Virulence Protein Pgp3 Is Insufficient To Mediate Plasmid-Dependent Infectivity of Chlamydia trachomatis.

Chlamydia trachomatis is the most common cause of infectious blindness and sexually transmitted bacterial infection globally. C. trachomatis contains a conserved chlamydial plasmid with eight coding sequences. Plasmid-cured Chlamydia strains are attenuated and display reduced infectivity in cell culture and in vivo genital infection of female mice. Mutants that do not express the plasmid-encoded proteins Pgp3, a secreted protein with unknown function, or Pgp4, a putative regulator of pgp3 and other chromosomal loci, display an infectivity defect similar to plasmid-deficient strains. Our objective was to determine the combined and individual contributions of Pgp3 and Pgp4 to this phenotype. Deletion of pgp3 and pgp4 resulted in an infectivity defect detected by competition assay in cell culture and in mice. The pgp3 locus was placed under the control of an anhydrotetracycline-inducible promoter to examine the individual contributions of Pgp3 and Pgp4 to infectivity. Expression of pgp3 was induced 100- to 1,000-fold after anhydrotetracycline administration, regardless of the presence or absence of pgp4. However, secreted Pgp3 was not detected when pgp4 was deleted, confirming a role for Pgp4 in Pgp3 secretion. We discovered that expression of pgp3 or pgp4 alone was insufficient to restore normal infectivity, which required expression of both Pgp3 and Pgp4. These results suggest Pgp3 and Pgp4 are both required for infectivity during C. trachomatis infection. Future studies are required to determine the mechanism by which Pgp3 and Pgp4 influence chlamydial infectivity as well as the potential roles of Pgp4-regulated loci.

The Chlamydia trachomatis Early Effector Tarp Outcompetes Fascin in Forming F-Actin Bundles In Vivo.

The intracellular pathogen Chlamydia trachomatis secretes multiple early effectors into the host cell to promote invasion. A key early effector during host cell entry, Tarp (translocated actin-recruiting phosphoprotein) is comprised of multiple protein domains known to have roles in cell signaling, G-actin nucleation and F-actin bundle formation. In vitro, the actin bundles generated by Tarp are uncharacteristically flexible, however, in vivo, the biological significance of Tarp-mediated actin bundles remains unknown. We hypothesize that Tarp's ability to generate unique actin bundles, in part, facilitates chlamydial entry into epithelial cells. To study the in vivo interaction between Tarp and F-actin, we transgenically expressed Tarp in Drosophila melanogaster tissues. Tarp expressed in Drosophila is phosphorylated and forms F-actin-enriched aggregates in tissues. To gain insight into the significance of Tarp actin bundles in vivo, we utilized the well-characterized model system of mechanosensory bristle development in Drosophila melanogaster. Tarp expression in wild type flies produced curved bristles, indicating a perturbation in F-actin dynamics during bristle development. Two F-actin bundlers, Singed/Fascin and Forked/Espin, are important for normal bristle shape. Surprisingly, Tarp expression in the bristles displaced Singed/Fascin away from F-actin bundles. Tarp's competitive behavior against Fascin during F-actin bundling was confirmed in vitro. Loss of either singed or forked in flies leads to highly deformed bristles. Strikingly, Tarp partially rescued the loss of singed, reducing the severity of the bristle morphology defect. This work provides in vivo confirmation of Tarp's F-actin bundling activity and further uncovers a competitive behavior against the host bundler Singed/Fascin during bundle assembly. Also, we demonstrate the utility of Drosophila melanogaster as an in vivo cell biological platform to study bacterial effector function.

The Chlamydia trachomatis inclusion membrane protein CT006 associates with lipid droplets in eukaryotic cells.

Chlamydia trachomatis causes genital and ocular infections in humans. This bacterial pathogen multiplies exclusively within host cells in a characteristic vacuole (inclusion) and delivers proteins such as inclusion membrane proteins (Incs) into the host cell. Here, we identified CT006 as a novel C. trachomatis protein that when expressed ectopically eukaryotic cells can associate with lipid droplets (LDs). A screen using Saccharomyces cerevisiae identified two Incs causing vacuolar protein sorting defects and seven Incs showing tropism for eukaryotic organelles. Ectopic expression in yeast and mammalian cells of genes encoding different fragments of CT006 revealed tropism for the endoplasmic reticulum and LDs. We identified a LD-targeting region within the first 88 amino acid residues of CT006, and positively charged residues important for this targeting. Comparing with the parental wild-type strain, cells infected by a newly generated C. trachomatis strain overproducing CT006 with a double hemagglutinin tag showed a slight increase in the area occupied by LDs within the inclusion region. However, we could not correlate this effect with the LD-targeting regions within CT006. We further showed that both the amino and carboxy-terminal regions of CT006, flanking the Inc-characteristic bilobed hydrophobic domain, are exposed to the host cell cytosol during C. trachomatis infection, supporting their availability to interact with host cell targets. Altogether, our data suggest that CT006 might participate in the interaction of LDs with C. trachomatis inclusions.

Chlamydia trachomatis induces lncRNA MIAT upregulation to regulate mitochondria-mediated host cell apoptosis and chlamydial development.

Chlamydia trachomatis persistent infection is the leading cause of male prostatitis and female genital tract diseases. Inhibition of host cell apoptosis is the key to maintaining Chlamydia survival in vivo, and long noncoding RNAs (lncRNAs) play important roles in its developmental cycle and pathogenesis. However, it is not clear how lncRNAs regulate persistent Chlamydia infection. Here, using a microarray method, we identified 1718 lncRNAs and 1741 mRNAs differentially expressed in IFN-γ-induced persistent C. trachomatis infection. Subsequently, 10 upregulated and 5 downregulated differentially expressed lncRNAs were verified by qRT-PCR to confirm the reliability of the chip data. The GO and KEGG analyses revealed that differentially regulated transcripts were predominantly involved in various signalling pathways related to host immunity and apoptosis response. Targeted silencing of three lncRNAs (MIAT, ZEB1-AS1 and IRF1) resulted in increased apoptosis rates. Furthermore, interference with lncRNA MIAT caused not only an obvious downregulation of the Bcl-2/Bax ratio but also a marked release of cytochrome c, resulting in a significantly elevated level of caspase-3 activation. Meanwhile, MIAT was involved in the regulation of chlamydial development during the persistent infection. Collectively, these observations shed light on the enormous complex lncRNA regulatory networks involved in mitochondria-mediated host cell apoptosis and the growth and development of C. trachomatis.

Mycoplasma genitalium Provokes Seminal Inflammation among Infertile Males.

The impact of sexually transmitted infections (STI) on male fertility is controversial. Aims: To investigate the prevalence of urethritis-associated STIs (chlamydia, gonorrhoeae, Mycoplasma genitalium, trichomoniasis) among infertile males; to analyze the effect of STIs on semen parameters and blood PSA. Case-control study. Study group (n = 2000): males with fertility problems or desire for fertility check. Control group (n = 248): male partners of pregnant women. Analyses: polymerase chain reaction for STI, seminal interleukin 6 (IL-6), semen and fractionated urine, blood analyses (PSA, reproductive hormones). The prevalence of M. genitalium and chlamydia in the study group was 1.1% and 1.2%, respectively. The prevalence of chlamydia in the control group was 1.6%, while there were no M. genitalium cases. No cases with gonorrhoeae or trichomoniasis or combined infections were observed in neither group. There was a higher seminal concentration of neutrophils and IL-6 among M. genitalium positives compared with STI negatives. There was a trend toward a lower total count of spermatozoa and progressive motility among STI positives. No impact of STIs on PSA was found. The prevalence of STIs among infertile males is low. M. genitalium is associated with seminal inflammation. The impact of STIs on semen parameters deserves further investigations.

Spread of clonal genovar E Chlamydia trachomatis among men who have sex with men.

In a previous study, we developed a Multi-Locus VNTRs Analysis (MLVA) typing system, called MLVA-5, for the discrimination of Chlamydia trachomatis genovar E strain. The results suggested the clonal spread of a MLVA-5 type 21 strain among men who have sex with men (MSM). We applied the MLVA-5 typing method on 157 French anorectal genovar E specimens and 19 Swedish specimens collected between 2010 and 2015. A total of 29 MLVA-5 types was obtained, with three predominant types among French samples: 78 specimens belonged to MLVA-5 type 21, two other types, 11 and 13, included 9 and 14 specimens, respectively. In 15 cases, one unique MLVA-5 type was observed for a single patient, 7 of which were new types not previously described. The distribution of MLVA-5 types according to sexual orientation showed that the 7 anorectal specimens from heterosexual patients belonged to 6 genotypes, and the 12 anorectal specimens from bisexual patients comprised eight types. The 95 anorectal specimens from MSM were distributed into 22 types, but 55 (57.9%) of them belonged to MLVA-5 type 21. Among the Swedish specimens from MSM, eight were from MLVA-type 21 (4 urines and 4 anorectal specimens). The results support the hypothesis of the spread of clonal genovar E strain among MSM.

Ascension of Chlamydia is moderated by uterine peristalsis and the neutrophil response to infection.

Chlamydia trachomatis is a common sexually transmitted infection that is associated with a range of serious reproductive tract sequelae including in women Pelvic Inflammatory Disease (PID), tubal factor infertility, and ectopic pregnancy. Ascension of the pathogen beyond the cervix and into the upper reproductive tract is thought to be necessary for these pathologies. However, Chlamydia trachomatis does not encode a mechanism for movement on its genome, and so the processes that facilitate ascension have not been elucidated. Here, we evaluate the factors that may influence chlamydial ascension in women. We constructed a mathematical model based on a set of stochastic dynamics to elucidate the moderating factors that might influence ascension of infections in the first month of an infection. In the simulations conducted from the stochastic model, 36% of infections ascended, but only 9% had more than 1000 bacteria ascend. The results of the simulations indicated that infectious load and the peristaltic contractions moderate ascension and are inter-related in impact. Smaller initial loads were much more likely to ascend. Ascension was found to be dependent on the neutrophil response. Overall, our results indicate that infectious load, menstrual cycle timing, and the neutrophil response are critical factors in chlamydial ascension in women.

Differential expression of urine-circulating micro-RNAs in Chlamydia trachomatis-induced recurrent spontaneous aborters.

Studies behind mechanisms of Chlamydia trachomatis-induced recurrent spontaneous abortion is still in its infancy. Possible strategy for preventing recurrent spontaneous abortion at molecular level is needed. Despite its multifactorial aetiology, Chlamydia trachomatis is important cause of RSA. However, mechanism leading to RSA in C. trachomatis-positive patients is not understood and novel strategies are needed. It is hypothesized that microRNAs play important role in RSA regulation during infection. Study aimed to elucidate expression/role of urine-circulating miRs-320b, 221-3p, 146b-5p,-16,-24,-559 in recurrent spontaneous aborters with C. trachomatis infection and to find their target genes by bioinformatic analysis. First-void urine was collected from 30 non-pregnant women with RSA (Group I) and 30 non-pregnant women with ≥2 successful deliveries (Group II; Controls) attending Department of Obstetrics and Gynaecology, Vardhman Mahavir Medical College, Safdarjung hospital, New Delhi (India). PCR was performed to detect C. trachomatis. Expression of miRNAs was studied by quantitative real-time PCR while target genes/functional annotations were predicted by GO/KEGG databases. Data was statistically evaluated. 05 RSA patients were C. trachomatis-positive. Group I was subdivided into Group Ia (C. trachomatis-positive RSA; n = 5) and Group Ib (C. trachomatis-negative RSA; internal controls). miR-320b, -221-3p, -146b-5p, -16, -24 were significantly upregulated (miR-16 showed maximum 4.3 fold-change) while miR-559 was downregulated (0.5 fold-change) in Group Ia versus controls ('p'<0.001). Bioinformatic analysis revealed that target genes of miRNAs in RSA are involved in apoptosis and AMPK signalling pathways. Results showed differential expression of miRNAs implyingmiR-16 and miR-559 as potential biomarkers of RSA in infected women. Furthermore, network of genes of differentially expressed miRNAs regulates RSA by targeting gene function in apoptosis, cell adhesion and angiogenesis.

Incidence and risk factors of C. trachomatis and N. gonorrhoeae among young women from the Western Cape, South Africa: The EVRI study.

OBJECTIVE: Young women in South Africa are highly affected by sexually transmitted infections (STI), like C. trachomatis (CT) and N. gonorrhoeae (NG). We aimed to estimate the incidence of CT and NG, and its determinants, among young women from the Western Cape, South Africa, participating in an HPV vaccine trial (the EVRI study). METHODS: HIV-negative women aged 16-24 years were enrolled between October 2012 and July 2013. At enrolment and month 6 participants were screened for CT and NG (Anyplex CT/NG real-time detection method). A questionnaire on demographic and sexual history characteristics was completed at enrolment and month 7. Treatment for CT and/or NG was offered to infected participants. Incidence rates (IR) of CT and NG were estimated. Determinants of incident CT and NG infections were assessed using Poisson regression. RESULTS: 365 women were tested for CT and/or NG at least twice. Prevalence of CT and NG at baseline was 33.7% and 10.4%, respectively. Prevalence of co-infection with CT and NG was 7.1%. During 113.3 person-years (py), 48 incident CT infections were diagnosed (IR = 42.4 per 100 py, 95% confidence interval (CI) 31.9-56.2). Twenty-nine incident NG were diagnosed during 139.3 py (IR = 20.8 per 100 py, 95%CI 14.5-29.9). Prevalent CT infection at baseline was associated with incident CT (adjusted incidence rate ratio (aIRR) 5.8, 95%CI 3.0-11.23. More than three lifetime sex partners increased the risk for incident NG (3-4 partners aIRR = 7.3, 95%CI 2.1-26.0; ≥5 partners aIRR = 4.3, 95%CI 1.1-17.5). CONCLUSIONS: The IR of bacterial STIs among young women in the Western Cape is very high. Besides being previously infected and a higher lifetime number of sex partners, no other risk factors were found for CT and NG, suggesting that the majority of these women were at risk. This indicates the need for intensified prevention of STIs as well as screening and treatment programs to increase sexual health in this region.

Chlamydia trachomatis Infection Impairs MHC-I Intracellular Trafficking and Antigen Cross-Presentation by Dendritic Cells.

During cross-presentation, exogenous antigens (i.e. intracellular pathogens or tumor cells) are internalized and processed within the endocytic system and also by the proteasome in the cytosol. Then, antigenic peptides are associated with Major Histocompatibility Complex (MHC) class I molecules and these complexes transit to the plasma membrane in order to trigger cytotoxic immune responses through the activation of CD8+ T lymphocytes. Dendritic cells (DCs) are particularly adapted to achieve efficient antigen cross-presentation and their endocytic network displays important roles during this process, including a sophisticated MHC-I transport dependent on recycling compartments. In this study, we show that C. trachomatis, an obligate intracellular pathogen that exhibits multiple strategies to evade the immune system, is able to induce productive infections in the murine DC line JAWS-II. Our results show that when C. trachomatis infects these cells, the bacteria-containing vacuole strongly recruits host cell recycling vesicles, but no other endosomal compartments. Furthermore, we found that chlamydial infection causes significant alterations of MHC-I trafficking in JAWS-II DCs: reduced levels of MHC-I expression at the cell surface, disruption of the perinuclear MHC-I intracellular pool, and impairment of MHC-I endocytic recycling to the plasma membrane. We observed that all these modifications lead to a hampered cross-presentation ability of soluble and particulate antigens by JAWS-II DCs and primary bone marrow-derived DCs. In summary, our findings provide substantial evidence that C. trachomatis hijacks the DC endocytic recycling system, causing detrimental changes on MHC-I intracellular transport, which are relevant for competent antigen cross-presentation.

Tryptophan Operon Diversity Reveals Evolutionary Trends among Geographically Disparate Chlamydia trachomatis Ocular and Urogenital Strains Affecting Tryptophan Repressor and Synthase Function.

The obligate intracellular pathogen Chlamydia trachomatis (Ct) is the leading cause of bacterial sexually transmitted infections and blindness globally. To date, Ct urogenital strains are considered tryptophan prototrophs, utilizing indole for tryptophan synthesis within a closed-conformation tetramer comprised of two α (TrpA)- and two ß (TrpB)-subunits. In contrast, ocular strains are auxotrophs due to mutations in TrpA, relying on host tryptophan pools for survival. It has been speculated that there is strong selective pressure for urogenital strains to maintain a functional operon. Here, we performed genetic, phylogenetic, and novel functional modeling analyses of 595 geographically diverse Ct ocular, urethral, vaginal, and rectal strains with complete operon sequences. We found that ocular and urogenital, but not lymphogranuloma venereum, TrpA-coding sequences were under positive selection. However, vaginal and urethral strains exhibited greater nucleotide diversity and a higher ratio of nonsynonymous to synonymous substitutions [Pi(a)/Pi(s)] than ocular strains, suggesting a more rapid evolution of beneficial mutations. We also identified nonsynonymous amino acid changes for an ocular isolate with a urogenital backbone in the intergenic region between TrpR and TrpB at the exact binding site for YtgR-the only known iron-dependent transcription factor in Chlamydia-indicating that selective pressure has disabled the response to fluctuating iron levels. In silico effects on protein stability, ligand-binding affinity, and tryptophan repressor (TrpR) affinity for single-stranded DNA (ssDNA) measured by calculating free energy changes (ΔΔG) between Ct reference and mutant tryptophan operon proteins were also analyzed. We found that tryptophan synthase function was likely suboptimal compared to other bacterial tryptophan prototrophs and that a diversity of urogenital strain mutations rendered the synthase nonfunctional or inefficient. The novel mutations identified here affected active sites in an orthosteric manner but also hindered α- and ß-subunit allosteric interactions from distant sites, reducing efficiency of the tryptophan synthase. Importantly, strains with mutant proteins were inclined toward energy conservation by exhibiting an altered affinity for their respective ligands compared to reference strains, indicating greater fitness. This is not surprising as l-tryptophan is one of the most energetically costly amino acids to synthesize. Mutations in the tryptophan repressor gene (trpR) among urogenital strains were similarly detrimental to function. Our findings indicate that urogenital strains are evolving more rapidly than previously recognized with mutations that impact tryptophan operon function in a manner that is energetically beneficial, providing a novel host-pathogen evolutionary mechanism for intracellular survival.IMPORTANCEChlamydia trachomatis (Ct) is a major global public health concern causing sexually transmitted and ocular infections affecting over 130 million and 260 million people, respectively. Sequelae include infertility, preterm birth, ectopic pregnancy, and blindness. Ct relies on available host tryptophan pools and/or substrates to synthesize tryptophan to survive. Urogenital strains synthesize tryptophan from indole using their intact tryptophan synthase (TS). Ocular strains contain a trpA frameshift mutation that encodes a truncated TrpA with loss of TS function. We found that TS function is likely suboptimal compared to other tryptophan prototrophs and that urogenital stains contain diverse mutations that render TS nonfunctional/inefficient, evolve more rapidly than previously recognized, and impact operon function in a manner that is energetically beneficial, providing an alternative host-pathogen evolutionary mechanism for intracellular survival. Our research has broad scientific appeal since our approach can be applied to other bacteria that may explain evolution/survival in host-pathogen interactions.

Where to go to in chlamydia control? From infection control towards infectious disease control.

OBJECTIVES: The clinical and public health relevance of widespread case finding by testing for asymptomatic chlamydia infections is under debate. We wanted to explore future directions for chlamydia control and generate insights that might guide for evidence-based strategies. In particular, we wanted to know the extent to which we should pursue testing for asymptomatic infections at both genital and extragenital sites. METHODS: We synthesised findings from published literature and from discussions among national and international chlamydia experts during an invitational workshop. We described changing perceptions in chlamydia control to inform the development of recommendations for future avenues for chlamydia control in the Netherlands. RESULTS: Despite implementing a range of interventions to control chlamydia, there is no practice-based evidence that population prevalence can be reduced by screening programmes or widespread opportunistic testing. There is limited evidence about the beneficial effect of testing on pelvic inflammatory disease prevention. The risk of tubal factor infertility resulting from chlamydia infection is low and evidence on the preventable fraction remains uncertain. Overdiagnosis and overtreatment with antibiotics for self-limiting and non-viable infections have contributed to antimicrobial resistance in other pathogens and may affect oral, anal and genital microbiota. These changing insights could affect the outcome of previous cost-effectiveness analysis. CONCLUSION: The balance between benefits and harms of widespread testing to detect asymptomatic chlamydia infections is changing. The opinion of our expert group deviates from the existing paradigm of 'test and treat' and suggests that future strategies should reduce, rather than expand, the role of widespread testing for asymptomatic chlamydia infections.

Identification of differentially expressed genes and signaling pathways in human conjunctiva and reproductive tract infected with Chlamydia trachomatis.

BACKGROUND: Currently, Chlamydia trachomatis-specific host defense mechanisms in humans remain poorly defined. To study the characteristics of host cells infected early with Chlamydia trachomatis, we used bioinformatics methods to analyze the RNA transcription profiles of the conjunctiva, fallopian tubes, and endometrium in humans infected with Chlamydia trachomatis. METHOD: The gene expression profiles of GSE20430, GSE20436, GSE26692, and GSE41075 were downloaded from the Gene Expression Synthesis (GEO) database. Then, we obtained the differentially expressed genes (DEGs) through the R 4.0.1 software. STRING was used to construct protein-protein interaction (PPI) networks; then, the Cytoscape 3.7.2 software was used to visualize the PPI and screen hub genes. GraphPad Prism 8.0 software was used to verify the expression of the hub gene. In addition, the gene-miRNA interaction was constructed on the NetworkAnalyst 3.0 platform using the miRTarBase v8.0 database. RESULTS: A total of 600 and 135 DEGs were screened out in the conjunctival infection group and the reproductive tract infection group, respectively. After constructing a PPI network and verifying the hub genes, CSF2, CD40, and CSF3 in the reproductive tract infection group proved to have considerable statistical significance. CONCLUSION: In our research, the key genes in the biological process of reproductive tract infection with Chlamydia trachomatis were clarified through bioinformatics analysis. These hub genes may be further used in clinical treatment and clinical diagnosis.

Etiologies of genital inflammation and ulceration in symptomatic Rwandan men and women responding to radio promotions of free screening and treatment services.

INTRODUCTION: The longstanding inadequacies of syndromic management for genital ulceration and inflammation are well-described. The Rwanda National Guidelines for sexually transmitted infection (STI) syndromic management are not yet informed by the local prevalence and correlates of STI etiologies, a component World Health Organization guidelines stress as critical to optimize locally relevant algorithms. METHODS: Radio announcements and pharmacists recruited symptomatic patients to seek free STI services in Kigali. Clients who sought services were asked to refer sexual partners and symptomatic friends. Demographic, behavioral risk factor, medical history, and symptom data were collected. Genital exams were performed by trained research nurses and physicians. We conducted phlebotomy for rapid HIV and rapid plasma reagin (RPR) serologies and vaginal pool swab for microscopy of wet preparation to diagnose Trichomonas vaginalis (TV), bacterial vaginosis (BV), and vaginal Candida albicans (VCA). GeneXpert testing for Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) were conducted. Here we assess factors associated with diagnosis of NG and CT in men and women. We also explore factors associated with TV, BV and VCA in women. Finally, we describe genital ulcer and RPR results by HIV status, gender, and circumcision in men. RESULTS: Among 974 men (with 1013 visits), 20% were positive for CT and 74% were positive for NG. Among 569 women (with 579 visits), 17% were positive for CT and 27% were positive for NG. In multivariate analyses, factors associated with CT in men included younger age, responding to radio advertisements, <17 days since suspected exposure, and not having dysuria. Factors associated with NG in men included not having higher education or full-time employment, <17 days since suspected exposure, not reporting a genital ulcer, and having urethral discharge on physical exam. Factors associated with CT in women included younger age and < = 10 days with symptoms. Factors associated with NG in women included younger age, lower education and lack of full-time employment, sometimes using condoms vs. never, using hormonal vs. non-hormonal contraception, not having genital ulcer or itching, having symptoms < = 10 days, HIV+ status, having BV, endocervical discharge noted on speculum exam, and negative vaginal wet mount for VCA. In multivariate analyses, only reporting >1 partner was associated with BV; being single and RPR+ was associated with TV; and having < = 1 partner in the last month, being pregnant, genital itching, discharge, and being HIV and RPR negative were associated with VCA. Genital ulcers and positive RPR were associated with being HIV+ and lack of circumcision among men. HIV+ women were more likely to be RPR+. In HIV+ men and women, ulcers were more likely to be herpetic rather than syphilitic compared with their HIV- counterparts. CONCLUSIONS: Syndromic management guidelines in Rwanda can be improved with consideration of the prevalence of confirmed infections from this study of symptomatic men and women representative of those who would seek care at government health centers. Inclusion of demographic and risk factor measures shown to be predictive of STI and non-STI dysbioses may also increase diagnostic accuracy.

T cell responses to Chlamydia.

Chlamydia trachomatis is the most commonly reported sexually transmitted infection in the United States. The high prevalence of infection and lack of a vaccine indicate a critical knowledge gap surrounding the host's response to infection and how to effectively generate protective immunity. The immune response to C. trachomatis is complex, with cells of the adaptive immune system playing a crucial role in bacterial clearance. Here, we discuss the CD4+ and CD8+ T cell response to Chlamydia, the importance of antigen specificity and the role of memory T cells during the recall response. Ultimately, a deeper understanding of protective immune responses is necessary to develop a vaccine that prevents the inflammatory diseases associated with Chlamydia infection.

Stochastic Chlamydia Dynamics and Optimal Spread.

Chlamydia trachomatis is an important bacterial pathogen that has an unusual developmental switch from a dividing form (reticulate body or RB) to an infectious form (elementary body or EB). RBs replicate by binary fission within an infected host cell, but there is a delay before RBs convert into EBs for spread to a new host cell. We developed stochastic optimal control models of the Chlamydia developmental cycle to examine factors that control the number of EBs produced. These factors included the probability and timing of conversion, and the duration of the developmental cycle before the host cell lyses. Our mathematical analysis shows that the observed delay in RB-to-EB conversion is important for maximizing EB production by the end of the intracellular infection.

Immunopathogenesis of genital Chlamydia infection: insights from mouse models.

Chlamydiae are pathogenic intracellular bacteria that cause a wide variety of diseases throughout the globe, affecting the eye, lung, coronary arteries and female genital tract. Rather than by direct cellular toxicity, Chlamydia infection generally causes pathology by inducing fibrosis and scarring that is largely mediated by host inflammation. While a robust immune response is required for clearance of the infection, certain elements of that immune response may also damage infected tissue, leading to, in the case of female genital infection, disease sequelae such as pelvic inflammatory disease, infertility and ectopic pregnancy. It has become increasingly clear that the components of the immune system that destroy bacteria and those that cause pathology only partially overlap. In the ongoing quest for a vaccine that prevents Chlamydia-induced disease, it is important to target mechanisms that can achieve protective immunity while preventing mechanisms that damage tissue. This review focuses on mouse models of genital Chlamydia infection and synthesizes recent studies to generate a comprehensive model for immunity in the murine female genital tract, clarifying the respective contributions of various branches of innate and adaptive immunity to both host protection and pathogenic genital scarring.

Community Hand-Dug Wells for Trachoma: A Cluster-Randomized Trial.

The WHO recommends improving access to water as part of a comprehensive strategy for elimination of trachoma as a public health problem; however, this recommendation is not based on evidence from randomized trials. In a region of Ethiopia with hyperendemic trachoma, seven communities were randomized to a hand-dug well (HDW) and seven communities to no intervention to determine the impact of HDWs on the community prevalence of ocular chlamydia infection (primary prespecified outcome). All communities continued to receive government hygiene and sanitation services and outreach. Participants were not masked, given the nature of the intervention, but laboratory personnel were masked to treatment allocation. Hand-dug wells were successfully built in six of the seven communities; five of these wells were still functional at the conclusion of the trial. At the end of the trial, an average of 74% of households reported traveling < 30 minutes to collect water in the HDW arm, compared with 45% in the control arm, and the daily volume of water used for hygiene was similar (e.g., mean of 0.7 L per person in each arm). The pseudo-median prevalence of ocular chlamydia among 0- to 5-year old children at the 24-month visit was 23% in the HDW group and 13% in the control group (P > 0.99). This small cluster-randomized trial provided no evidence to suggest that simply constructing HDWs, in the absence of other hygiene promotion activities, is effective for reducing transmission of ocular chlamydia.

Got mutants? How advances in chlamydial genetics have furthered the study of effector proteins.

Chlamydia trachomatis is the leading cause of infectious blindness and a sexually transmitted infection. All chlamydiae are obligate intracellular bacteria that replicate within a membrane-bound vacuole termed the inclusion. From the confines of the inclusion, the bacteria must interact with many host organelles to acquire key nutrients necessary for replication, all while promoting host cell viability and subverting host defense mechanisms. To achieve these feats, C. trachomatis delivers an arsenal of virulence factors into the eukaryotic cell via a type 3 secretion system (T3SS) that facilitates invasion, manipulation of host vesicular trafficking, subversion of host defense mechanisms and promotes bacteria egress at the conclusion of the developmental cycle. A subset of these proteins intercalate into the inclusion and are thus referred to as inclusion membrane proteins. Whereas others, referred to as conventional T3SS effectors, are released into the host cell where they localize to various eukaryotic organelles or remain in the cytosol. Here, we discuss the functions of T3SS effector proteins with a focus on how advances in chlamydial genetics have facilitated the identification and molecular characterization of these important factors.

Incidence and duration of incident oropharyngeal gonorrhoea and chlamydia infections among men who have sex with men: prospective cohort study.

OBJECTIVES: This prospective cohort study aimed to determine the natural history and incidence of oropharyngeal gonorrhoea and chlamydia among a cohort of men who have sex with men (MSM) over a 12-week period, and to examine risk factors associated with incident oropharyngeal infections. METHODS: MSM either aged ≥18 years and had a diagnosis of oropharyngeal gonorrhoea by nucleic acid amplification test (NAAT) in the past 3 months or aged 18-35 years who were HIV-negative taking pre-exposure prophylaxis (PrEP) were eligible for this study. Enrolled men were followed up for 12 weeks. Oropharyngeal swabs were collected at week 0 (baseline) and week 12 (end of study). Between these time points, weekly saliva specimens and the number of tongue kissing, penile-oral and insertive rimming partners were collected by post. Oropharyngeal swabs and saliva specimens were tested by NAAT for Neisseria gonorrhoeae and Chlamydia trachomatis. Poisson regression was performed to examine the risk factors (weekly number of partners) associated with incident oropharyngeal gonorrhoea. RESULTS: A total of 100 MSM were recruited. The incidence of oropharyngeal gonorrhoea and chlamydia was 62 (95% CI 37 to 105) and 9 (95% CI 2 to 35)/100 person-years, respectively. The median duration of incident oropharyngeal infection with gonorrhoea was 28 days (IQR=21-36, n=7). The incidence rate ratio (IRR) for oropharyngeal gonorrhoea increased with an increased number of kissing partners (IRR=1.08; 95% CI 1.03 to 1.12) an increased number of penile-oral sex partners (IRR=1.07, 95% CI 1.01 to 1.14) but not with an increased number of insertive rimming partners (IRR=1.11, 95% CI 0.96 to 1.29) or other demographic factors. The IRR and duration of incident oropharyngeal chlamydia were not calculated due to the small number of cases (n=2). CONCLUSIONS: MSM have a high incidence of oropharyngeal gonorrhoea and the median duration of infection was less than 3 months.