Trachoma

Chlamydia trachomatis Infection Is Associated with E-Cadherin Promoter Methylation, Downregulation of E-Cadherin Expression, and Increased Expression of Fibronectin and α-SMA-Implications for Epithelial-Mesenchymal Transition

Chlamydia trachomatis (Ct) can induce scarring disease of the ocular mucosa, known as trachoma, the most common infectious cause of blindness worldwide. We hypothesized that epithelial-mesenchymal transition (EMT) contributes to the fibrotic process in trachomatous scarring. Infection of human conjunctival epithelial cells (HCjE) with Ct activated signaling pathways involved in EMT induction, which was correlated with decreased expression of E-cadherin, guardian of the epithelial phenotype. In addition, Ct infection was associated with increased expression of two mesenchymal cell markers: fibronectin and α-SMA. The DNA methylation statuses of selected regions of E-cadherin, fibronectin, and α-SMA genes revealed that Ct infection was accompanied with changes in DNA methylation of the E-cadherin promoter, while the expression of the two mesenchymal markers was not related with this epigenetic event. Our data suggest that Ct infection of conjunctival epithelial cells induces EMT-like changes that go along with modification of the methylation profile of the E-cadherin promoter and could, as one of the earliest events, contribute to processes triggering conjunctival scarring.

Profiling and validation of individual and patterns of Chlamydia trachomatis-specific antibody responses in trachomatous trichiasis

BACKGROUND

Ocular Chlamydia trachomatis (Ct) infection causes trachoma, the leading infectious cause of blindness. A Ct D/UW3 proteome microarray and sera from Gambian adults with trachomatous trichiasis (TT) or healthy matched controls previously identified several novel antigens, which suggested differential recognition in adults with TT.

METHODS

We re-analysed this serological microarray data using more robust microarray analysis techniques accounting for typical problems associated with highly dimensional data. We examined the Ct-specific antibody profile concerning the overall diversity of responses, antigen expression stage and cellular localisation of antigens. We tested differentially recognised antigens by further serological testing of the screened sera and used larger independent sample sets for validation.

RESULTS

Antibody responses identified High-Performance on antigens expressed early and late in the Ct developmental cycle and those secreted or localised to the outer membrane. Eight antigens were preferentially recognised by scarred individuals and one antigen by healthy individuals. Three of these antigens, two associated with scarring (CT667 and CT706) and one healthy-associated (CT442), were not associated with the presence or absence of scarring following specific serological testing of the arrayed sera and sera from larger, independent case-control cohorts.

CONCLUSIONS

This study identified focussed Ct-specific antibody profiles targeting proteins expressed during entry and exit from cells and localised to interact with the host. A small panel of antibody responses could discriminate between adults with and without TT in a trachoma-endemic community. Heterogenous responses in the independent validation of these antibody targets highlighted the need for large sample sizes, clearly defined clinical phenotypes and follow-up work.

Prevalence of Trachoma in Benishangul Gumuz Region, Ethiopia: Results of Seven Population-Based Surveys from the Global Trachoma Mapping Project

Purpose: Trachoma is a major cause of blindness in Ethiopia, and targeted for elimination as a public health problem by the year 2020. Prevalence data are needed to plan interventions. We set out to estimate the prevalence of trachoma in each evaluation unit of grouped districts (“woredas”) in Benishangul Gumuz region, Ethiopia.

Methods: We conducted seven cross-sectional community-based surveys, covering 20 woredas, between December 2013 and January 2014, as part of the Global Trachoma Mapping Project (GTMP). The standardized GTMP training package and methodologies were used.

Results: A total of 5828 households and 21,919 individuals were enumerated in the surveys. 19,583 people (89.3%) were present when survey teams visited. A total of 19,530 (99.7%) consented to examination, 11,063 (56.6%) of whom were female. The region-wide age- and sex-adjusted trichiasis prevalence in adults aged ≥15 years was 1.3%. Two evaluation units covering four woredas (Pawe, Mandura, Bulen and Dibate) with a combined rural population of 166,959 require implementation of the A, F and E components of the SAFE strategy (surgery, antibiotics, facial cleanliness and environmental improvement) for at least three years before re-survey, and intervention planning should begin for these woredas as soon as possible.

Conclusion: Both active trachoma and trichiasis are public health problems in Benishangul Gumuz, which needs implementation of the full SAFE strategy.

Low-cost, real-time, continuous flow PCR system for pathogen detection

In this paper, we present a portable and low cost point-of-care (POC) PCR system for quantitative detection of pathogens. Our system is based on continuous flow PCR which maintains fixed temperatures zones and pushes the PCR solution between two heated areas allowing for faster heat transfer and as a result, a faster PCR. The PCR system is built around a 46.0 mm × 30.9 mm × 0.4 mm disposable thermoplastic chip. In order to make the single-use chip economically viable, it was manufactured by hot embossing and was designed to be compatible with roll-to-roll embossing for large scale production. The prototype instrumentation surrounding the chip includes two heaters, thermal sensors, and an optical system. The optical system allows for pathogen detection via real time fluorescence measurements. FAM probes were used as fluorescent reporters of the amplicons generated during the PCR. To demonstrate the function of the chip, two infectious bacteria targets were selected: Chlamydia trachomatis and Escherichia coli O157:H7. For both bacteria, the limit of detection of the system was determined, PCR efficiencies were calculated, and different flow velocities were tested. We have demonstrated successful detection for these two bacterial pathogens highlighting the versatility and broad utility of our portable, low-cost, and rapid PCR diagnostic device.

Tryptophan Codon-Dependent Transcription in Chlamydia pneumoniae during Gamma Interferon-Mediated Tryptophan Limitation

In evolving to an obligate intracellular niche, Chlamydia has streamlined its genome by eliminating superfluous genes as it relies on the host cell for a variety of nutritional needs like amino acids. However, Chlamydia can experience amino acid starvation when the human host cell in which the bacteria reside is exposed to interferon gamma (IFN-γ), which leads to a tryptophan (Trp)-limiting environment via induction of the enzyme indoleamine-2,3-dioxygenase (IDO). The stringent response is used to respond to amino acid starvation in most bacteria but is missing from Chlamydia Thus, how Chlamydia, a Trp auxotroph, responds to Trp starvation in the absence of a stringent response is an intriguing question. We previously observed that C. pneumoniae responds to this stress by globally increasing transcription while globally decreasing translation, an unusual response. Here, we sought to understand this and hypothesized that the Trp codon content of a given gene would determine its transcription level. We quantified transcripts from C. pneumoniae genes that were either rich or poor in Trp codons and found that Trp codon-rich transcripts were increased, whereas those that lacked Trp codons were unchanged or even decreased. There were exceptions, and these involved operons or large genes with multiple Trp codons: downstream transcripts were less abundant after Trp codon-rich sequences. These data suggest that ribosome stalling on Trp codons causes a negative polar effect on downstream sequences. Finally, reassessing previous C. pneumoniae microarray data based on codon content, we found that upregulated transcripts were enriched in Trp codons, thus supporting our hypothesis.

Lateral flow-based antibody testing for Chlamydia trachomatis

We describe here a lateral flow-based assay (LFA) for the detection of antibodies against immunodominant antigen Pgp3 from Chlamydia trachomatis, the causative agent of urogenital chlamydia infection and ocular trachoma. Optimal signal detection was achieved when the gold-conjugate and test line contained Pgp3, creating a dual sandwich capture assay. The LFA yielded positive signals with serum and whole blood but not with eluted dried blood spots. For serum, the agreement of the LFA with the non-reference multiplex assay was 96%, the specificity using nonendemic pediatric sera was 100%, and the inter-rater agreement was κ=0.961. For whole blood, the agreement of LFA with multiplex was 81.5%, the specificity was 100%, and the inter-rater agreement was κ=0.940. The LFA was tested in a field environment and yielded similar results to those from laboratory-based testing. These data show the successful development of a lateral flow assay for detection of antibodies against Pgp3 with reliable use in field settings, which would make antibody-based testing for trachoma surveillance highly practical, especially after cessation of trachoma elimination programs.

Baseline Trachoma Mapping in Malawi with the Global Trachoma Mapping Project (GTMP)

Purpose: To determine the prevalence of trachoma in all suspected endemic districts in Malawi.

Methods: A population-based survey conducted in 16 evaluation units from 12 suspected endemic districts in Malawi (population 6,390,517), using the standardized Global Trachoma Mapping Project (GTMP) protocol. A 2-stage cluster-random sampling design selected 30 households from each of 30 clusters per evaluation unit; all residents aged 1 year and older in selected households were examined for evidence of follicular trachoma (TF), intense trachomatous inflammation (TI), and trachomatous trichiasis (TT).

Results: Four of the 16 evaluation units were found to be endemic for trachoma, with a prevalence range of 10.0–13.5% for TF and 0.2–0.6% for TT. Nine evaluation units had a TF prevalence between 5.0% and 9.9% while three evaluation units had a TF prevalence <5.0%.

Conclusion: The prevalence rates of active trachoma in Malawi were not uniform among suspected endemic evaluation units, with rates higher than the World Health Organization (WHO) threshold for implementation of community-based control measures (TF ≥ 10.0%) in only 4 of the 16 evaluation units. Trachoma remains a disease of public health importance in some parts of Malawi and adjoining (unmapped) districts should be prioritized for mapping. According to the survey, an additional 3,169,362 people require intervention to reduce active disease and 1557 trichiasis surgeries are needed to reduce the prevalence of TT below WHO recommended thresholds.

Pharmacophore based virtual screening for identification of marine bioactive compounds as inhibitors against macrophage infectivity potentiator (Mip) protein of Chlamydia trachomatis

Macrophage infectivity potentiator (Mip) is the virulence factor fromChlamydia trachomatisthat is primarily responsible for causing sexually transmitted diseases (STDs) and blindness.

Assessment of a Novel Approach to Identify Trichiasis Cases Using Community Treatment Assistants in Tanzania

Background

Simple surgical intervention advocated by the World Health Organization can alleviate trachomatous trichiasis (TT) and prevent subsequent blindness. A large backlog of TT cases remain unidentified and untreated. To increase identification and referral of TT cases, a novel approach using standard screening questions, a card, and simple training for Community Treatment Assistants (CTAs) to use during Mass Drug Administration (MDA) was developed and evaluated in Kongwa District, a trachoma-endemic area of central Tanzania.

Methodology/Principal Findings

A community randomized trial was conducted in 36 communities during MDA. CTAs in intervention villages received an additional half-day of training and a TT screening card in addition to the training received by CTAs in villages assigned to usual care. All MDA participants 15 years and older were screened for TT, and senior TT graders confirmed case status by evaluating all screened-positive cases. A random sample of those screened negative for TT and those who did not present at MDA were also evaluated by the master graders. Intervention CTAs identified 5.6 times as many cases (n = 50) as those assigned to usual care (n = 9, p < 0.05). While specificity was above 90% for both groups, the sensitivity for the novel screening tool was 31.2% compared to 5.6% for the usual care group (p < 0.05).

Conclusions/Significance

CTAs appear to be viable resources for the identification of TT cases. Additional training and use of a TT screening card significantly increased the ability of CTAs to recognize and refer TT cases during MDA; however, further efforts are needed to improve case detection and reduce the number of false positive cases.

Surgical management of trachomatous trichiasis (TT) is recommended by the WHO as a cost-effective strategy to mitigate blinding trachoma. However, a large surgical backlog exists and many individuals suffering with TT remain unknown to the health system. To identify TT cases, we designed a standard set of screening questions, a card, and simple training for Community Treatment Assistants (CTAs) to identify trichiasis during community-wide Mass Drug Administrations (MDA). To evaluate the sensitivity, specificity, and positive predictive value of this approach, we conducted a community randomized trial in 36 communities in trachoma-endemic Kongwa District, Tanzania. Additional training and the use of a TT screening card increased the sensitivity of TT identification and resulted in more cases identified compared to the usual training of CTAs. The positive predictive value was low, indicating a need for further verification of TT cases identified by the enhanced screening. MDA appears to be a good opportunity for TT screening by CTAs, but further training to improve screening sensitivity is suggested.

Short-term Forecasting of the Prevalence of Trachoma: Expert Opinion, Statistical Regression, versus Transmission Models

Background

Trachoma programs rely on guidelines made in large part using expert opinion of what will happen with and without intervention. Large community-randomized trials offer an opportunity to actually compare forecasting methods in a masked fashion.

Methods

The Program for the Rapid Elimination of Trachoma trials estimated longitudinal prevalence of ocular chlamydial infection from 24 communities treated annually with mass azithromycin. Given antibiotic coverage and biannual assessments from baseline through 30 months, forecasts of the prevalence of infection in each of the 24 communities at 36 months were made by three methods: the sum of 15 experts’ opinion, statistical regression of the square-root-transformed prevalence, and a stochastic hidden Markov model of infection transmission (Susceptible-Infectious-Susceptible, or SIS model). All forecasters were masked to the 36-month results and to the other forecasts. Forecasts of the 24 communities were scored by the likelihood of the observed results and compared using Wilcoxon’s signed-rank statistic.

Findings

Regression and SIS hidden Markov models had significantly better likelihood than community expert opinion (p = 0.004 and p = 0.01, respectively). All forecasts scored better when perturbed to decrease Fisher’s information. Each individual expert’s forecast was poorer than the sum of experts.

Interpretation

Regression and SIS models performed significantly better than expert opinion, although all forecasts were overly confident. Further model refinements may score better, although would need to be tested and compared in new masked studies. Construction of guidelines that rely on forecasting future prevalence could consider use of mathematical and statistical models.

Forecasts of infectious diseases are rarely made in a falsifiable manner. Trachoma trials offer an opportunity to actually compare forecasting methods in a masked fashion. The World Health Organization recommends at least three annual antibiotic mass drug administrations where the prevalence of trachoma is greater than 10% in children aged 1–9 years, with coverage at least at 80%. The Program for the Rapid Elimination of Trachoma trials estimated longitudinal prevalence of ocular chlamydial infection from 24 communities treated annually with mass azithromycin. Here, we compared forecasts of the prevalence of infection in each of the 24 communities at 36 months (given antibiotic coverage and biannual assessments from baseline through 30 months, and masked to the 36-month assessments) made by experts, statistical regression, and a transmission model. The transmission model was better than regression, with both far better than experts’ opinion. Construction of guidelines that rely on forecasting future prevalence could consider use of mathematical and statistical models.

The Potential Use of Natural and Structural Analogues of Antimicrobial Peptides in the Fight against Neglected Tropical Diseases

Recently, research into the development of new antimicrobial agents has been driven by the increase in resistance to traditional antibiotics and Emerging Infectious Diseases. Antimicrobial peptides (AMPs) are promising candidates as alternatives to current antibiotics in the treatment and prevention of microbial infections. AMPs are produced by all known living species, displaying direct antimicrobial killing activity and playing an important role in innate immunity. To date, more than 2000 AMPs have been discovered and many of these exhibit broad-spectrum antibacterial, antiviral and anti-parasitic activity. Neglected tropical diseases (NTDs) are caused by a variety of pathogens and are particularly wide-spread in low-income and developing regions of the world. Alternative, cost effective treatments are desperately needed to effectively battle these medically diverse diseases. AMPs have been shown to be effective against a variety of NTDs, including African trypanosomes, leishmaniosis and Chagas disease, trachoma and leprosy. In this review, the potential of selected AMPs to successfully treat a variety of NTD infections will be critically evaluated.

Prevalence of sexually transmitted infections in female clinic attendees in Honiara, Solomon Islands

OBJECTIVES

This study sought to determine the prevalence of common bacterial sexually transmitted infections, including Chlamydia trachomatis and Neisseria gonorrhoeae, in women attending clinics in the Solomon Islands.

METHODS

We conducted a sexual health survey among women attending three nurse-led community outpatient clinics in August 2014, to establish the prevalence of bacterial sexually transmitted infections in female clinic attenders in Honiara, Solomon Islands. Vaginal swab samples were tested for infection with C. trachomatis and N. gonorrhoeae using a commercial strand displacement amplification assay. Serum samples were tested for syphilis.

RESULTS

We enrolled 296 women, aged 16-49, attending three clinics. Knowledge of safe sexual practices was high but reported condom usage was low. The prevalence of infection with C. trachomatis was 20%. The prevalence of infection with N. gonorrhoeae and syphilis were 5.1% and 4.1%, respectively.

CONCLUSIONS

Bacterial sexually transmitted infections are a major health problem in the Solomon Islands. Interventions are urgently needed.

EphrinA2 receptor (EphA2) is an invasion and intracellular signaling receptor for Chlamydia trachomatis

The obligate intracellular bacterium Chlamydia trachomatis invades into host cells to replicate inside a membrane-bound vacuole called inclusion. Multiple different host proteins are recruited to the inclusion and are functionally modulated to support chlamydial development. Invaded and replicating Chlamydia induces a long-lasting activation of the PI3 kinase signaling pathway that is required for efficient replication. We identified the cell surface tyrosine kinase EphrinA2 receptor (EphA2) as a chlamydial adherence and invasion receptor that induces PI3 kinase (PI3K) activation, promoting chlamydial replication. Interfering with binding of C. trachomatis serovar L2 (Ctr) to EphA2, downregulation of EphA2 expression or inhibition of EphA2 activity significantly reduced Ctr infection. Ctr interacts with and activates EphA2 on the cell surface resulting in Ctr and receptor internalization. During chlamydial replication, EphA2 remains active accumulating around the inclusion and interacts with the p85 regulatory subunit of PI3K to support the activation of the PI3K/Akt signaling pathway that is required for normal chlamydial development. Overexpression of full length EphA2, but not the mutant form lacking the intracellular cytoplasmic domain, enhanced PI3K activation and Ctr infection. Despite the depletion of EphA2 from the cell surface, Ctr infection induces upregulation of EphA2 through the activation of the ERK pathway, which keeps the infected cell in an apoptosis-resistant state. The significance of EphA2 as an entry and intracellular signaling receptor was also observed with the urogenital C. trachomatis-serovar D. Our findings provide the first evidence for a host cell surface receptor that is exploited for invasion as well as for receptor-mediated intracellular signaling to facilitate chlamydial replication. In addition, the engagement of a cell surface receptor at the inclusion membrane is a new mechanism by which Chlamydia subverts the host cell and induces apoptosis resistance.

Chlamydia trachomatis are major human pathogens causing ocular and sexually transmitted diseases with hundreds of millions of cases per year. Chlamydia replicate inside the host cell in a membrane bound vacuole called inclusion. The current concept on how Chlamydia communicates with the host cell during its replication is based on the identification of the host protein that interacts with Chlamydia. Here, we describe that C. trachomatis-serovar L2 and D use EphA2, a member of the largest class of human receptor tyrosine kinases, as an adherence and entry receptor that is endocytosed together with the bacteria. Cell surface EphA2 receptor is adopted by Chlamydia to function also at the inclusion to support growth and replication and to keep the infected cell in an apoptosis resistant state. Thus, we show that EphA2 is an undiscovered important surface and intracellular signaling receptor that is crucial for chlamydial infection and development.

Serology for trachoma surveillance after cessation of mass drug administration

Background

Trachoma, caused by Chlamydia trachomatis (Ct), is the leading infectious cause of blindness worldwide. Yearly azithromycin mass drug administration (MDA) plays a central role in efforts to eliminate blinding trachoma as a public health problem. Programmatic decision-making is currently based on the prevalence of the clinical sign “trachomatous inflammation-follicular” (TF) in children. We sought to test alternative tools for trachoma surveillance based on serology in the 12-year cohort of Kahe Mpya, Rombo District, Tanzania, where ocular chlamydial infection was eliminated with azithromycin MDA by 2005.

Methodology and Principal Findings

The present study was a community-based cross-sectional survey in Kahe Mpya. Of 989 residents, 571 people aged 6 months to 87 years were enrolled: 58% of the total population and 73% of 1–9 year olds, the key WHO indicator age group. Participants were examined for TF, had conjunctival swabs collected for nucleic acid amplification test (NAAT)-based detection of Ct, and blood collected for analysis of antibodies to the Ct antigens pgp3 and CT694 by multiplex bead-based immunoassay. Seroconversion rate was used to estimate changes in the force of infection in a reversible catalytic model. No conjunctival swabs tested positive for Ct infection by NAAT. Among 1–9 year olds, TF prevalence was 6.5%, whereas only 3.5% were seropositive. Force of infection modelling indicated a 10-fold decrease in seroconversion rate at a time corresponding to MDA commencement. Without baseline serological data, the inferences we can make about antibody status before MDA and the longevity of the antibody response are limited, though our use of catalytic modelling overcomes some of these limitations.

Conclusions/Significance

Serologic tests support NAAT findings of very low to zero prevalence of ocular Ct in this community and have potential to provide objective measures of transmission and useful surveillance tools for trachoma elimination programs.

Trachoma is the leading infectious cause of blindness. The infectious agent, Chlamydia trachomatis, can be treated with a single oral dose of azithromycin. Donated drug is a cornerstone of programs dedicated to the elimination of trachoma as a public health problem. Azithromycin is given to the entire district for 3–5 years when 10% or more of 1–9 year-olds in the district have signs of a defined follicular conjunctivitis in one or both eyes. However, follicles can be difficult to reliably diagnose and can be caused by other pathogens, especially in settings with low trachoma prevalence. More sensitive and specific ways to assess communities for trachoma transmission at program endpoints are needed. Herein we examined antibody responses in children living in a community in Tanzania born after stopping drug treatment 10 years previously. Low antibody levels (3.5% in 1–9 year-olds) reflected the lack of ocular chlamydial infection in these children. We also modelled the data to show that changes in age-specific antibody prevalence occurred when the mass drug treatment stopped. These data suggest that the age-specific prevalence of antibody responses may be of use to programs seeking to demonstrate the impact of interventions against trachoma.

Characterization of interactions between inclusion membrane proteins from Chlamydia trachomatis

Chlamydiae are obligate intracellular pathogens of eukaryotes. The bacteria grow in an intracellular vesicle called an inclusion, the membrane of which is heavily modified by chlamydial proteins called Incs (Inclusion membrane proteins). Incs represent 7-10% of the genomes of Chlamydia and, given their localization at the interface between the host and the pathogen, likely play a key role in the development and pathogenesis of the bacterium. However, their functions remain largely unknown. Here, we characterized the interaction properties between various Inc proteins of C. trachomatis, using a bacterial two-hybrid (BACTH) method suitable for detecting interactions between integral membrane proteins. To validate this approach, we first examined the oligomerization properties of the well-characterized IncA protein and showed that both the cytoplasmic domain and the transmembrane region independently contribute to IncA oligomerization. We then analyzed a set of Inc proteins and identified novel interactions between these components. Two small Incs, IncF, and Ct222, were found here to interact with many other Inc proteins and may thus represent interaction nodes within the inclusion membrane. Our data suggest that the Inc proteins may assemble in the membrane of the inclusion to form specific multi-molecular complexes in an hierarchical and temporal manner. These studies will help to better define the putative functions of the Inc proteins in the infectious process of Chlamydia.

Non-participation during azithromycin mass treatment for trachoma in The Gambia: heterogeneity and risk factors

BACKGROUND

There is concern that untreated individuals in mass drug administration (MDA) programs for neglected tropical diseases can reduce the impact of elimination efforts by maintaining a source of transmission and re-infection.

METHODOLOGY/PRINCIPAL FINDINGS

Treatment receipt was recorded against the community census during three MDAs with azithromycin for trachoma in The Gambia, a hypo-endemic setting. Predictors of non-participation were investigated in 1-9 year olds using random effects logistic regression of cross-sectional data for each MDA. Two types of non-participators were identified: present during MDA but not treated (PNT) and eligible for treatment but absent during MDA (EBA). PNT and EBA children were compared to treated children separately. Multivariable models were developed using baseline data and validated using year one and two data, with a priori adjustment for previous treatment status. Analyses included approximately 10000 children at baseline and 5000 children subsequently. There was strong evidence of spatial heterogeneity, and persistent non-participation within households and individuals. By year two, non-participation increased significantly to 10.4% overall from 6.2% at baseline, with more, smaller geographical clusters of non-participating households. Multivariable models suggested household level predictors of non-participation (increased time to water and household head non-participation for both PNT and EBA; increased household size for PNT status only; non-inclusion in a previous trachoma examination survey and younger age for EBA only). Enhanced coverage efforts did not decrease non-participation. Few infected children were detected at year three and only one infected child was EBA previously. Infected children were in communities close to untreated endemic areas with higher rates of EBA non-participation during MDA.

CONCLUSIONS/SIGNIFICANCE

In hypo-endemic settings, with good coverage and no association between non-participation and infection, efforts to improve participation during MDA may not be required. Further research could investigate spatial hotspots of infection and non-participation in other low and medium prevalence settings before allocating resources to increase participation.

Analysis of MreB interactors in Chlamydia reveals a RodZ homolog but fails to detect an interaction with MraY

Chlamydia is an obligate intracellular bacterial pathogen that has significantly reduced its genome in adapting to the intracellular environment. One class of genes for which the bacterium has few annotated examples is cell division, and Chlamydia lacks FtsZ, a central coordinator of the division apparatus. We have previously implicated MreB as a potential substitute for FtsZ in Chlamydia (Ouellette et al., 2012). Thus, to identify new chlamydial cell division components, we searched for proteins that interacted with MreB. We performed a small-scale screen using a Gateway® compatible version of the Bacterial Adenylate Cyclase Two Hybrid (BACTH) system, BACTHGW, to detect proteins interacting with chlamydial MreB and identified a RodZ (YfgA) homolog. The chlamydial RodZ aligns well with the cytoplasmic domain of E. coli RodZ but lacks the periplasmic domain that is dispensable for rod cell shape maintenance in E. coli. The expression pattern of yfgA/rodZ was similar to that of mreB and ftsI, suggesting that these genes may operate in a common functional pathway. The chlamydial RodZ correctly localized to the membrane of E. coli but was unable to complement an E. coli rodZ mutant strain, likely because of the inability of chlamydial RodZ to interact with the native E. coli MreB. Finally, we also tested whether chlamydial MreB could interact with MraY, as suggested by Gaballah et al. (2011). However, we did not detect an interaction between these proteins even when using an implementation of the BACTH system to allow native orientation of the N- and C-termini of MraY in the periplasm. Thus, further work will be needed to establish this proposed interaction. In sum, we have added to the repertoire of potential cell division proteins of Chlamydia.

Towards a safe and effective chlamydial vaccine: lessons from the eye

As well as being the most common bacterial sexually transmitted infection, Chlamydia trachomatis (Ct) is the leading infectious cause of blindness. The pathogenesis of ocular chlamydial infection (trachoma) is similar to that of genital infection. In the 1960s the efficacy of Ct vaccines against ocular infection was evaluated in major field trials in Saudi Arabia, Taiwan, The Gambia, India and Ethiopia. These trials showed that it was possible to induce short term immunity to ocular infection, and to reduce the incidence of inflammatory trachoma, by parenteral immunisation with killed or live whole organism vaccines. In one study, it was also shown that the incidence of scarring sequelae was reduced in vaccinated children. Detailed studies in non-human primates conducted at this time suggested that vaccination could lead to more severe inflammatory disease on subsequent challenge. Since that time there have been many studies on the immunological correlates of protective immunity and immunopathology in ocular Ct infection in humans and non-human primates, and on host genetic polymorphisms associated with protection from adverse sequelae. These have provided important information to guide the development and evaluation of a human Ct vaccine.

Chlamydial metabolism revisited: interspecies metabolic variability and developmental stage-specific physiologic activities

Chlamydiae are a group of obligate intracellular bacteria comprising important human and animal pathogens as well as symbionts of ubiquitous protists. They are characterized by a developmental cycle including two main morphologically and physiologically distinct stages, the replicating reticulate body and the infectious nondividing elementary body. In this review, we reconstruct the history of studies that have led to our current perception of chlamydial physiology, focusing on their energy and central carbon metabolism. We then compare the metabolic capabilities of pathogenic and environmental chlamydiae highlighting interspecies variability among the metabolically more flexible environmental strains. We discuss recent findings suggesting that chlamydiae may not live as energy parasites throughout the developmental cycle and that elementary bodies are not metabolically inert but exhibit metabolic activity under appropriate axenic conditions. The observed host-free metabolic activity of elementary bodies may reflect adequate recapitulation of the intracellular environment, but there is evidence that this activity is biologically relevant and required for extracellular survival and maintenance of infectivity. The recent discoveries call for a reconsideration of chlamydial metabolism and future in-depth analyses to better understand how species- and stage-specific differences in chlamydial physiology may affect virulence, tissue tropism, and host adaptation.

Comparing the performance of cluster random sampling and integrated threshold mapping for targeting trachoma control, using computer simulation

BACKGROUND

Implementation of trachoma control strategies requires reliable district-level estimates of trachomatous inflammation-follicular (TF), generally collected using the recommended gold-standard cluster randomized surveys (CRS). Integrated Threshold Mapping (ITM) has been proposed as an integrated and cost-effective means of rapidly surveying trachoma in order to classify districts according to treatment thresholds. ITM differs from CRS in a number of important ways, including the use of a school-based sampling platform for children aged 1-9 and a different age distribution of participants. This study uses computerised sampling simulations to compare the performance of these survey designs and evaluate the impact of varying key parameters.

METHODOLOGY/PRINCIPAL FINDINGS

Realistic pseudo gold standard data for 100 districts were generated that maintained the relative risk of disease between important sub-groups and incorporated empirical estimates of disease clustering at the household, village and district level. To simulate the different sampling approaches, 20 clusters were selected from each district, with individuals sampled according to the protocol for ITM and CRS. Results showed that ITM generally under-estimated the true prevalence of TF over a range of epidemiological settings and introduced more district misclassification according to treatment thresholds than did CRS. However, the extent of underestimation and resulting misclassification was found to be dependent on three main factors: (i) the district prevalence of TF; (ii) the relative risk of TF between enrolled and non-enrolled children within clusters; and (iii) the enrollment rate in schools.

CONCLUSIONS/SIGNIFICANCE

Although in some contexts the two methodologies may be equivalent, ITM can introduce a bias-dependent shift as prevalence of TF increases, resulting in a greater risk of misclassification around treatment thresholds. In addition to strengthening the evidence base around choice of trachoma survey methodologies, this study illustrates the use of a simulated approach in addressing operational research questions for trachoma but also other NTDs.

The added value of water, sanitation, and hygiene interventions to mass drug administration for reducing the prevalence of trachoma: a systematic review examining

Trachoma is the leading cause of infectious blindness worldwide. The SAFE strategy, the World Health Organization-recommended method to eliminate blinding trachoma, combines developments in water, sanitation, surgery, and antibiotic treatment. Current literature does not focus on the comprehensive effect these components have on one another. The present systematic review analyzes the added benefit of water, sanitation, and hygiene education interventions to preventive mass drug administration of azithromycin for trachoma. Trials were identified from the PubMed database using a series of search terms. Three studies met the complete criteria for inclusion. Though all studies found a significant change in reduction of active trachoma prevalence, the research is still too limited to suggest the impact of the “F” and “E” components on trachoma prevalence and ultimately its effects on blindness.

A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM)(a)

The critical role of the microbiology laboratory in infectious disease diagnosis calls for a close, positive working relationship between the physician and the microbiologists who provide enormous value to the health care team. This document, developed by both laboratory and clinical experts, provides information on which tests are valuable and in which contexts, and on tests that add little or no value for diagnostic decisions. Sections are divided into anatomic systems, including Bloodstream Infections and Infections of the Cardiovascular System, Central Nervous System Infections, Ocular Infections, Soft Tissue Infections of the Head and Neck, Upper Respiratory Infections, Lower Respiratory Tract infections, Infections of the Gastrointestinal Tract, Intraabdominal Infections, Bone and Joint Infections, Urinary Tract Infections, Genital Infections, and Skin and Soft Tissue Infections; or into etiologic agent groups, including Tickborne Infections, Viral Syndromes, and Blood and Tissue Parasite Infections. Each section contains introductory concepts, a summary of key points, and detailed tables that list suspected agents; the most reliable tests to order; the samples (and volumes) to collect in order of preference; specimen transport devices, procedures, times, and temperatures; and detailed notes on specific issues regarding the test methods, such as when tests are likely to require a specialized laboratory or have prolonged turnaround times. There is redundancy among the tables and sections, as many agents and assay choices overlap. The document is intended to serve as a reference to guide physicians in choosing tests that will aid them to diagnose infectious diseases in their patients.

Doxycycline prevents matrix remodeling and contraction by trichiasis-derived conjunctival fibroblasts

PURPOSE

Trachoma is a conjunctival scarring disease, which is the leading infectious cause of blindness worldwide. Elimination of blinding trachoma is being held back by the high rate of trichiasis recurrence following surgery. There is currently no treatment available to suppress the profibrotic state and reduce recurrence. Although the mechanisms underlying trichiasis development are unknown, the profibrotic phenotype has been linked to matrix metalloproteinase (MMP) expression. Doxycycline, a well-known tetracycline antibiotic, can act as a broad MMP inhibitor and has showed some success in preventing fibrosis in various clinical contexts. The purpose of this work was to assess the antiscarring properties of doxycycline in an in vitro model of trichiasis fibroblast-mediated tissue contraction.

METHODS

Primary cultures of fibroblasts were established from conjunctival samples obtained from normal donors or during surgery for trachomatous trichiasis. The effect of doxycycline on matrix contraction was investigated in our standard collagen gel contraction model. Cell morphology and matrix integrity were assessed using confocal reflection microscopy. Quantitative real time polymerase chain reaction and a FRET-based assay were used to measure MMP expression and activity, respectively.

RESULTS

Doxycycline treatment successfully suppressed the contractile phenotype of trichiasis fibroblasts, matrix degradation, and significantly altered the expression of MMP1, MMP9, and MMP12 associated with the profibrotic phenotype.

CONCLUSIONS

In view of the results presented here and the wider use of doxycycline in clinical settings, we propose that doxycycline might be useful as a treatment to prevent recurrence following trichiasis surgery.

Rapid assessment of trachoma in underserved population of Car-Nicobar Island, India

PURPOSE

To determine the burden of trachoma and its related risk factors amongst the native population of Car-Nicobar Island in India.

METHODS

Rapid assessment for trachoma was conducted in ten villages of Car-Nicobar Island according to standard WHO guidelines. An average of 50 children aged 1-9 years were assessed clinically for signs of active trachoma and facial cleanliness in each village. Additionally, all adults above 15 years of age in these households were examined for evidence of trachomatous trichiasis and corneal opacity. Environmental risk factors contributing to trachoma like limited access to potable water & functional latrine, presence of animal pen and garbage within the Nicobari hut were also noted in all villages.

RESULTS

Out of a total of fifteen villages in Car-Nicobar Island, ten villages were selected for trachoma survey depending on evidence of socio-developmental indicators like poverty and decreased access to water, sanitation and healthcare facilities. The total population of the selected clusters was 7277 in the ten villages. Overall, 251 of 516 children (48.6%;CI: 46.5-55.1) had evidence of follicular stage of trachoma and 11 children (2.1%;CI:1.0-3.4) had evidence of inflammatory stage of trachoma. Nearly 15%(CI:12.1-18.3) children were noted to have unclean faces in the ten villages. Trachomatous trichiasis was noted in 73 adults (1.0%;CI:0.8-1.2). The environmental sanitation was not found to be satisfactory in the surveyed villages mainly due to the co-habitance of Nicobari people with domestic animals like pigs, hens, goats, dogs, cats etc in most (96.4%) of the households.

CONCLUSION

Active trachoma and trachomatous trichiasis was observed in all the ten villages surveyed, wherein trachoma control measures are needed.

PORF5 plasmid protein of Chlamydia trachomatis induces MAPK-mediated pro-inflammatory cytokines via TLR2 activation in THP-1 cells

Infection with Chlamydia trachomatis induces inflammatory pathologies in the urogenital tract that can lead to infertility and ectopic pregnancy. Pathogenesis of infection has been mostly attributed to excessive cytokine production. However, precise mechanisms on how C. trachomatis triggers this production, and which protein(s) stimulate inflammatory cytokines remains unknown. In the present study, the C. trachomatis pORF5 protein induced tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-8 (IL-8) in dose- and time-dependent manners in the THP-1 human monocyte cell line. We found that intracellular p38/mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)/MAPK signaling pathways were required for the induction of TNF-α, IL-1β and IL-8. Blockade of toll-like receptor 2 (TLR2) signaling reduced induction levels of TNF-α, IL-8 and IL-1β. We concluded that the C. trachomatis pORF5 protein might contribute to the inflammatory processes associated with chlamydial infections.

Association between water related factors and active trachoma in Hai district, Northern Tanzania

BACKGROUND

Trachoma is widely distributed in sub-Saharan Africa and is mainly associated with poor water accessibility. However, these associations have never been demonstrated in some of the communities, especially in northern Tanzania. To cover that gap, the present case control study was conducted to assess the association of water related factors, general hygiene and active trachoma among preschool and school age children in Hai district, northern Tanzania.

RESULTS

Families reported to use > 60 litres of water per day were less likely to have active disease (OR= 0.4, 95% CI: 0.1 - 0.3; P<0.001) compared to households collecting ≤ 60 litres. The risk of having trachoma increased with increase in distance to the water point (OR= 6.5, 95% CI; 1.8 - 16.7; P= 0.003). Households members who reported to use < 2 liters of water for face washing were more likely to be trachomatous (OR= 5.12, 95% CI: 1.87-14.6, P = 0.001). Increased number of preschool children in the household was also associated with increased risk of active trachoma by 2.46 folds.

CONCLUSIONS

Improving water supply near the households and providing public health education focusing on improving households socio-economic status and individual hygiene especially in pre-school children in part will help to reduce the prevalence of the disease. In addition, integrating public health education with other interventions such as medical interventions remains important.

Risk of trachoma in a SAFE intervention area

To determine prevalence and risk factors of trachoma in communities receiving intervention with the SAFE strategy (surgery, antibiotic, face washing, environmental hygiene), a cross-sectional trachoma survey was undertaken in 2006 in the Enemor district of southern Ethiopia where the SAFE program has been implemented for over five years. A sample of 374 household heads and 2,080 individuals were interviewed and examined for trachoma using an established trachoma grading system of the World Health Organization. The most prominent risk factors were identified with logistic regression analysis. Among individuals >14 years of age, the prevalence of trichiasis was 9.04 % [confidence interval (CI) 7.4-10.6]. People >40 years of age [odds ratio (OR) 1.7; CI 1.2-2.7), women (OR 2.2; CI 1.1-4.3), and illiterates (OR 3; CI 1.4-6.8) had increased risk of trichiasis. Coverage of surgical and antibiotic services was 46 and 85.5 %, respectively. Prevalence of active follicular trachoma (TF) in children aged 1-9 years was 33.1 % (CI 29.4-37.1). Unclean faces (OR 5.9; CI 4.3-8.3) and not being in school (OR 2.1; CI 1.3-3.3) were significantly associated with TF. Clean faces were observed in 56.1 % of children and improved with age and schooling (P < 0.001, Chi-squared test). Household latrine use (74.4 %) was associated with knowledge about SAFE and economic level (P ≤ 0.004, Chi-squared tests). Elderly illiterate women remain at risk of becoming blind from trachoma even in intervention areas. Trachoma particularly affects children without clean faces or opportunity for schooling. Provision of SAFE services with high coverage should be sustained in trachoma-hyperendemic areas.

Prevalence of and risk factors for trachoma in Kano state, Nigeria

Background

In northern Nigeria, trachoma is an important public health problem, but there are currently few population-based data on prevalence of disease and no formal trachoma control programs.

Methodology / Principal Findings

In Kano state, Nigeria, we conducted a population-based cross-sectional survey using multistage cluster random sampling, combining examination for clinical signs of trachoma and application of questionnaires assessing potential household-level risk factors. A total of 4491 people were examined in 40 clusters, of whom 1572 were aged 1–9 years, and 2407 (53.6%) were female. In 1–9 year-olds, the prevalence of trachomatous inflammation–follicular (TF) was 17.5% (95% CI: 15.7–19.5%). In a multivariate model, independent risk factors for active trachoma were the presence of flies on the face (OR 1.98, 95% CI 1.30–3.02); a dirty face (OR 2.45, 95% CI 1.85–3.25) and presence of animal dung within the compound of residence (OR 3.46, 95% CI 1.62–7.41). The prevalence of trachomatous trichiasis in persons aged ≥15years was 10.9% (95% CI: 9.7–12.2%). Trichiasis was significantly more common in adult females than in adult males.

Conclusion/Significance

There is an urgent need for a trachoma control program in Kano state, with emphasis given to provision of good quality trichiasis surgery. Particular effort will need to be made to identify women with trichiasis and engage them with appropriate services while also taking steps to secure azithromycin for mass treatment and ensuring personal and environmental hygiene.

Chlamydia co-opts the rod shape-determining proteins MreB and Pbp2 for cell division

Chlamydiae are obligate intracellular bacterial pathogens that have extensively reduced their genome in adapting to the intracellular environment. The chlamydial genome contains only three annotated cell division genes and lacks ftsZ. How this obligate intracellular pathogen divides is uncharacterized. Chlamydiae contain two high-molecular-weight (HMW) penicillin binding proteins (Pbp) implicated in peptidoglycan synthesis, Pbp2 and Pbp3/FtsI. We show here, using HMW Pbp-specific penicillin derivatives, that both Pbp2 and Pbp3 are essential for chlamydial cell division. Ultrastructural analyses of antibiotic-treated cultures revealed distinct phenotypes: Pbp2 inhibition induced internal cell bodies within a single outer membrane whereas Pbp3 inhibition induced elongated phenotypes with little internal division. Each HMW Pbp interacts with the Chlamydia cell division protein FtsK. Chlamydiae are coccoid yet contain MreB, a rod shape-determining protein linked to Pbp2 in bacilli. Using MreB-specific antibiotics, we show that MreB is essential for chlamydial growth and division. Importantly, co-treatment with MreB-specific and Pbp-specific antibiotics resulted in the MreB-inhibited phenotype, placing MreB upstream of Pbp function in chlamydial cell division. Finally, we showed that MreB also interacts with FtsK. We propose that, in Chlamydia, MreB acts as a central co-ordinator at the division site to substitute for the lack of FtsZ in this bacterium.

Two-day dosing versus one-day dosing of azithromycin in children with severe trachoma in Tanzania

PURPOSE

To determine whether 2-day dosing of azithromycin may improve the efficacy of azithromycin dosing in children with severe trachoma.

METHODS

Fifty children with severe trachoma (defined as either trachoma intense or follicular trachoma with ten or more follicles) were enrolled from five villages in Kongwa, Tanzania. Enrollment occurred within 1 month and within the same district as the historical control population of 99 children with severe trachoma, all of whom received 1-day dosing. Baseline data on age, sex, and trachoma status were obtained, and swabs for determination of Chlamydia trachomatis were taken. All 50 children received 20 mg/kg azithromycin daily for 2 days, which was directly observed. Children were followed up at 6 weeks for trachoma and infection. The laboratory was masked to treatment assignment.

RESULTS

Baseline characteristics were similar between the treatment group and the control group. A total of 1/46 (2.2%) of children in the treatment group were polymerase chain reaction (PCR)-positive at 6 weeks, a 96.3% reduction from baseline, compared to 13/96 (13.5%) in the historical control group, an 89.4% reduction. This difference was statistically significant. However when modeled using logistic regression and accounting for age, gender, weight, and baseline percent PCR positivity, the difference was not significant. Prevalence of clinical trachoma did not differ between the groups at 6 weeks.

CONCLUSION

For children with severe trachoma, a randomized controlled trial of 2-day versus 1-day treatment may be warranted.

Nucleotide and phylogenetic analyses of the Chlamydia trachomatis ompA gene indicates it is a hotspot for mutation

Background

Serovars of the human pathogen Chlamydia trachomatis occupy one of three specific tissue niches. Genomic analyses indicate that the serovars have a phylogeny congruent with their pathobiology and have an average substitution rate of less than one nucleotide per kilobase. In contrast, the gene that determines serovar specificity, ompA, has a phylogenetic association that is not congruent with tissue tropism and has a degree of nucleotide variability much higher than other genomic loci. The ompA gene encodes the major surface-exposed antigenic determinant, and the observed nucleotide diversity at the ompA locus is thought to be due to recombination and host immune selection pressure. The possible contribution of a localized increase in mutation rate, however, has not been investigated.

Results

Nucleotide diversity and phylogenetic relationships of the five constant and four variable domains of the ompA gene, as well as several loci surrounding ompA, were examined for each serovar. The loci flanking the ompA gene demonstrated that nucleotide diversity increased monotonically as ompA is approached and that their gene trees are not congruent with either ompA or tissue tropism. The variable domains of the ompA gene had a very high level of non-synonymous change, which is expected as these regions encode the surface-exposed epitopes and are under positive selection. However, the synonymous changes are clustered in the variable regions compared to the constant domains; if hitchhiking were to account for the increase in synonymous changes, these substitutions should be more evenly distributed across the gene. Recombination also cannot entirely account for this increase as the phylogenetic relationships of the constant and variable domains are congruent with each other.

Conclusions

The high number of synonymous substitutions observed within the variable domains of ompA appears to be due to an increased mutation rate within this region of the genome, whereas the increase in nucleotide substitution rate and the lack of phylogenetic congruence in the regions flanking ompA are characteristic motifs of gene conversion. Together, the increased mutation rate in the ompA gene, in conjunction with gene conversion and positive selection, results in a high degree of variability that promotes host immune evasion.

Population-based survey of active trachoma in 11 districts of Burundi

PURPOSE

To establish that trachoma is a public health problem in Burundi, and to provide baseline data on the prevalence of active trachoma and unclean faces prior to the commencement of trachoma elimination activities in endemic districts.

METHODS

For each of 11 pilot districts, eight collines (hills) (estimated population generally 1000-8000) were selected at random using a population-proportional-to-size technique; from each selected colline, one sous-colline (of which there are generally 3-5 per colline) was selected at random by simple random draw. In each selected sous-colline, all available 1-9-year-old children were examined for clinical signs of trachoma, and for signs of an unclean face (defined as eye discharge, nose discharge and/or presence of one or more flies on the face during the time taken to examine the eyes).

RESULTS

A mean of 230 children were examined per sous-colline (range 44-600); in all, 20,659 children were examined in 90 sous-collines of 11 districts. (In one district, 10 rather than eight sous-collines were selected.) In three contiguous districts (Buhiga, Nyabikere and Muyinga) in the country's north-east, the prevalence of the sign "trachomatous inflammation-follicular" (TF) in 1-9-year-olds was >10%. In nine districts, the prevalence of unclean faces was >10%.

CONCLUSION

Trachoma is a public health problem in Burundi. Implementation of trachoma control activities is indicated in at least Buhiga, Nyabikere and Muyinga. Further work should be carried out to establish the likely backlog of unoperated trachomatous trichiasis.

Integrated monitoring and evaluation and environmental risk factors for urogenital schistosomiasis and active trachoma in Burkina Faso before preventative chemotherapy using sentinel sites

Background

Over 1 billion of the world's poorest inhabitants are afflicted by neglected tropical diseases (NTDs). Integrated control programmes aimed at tackling these debilitating NTDs have been recently initiated, mainly using preventative chemotherapy. Monitoring and evaluation (M&E) of these integrated programs presents particular challenges over and above those required for single disease vertical programmes. We used baseline data from the National NTD Control Programme in Burkina Faso in order to assess the feasibility of an integrated survey design, as well as to elucidate the contribution of environmental variables to the risk of either Schistosoma haematobium, trachoma, or both among school-aged children.

Methods

S. haematobium infection was diagnosed by detecting eggs in urine. A trachoma case was defined by the presence of Trachomatous inflammation-Follicular (TF) and/or Trachomatous inflammation-Intense (TI) in either eye. Baseline data collected from 3,324 children aged 7-11 years in 21 sentinel sites across 11 regions of Burkina Faso were analyzed using simple and multivariable hierarchical binomial logistic regression models fitted by Markov Chain Monte Carlo estimation methods. Probabilities of the risk of belonging to each infection/disease category were estimated as a function of age, gender (individual level), and environmental variables (at sentinel site level, interpolated from national meteorological stations).

Results

Overall prevalence at the sentinel sites was 11.79% (95% CI: 10.70-12.89) for S. haematobium; 13.30% (12.14-14.45) for trachoma and 0.84% (0.53-1.15) for co-infections. The only significant predictor of S. haematobium infection was altitude. There were significant negative associations between the prevalence of active trachoma signs and minimum temperature, and air pressure. Conditional upon these predictors, these data are consistent with the two pathogens being independent.

Conclusions

Urogenital schistosomiasis and trachoma constitute public health problems in Burkina Faso. Sentinel site (at school level) surveys for these two NTDs can be implemented simultaneously. However, to support MDA treatment decisions in Burkina Faso, the protocol used in this study would only be applicable to hypoendemic trachoma areas. More research is needed to confirm if these findings can be generalized to West Africa and beyond.

Relationship between distance to social gathering facilities and risk of trachoma for households in rural Tanzanian communities

Few studies have examined the physical isolation of households with trachoma cases. Thus, in this study, we sought to examine the association between household isolation, as measured by distance to social gathering facilities, and risk of trachoma. We hypothesized that households located closer to such facilities would have a decreased risk of trachoma, due to a variety of social, economic, and cultural reasons. To test this hypothesis we conducted a case-control study of 668 households (93 cases, 575 controls) in eight villages in Kongwa District, Tanzania, in 2007. Case households were defined as having a child aged 1-5 years with clinical signs of trachoma. Distance of household's place of residence to three main social gathering facilities - bars/cafés, religious establishments, and commercial/government center - was measured with a portable geographic positioning system. Multiple logistic regression analyses, which controlled for potential confounders and accounted for clustering, demonstrated increased risk of trachoma with increasing distance to social gathering facilities. Compared with distances of ≤700 m, odds of trachoma were approximately two-fold higher for households living >1400 m from bars/cafés and from religious establishments, suggesting increased risk of trachoma for households at the fringes of communities. Targeting these isolated households with special programming along with dissemination through trusted social gathering facilities may improve effectiveness of current prevention efforts.

Chlamydia species-dependent differences in the growth requirement for lysosomes

Genome reduction is a hallmark of obligate intracellular pathogens such as Chlamydia, where adaptation to intracellular growth has resulted in the elimination of genes encoding biosynthetic enzymes. Accordingly, chlamydiae rely heavily on the host cell for nutrients yet their specific source is unclear. Interestingly, chlamydiae grow within a pathogen-defined vacuole that is in close apposition to lysosomes. Metabolically-labeled uninfected host cell proteins were provided as an exogenous nutrient source to chlamydiae-infected cells, and uptake and subsequent labeling of chlamydiae suggested lysosomal degradation as a source of amino acids for the pathogen. Indeed, Bafilomycin A1 (BafA1), an inhibitor of the vacuolar H⁺/ATPase that blocks lysosomal acidification and functions, impairs the growth of C. trachomatis and C. pneumoniae, and these effects are especially profound in C. pneumoniae. BafA1 induced the marked accumulation of material within the lysosomal lumen, which was due to the inhibition of proteolytic activities, and this response inhibits chlamydiae rather than changes in lysosomal acidification per se, as cathepsin inhibitors also inhibit the growth of chlamydiae. Finally, the addition of cycloheximide, an inhibitor of eukaryotic protein synthesis, compromises the ability of lysosomal inhibitors to block chlamydial growth, suggesting chlamydiae directly access free amino acids in the host cytosol as a preferred source of these nutrients. Thus, chlamydiae co-opt the functions of lysosomes to acquire essential amino acids.

Systemic effector and regulatory immune responses to chlamydial antigens in trachomatous trichiasis

Trachomatous trichiasis (TT) caused by repeated or chronic ocular infection with Chlamydia trachomatis is the result of a pro-fibrotic ocular immune response. At the conjunctiva, the increased expression of both inflammatory (IL1B, TNF) and regulatory cytokines (IL10) have been associated with adverse clinical outcomes. We measured in vitro immune responses of peripheral blood to a number of chlamydial antigens. Peripheral blood effector cells (CD4, CD69, IFNγ, IL-10) and regulatory cells (CD4, CD25, FOXP3, CTLA4/GITR) were readily stimulated by C. trachomatis antigens but neither the magnitude (frequency or stimulation index) or the breadth and amount of cytokines produced in vitro [IL-5, IL-10, IL-12 (p70), IL-13, IFNγ, and TNFα] were significantly different between TT cases and their non-diseased controls. Interestingly we observed that CD4+ T cells account for <50% of the IFNγ positive cells induced following stimulation. Further investigation in individuals selected from communities where exposure to ocular infection with C. trachomatis is endemic indicated that CD3-CD56+ (classical natural killer cells) were a major early source of IFNγ production in response to C. trachomatis elementary body stimulation and that the magnitude of this response increased with age. Future efforts to unravel the contribution of the adaptive immune response to conjunctival fibrosis should focus on the early events following infection and the interaction with innate immune mediated mechanisms of inflammation in the conjunctiva.

Haptoglobin and sickle cell polymorphisms and risk of active trachoma in Gambian children

Background

Susceptibility and resistance to trachoma, the leading infectious cause of blindness, have been associated with a range of host genetic factors. In vitro studies of the causative organism, Chlamydia trachomatis, demonstrate that iron availability regulates its growth, suggesting that host genes involved in regulating iron status and/or availability may modulate the risk of trachoma. The objective was to investigate whether haptoglobin (Hp) haplotypes constructed from the functional polymorphism (Hp1/Hp2) plus the functional promoter SNPs -61A-C (rs5471) and -101C-G (rs5470), or sickle cell trait (HbAS, rs334) were associated with risk of active trachoma when stratified by age and sex, in rural Gambian children.

Methodology and Principal Findings

In two cross sectional surveys of children aged 6–78 months (n = 836), the prevalence of the clinical signs of active trachoma was 21.4%. Within boys, haplotype E (-101G, -61A, Hp1), containing the variant allele of the -101C-G promoter SNP, was associated with a two-fold increased risk of active trachoma (OR = 2.0 [1.17–3.44]). Within girls, an opposite association was non-significant (OR = 0.58 [0.32–1.04]; P = 0.07) and the interaction by sex was statistically significant (P = 0.001). There was no association between trachoma and HbAS.

Conclusions

These data indicate that genetic variation in Hp may affect susceptibility to active trachoma differentially by sex in The Gambia.

Epidemiology and control of trachoma: systematic review

Trachoma is the commonest infectious cause of blindness. Recurrent episodes of infection with serovars A-C of Chlamydia trachomatis cause conjunctival inflammation in children who go on to develop scarring and blindness as adults. It was estimated that in 2002 at least 1.3 million people were blind from trachoma, and currently 40 million people are thought to have active disease and 8.2 million to have trichiasis. The disease is largely found in poor, rural communities in developing countries, particularly in sub-Saharan Africa. The WHO promotes trachoma control through a multifaceted approach involving surgery, mass antibiotic distribution, encouraging facial cleanliness and environmental improvements. This has been associated with significant reductions in the prevalence of active disease over the past 20 years, but there remain a large number of people with trichiasis who are at risk of blindness.

Autoprocessing and self-activation of the secreted protease CPAF in Chlamydia-infected cells

The Chlamydia-secreted protease/proteasome-like activity factor (CPAF) is synthesized as a proenzyme (proCPAF) and requires processing for proteolytic activity. Recent structural studies have further demonstrated that CPAF is a serine protease that can undergo autoprocessing and self-activation in a concentration-dependent manner in vitro. However, it is not known how CPAF is processed and activated during chlamydial infection. In the current study, we used a mutant CPAF designated as CPAF(E558A) that is deficient in processing by itself as a substrate to search for putative CPAF activation factor(s) in Chlamydia-infected cells. CPAF(E558A) was processed by the lysates made from Chlamydia-infected cells and the processing activity correlated with the presence of endogenous active CPAF in the fractionated lysate samples. CPAF produced in the Chlamydia-infected cells is required for processing the mutant CPAF(E558A) since the processing activity was removed by depletion with anti-CPAF but not control antibodies. Furthermore, a purified and activated wild type CPAF alone was sufficient for processing CPAF(E558A) and no other chlamydial proteases are required. Finally, fusion tag-induced oligomerization can lead to autoprocessing and self-activation of the wild type CPAF in mammalian cells. These observations together have demonstrated that CPAF undergoes autoprocessing and self-activation during chlamydial infection.

Pathway-focused arrays reveal increased matrix metalloproteinase-7 (matrilysin) transcription in trachomatous trichiasis

PURPOSE

Several genes that are associated with protection from or susceptibility to trachomatous trichiasis (TT) have been identified through genetic association studies. Yet there have been few studies in which gene expression profiles were assessed in TT cases and disease-free controls. The purpose was to identify genes that are differentially expressed in the upper tarsal conjunctiva of subjects with TT.

METHOD

Pathway-focused gene arrays were used to screen conjunctival RNA expression of 226 gene transcripts of interest. The screening was followed by validation of differentially expressed genes by qRT-PCR on an independent set of samples. Three different techniques were then used to test for quantitative differences in the recovered conjunctival protein fraction.

RESULTS

Focused arrays identified a set of 13 differentially expressed genes. Validation by qRT-PCR confirmed differential expression in four of these genes (COL1A1, COL7A1, MMP7, and TLR6). Increased expression of MMP7 was the only consistent differentially regulated gene in the conjunctival samples of trichiasis subjects. MMP7 was present in isolated conjunctival proteins and in the tissue culture supernatants of peripheral blood lymphocytes after stimulation.

CONCLUSIONS

There is an imbalance in extracellular matrix turnover with minimal contribution of adaptive immune responses at this stage of trichiasis. There was little evidence of broad differential expression in genes characteristic of polar responses of adaptive T cells or macrophages. The control of the MMP7 response and its activity appears significant in the fibrotic changes observed in TT.