Cervical Cytokines Associated With Chlamydia trachomatis Susceptibility and Protection

Safety and efficacy of C. muridarum vaccines adjuvanted with CpG-1826 and four concentrations of Montanide-ISA-720-VG

It is recommended that the adjuvant Montanide ISA 720 VG be used at a concentration of 70% v/v. At this concentration, Montanide causes at the site of immunization a local granuloma that can last for several weeks. To determine the safety and protective efficacy of a Chlamydia muridarum MOMP vaccine, formulated with CpG-1826 and four different concentrations of Montanide (70%, 50%, 30% and 10%), BALB/c (H-2d) female mice were immunized twice intramuscularly. Local reactogenicity was significant for vaccines formulated with 70% or 50% Montanide but not for those inoculated with 30% or 10% Montanide. Robust humoral and cell mediated memory immune responses were elicited by the 70%, 50% and 30% Montanide formulations. Mice were challenged intranasally with 104 C. muridarum inclusion forming units (IFU). Based on changes in body weight, lungs's weight and number of IFU recovered, mice vaccinated with the 70%, 50% and 30% Montanide formulations were significantly protected, but not mice receiving 10% Montanide. To conclude, we recommend the 30% Montanide concentration to be tested in humans and animal models to determine its safety and efficacy, in comparison to the 70% Montanide concentration currently used. The 30% Montanide formulation could significantly facilitate licensing of this adjuvant for human use.

Human antibody signatures towards the Chlamydia trachomatis major outer membrane protein after natural infection and vaccination

BACKGROUND

Chlamydia trachomatis (CT) Major Outer Membrane Protein (MOMP) holds a neutralising epitope in the Variable Domain 4 (VD4), and this region's immune dominance during infection is well known. This study aimed to assess the antibody response induced after infection and compare it for specificity and functionality to the response following vaccination with the vaccine CTH522, which contains VD4's from serovars D, E, F, and G.

METHODS

We assessed the antibody epitopes in MOMP by a high density peptide array. Furthermore, the role of the VD4 epitope in neutralisation was explored by competitive inhibition experiments with a fusion protein holding the neutralising VD4 linear epitope. This was done in two independent groups: 1) MOMP seropositive individuals infected with CT (n = 10, from case-control study) and 2) CTH522/CAF®01-vaccinated females (n = 14) from the CHLM-01 clinical trial.

FINDINGS

We identified the major antigenic regions in MOMP as VD4 and the conserved region just before VD3 in individuals infected with CT. The same regions, with the addition of VD1, were identified in vaccine recipients. Overall, the VD4 peptide responses were uniform in vaccinated individuals and led to inhibition of infection in vitro in all tested samples, whereas the VD4 responses were more heterogenous in individuals infected with CT, and only 2 out of 10 samples had VD4-mediated neutralising antibody responses.

INTERPRETATION

These data provide insights into the role of antibodies against MOMP VD4 induced after infection and vaccination, and show that their functionality differs. The induction of functional VD4-specific antibodies in vaccine recipients mimics previous results from animal models.

FUNDING

This work was supported by the European Commission through contract FP7-HEALTH-2011.1.4-4-280873 (ADITEC) and Fonden til Lægevidenskabens Fremme.

Murine modeling of menstruation identifies immune correlates of protection during Chlamydia muridarum challenge

The menstrual cycle influences the risk of acquiring sexually transmitted infections (STIs), including Chlamydia trachomatis (C. trachomatis), although the underlying immune contributions are poorly defined. A mouse model simulating the immune-mediated process of menstruation could provide valuable insights into tissue-specific determinants of protection against chlamydial infection within the cervicovaginal and uterine mucosae comprising the female reproductive tract (FRT). Here, we used the pseudopregnancy approach in naïve C57Bl/6 mice and performed vaginal challenge with Chlamydia muridarum (C. muridarum) at decidualization, endometrial tissue remodeling, or uterine repair. This strategy identified that the time frame comprising uterine repair correlated with robust infection and greater bacterial burden as compared with mice on hormonal contraception, while challenges during endometrial remodeling were least likely to result in a productive infection. By comparing the infection site at early time points following chlamydial challenge, we found that a greater abundance of innate effector populations and proinflammatory signaling, including IFNγ correlated with protection. FRT immune profiling in uninfected mice over pseudopregnancy or in pig-tailed macaques over the menstrual cycle identified NK cell infiltration into the cervicovaginal tissues and lumen over the course of endometrial remodeling. Notably, NK cell depletion over this time frame reversed protection, with mice now productively infected with C. muridarum following challenge. This study shows that the pseudopregnancy murine menstruation model recapitulates immune changes in the FRT as a result of endometrial remodeling and identifies NK cell localization at the FRT as essential for immune protection against primary C. muridarum infection.

IFNγ insufficiency during mouse intra-vaginal Chlamydia trachomatis infection exacerbates alternative activation in macrophages with compromised CD40 functions

Chlamydia trachomatis (C.tr), an obligate intracellular pathogen, causes asymptomatic genital infections in women and is a leading cause of preventable blindness. We have developed in vivo mouse models of acute and chronic C. trachomatis genital infection to explore the significance of macrophage-directed response in mediating immune activation/suppression. Our findings reveal that during chronic and repeated C. trachomatis infections, Th1 response is abated while Treg response is enhanced. Additionally, an increase in exhaustion (PD1, CTLA4) and anergic (Klrg3, Tim3) T cell markers is observed during chronic infection. We have also observed that M2 macrophages with low CD40 expression promote Th2 and Treg differentiation leading to sustained C. trachomatis genital infection. Macrophages infected with C. trachomatis or treated with supernatant of infected epithelial cells drive them to an M2 phenotype. C. trachomatis infection prevents the increase in CD40 expression as observed in western blots and flow cytometric analysis. Insufficient IFNγ, as observed during chronic infection, leads to incomplete clearance of bacteria and poor immune activation. C. trachomatis decapacitates IFNγ responsiveness in macrophages via hampering IFNγRI and IFNγRII expression which can be correlated with poor expression of MHC-II, CD40, iNOS and NO release even following IFNγ supplementation. M2 macrophages during C. trachomatis infection express low CD40 rendering immunosuppressive, Th2 and Treg differentiation which could not be reverted even by IFNγ supplementation. The alternative macrophages also harbour high bacterial load and are poor responders to IFNγ, thus promoting immunosuppression. In summary, C. trachomatis modulates the innate immune cells, attenuating the anti-chlamydial functions of T cells in a manner that involves decreased CD40 expression on macrophages.

Immune signature of Chlamydia vaccine CTH522/CAF®01 translates from mouse-to-human and induces durable protection in mice

The clinical development of an effective Chlamydia vaccine requires in-depth understanding of how well protective pre-clinical immune signatures translate to humans. Here, we report a comparative immunological characterization of CTH522/CAF®01 in female mice and humans. We find a range of immune signatures that translate from mouse to human, including a Th1/Th17 cytokine profile and antibody functionality. We identify vaccine-induced T cell epitopes, conserved among Chlamydia serovars, and previously found in infected individuals. Using the mouse model, we show that the common immune signature protected against ascending infection in mice, and vaccine induced antibodies could delay bacterial ascension to the oviduct, as well as development of pathology, in a T cell depleted mouse model. Finally, we demonstrate long-lasting immunity and protection of mice one year after vaccination. Based on the results obtained in the present study, we propose to further investigate CTH522/CAF®01 in a phase IIb study.

Contributions of diverse models of the female reproductive tract to the study of Chlamydia trachomatis-host interactions

Chlamydia trachomatis is a common cause of sexually transmitted infections in humans with devastating sequelae. Understanding of disease on all scales, from molecular details to the immunology underlying pathology, is essential for identifying new ways of preventing and treating chlamydia. Infection models of various complexity are essential to understand all aspects of chlamydia pathogenesis. Cell culture systems allow for research into molecular details of infection, including characterization of the unique biphasic Chlamydia developmental cycle and the role of type-III-secreted effectors in modifying the host environment to allow for infection. Multicell type and organoid culture provide means to investigate how cells other than the infected cells contribute to the control of infection. Emerging comprehensive three-dimensional biomimetic systems may fill an important gap in current models to provide information on complex phenotypes that cannot be modeled in simpler in vitro models.

Unique T cell signatures are associated with reduced Chlamydia trachomatis reinfection in a highly exposed cohort

Chlamydia trachomatis (CT) is the most common bacterial sexually transmitted infection (STI) in the United States, despite effective antibiotics. Information regarding natural immunity to CT will inform vaccine design. The objectives of this study were to determine immune cell populations and functional features associated with reduced risk of CT reinfection or endometrial CT infection. PBMCs were collected from a cohort of CT-exposed women who were tested for CT and other STIs at the cervix and endometrium (to determine ascension) and were repeatedly tested over the course of a year (to determine reinfection). Mass cytometry identified major immune populations and T cell subsets. Women with CT had increased CD4+ effector memory T cells (TEM) compared to uninfected women. Specifically, Th2, Th17, and Th17 DN CD4+ TEM were increased. Th17 and Th17 DN CD4+ central memory T cells (TCM) were increased in women who did not experience follow-up CT infection, suggesting that these cells may be important for protection. These data indicate that peripheral T cells display distinct features that correlate with natural immunity to CT and suggest that the highly plastic Th17 lineage plays a role in protection against reinfection.

Decomposition of variation of mixed variables by a latent mixed Gaussian copula model

Many biomedical studies collect data of mixed types of variables from multiple groups of subjects. Some of these studies aim to find the group-specific and the common variation among all these variables. Even though similar problems have been studied by some previous works, their methods mainly rely on the Pearson correlation, which cannot handle mixed data. To address this issue, we propose a latent mixed Gaussian copula (LMGC) model that can quantify the correlations among binary, ordinal, continuous, and truncated variables in a unified framework. We also provide a tool to decompose the variation into the group-specific and the common variation over multiple groups via solving a regularized M-estimation problem. We conduct extensive simulation studies to show the advantage of our proposed method over the Pearson correlation-based methods. We also demonstrate that by jointly solving the M-estimation problem over multiple groups, our method is better than decomposing the variation group by group. We also apply our method to a Chlamydia trachomatis genital tract infection study to demonstrate how it can be used to discover informative biomarkers that differentiate patients.

Cytokine profiling of samples positive for Chlamydia trachomatis and Human papillomavirus

Persistent human papillomavirus (HPV) infection is closely associated with cervical carcinoma. Co-infection in the endocervical environment with other microorganisms, such as Chlamydia trachomatis, may increase the risk of HPV infection and neoplastic progression. While in some individuals, Chlamydia trachomatis infection is resolved with the activation of Th1/IFN-γ-mediated immune response, others develop a chronic infection marked by Th2-mediated immune response, resulting in intracellular persistence of the bacterium and increasing the risk of HPV infection. This work aimed to quantify cytokines of the Th1/Th2/Th17 profile in exfoliated cervix cells (ECC) and peripheral blood (PB) of patients positive for Chlamydia trachomatis DNA, patients positive for Papillomavirus DNA, and healthy patients. Cytokine levels were quantified by flow cytometry in ECC and PB samples from patients positive for C. trachomatis DNA (n = 18), patients positive for HPV DNA (n = 30), and healthy patients (n = 17) treated at the Hospital de Amor, Campo Grande-MS. After analysis, a higher concentration of IL-17, IL-6, and IL-4 (p <0.05) in ECC; INF-γ and IL-10 (p <0.05) in PB was found in samples from patients positive for C. trachomatis DNA compared to samples from healthy patients. When comparing samples from patients positive for HPV DNA, there was a higher concentration of cytokines IL-17, IL-10, IL-6, and IL-4 (p <0.05) in ECC and IL-4 and IL-2 (p <0.05) in PB of patients positive for C. trachomatis DNA. These results suggest that induction of Th2- and Th17 mediated immune response occurs in patients positive for C. trachomatis DNA, indicating chronic infection. Our results also demonstrate a high concentration of pro-inflammatory cytokines in ECC of patients positive for C. trachomatis DNA.

Genetic susceptibility loci for Chlamydia trachomatis endometrial infection influence expression of genes involved in T cell function, tryptophan metabolism and epithelial integrity

Objectives

Identify genetic loci of enhanced susceptibility to Chlamydial trachomatis (Ct) upper genital tract infection in women.

Methods

We performed an integrated analysis of DNA genotypes and blood-derived mRNA profiles from 200 Ct-exposed women to identify expression quantitative trait loci (eQTL) and determine their association with endometrial chlamydial infection using a mediation test. We further evaluated the effect of a lead eQTL on the expression of CD151 by immune cells from women with genotypes associated with low and high whole blood expression of CD151, respectively.

Results

We identified cis-eQTLs modulating mRNA expression of 81 genes (eGenes) associated with altered risk of ascending infection. In women with endometrial infection, eGenes involved in proinflammatory signaling were upregulated. Downregulated eGenes included genes involved in T cell functions pivotal for chlamydial control. eGenes encoding molecules linked to metabolism of tryptophan, an essential chlamydial nutrient, and formation of epithelial tight junctions were also downregulated in women with endometrial infection. A lead eSNP rs10902226 was identified regulating CD151, a tetrospanin molecule important for immune cell adhesion and migration and T cell proliferation. Further in vitro experiments showed that women with a CC genotype at rs10902226 had reduced rates of endometrial infection with increased CD151 expression in whole blood and T cells when compared to women with a GG genotype.

Conclusions

We discovered genetic variants associated with altered risk for Ct ascension. A lead eSNP for CD151 is a candidate genetic marker for enhanced CD4 T cell function and reduced susceptibility.

Human genetic diversity regulating the TLR10/TLR1/TLR6 locus confers increased cytokines in response to Chlamydia trachomatis

Human genetic diversity can have profound effects on health outcomes upon exposure to infectious agents. For infections with Chlamydia trachomatis (C. trachomatis), the wide range of genital and ocular disease manifestations are likely influenced by human genetic differences that regulate interactions between C. trachomatis and host cells. We leveraged this diversity in cellular responses to demonstrate the importance of variation at the Toll-like receptor 1 (TLR1), TLR6, and TLR10 locus to cytokine production in response to C. trachomatis. We determined that a single-nucleotide polymorphism (SNP) (rs1057807), located in a region that forms a loop with the TLR6 promoter, is associated with increased expression of TLR1, TLR6, and TLR10 and secreted levels of ten C. trachomatis-induced cytokines. Production of these C. trachomatis-induced cytokines is primarily dependent on MyD88 and TLR6 based on experiments using inhibitors, blocking antibodies, RNAi, and protein overexpression. Population genetic analyses further demonstrated that the mean IL-6 response of cells from two European populations were higher than the mean response of cells from three African populations and that this difference was partially attributable to variation in rs1057807 allele frequency. In contrast, a SNP associated with a different pro-inflammatory cytokine (rs2869462 associated with the chemokine CXCL10) exhibited an opposite response, underscoring the complexity of how different genetic variants contribute to an individual's immune response. This multidisciplinary study has identified a long-range chromatin interaction and genetic variation that regulates TLR6 to broaden our understanding of how human genetic variation affects the C. trachomatis-induced immune response.

Host-Pathogen Interactions of Chlamydia trachomatis in Porcine Oviduct Epithelial Cells

Chlamydia trachomatis (Ct) causes the most prevalent bacterial sexually transmitted disease leading to ectopic pregnancy and infertility. Swine not only have many similarities to humans, but they are also susceptible to Ct. Despite these benefits and the ease of access to primary tissue from this food animal, in vitro research in swine has been underutilized. This study will provide basic understanding of the Ct host–pathogen interactions in porcine oviduct epithelial cells (pOECs)—the counterparts of human Fallopian tube epithelial cells. Using NanoString technology, flow cytometry, and confocal and transmission-electron microscopy, we studied the Ct developmental cycle in pOECs, the cellular immune response, and the expression and location of the tight junction protein claudin-4. We show that Ct productively completes its developmental cycle in pOECs and induces an immune response to Ct similar to human cells: Ct mainly induced the upregulation of interferon regulated genes and T-cell attracting chemokines. Furthermore, Ct infection induced an accumulation of claudin-4 in the Ct inclusion with a coinciding reduction of membrane-bound claudin-4. Downstream effects of the reduced membrane-bound claudin-4 expression could potentially include a reduction in tight-junction expression, impaired epithelial barrier function as well as increased susceptibility to co-infections. Thereby, this study justifies the investigation of the effect of Ct on tight junctions and the mucosal epithelial barrier function. Taken together, this study demonstrates that primary pOECs represent an excellent in vitro model for research into Ct pathogenesis, cell biology and immunity.

Tumor Necrosis Factor Alpha-Induced Interleukin-1 Alpha Synthesis and Cell Death Is Increased in Mouse Epithelial Cells Infected With Chlamydia muridarum

Chlamydia trachomatis-genital infection in women can be modeled in mice using Chlamydia muridarum. Using this model, it has been shown that the cytokines tumor necrosis factor (TNF)α and interleukin (IL)-1α lead to irreversible tissue damage in the oviducts. In this study, we investigated the contribution of TNFα on IL-1α synthesis in infected epithelial cells. We show that C muridarum infection enhanced TNFα-induced IL-1α expression and release in a mouse epithelial cell line. In addition to IL-1α, several TNFα-induced inflammatory genes were also highly induced, and infection enhanced TNF-induced cell death. In the mouse model of genital infection, oviducts from mice lacking the TNFα receptor displayed minimal staining for IL-1α compared with wild-type oviducts. Our results suggest TNFα and IL-1α enhance each other's downstream effects resulting in a hyperinflammatory response to chlamydial infection. We propose that biologics targeting TNF-induced IL-1α synthesis could be used to mitigate tissue damage during chlamydial infection.

A Commentary on Current Diagnostic Challenges and Research Needs for Evaluating Reproductive Sequelae of Sexually Transmitted Infections

Advancing the understanding of pelvic inflammatory disease (PID) requires access to advanced diagnostic approaches for evaluating reproductive sequelae of sexually transmitted infections (STIs). Current limitations of clinical criteria and advanced imaging technologies for diagnosing reproductive sequelae make diagnosis and surveillance of PID a challenge. We summarize and comment on major challenges in diagnostic evaluation of reproductive sequelae: limited point-of-care clinical diagnostic options for reproductive sequelae, economic and geographical obstacles to accessing state-of-the-art diagnostics, an expanding list of STIs that may cause reproductive sequelae and the complexities in evaluating them, and the need for coordinated research efforts to systematically evaluate biomarkers with gold-standard, well-defined specimens and associated clinical data. The future use of biomarkers in readily accessible mucosal or blood-derived specimens as a noninvasive approach to determining STI etiologies may be fruitful and requires more research. Biomarkers under consideration include cytokines, STI-specific antibody responses, and mRNA transcriptional profiles of inflammatory markers.

Pelvic Inflammatory Disease Due to Neisseria gonorrhoeae and Chlamydia trachomatis: Immune Evasion Mechanisms and Pathogenic Disease Pathways

Pelvic inflammatory disease (PID) results from ascension of sexually transmitted pathogens from the lower genital tract to the uterus and/or fallopian tubes in women, with potential spread to neighboring pelvic organs. Patients may present acutely with lower abdominal or pelvic pain and pelvic organ tenderness. Many have subtle symptoms or are asymptomatic and present later with tubal factor infertility, ectopic pregnancy, or chronic pelvic pain. Neisseria gonorrhoeae and Chlamydia trachomatis are the 2 most commonly recognized PID pathogens. Their ability to survive within host epithelial cells and neutrophils highlights a need for T-cell-mediated production of interferon γ in protection. Data indicate that for both pathogens, antibody can accelerate clearance by enhancing opsonophagocytosis and bacterial killing when interferon γ is present. A study of women with N. gonorrhoeae- and/or C. trachomatis-induced PID with histologic endometritis revealed activation of myeloid cell, cell death, and innate inflammatory pathways in conjunction with dampening of T-cell activation pathways. These findings are supported by multiple studies in mouse models of monoinfection with N. gonorrhoeae or Chlamydia spp. Both pathogens exert multiple mechanisms of immune evasion that benefit themselves and each other at the expense of the host. However, similarities in host immune mechanisms that defend against these 2 bacterial pathogens instill optimism for the prospects of a combined vaccine for prevention of PID and infections in both women and men.

Insights Into Host Cell Cytokines in Chlamydia Infection

Chlamydial infection causes a number of clinically relevant diseases and induces significant morbidity in humans. Immune and inflammatory responses contribute to both the clearance of Chlamydia infection and pathology in host tissues. Chlamydia infection stimulates host cells to produce a large number of cytokines that trigger and regulate host immune responses against Chlamydia. However, inappropriate responses can occur with excessive production of cytokines, resulting in overreactive inflammatory responses and alterations in host or Chlamydia metabolism. As a result, Chlamydia persists and causes wound healing delays, leading to more severe tissue damage and triggering long-lasting fibrotic sequelae. Here, we summarize the roles of cytokines in Chlamydia infection and pathogenesis, thus advancing our understanding chlamydial infection biology and the pathogenic mechanisms involved.

Cytokine response following perturbation of the cervicovaginal milieu during HPV genital infection

Human papillomaviruses (HPVs) are oncogenic viruses causing most cervical cancers. Highly prevalent in young, sexually active women, only a minority of HPV infections persist. To better characterize the immuno-modulatory impact of early HPV infections, we measured changes in a panel of 20 cytokines in cervicovaginal samples collected from young women who were tested for HPV and self-reported for genital inflammation and infection symptoms. Multi-factor statistical analyses revealed that increased IL-1Alpha and IL-12/IL-23p40 concentrations were associated with HPV infection and that macrophage inflammatory proteins were associated in particular with high-risk HPV infections. ClinicalTrials.gov identifier NCT02946346.

Chlamydia trachomatis vaccines for genital infections: where are we and how far is there to go?

INTRODUCTION

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen in the world. Antibiotic treatment does not prevent against reinfection and a vaccine is not yet available.

AREAS COVERED

We focus the review on the progress made of our understanding of the immunological responses required for a vaccine to elicit protection, and on the antigens, adjuvants, routes of immunization and delivery systems that have been tested in animal models. PubMed and Google Scholar were used to search publication on these topics for the last 5 years and recent Reviews were examined.

EXPERT OPINION

The first Phase 1 clinical trial of a C. trachomatis vaccine to protect against genital infections was successfully completed. We expect that, in the next five years, additional vaccine clinical trials will be implemented.

Chlamydia trachomatis: Cell biology, immunology and vaccination

Chlamydia trachomatis is the causative agent of a highly prevalent sexually transmitted bacterial disease and is associated with a number of severe disease complications. Current therapy options are successful at treating disease, but patients are left without protective immunity and do not benefit the majority asymptomatic patients who do not seek treatment. As such, there is a clear need for a broad acting, protective vaccine that can prevent transmission and protect against symptomatic disease presentation. There are three key elements that underlie successful vaccine development: 1) Chlamydia biology and immune-evasion adaptations, 2) the correlates of protection that prevent disease in natural and experimental infection, 3) reflection upon the evidence provided by previous vaccine attempts. In this review, we give an overview of the unique intra-cellular biology of C. trachomatis and give insight into the dynamic combination of adaptations that allow Chlamydia to subvert host immunity and survive within the cell. We explore the current understanding of chlamydial immunity in animal models and in humans and characterise the key immune correlates of protection against infection. We discuss in detail the specific immune interactions involved in protection, with relevance placed on the CD4+ T lymphocyte and B lymphocyte responses that are key to pathogen clearance. Finally, we provide a timeline of C. trachomatis vaccine research to date and evaluate the successes and failures in development so far. With insight from these three key elements of research, we suggest potential solutions for chlamydial vaccine development and promising avenues for further exploration.

Determinants associated with viable genital or rectal Chlamydia trachomatis bacterial load (FemCure)

BACKGROUND

Chlamydia trachomatis (CT) is routinely diagnosed by nucleic acid amplification tests (NAATs), which are unable to distinguish between nucleic acids from viable and non-viable CT organisms.

OBJECTIVES

We applied our recently developed sensitive PCR (viability PCR) technique to measure viable bacterial CT load and explore associated determinants in 524 women attending Dutch sexual health centres (STI clinics), and who had genital or rectal CT.

METHODS

We included women participating in the FemCure study (Netherlands, 2016-2017). At the enrolment visit (pre-treatment), 524 were NAAT positive (n=411 had genital and rectal CT, n=88 had genital CT only and n=25 had rectal CT only). We assessed viable rectal and viable genital load using V-PCR. We presented mean load (range 0 (non-viable) to 6.5 log₁₀ CT/mL) and explored potential associations with urogenital symptoms (coital lower abdominal pain, coital blood loss, intermenstrual bleeding, altered vaginal discharge, painful or frequent micturition), rectal symptoms (discharge, pain, blood loss), other anatomical site infection and sociodemographics using multivariable regression analyses.

RESULTS

In genital (n=499) CT NAAT-positive women, the mean viable load was 3.5 log₁₀ CT/mL (SD 1.6). Genital viable load was independently associated with urogenital symptoms-especially altered vaginal discharge (Beta=0.35, p=0.012) and with concurrent rectal CT (aBeta=1.79; p<0.001). Urogenital symptoms were reported by 50.3% of women; their mean genital viable load was 3.6 log₁₀ CT/mL (vs 3.3 in women without symptoms). Of 436 rectal CT NAAT-positive women, the mean rectal viable load was 2.2 log₁₀ CT/mL (SD 2.0); rectal symptoms were reported by 2.5% (n=11) and not associated with rectal viable load.

CONCLUSION

Among women diagnosed with CT in an outpatient clinical setting, viable genital CT load was higher in those reporting urogenital symptoms, but the difference was small. Viable genital load was substantially higher when women also had a concurrent rectal CT.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT02694497.

Modeling of variables in cellular infection reveals CXCL10 levels are regulated by human genetic variation and the Chlamydia-encoded CPAF protease

Susceptibility to infectious diseases is determined by a complex interaction between host and pathogen. For infections with the obligate intracellular bacterium Chlamydia trachomatis, variation in immune activation and disease presentation are regulated by both host genetic diversity and pathogen immune evasion. Previously, we discovered a single nucleotide polymorphism (rs2869462) associated with absolute abundance of CXCL10, a pro-inflammatory T-cell chemokine. Here, we report that levels of CXCL10 change during C. trachomatis infection of cultured cells in a manner dependent on both host and pathogen. Linear modeling of cellular traits associated with CXCL10 levels identified a strong, negative correlation with bacterial burden, suggesting that C. trachomatis actively suppresses CXCL10. We identified the pathogen-encoded factor responsible for this suppression as the chlamydial protease- or proteasome-like activity factor, CPAF. Further, we applied our modeling approach to other host cytokines in response to C. trachomatis and found evidence that RANTES, another T-cell chemoattractant, is actively suppressed by Chlamydia. However, this observed suppression of RANTES is not mediated by CPAF. Overall, our results demonstrate that CPAF suppresses CXCL10 to evade the host cytokine response and that modeling of cellular infection parameters can reveal previously unrecognized facets of host-pathogen interactions.

IL-1α Is Essential for Oviduct Pathology during Genital Chlamydial Infection in Mice

Chlamydia trachomatis infection of the female genital tract can lead to irreversible fallopian tube scarring. In the mouse model of genital infection using Chlamydia muridarum, IL-1R signaling plays a critical role in oviduct tissue damage. In this study, we investigated the pathologic role of IL-1α, one of the two proinflammatory cytokines that bind to IL-1R. Il1a^-/- mice infected with C. muridarum cleared infection at their cervix at the same rate as wild-type (WT) mice, but were significantly protected from end point oviduct damage and fibrosis. The contribution of IL-1α to oviduct pathology was more dramatic than observed in mice deficient for IL-1β. Although chlamydial burden was similar in WT and Il1a^-/- oviduct during peak days of infection, levels of IL-1β, IL-6, CSF3, and CXCL2 were reduced in Il1a^-/- oviduct lysates. During infection, Il1a^-/- oviducts and uterine horns exhibited reduced neutrophil infiltration, and this reduction persisted after the infection resolved. The absence of IL-1α did not compromise CD4 T cell recruitment or function during primary or secondary chlamydial infection. IL-1α is expressed predominantly by luminal cells of the genital tract in response to infection, and low levels of expression persisted after the infection cleared. Ab-mediated depletion of IL-1α in WT mice prevented infection-induced oviduct damage, further supporting a key role for IL-1α in oviduct pathology.

Koala immunogenetics and chlamydial strain type are more directly involved in chlamydial disease progression in koalas from two south east Queensland koala populations than koala retrovirus subtypes

Chlamydial disease control is increasingly utilised as a management tool to stabilise declining koala populations, and yet we have a limited understanding of the factors that contribute to disease progression. To examine the impact of host and pathogen genetics, we selected two geographically separated south east Queensland koala populations, differentially affected by chlamydial disease, and analysed koala major histocompatibility complex (MHC) genes, circulating strains of Chlamydia pecorum and koala retrovirus (KoRV) subtypes in longitudinally sampled, well-defined clinical groups. We found that koala immunogenetics and chlamydial genotypes differed between the populations. Disease progression was associated with specific MHC alleles, and we identified two putative susceptibility (DCb 03, DBb 04) and protective (DAb 10, UC 01:01) variants. Chlamydial genotypes belonging to both Multi-Locus Sequence Typing sequence type (ST) 69 and ompA genotype F were associated with disease progression, whereas ST 281 was associated with the absence of disease. We also detected different ompA genotypes, but not different STs, when long-term infections were monitored over time. By comparison, KoRV profiles were not significantly associated with disease progression. These findings suggest that chlamydial genotypes vary in pathogenicity and that koala immunogenetics and chlamydial strains are more directly involved in disease progression than KoRV subtypes.

Human Fallopian Tube Epithelial Cell Culture Model To Study Host Responses to Chlamydia trachomatis Infection

Chlamydia trachomatis infection of the human fallopian tubes can lead to damaging inflammation and scarring, ultimately resulting in infertility. To study the human cellular responses to chlamydial infection, researchers have frequently used transformed cell lines that can have limited translational relevance. We developed a primary human fallopian tube epithelial cell model based on a method previously established for culture of primary human bronchial epithelial cells. After protease digestion and physical dissociation of excised fallopian tubes, epithelial cell precursors were expanded in growth factor-containing medium. Expanded cells were cryopreserved to generate a biobank of cells from multiple donors and cultured at an air-liquid interface. Culture conditions stimulated cellular differentiation into polarized mucin-secreting and multiciliated cells, recapitulating the architecture of human fallopian tube epithelium. The polarized and differentiated cells were infected with a clinical isolate of C. trachomatis, and inclusions containing chlamydial developmental forms were visualized by fluorescence and electron microscopy. Apical secretions from infected cells contained increased amounts of proteins associated with chlamydial growth and replication, including transferrin receptor protein 1, the amino acid transporters SLC3A2 and SLC1A5, and the T-cell chemoattractants CXCL10, CXCL11, and RANTES. Flow cytometry revealed that chlamydial infection induced cell surface expression of T-cell homing and activation proteins, including ICAM-1, VCAM-1, HLA class I and II, and interferon gamma receptor. This human fallopian tube epithelial cell culture model is an important tool with translational potential for studying cellular responses to Chlamydia and other sexually transmitted pathogens.

Development of vaccines against the sexually transmitted infections gonorrhoea, syphilis, Chlamydia, herpes simplex virus, human immunodeficiency virus and Zika virus

The success in preventing hepatitis B virus and human papillomavirus infections by means of vaccination paves the way for the development of other vaccines to prevent sexually transmitted infections (STIs) such as gonorrhoea, syphilis, chlamydia, herpes simplex virus, human immunodeficiency virus and Zika virus. The current status of vaccine development for these infections will be explored in this review.

The general principles for success include the need for prevention of latency, persistence and repeat infections. A reduction in transmission of STIs would reduce the global burden of disease. Therapeutic activity of vaccines against STIs would be advantageous over preventative activity alone, and prevention of congenital and neonatal infections would be an added benefit. There would be an added value in the prevention of long-term consequences of STIs. It may be possible to re-purpose ‘old’ vaccines for new indications. One of the major challenges is the determination of the target populations for STI vaccination.

Inferring Regulatory Networks From Mixed Observational Data Using Directed Acyclic Graphs

Construction of regulatory networks using cross-sectional expression profiling of genes is desired, but challenging. The Directed Acyclic Graph (DAG) provides a general framework to infer causal effects from observational data. However, most existing DAG methods assume that all nodes follow the same type of distribution, which prohibit a joint modeling of continuous gene expression and categorical variables. We present a new mixed DAG (mDAG) algorithm to infer the regulatory pathway from mixed observational data containing both continuous variables (e.g. expression of genes) and categorical variables (e.g. categorical phenotypes or single nucleotide polymorphisms). Our method can identify upstream causal factors and downstream effectors closely linked to a variable and generate hypotheses for causal direction of regulatory pathways. We propose a new permutation method to test the conditional independence of variables of mixed types, which is the key for mDAG. We also utilize an L₁ regularization in mDAG to ensure it can recover a large sparse DAG with limited sample size. We demonstrate through extensive simulations that mDAG outperforms two well-known methods in recovering the true underlying DAG. We apply mDAG to a cross-sectional immunological study of Chlamydia trachomatis infection and successfully infer the regularity network of cytokines. We also apply mDAG to a large cohort study, generating sensible mechanistic hypotheses underlying plasma adiponectin level. The R package mDAG is publicly available from CRAN at https://CRAN.R-project.org/package=mDAG.

Immune responses in the human female reproductive tract

Mucosal surfaces are key interfaces between the host and its environment, but also constitute ports of entry for numerous pathogens. The gut and lung mucosae act as points of nutrient and gas exchange, respectively, but the physiological purpose of the female reproductive tract (FRT) is to allow implantation and development of the fetus. Our understanding of immune responses in the FRT has traditionally lagged behind our grasp of the situation at other mucosal sites, but recently reproductive immunologists have begun to make rapid progress in this challenging area. Here, we review current knowledge of immune responses in the human FRT and their heterogeneity within and between compartments. In the commensal-rich vagina, the immune system must allow the growth of beneficial microbes, whereas the key challenge in the uterus is allowing the growth of the semi-allogeneic fetus. In both compartments, these objectives must be balanced with the need to eliminate pathogens. Our developing understanding of immune responses in the FRT will help us develop interventions to prevent the spread of sexually transmitted diseases and to improve outcomes of pregnancy for mothers and babies.