum of Chlamydia trachomatis-infected women undergoing incomplete spontaneous abortion

The study aimed to elucidate role of Th1/Th2/Th17 cytokines in the immunopathogenesis of spontaneous abortion in Chlamydia trachomatis (Ct)-positive first-trimester aborters. Endometrial curettage tissue and serum were collected from 145 aborters (spontaneous abortion (SA) group, n = 85; recurrent miscarriage (RM) group, n = 60) and 120 controls attending Department of Obstetrics & Gynecology at Safdarjung hospital, New Delhi (India). Polymerase chain reaction was used to detect Ct plasmid/MOMP, while commercial cytometric bead array kit was utilized to estimate circulating serum cytokines. 13.7% aborters were Ct-positive, however, none was found to be infected among controls. IFN-γ, TNF-α, IL-2, IL-6 and IL-17A cytokines were significantly increased in SA group/RM group (Ct-infected) versus controls. IL-4 showed no difference between groups, while IL-10 was significantly elevated in controls versus Ct-infected subjects in SA group/RM group. Furthermore, IFN-γ, TNF-α, IL-6, IL-17A cytokines were significantly elevated in Ct-positive RM group versus Chlamydia-infected SA group. However, IL-2, IL-4 and IL-10 cytokines showed no significant difference between Ct-positive SA group versus infected RM group. Positive correlation was found between few cytokines (TNF-α and IFN-γ/IL-17A; IL-17A and IFN-γ/IL-6) in Ct-positive aborters. Our study clearly established the role of Th1/Th2/Th17 cytokines in the pathogenesis of spontaneous abortion in Ct-infected subjects and found that Chlamydia-positive recurrent aborters had a predominant Th1/Th17 bias.

Macrophage Exosomes Induce Placental Inflammatory Cytokines: A Novel Mode of Maternal–Placental Messaging

Exosome trafficking from the placenta into the maternal circulation is well documented; the possibility that this trafficking is bi‐directional was unknown. We demonstrated clathrin‐mediated endocytosis of macrophage exosomes by the human placenta. We also demonstrated that macrophage exosomes induced placental production of cytokines interleukin (IL)‐6, IL‐8 and IL‐10. Exosomes therefore comprise an additional mechanism of immune cell signalling to the placenta, potentially facilitating protective responses to maternal inflammation and infection in pregnancy. This represents a novel mode of maternal–placental messaging.

Proinflammatory Response of Human Trophoblastic Cells to Brucella abortus Infection and upon Interactions with Infected Phagocytes

Trophoblasts are targets of infection by Brucella spp. but their role in the pathophysiology of pregnancy complications of brucellosis is unknown. Here we show that Brucella abortus invades and replicates in the human trophoblastic cell line Swan-71 and that the intracellular survival of the bacterium depends on a functional virB operon. The infection elicited significant increments of interleukin 8 (IL8), monocyte chemotactic protein 1 (MCP-1), and IL6 secretion, but levels of IL1beta and tumor necrosis factor-alpha (TNF-alpha) did not vary significantly. Such proinflammatory response was not modified by the absence of the Brucella TIR domain-containing proteins BtpA and BtpB. The stimulation of Swan-71 cells with conditioned medium (CM) from B. abortus-infected human monocytes (THP-1 cells) or macrophages induced a significant increase of IL8, MCP-1 and IL6 as compared to stimulation with CM from non-infected cells. Similar results were obtained when stimulation was performed with CM from infected neutrophils. Neutralization studies showed that IL1beta and/or TNF-alpha mediated the stimulating effects of CM from infected phagocytes. Reciprocally, stimulation of monocytes and neutrophils with CM from Brucella-infected trophoblasts increased IL8 and/or IL6 secretion. These results suggest that human trophoblasts may provide a local inflammatory environment during B. abortus infections either through a direct response to the pathogen or through interactions with monocytes/macrophages or neutrophils, potentially contributing to the pregnancy complications of brucellosis.

Waddlia chondrophila induces systemic infection, organ pathology, and elicits Th1-associated humoral immunity in a murine model of genital infection

Waddlia chondrophila is a known bovine abortigenic Chlamydia-related bacterium that has been associated with adverse pregnancy outcomes in human. However, there is a lack of knowledge regarding how W. chondrophila infection spreads, its ability to elicit an immune response and induce pathology. A murine model of genital infection was developed to investigate the pathogenicity and immune response associated with a W. chondrophila infection. Genital inoculation of the bacterial agent resulted in a dose-dependent infection that spread to lumbar lymph nodes and successively to spleen and liver. Bacterial-induced pathology peaked on day 14, characterized by leukocyte infiltration (uterine horn, liver, and spleen), necrosis (liver) and extramedullary hematopoiesis (spleen). Immunohistochemistry demonstrated the presence of a large number of W. chondrophila in the spleen on day 14. Robust IgG titers were detected by day 14 and remained high until day 52. IgG isotypes consisted of high IgG2a, moderate IgG3 and no detectable IgG1, indicating a Th1-associated immune response. This study provides the first evidence that W. chondrophila genital infection is capable of inducing a systemic infection that spreads to major organs, induces uterus, spleen, and liver pathology and elicits a Th1-skewed humoral response. This new animal model will help our understanding of the mechanisms related to intracellular bacteria-induced miscarriages, the most frequent complication of pregnancy that affects one in four women.

Chlamydia muridarum infection associated host MicroRNAs in the murine genital tract and contribution to generation of host immune response

PROBLEM

Chlamydia trachomatis (CT) is the leading sexually transmitted bacterial infection in humans and is associated with reproductive tract damage. However, little is known about the involvement and regulation of microRNAs (miRs) in genital CT.

METHODS

We analyzed miRs in the genital tract (GT) following C. muridarum (murine strain of CT) challenge of wild type (WT) and CD4(+) T-cell deficient (CD4(-/-)) C57BL/6 mice at days 6 and 12 post-challenge.

RESULTS

At day 6, miRs significantly downregulated in the lower GT were miR-125b-5p, -16, -214, -23b, -135a, -182, -183, -30c, and -30e while -146 and -451 were significantly upregulated, profiles not exhibited at day 12 post-bacterial challenge. Significant differences in miR-125b-5p (+5.06-fold change), -135a (+4.9), -183 (+7.9), and -182 (+3.2) were observed in C. muridarum-infected CD4(-/-) compared to WT mice. In silico prediction and mass spectrometry revealed regulation of miR-135a and -182 and associated proteins, that is, heat-shock protein B1 and alpha-2HS-glycoprotein.

CONCLUSION

This study provides evidence on regulation of miRs following genital chlamydial infection suggesting a role in pathogenesis and host immunity.

Chlamydia trachomatis infection results in a modest pro-inflammatory cytokine response and a decrease in T cell chemokine secretion in human polarized endocervical epithelial cells

The endocervical epithelium is a major reservoir for Chlamydia trachomatis in women, and genital infections are extended in their duration. Epithelial cells act as mucosal sentinels by secreting cytokines and chemokines in response to pathogen challenge and infection. We therefore determined the signature cytokine and chemokine response of primary-like endocervix-derived epithelial cells in response to a common genital serovar (D) of C. trachomatis. For these studies, we used a recently-established polarized, immortalized, endocervical epithelial cell model (polA2EN) that maintains, in vitro, the architectural and functional characteristics of endocervical epithelial cells in vivo including the production of pro-inflammatory cytokines. PolA2EN cells were susceptible to C. trachomatis infection, and chlamydiae in these cells underwent a normal developmental cycle as determined by a one-step growth curve. IL1α protein levels were increased in both apical and basolateral secretions of C. trachomatis infected polA2EN cells, but this response did not occur until 72h after infection. Furthermore, protein levels of the pro-inflammatory cytokines and chemokines IL6, TNFα and CXCL8 were not significantly different between C. trachomatis infected polA2EN cells and mock infected cells at any time during the chlamydial developmental cycle up to 120h post-infection. Intriguingly, C. trachomatis infection resulted in a significant decrease in the constitutive secretion of T cell chemokines IP10 and RANTES, and this required a productive C. trachomatis infection. Examination of anti-inflammatory cytokines revealed a high constitutive apical secretion of IL1ra from polA2EN cells that was not significantly modulated by C. trachomatis infection. IL-11 was induced by C. trachomatis, although only from the basolateral membrane. These results suggest that C. trachomatis can use evasion strategies to circumvent a robust pro-inflammatory cytokine and chemokine response. These evasion strategies, together with the inherent immune repertoire of endocervical epithelial cells, may aid chlamydiae in establishing, and possibly sustaining, an intracellular niche in microenvironments of the endocervix in vivo.

Nod1, but not the ASC inflammasome, contributes to induction of IL-1β secretion in human trophoblasts after sensing of Chlamydia trachomatis

Chlamydia trachomatis (Ct) is an obligate intracellular bacterial pathogen. Previously, we showed that infection of human trophoblast cells by Ct triggers the secretion of the pro-inflammatory cytokine, interleukin (IL)-1β. The aim of this study was to understand the innate immune pathways involved in trophoblast production of IL-1β after Ct infection. The approach we took was to inhibit the expression or function of the key Toll-like receptors (TLRs), Nod-like receptors, and inflammasome components that have been associated with chlamydia infection. In this study, we report that Ct-induced trophoblast IL-1β secretion is associated with the transcription of IL-1β mRNA, the translation and processing of pro-IL-1β, and the activation of caspase-1. In addition, we demonstrate that Ct-induced IL-1β production and secretion by the trophoblast is independent of TLR2, TLR4, MyD88, and the Nalp3/ASC inflammasome. Instead we report, for the first time, the importance of Nod1 for mediating trophoblast IL-1β secretion in response to a Ct infection.

Evolutionary-developmental perspectives on immune system interactions among the pregnant woman, placenta, and fetus, and responses to sexually transmitted infectious agents

A balance has evolved over deep time between the various immune systems of the "triad" that is linked together for a short period: the pregnant woman, the fetus, and the placenta. This balance is affected by, and helps to determine, the immune responses to maternal infectious agents that may be transmitted to the fetus/infant transplacentally, intrapartum, or via breast milk. This review identifies newer evolutionary concepts and processes related particularly to the human placenta, innate and adaptive immune systems involved in tolerance, and in responses to sexually transmitted infectious (STI) agents that may be pathogenic to the fetus/infant at different gestational periods and in the first year of life. An evolutionary-developmental (EVO-DEVO) perspective has been applied to the complexities within, and among, the different actors and their beneficial or deleterious outcomes. Such a phylogenetic and ontogenic approach has helped to stimulate several basic questions and suggested possible explanations and novel practical interventions.

Nod1 activation by bacterial iE-DAP induces maternal-fetal inflammation and preterm labor

There is a strong association between infection and prematurity; however, the underlying mechanisms remain largely unknown. Nod1 and Nod2 are intracellular pattern recognition receptors that are activated by bacterial peptides and mediate innate immunity. We previously demonstrated that human first-trimester trophoblasts express Nod1 and Nod2, which trigger inflammation upon stimulation. This study sought to determine the expression and function of Nod1 and Nod2 in third-trimester trophoblasts, and to characterize the in vivo effects of Nod1 activation on pregnancy outcome. Human term placental tissues and isolated term trophoblast expressed Nod1, but not Nod2. Activation of Nod1 by its agonist, bacterial γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP), in term trophoblast cultures induced a proinflammatory cytokine profile, characterized by elevated levels of secreted IL-6, GRO-α, and MCP-1, when compared with the control. However, these cytokines were not upregulated in response to Nod2 stimulation with bacterial MDP. Administration of high-dose bacterial iE-DAP to pregnant C57BL/6J mice on embryonic day 14.5 triggered preterm delivery within 24 h. iE-DAP at a lower dose that did not induce prematurity, reduced fetal weight, altered the cytokine profile at the maternal-fetal interface, and induced fetal inflammation. Thus, functional Nod1 is expressed by trophoblast cells across gestation and may have a role in mediating infection-associated inflammation and prematurity. This study demonstrates that pattern recognition receptors, other than the TLRs, may be implicated or involved in infection-associated preterm labor.

Chlamydia trachomatis immune evasion via downregulation of MHC class I surface expression involves direct and indirect mechanisms

Genital C. trachomatis infections typically last for many months in women. This has been attributed to several strategies by which C. trachomatis evades immune detection, including well-described methods by which C. trachomatis decreases the cell surface expression of the antigen presenting molecules major histocompatibility complex (MHC) class I, MHC class II, and CD1d in infected genital epithelial cells. We have harnessed new methods that allow for separate evaluation of infected and uninfected cells within a mixed population of chlamydia-infected endocervical epithelial cells to demonstrate that MHC class I downregulation in the presence of C. trachomatis is mediated by direct and indirect (soluble) factors. Such indirect mechanisms may aid in priming surrounding cells for more rapid immune evasion upon pathogen entry and help promote unfettered spread of C. trachomatis genital infections.

Immunity and vaccines against sexually transmitted Chlamydia trachomatis infection

PURPOSE OF REVIEW

The aim is to review recent findings on immunity and vaccine development to Chlamydia trachomatis.

RECENT FINDINGS

There is increasing knowledge on the interactions between C. trachomatis and infected host cells. During genital infection the organism avoids generating protective immunity but immune responses to a number of chlamydial proteins have been associated with reproductive tract pathology. Various vaccine and adjuvant preparations have been tried experimentally. Information generated by proteomics and complex studies of serological and T-lymphocyte immune responses points to novel vaccine candidates.

SUMMARY

C. trachomatis, an obligate intracellular bacterium, is the commonest sexually transmitted infection worldwide and is associated with reproductive pathology. To develop rational vaccines it is necessary to understand the complex lifecycle of the organism, the host immune response to infection and how these relate to disease. Infection does not prevent re-infection and antibiotic treatment prevents antibody production at a population level. It remains unclear what type of immune response would be sufficient to prevent infection and/or re-infection. Although the prevalence and demographics of infection and the severity of disease associations suggest that it would be desirable, there is no vaccine currently available. A number of studies have identified novel vaccine candidates.

Peptidoglycan induces necrosis and regulates cytokine production in murine trophoblast stem cells

PROBLEM

Intrauterine bacterial infection during pregnancy may lead to adverse outcome. The objective of this study was to assess whether peptidoglycan (PGN) derived from Gram-positive bacteria induces trophoblast stem (TS) cell death or alters TS cell cytokine production.

METHOD OF STUDY

Toll-like receptor (TLR) transcript expression was assessed by RT-PCR. Protein expression was determined by confocal microscopy or flow cytometry. 7-Aminoactinomycin D (7-AAD) staining was used to assess TS cell death. Morphological features of cell death were evaluated by transmission electron microscopy. The presence of cleaved caspase-3 and high mobility group box 1 (HMGB1) protein was examined by Western blot. Cytokine levels in cell supernatants were determined using a mouse cytokine 23-plex panel.

RESULTS

Toll-like receptor 2 and TLR4 protein was expressed from the 1-cell stage through the blastocyst stage of murine embryo development. Murine TS cells expressed TLR2 and TLR6 but not TLR1 or TLR4 RNA. Only TLR2 protein was detected at the plasma membrane of TS cells. PGN induced TS cell death by a caspase-3-independent mechanism. The cell death pathway induced by PGN was morphologically consistent with necrosis. Finally, PGN induced HMGB1 release and increased MIP-1β secretion while inhibiting the constitutive release of RANTES.

CONCLUSION

Peptidoglycan-induced TS cell necrosis and the subsequent release of HMGB1 and MIP-1β may regulate an infection-induced inflammatory response at the maternal-fetal interface and thus may play a role in the pathogenesis of infection-associated pregnancy complications.

Toll-like receptors in pregnancy disorders and placental dysfunction

The Toll receptor was originally identified as a regulator of embryogenesis in Drosophila. Toll-like receptors (TLRs) in mammals recognize infectious agents and other danger signals. Activation of TLRs on trophoblast influences immune cell recruitment, cytokine secretion, and decidual responses to invading pathogens during pregnancy. Importantly, biological effects of TLR signal transduction at multiple maternal-fetal interfaces may contribute to several pregnancy pathologies associated with placental dysfunction, including pre-eclampsia, intrauterine growth restriction, and preterm labor. We herein discuss mechanisms by which TLRs regulate the maternal immune response during normal and abnormal gestation, and we highlight recent data that assign a role to TLRs in the pathophysiology of selected pregnancy-associated complications.

The role of the Nod-like receptor family in trophoblast innate immune responses

There is a strong clinical association between intrauterine infections and pregnancy complications, such as preterm labor. The placenta functions as an active barrier whereby the trophoblast recognizes microbes through pattern recognition receptors, such as the well characterized Toll-like receptors, in order to respond to pathogens at the maternal-fetal interface. Consequently, either an inefficient or overactive placental response to an infectious trigger, may have a significant impact on pregnancy outcome. Recently the placenta has been shown to express a newly identified family of pattern recognition receptors, the cytoplasmic-based Nod-like receptors (NLRs). As a result of their restricted localization, NLRs function as intracellular receptors that respond to infectious components, which have gained access to the cytoplasmic compartment. Thus, NLRs may provide the trophoblast with a recognition system that may be critical in placental responses to microorganisms or their cell wall components that have gained access to the cell's intracellular space, or that have evaded recognition by the TLRs. This review will discuss what is currently known about the role of NOD proteins, NALP proteins, and the inflammasome at the maternal-fetal interface, and their potential role in infection-associated pregnancy complications, like preterm labor. As we learn more about their function at the maternal-fetal interface, we will have a better understanding of their function in normal pregnancy and their potential to contribute to the pathogenesis of infection- and inflammation-associated pregnancy complications.

Coxiella burnetii, the agent of Q fever, replicates within trophoblasts and induces a unique transcriptional response

Q fever is a zoonosis caused by Coxiella burnetii, an obligate intracellular bacterium typically found in myeloid cells. The infection is a source of severe obstetrical complications in humans and cattle and can undergo chronic evolution in a minority of pregnant women. Because C. burnetii is found in the placentas of aborted fetuses, we investigated the possibility that it could infect trophoblasts. Here, we show that C. burnetii infected and replicated in BeWo trophoblasts within phagolysosomes. Using pangenomic microarrays, we found that C. burnetii induced a specific transcriptomic program. This program was associated with the modulation of inflammatory responses that were shared with inflammatory agonists, such as TNF, and more specific responses involving genes related to pregnancy development, including EGR-1 and NDGR1. In addition, C. burnetii stimulated gene networks organized around the IL-6 and IL-13 pathways, which both modulate STAT3. Taken together, these results revealed that trophoblasts represent a protective niche for C. burnetii. The activation program induced by C. burnetii in trophoblasts may allow bacterial replication but seems unable to interfere with the development of normal pregnancy. Such pathophysiologocal processes should require the activation of immune placental cells associated with trophoblasts.

The isolation and characterization of a novel telomerase immortalized first trimester trophoblast cell line, Swan 71

Studies using first trimester trophoblast cells may be limited by the inability to obtain patient samples and/or adequate cell numbers. First trimester trophoblast cell lines have been generated by SV40 transformation or similar methods, however, this approach is known to induce phenotypic and karyotypic abnormalities. The introduction of telomerase has been proposed to be a viable alternative for the immortalization of primary human cells. To investigate whether telomerase-induced immortalization might be a more feasible approach for the generation of first trimester trophoblast cell lines, we isolated primary trophoblast cells from a 7-week normal placenta and infected the cells with human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. Although this hTERT-infected first trimester trophoblast cell line, which we have named Swan 71, has been propagated for more than 100 passages, it still has attributes that are characteristic of primary first trimester trophoblast cells. The Swan 71 cells are positive for the expression of cytokeratin 7, vimentin and HLA-G, but do not express CD45, CD68 or the Fibroblast Specific Antigen (FSA), CD90/Thy-1. In addition, we also demonstrated that the Swan 71 cells secrete fetal fibronectin (FFN) as well as low levels of human Chorionic Gonadotrophin (hCG). Moreover, the Swan 71 cells exhibit a cytokine and growth factor profile that is similar to primary trophoblast cells and are resistant to Fas, but not TNF-alpha-induced apoptosis. This suggests that the Swan 71 cells may represent a valuable model for future in vitro trophoblast studies.