Human Chlamydial Infections Research Articles

Preventative interventions by dental care professionals in Africa on oral human papillomavirus, gonorrheal, chlamydial, syphilitic and trichomonas infections: A scoping review.

Oral human papillomavirus (HPV), gonorrheal, chlamydial, syphilitic and trichomonas infections are very common sexually transmitted diseases (STDs) in Africa. However, no known study has reviewed the available evidence concerning the preventative interventions by dental care professionals (DCPs) in Africa on oral STDs; hence, this scoping review was conducted to evaluate the research landscape of this topic area in Africa. The scoping review methodology and documentation were informed by the Arksey and O'Malley's guideline, the Preferred Reporting Items for Systematic Reviews and Meta-analysis extension for conducting Scoping Reviews (PRISMA-ScR) checklist, and the AMSTAR-2 guideline. Ten electronic research databases were searched to retrieve literatures relevant to the scoping review question. The retrieved literature were deduplicated and screened for eligibility based on the review's selection criteria. Data charting, collation and summarization were intended to be done in this review, but it could not be done because no relevant literature was found eligible for inclusion into this scoping review. A total of 523 literature were retrieved. After deduplication of the retrieved literatures, the residual literatures (n = 353) were screened for eligibility for inclusion into the review, of which no eligible article was found. Hence, this scoping review was an empty review. This empty scoping review demonstrates that DCPs in Africa do not engage in research-based oral STD prevention. Therefore, the implementation of research-based preventative interventions, by DCPs, on oral STDs should be encouraged in Africa.

Celebrating 60 Years of Research at the 15th International Symposium on Human Chlamydial Infections.

Celebrating 60 Years of Research at the 15th International Symposium on Human Chlamydial Infections.

Virtual screening, pharmacokinetics, and molecular dynamics simulations studies to identify potent approved drugs for Chlamydia trachomatis treatment

BackgroundThe most frequent bacterial sexually transmitted disease is Chlamydia trachomatis (STD). In 2010, the Centers for Disease Control and Prevention (CDC) received 1.3 million reports of cases (CDC). Human chlamydial infections are linked to a variety of clinical symptoms. Inclusion (IncA) membranes are a promising drug target for the treatment of Chlamydia trachomatis. In the present study, molecular docking, ADMET, golden triangle, and molecular dynamics (MD) simulation studies were performed on a series of salicylidene acylhydrazides derivatives against Chlamydia trachomatis. Three types of docking software with different algorithms were used to screen the potential candidate against Chlamydia trachomatis.ResultsThe results obtained from the docking analysis succeeded in screening nine novel hit compounds with high affinity to IncA membranes. Then, pharmacokinetics properties were calculated to spot out the drug-likeness of the selected compounds. Also, golden triangles were performed on the selected compounds. Compounds outside the golden triangle indicate that they would have clearance problems. Out of the nine novel hits drugs, four compounds pass the golden triangle screening and virtually all the quality assurance tests proposed by the model and were used for further analysis. One-ns molecular dynamics simulations on the docked complex of compound 44 (one of the highly active selected compounds of the dataset) aided in the further exploration of the binding interactions. Some crucial residues such as Ser111, Gln114, Asn107, Leu142, Gly144, Gln143, Lys104, Tyr149, Phe108, Phe145, and Arg146 were identified. Conventional and carbon–hydrogen bond interactions with amino residues Arg146, Asn107, Phe145, and Ser111 were critical for the binding of inclusion (IncA) membranes inhibitors.ConclusionOutcomes of the study can further be exploited to develop potent inclusion (IncA) membranes inhibitors.

In vitro inhibitory effect of Hydrocotyle bonariensis Lam. extracts over Chlamydia trachomatis and Chlamydia pneumoniae on different stages of the chlamydial life cycle

Chlamydial infections in humans are widely distributed and are responsible for a variety of acute and chronic diseases. Both Chlamydia trachomatis and Chlamydia pneumoniae can lead to chronic conditions that have been linked to complications and sequelae.This study aimed to develop a culture method in order to detect in vitro antichlamydial activity of different extracts obtained from native Argentinian plants used as antimicrobials in local ethnomedicine and to evaluate their inhibitory activity over Chlamydia trachomatis and Chlamydia pneumoniae growth. The inhibitory activity over different stages of the chlamydial life cycle on cell culture was assessed: the entry, the inclusion developing after entry, and the exponential growth stage. Also, the capability of rendering the cell refractory to chlamydial infection by pre-incubation with the extracts was assayed.Inhibitory activity of water-based and organic-based extracts obtained from Hydrocotyle bonariensis Lam. (Araliaceae), Lithraea molleoides (Vell.) Engl. (Anacardiaceae) and Hybanthus parviflorus (Mutis ex L.f.) Baill. (Violaceae) were tested against five strains of Chlamydia trachomatis (L2/434/BU and four clinical isolates form both neonatal conjunctivitis and adult genital infections, genotypes D, E, and K) and against Chlamydia pneumoniae AR39.The Hydrocotyle bonariensis dichloromethane extract showed a broad inhibitory activity over the exponential growth stage of Chlamydia trachomatis and Chlamydia pneumoniae independently from the chlamydial strain and the cell line. These results suggest a high inhibitory potential on both Chlamydiae species.In order to characterize the Hydrocotyle bonariensis dichloromethane active extract, an 1H-NMR was performed. The 1H-NMR characterization showed a spectrum with characteristic signals of the fatty acid moiety of lipids or cerebrosides, volatile phenolics, phytosterols, methyl triterpenes signals, and glucose moiety of the cerebrosides.

Chlamydia muridarum Can Invade the Central Nervous System via the Olfactory and Trigeminal Nerves and Infect Peripheral Nerve Glial Cells.

Chlamydia pneumoniae can infect the brain and has been linked to late-onset dementia. Chlamydia muridarum, which infects mice, is often used to model human chlamydial infections. While it has been suggested to be also important for modelling brain infection, nervous system infection by C. muridarum has not been reported in the literature. C. pneumoniae has been shown to infect the olfactory bulb in mice after intranasal inoculation, and has therefore been suggested to invade the brain via the olfactory nerve; however, nerve infection has not been shown to date. Another path by which certain bacteria can reach the brain is via the trigeminal nerve, but it remains unknown whether Chlamydia species can infect this nerve. Other bacteria that can invade the brain via the olfactory and/or trigeminal nerve can do so rapidly, however, whether Chlamydia spp. can reach the brain earlier than one-week post inoculation remains unknown. In the current study, we showed that C. muridarum can within 48 h invade the brain via the olfactory nerve, in addition to infecting the trigeminal nerve. We also cultured the glial cells of the olfactory and trigeminal nerves and showed that C. muridarum readily infected the cells, constituting a possible cellular mechanism explaining how the bacteria can invade the nerves without being eliminated by glial immune functions. Further, we demonstrated that olfactory and trigeminal glia differed in their responses to C. muridarum, with olfactory glia showing less infection and stronger immune response than trigeminal glia.

Multi-locus sequence analysis reveals a novel sequence type of Chlamydia trachomatis in Saratov Region, Russia

Chlamydia trachomatis is the causative agent of a variety of chlamydial infections in humans with a predominantly (up to 80%) asymptomatic course of disease. In this study, a potentially novel C. trachomatis sequence type (ST) was detected in an asymptomatic man who has sex with a man among the nine STs revealed in urogenital swabs from individuals with chlamydia (n = 18). Phylogenetically this ST270 clustered separately as a single clade to an ST13-founded group of C. trachomatis strains and differed from the latter by a single allele, hflX. This finding emphasizes the importance of careful investigation of individuals with asymptomatic chlamydia infections.

Recombinant protein CPSIT_0846 induces protective immunity against Chlamydia psittaci infection in BALB/c mice

Chlamydia psittaci is an obligate intracellular bacteria that causes respiratory disease in poultry and humans. Currently, there are no licensed vaccines against chlamydial infection in humans. The transmembrane head protein CPSIT_0846 of C. psittaci is a putative member of the larger Inc protein family. In this study, we investigated immunogenicity and protective efficacy of the recombinant CPSIT_0846 protein in BALB/c mice. Mice immunized with CPSIT_0846 developed strong T-lymphocyte responses that were recalled by the immunogen CPSIT_0846 in an in vitro restimulation assay. These T cells displayed a strong Th1-biased cytokine profile with high levels of IFN-γ. At the same time, a strong humoral immune response was also detected in the immunized mice with high titers of Chlamydia psittaci-specific serum IgG antibodies. More importantly, the robust immune responses correlated well with significantly reduced chlamydial burden and inflammatory pathology in the mouse lungs upon an airway challenge infection. The above results together suggest that the CPSIT_0846 protein may be a potential vaccine candidate antigen for inducing protection against C. psittaci infection and disease in the airway.

Identification, characterisation and expression analysis of natural killer receptor genes in Chlamydia pecorum infected koalas (Phascolarctos cinereus).

BackgroundKoalas (Phascolarctos cinereus), an iconic Australian marsupial, are being heavily impacted by the spread of Chlamydia pecorum, an obligate intracellular bacterial pathogen. Koalas vary in their response to this pathogen, with some showing no symptoms, while others suffer severe symptoms leading to infertility, blindness or death. Little is known about the pathology of this disease and the immune response against it in this host. Studies have demonstrated that natural killer (NK) cells, key components of the innate immune system, are involved in the immune response to chlamydial infections in humans. These cells can directly lyse cells infected by intracellular pathogens and their ability to recognise these infected cells is mediated through NK receptors on their surface. These are encoded in two regions of the genome, the leukocyte receptor complex (LRC) and the natural killer complex (NKC). These two families evolve rapidly and different repertoires of genes, which have evolved by gene duplication, are seen in different species.MethodsIn this study we aimed to characterise genes belonging to the NK receptor clusters in the koala by searching available koala transcriptomes using a combination of search methods. We developed a qPCR assay to quantify relative expression of four genes, two encoded within the NK receptor cluster (CLEC1B, CLEC4E) and two known to play a role in NK response to Chalmydia in humans (NCR3, PRF1).ResultsWe found that the NK receptor repertoire of the koala closely resembles that of the Tasmanian devil, with minimal genes in the NKC, but with lineage specific expansions in the LRC. Additional genes important for NK cell activity, NCR3 and PRF1, were also identified and characterised. In a preliminary study to investigate whether these genes are involved in the koala immune response to infection by its chlamydial pathogen, C. pecorum, we investigated the expression of four genes in koalas with active chlamydia infection, those with past infection and those without infection using qPCR. This analysis revealed that one of these four, CLEC4E, may be upregulated in response to chlamydia infection.ConclusionWe have characterised genes of the NKC and LRC in koalas and have discovered evidence that one of these genes may be upregulated in koalas with chlamydia, suggesting that these receptors may play a role in the immune response of koalas to chlamydia infection.

Porcine retinal cell line VIDO R1 and Chlamydia suis to modelize ocular chlamydiosis

Human ocular Chlamydia trachomatis infections can lead to trachoma, the major cause of infectious blindness worldwide. Trachoma control strategies are very helpful but logistically challenging, and a trachoma vaccine is needed but not available. Pigs are a valuable large animal model for various immunological questions and could facilitate the study of human ocular chlamydial infections. In addition, a recent study identified the zoonotic potential of Chlamydia suis, the natural pathogen of pigs. In terms of the One Health Initiative, understanding the host–pathogen-interactions and finding a vaccine for porcine chlamydia infections would also benefit human health. Thus, we infected the porcine retinal cell line VIDO R1 with C. suis and analyzed the chlamydial life cycle and the innate immune response of the infected cells. Our results indicate that C. suis completes its life cycle in VIDO R1 cells within 48h, comparable to C. trachomatis in humans. C. suis infection of VIDO R1 cells led to increased levels of various innate immune mediators like pathogen recognition receptors, cytokines and chemokines including IL6, TNFα, and MMP9, also most relevant in human C. trachomatis infections. These results illustrate the first steps in the host–pathogen-interactions of ocular C. suis infections in pigs and show their similarity to C. trachomatis infections in humans, justifying further testing of pigs as an animal model for human trachoma.

Chlamydia psittaci: New insights into genomic diversity, clinical pathology, host–pathogen interaction and anti-bacterial immunity

The distinctive and unique features of the avian and mammalian zoonotic pathogen Chlamydia (C.) psittaci include the fulminant course of clinical disease, the remarkably wide host range and the high proportion of latent infections that are not leading to overt disease. Current knowledge on associated diseases is rather poor, even in comparison to other chlamydial agents. In the present paper, we explain and summarize the major findings of a national research network that focused on the elucidation of host–pathogen interactions in vitro and in animal models of C. psittaci infection, with the objective of improving our understanding of genomics, pathology, pathophysiology, molecular pathogenesis and immunology, and conceiving new approaches to therapy. We discuss new findings on comparative genome analysis, the complexity of pathophysiological interactions and systemic consequences, local immune response, the role of the complement system and antigen presentation pathways in the general context of state-of-the-art knowledge on chlamydial infections in humans and animals and single out relevant research topics to fill remaining knowledge gaps on this important yet somewhat neglected pathogen.

The Mouse Model of Chlamydia Genital Tract Infection: A Review of Infection, Disease, Immunity and Vaccine Development

Chlamydia trachomatis is the most common sexually transmitted bacterial infection worldwide. The impact of this pathogen on human reproduction has intensified research efforts to better understand chlamydial infection and pathogenesis. Whilst there are animal models available that mimic many aspects of human chlamydial infection, the mouse is regarded as the most practical and widely used of the models. Studies in mice have greatly contributed to our understanding of the host-pathogen interaction and provided an excellent medium for evaluating vaccines. Here we explore the advantages and disadvantages of all animal models of chlamydial genital tract infection, with a focus on the murine model and what we have learnt from it so far.

Recent advances in understanding the biology, epidemiology and control of chlamydial infections in koalas

The koala (Phascolarctos cinereus) is recognised as a threatened wildlife species in various parts of Australia. A major contributing factor to the decline and long-term viability of affected populations is disease caused by the obligate intracellular bacteria, Chlamydia. Two chlamydial species infect the koala, Chlamydia pecorum and Chlamydia pneumoniae, and have been reported in nearly all mainland koala populations. Chlamydial infections of koalas are associated with ocular infections leading to blindness and genital tract infections linked to infertility, among other serious clinical manifestations. Diagnosis can be based on clinical presentation alone, however, it is complicated by the observation that many koala chlamydial infections occur with no overt signs of clinical disease. Instead, accurate diagnosis requires detailed clinical assessment and confirmatory testing by a range of PCR-based assays. Antibiotic treatment for koala chlamydial infection is possible, however, results on its success are mixed. A more practical solution for the protection of diseased populations is the application of a koala Chlamydia vaccine, with recent trials indicating promising results. Interestingly, molecular epidemiology studies of koala C. pecorum infections and recent comparative genomic analyses of koala C. pneumoniae have revealed potential differences in their origin that will have wider ramifications for our understanding of human chlamydial infections and host adaptation of the chlamydiae. This review summarises changes to the taxonomy of koala chlamydial infections and recent advances in our understanding of the epidemiology, diagnosis, treatment, control and evolution of Chlamydia infections in this iconic wildlife species.

Laboratory diagnosis of persistent human chlamydial infection

Diagnostic assays for persistent chlamydial infection are much needed to conduct high-quality, large-scale studies investigating the persistent state in vivo, its disease associations and the response to therapy. Yet in most studies the distinction between acute and persistent infection is based on the interpretation of the data obtained by the assays developed to diagnose acute infections or on complex assays available for research only and/or difficult to establish for clinical use. Novel biomarkers for detection of persistent chlamydial infection are urgently needed. Chlamydial whole genome proteome arrays are now available and they can identify chlamydial antigens that are differentially expressed between acute infection and persistent infection. Utilizing these data will lead to the development of novel diagnostic assays. Carefully selected specimens from well-studied patient populations are clearly needed in the process of translating the proteomic data into assays useful for clinical practice. Before such antigens are identified and validated assays become available, we face a challenge of deciding whether the persistent infection truly induced appearance of the proposed marker or do we just base our diagnosis of persistent infection on the presence of the suggested markers. Consequently, we must bear this in mind when interpreting the available data.

Fluorometric High-Throughput Assay for Measuring Chlamydial Neutralizing Antibody

Chlamydia trachomatis is an obligate intracellular mucosotropic pathogen that causes human infections of global importance. C. trachomatis causes trachoma, the leading cause of preventable blindness worldwide, and is the most common cause of bacterial sexually transmitted disease. Although oculogenital infections are treatable with antibiotics, a vaccine is needed to control C. trachomatis infection. Ideally, a vaccine would provide coverage against most, if not all, naturally occurring antigenically distinct serovariants. The development of a subunit vaccine to prevent oculogenital disease could be advanced by identifying chlamydial antigens that elicit pan-neutralizing antibodies, particularly among infected human populations of known risk factors. There is currently no objective high-throughput in vitro assay to screen human sera for neutralization to aid in identification of these antigens. This report describes an objective, high-throughput in vitro assay that measures C. trachomatis-neutralizing antibodies. Antibody-mediated neutralization of chlamydial infection was performed in a 96-well microtiter format, and neutralization was quantified by immunostaining fixed cells followed by automated fluorometric analysis. This report shows that fluorometric analysis of C. trachomatis infection directly correlates to labor-intensive manual inclusion counts. Furthermore, this report shows that fluorometry can be used to identify C. trachomatis serovar- and serocomplex-specific neutralization. This objective, high-throughput analysis of serum neutralization is amenable to epidemiological studies of human chlamydial infection, human clinical vaccine trials, and preclinical animal model experiments of Chlamydia infection.

Research methods for molecular markers of the individual genetic risk for development ofcomplications of the urogenital chlamydia infection

The authors present the results of the first four stages of research conducted under Government Contract No. 02.740.11.0774: Development of a Technology for Molecular Diagnostics of the Individual Genetic Risk of Development of Reproductive Function Disorders Associated with Human Urogenital Chlamydial Infection.

Toll-Like Receptor 2 Activation by Chlamydia trachomatis Is Plasmid Dependent, and Plasmid-Responsive Chromosomal Loci Are Coordinately Regulated in Response to Glucose Limitation by C. trachomatis but Not by C. muridarum

We previously demonstrated that plasmid-deficient Chlamydia muridarum retains the ability to infect the murine genital tract but does not elicit oviduct pathology because it fails to activate Toll-like receptor 2 (TLR2). We derived a plasmid-cured derivative of the human genital isolate Chlamydia trachomatis D/UW-3/Cx, strain CTD153, which also fails to activate TLR2, indicating this virulence phenotype is associated with plasmid loss in both C. trachomatis and C. muridarum. As observed with plasmid-deficient C. muridarum, CTD153 displayed impaired accumulation of glycogen within inclusions. Transcriptional profiling of the plasmid-deficient strains by using custom microarrays identified a conserved group of chromosomal loci, the expression of which was similarly controlled in plasmid-deficient C. muridarum strains CM972 and CM3.1 and plasmid-deficient C. trachomatis CTD153. However, although expression of glycogen synthase, encoded by glgA, was greatly reduced in CTD153, it was unaltered in plasmid-deficient C. muridarum strains. Thus, additional plasmid-associated factors are required for glycogen accumulation by this chlamydial species. Furthermore, in C. trachomatis, glgA and other plasmid-responsive chromosomal loci (PRCLs) were transcriptionally responsive to glucose limitation, indicating that additional regulatory elements may be involved in the coordinated expression of these candidate virulence effectors. Glucose-limited C. trachomatis displayed reduced TLR2 stimulation in an in vitro assay. During human chlamydial infection, glucose limitation may decrease chlamydial virulence through its effects on plasmid-responsive chromosomal genes.

Antibody-neutralizing activity against all urogenital Chlamydia trachomatis serovars in Chlamydia suis-infected pigs

It is known that neutralizing species-specific or serovar-specific antibodies are produced in response to chlamydial infection in humans and in some animal species. In a previous study, a strong in vitro neutralizing activity to Chlamydia suis in 80% of sera from C. suis-infected pigs had been observed. In view of the close relationship between C. suis and Chlamydia trachomatis, in the present study, the neutralizing activity against D-K C. trachomatis and C. suis purified elementary bodies (EBs) in sera collected from C. trachomatis-infected patients and C. suis-infected pigs was evaluated. A neutralizing activity of 50-70% was observed in the human sera against the homologous serovar and one to five heterologous C. trachomatis serovars. These sera were also able to neutralize C. suis EBs. The pig sera showed a strong neutralizing activity (70-100%) against C. suis EBs and all eight urogenital C. trachomatis serovars. These results suggested the presence of common immunogenic antigens in C. trachomatis and C. suis. Immunoblot analysis, performed to elucidate the target of this neutralizing activity, showed a clear reactivity in human and pig sera against two proteins of 150 and 40 kDa MW, when tested either with C. trachomatis or with C. suis EBs.

Duration of Untreated, UncomplicatedChlamydia trachomatisGenital Infection and Factors Associated with Chlamydia Resolution: A Review of Human Studies

The majority of Chlamydia trachomatis genital infections in humans are asymptomatic and without clinical evidence of complications at the time of diagnosis. The natural history of chlamydial infection in humans, including the duration of infection and factors influencing resolution of infection, is not yet completely understood. This is in part attributable to the inherent challenges and ethical considerations in studying untreated chlamydia in humans. An improved understanding of the natural history of chlamydia in humans has implications for chlamydia screening and treatment recommendations. In April 2008, the Centers for Disease Control and Prevention convened an advisory group for the Chlamydia Immunology and Control Expert Advisory Meeting, in which studies related to chlamydia natural history, pathogenesis, and immunobiology were reviewed and gaps in our knowledge that would have implications for prevention and control of C. trachomatis infection were identified. This article summarizes the key questions posed and the evidence reviewed on the duration of untreated, uncomplicated genital chlamydial infection in humans and the factors associated with chlamydia resolution.

Protective immunity to Chlamydia trachomatis genital infection: evidence from human studies.

Background. Some screening and treatment programs implemented to control Chlamydia trachomatis genital infections and their complications have shown initial reductions in infection prevalence, followed by increases to preprogram levels or higher. One hypothesis is that treatment shortens duration of infection, attenuates development of protective immunity, and thereby, increases risk of reinfection. Methods. A literature review was undertaken to assess evidence supporting the concept of protective immunity,its characteristics, and its laboratory correlates in human chlamydial infection. The discussion is organized around key questions formulated in preparation for the Chlamydia Immunology and Control Expert Advisory Meeting held by the Centers for Disease Control and Prevention in April 2008. Results. Definitive human studies are not available, but cross-sectional studies show that chlamydia prevalence,organism load, and concordance rates in couples decrease with age, and organism load is lower in those with repeat infections, supporting the concept of protective immunity. The protection appears partial and can be overcome after reexposure, similar to what has been found in rodent models of genital infection. No data are available to define the duration of infection required to confer a degree of immunity or the time course of immunity after resolution of untreated infection. In longitudinal studies involving African sex workers, a group presumed to have frequent and ongoing exposure to chlamydial infection, interferon-g production by peripheral blood mononuclear cells in response to chlamydial heat-shock protein 60 was associated with low risk of incident infection.In cross-sectional studies, relevant T helper 1-type responses were found in infected persons, paralleling the studies in animal models. Conclusions. The data support the concept that some degree of protective immunity against reinfection develops after human genital infection, although it appears, at best, to be partial. It is likely that factors besides population levels of immunity contribute to trends in prevalence observed in screening and treatment programs.Future studies of protective immunity in humans will require longitudinal follow-up of individuals and populations,frequent biological and behavioral sampling, and special cohorts to help control for exposure.

Chlamydia trachomatis Native Major Outer Membrane Protein Induces Partial Protection in Nonhuman Primates: Implication for a Trachoma Transmission-Blocking Vaccine

A vaccine is likely the most effective strategy for controlling human chlamydial infections. Recent studies have shown immunization with Chlamydia muridarum major outer membrane protein (MOMP) can induce significant protection against infection and disease in mice if its native trimeric structure is preserved (nMOMP). The objective of this study was to investigate the immunogenicity and vaccine efficacy of Chlamydia trachomatis nMOMP in a nonhuman primate trachoma model. Cynomolgus monkeys (Macaca fascicularis) were immunized systemically with nMOMP, and monkeys were challenged ocularly. Immunization induced high serum IgG and IgA ELISA Ab titers, with Abs displaying high strain-specific neutralizing activity. The PBMCs of immunized monkeys produced a broadly cross-reactive, Ag-specific IFN-gamma response equivalent to that induced by experimental infection. Immunized monkeys exhibited a significant decrease in infectious burden during the early peak shedding periods (days 3-14). However, at later time points, they exhibited no difference from control animals in either burden or duration of infection. Immunization had no effect on the progression of ocular disease. These results show that systemically administered nMOMP is highly immunogenic in nonhuman primates and elicits partially protective immunity against ocular chlamydial challenge. This is the first time a subunit vaccine has shown a significant reduction in ocular shedding in nonhuman primates. A partially protective vaccine, particularly one that reduces infectious burden after primary infection of children, could interrupt the natural trachoma reinfection cycle. This would have a beneficial effect on the transmission between children and sensitized adults which drives blinding inflammatory disease.