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Background: Trachoma is a leading cause of infection-related blindness worldwide. This disease is caused by recurrent Chlamydia trachomatis (Ct) infections of the conjunctiva and develops in two phases: i) active (acute trachoma, characterized by follicular conjunctivitis), then long-term: ii) scarring (chronic trachoma, characterized by conjunctival fibrosis, corneal opacification and eyelid malposition). Scarring trachoma is driven by the number and severity of reinfections. The immune system plays a pivotal role in trachoma including exacerbation of the disease. Hence the immune system may also be key to developing a trachoma vaccine. Therefore, we characterized clinical and local immune response kinetics in a non-human primate model of acute conjunctival Ct infection and disease., Methodology/principal Findings: The conjunctiva of non-human primate (NHP, Cynomolgus monkeys-Macaca fascicularis-) were inoculated with Ct (B/Tunis-864 strain, B serovar). Clinical ocular monitoring was performed using a standardized photographic grading system, and local immune responses were assessed using multi-parameter flow cytometry of conjunctival cells, tear fluid cytokines, immunoglobulins, and Ct quantification. Clinical findings were similar to those observed during acute trachoma in humans, with the development of typical follicular conjunctivitis from the 4th week post-exposure to the 11th week. Immunologic analysis indicated an early phase influx of T cells in the conjunctiva and elevated interleukins 4, 8, and 5, followed by a late phase monocytic influx accompanied with a decrease in other immune cells, and tear fluid cytokines returning to initial levels., Conclusion/significance: Our NHP model accurately reproduces the clinical signs of acute trachoma, allowing for an accurate assessment of the local immune responses in infected eyes. A progressive immune response occurred for weeks after exposure to Ct, which subsided into a persistent innate immune response. An understanding of these local responses is the first step towards using the model to assess new vaccine and therapeutic strategies for disease prevention., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Paulet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Chlamydia trachomatis (Ct) is the most common infectious cause of blindness and bacterial sexually transmitted infection worldwide. Ct strain-specific differences in clinical trachoma suggest that genetic polymorphisms in Ct may contribute to the observed variability in severity of clinical disease., Methods: Using Ct whole genome sequences obtained directly from conjunctival swabs, we studied Ct genomic diversity and associations between Ct genetic polymorphisms with ocular localization and disease severity in a treatment-naïve trachoma-endemic population in Guinea-Bissau, West Africa., Results: All Ct sequences fall within the T2 ocular clade phylogenetically. This is consistent with the presence of the characteristic deletion in trpA resulting in a truncated non-functional protein and the ocular tyrosine repeat regions present in tarP associated with ocular tissue localization. We have identified 21 Ct non-synonymous single nucleotide polymorphisms (SNPs) associated with ocular localization, including SNPs within pmpD (odds ratio, OR = 4.07, p* = 0.001) and tarP (OR = 0.34, p* = 0.009). Eight synonymous SNPs associated with disease severity were found in yjfH (rlmB) (OR = 0.13, p* = 0.037), CTA0273 (OR = 0.12, p* = 0.027), trmD (OR = 0.12, p* = 0.032), CTA0744 (OR = 0.12, p* = 0.041), glgA (OR = 0.10, p* = 0.026), alaS (OR = 0.10, p* = 0.032), pmpE (OR = 0.08, p* = 0.001) and the intergenic region CTA0744-CTA0745 (OR = 0.13, p* = 0.043)., Conclusions: This study demonstrates the extent of genomic diversity within a naturally circulating population of ocular Ct and is the first to describe novel genomic associations with disease severity. These findings direct investigation of host-pathogen interactions that may be important in ocular Ct pathogenesis and disease transmission.

Chlamydia trachomatis (Ct) is the most common cause of bacterial sexually transmitted infection and infectious cause of blindness (trachoma) worldwide. Understanding the spatial distribution of Ct infection may enable us to identify populations at risk and improve our understanding of Ct transmission. In this study, we sought to investigate the spatial distribution of Ct infection and the clinical features associated with high Ct load in trachoma-endemic communities on the Bijagós Archipelago (Guinea Bissau). We collected 1507 conjunctival samples and corresponding detailed clinical data during a cross-sectional population-based geospatially representative trachoma survey. We used droplet digital PCR to estimate Ct load on conjunctival swabs. Geostatistical tools were used to investigate clustering of ocular Ct infections. Spatial clusters (independent of age and gender) of individuals with high Ct loads were identified using local indicators of spatial association. We did not detect clustering of individuals with low load infections. These data suggest that infections with high bacterial load may be important in Ct transmission. These geospatial tools may be useful in the study of ocular Ct transmission dynamics and as part of trachoma surveillance post-treatment, to identify clusters of infection and thresholds of Ct load that may be important foci of re-emergent infection in communities., (© FEMS 2017.)

Background: Mass drug administration (MDA) treatment of active trachoma with antibiotic is recommended to be initiated in any district where the prevalence of trachoma inflammation, follicular (TF) is ≥ 10% in children aged 1-9 years, and then to continue for at least three annual rounds before resurvey. In The Gambia the PRET study found that discontinuing MDA based on testing a sample of children for ocular Chlamydia trachomatis(Ct) infection after one MDA round had similar effects to continuing MDA for three rounds. Moreover, one round of MDA reduced disease below the 5% TF threshold. We compared the costs of examining a sample of children for TF, and of testing them for Ct, with those of MDA rounds., Methods: The implementation unit in PRET The Gambia was a census enumeration area (EA) of 600-800 people. Personnel, fuel, equipment, consumables, data entry and supervision costs were collected for census and treatment of a sample of EAs and for the examination, sampling and testing for Ct infection of 100 individuals within them. Programme costs and resource savings from testing and treatment strategies were inferred for the 102 EAs in the study area, and compared., Results: Census costs were $103.24 per EA plus initial costs of $108.79. MDA with donated azithromycin cost $227.23 per EA. The mean cost of examining and testing 100 children was $796.90 per EA, with Ct testing kits costing $4.80 per result. A strategy of testing each EA for infection is more expensive than two annual rounds of MDA unless the kit cost is less than $1.38 per result. However stopping or deciding not to initiate treatment in the study area based on testing a sample of EAs for Ct infection (or examining children in a sample of EAs) creates savings relative to further unnecessary treatments., Conclusion: Resources may be saved by using tests for chlamydial infection or clinical examination to determine that initial or subsequent rounds of MDA for trachoma are unnecessary.

Objectives: Trachoma is the principal cause of infectious blindness. As part of its strategy to eliminate trachoma, the World Health Organization recommends annual mass antibiotic treatment for at least 3 years with an 80% population coverage target. However, to date, ideal population coverage and mass treatment duration have not been determined and further evaluation of treatment recommendations in areas of varying endemicity is warranted. The studies presented here evaluate the impact of coverage level and frequency of mass treatment with single dose azithromycin on trachoma and ocular C. trachomatis infection., Methods: The Partnership for the Rapid Elimination of Trachoma supervises 2 randomized, community-based clinical trials in Tanzania and The Gambia. Although each trial is a stand-alone effort, protocols, data collection, and analytic approaches have been harmonized to permit generalizations. Communities in each site were randomized using a 2X2 factorial design to standard (80%-90.0%) versus high (over 90.0%) treatment coverage; communities were further randomized to annual treatment for 3 years versus a "graduation" rule where evidence indicates an absence of follicular trachoma or infection and annual treatment is halted., Results: Average prevalence of follicular trachoma in children age less than 5 years was 32.2% in Tanzania and 5.96% in The Gambia. Randomization appeared to be effective, as prevalence was not statistically different between the arms within each country., Conclusions: There are challenges in harmonizing 2, large trials in Africa. Study outcomes will provide critical data to national trachoma control programs on treatment methodology and resource allocation toward elimination of the disease.

Background: Trachoma, a chronic keratoconjunctivitis caused by Chlamydia trachomatis, is the world's commonest infectious cause of blindness. Blindness is due to progressive scarring of the conjunctiva (trachomatous scarring) leading to in-turning of eyelashes (trichiasis) and corneal opacification. We evaluated the contribution of genetic variation across the chemokine and cytokine clusters in chromosomes 4q and 5q31 respectively to risk of scarring trachoma and trichiasis in a large case-control association study in a Gambian population., Methods: Linkage disequilibrium (LD) mapping was used to investigate risk effects across the 4q and 5q31 cytokine clusters in relation to the risk of scarring sequelae of ocular Ct infection. Disease association and epistatic effects were assessed in a population based study of 651 case-control pairs by conditional logistic regression (CLR) analyses., Results: LD mapping suggested that genetic effects on risk within these regions mapped to the pro-inflammatory innate immune genes interleukin 8 (IL8) and granulocyte-macrophage colony stimulatory factor (CSF2) loci. The IL8-251 rare allele (IL8-251 TT) was associated with protection from scarring trachoma (OR = 0.29 p = 0.027). The intronic CSF2_27348 A allele in chromosome 5q31 was associated with dose dependent protection from trichiasis, with each copy of the allele reducing risk by 37% (p = 0.005). There was evidence of epistasis, with effects at IL8 and CSF2 loci interacting with those previously reported at the MMP9 locus, a gene acting downstream to IL8 and CSF2 in the inflammatory cascade., Conclusion: innate immune response SNP-haplotypes are linked to ocular Ct sequelae. This work illustrates the first example of epistatic effects of two genes on trachoma.

Several human and animal models and methods have been used to dissect genetic contributions to immunity and pathogenesis of chlamydial diseases. Considerable achievements have been made in this field of host genetics. The hope is that these studies will lead to medical applications by helping to elicit the function of genes that are involved in host defense against chlamydia and in progression to severe sequelae. In the present article, we review a selection of findings in the forward genetics of ocular Chlamydia trachomatis infection in humans., (Copyright 2009 Prous Science, S.A.U. or its licensors. All rights reserved.)

Trachoma has been endemic in The Gambia for decades but national surveys indicate that the prevalence is falling. Risk factor data can help guide trachoma control efforts. This study investigated risk factors for active trachoma and ocular Chlamydia trachomatis infection in children aged below 10 years in two Gambian regions. The overall prevalence of C. trachomatis infection was only 0.3% (3/950) compared with 10.4% (311/2990) for active trachoma, therefore analyses were only performed for active trachoma. After adjustment, increased risk of trachoma was associated with being aged 1-2 years (odds ratio (OR) 2.20, 95% CI 1.07-4.52) and 3-5 years (OR 3.62, 95% CI 1.80-7.25) compared with <1 year, nasal discharge (OR 2.07, 95% CI 1.53-2.81), ocular discharge (OR 2.68, 95% CI 1.76-4.09) and there being at least one other child in the household with active trachoma (OR 11.28, 95% CI 8.31-15.31). Compared with other occupations, children of traders had reduced risk (OR 0.53, 95% CI 0.30-0.94). At the household level, only the presence of another child in the household with active trachoma was associated with increased risk of active trachoma, suggesting that current trachoma control interventions are effective at this level. In contrast, child-level factors were associated with increased risk after adjustment, indicating a need to increase control efforts at the child level.

Tumor necrosis factor (TNF) is thought to be a key mediator of the inflammatory and fibrotic response to Chlamydia trachomatis (Ct) infection. A large matched-pair case-control study investigated putative functional single nucleotide polymorphisms (SNPs) across the major histocompatibility complex (MHC) class III region, including TNF and its immediate neighbors nuclear factor of kappa light polypeptide gene enhancer in B cells (IkappaBL), inhibitor like 1 and lymphotoxin alpha (LTA) in relation to the risk of scarring sequelae of ocular Ct infection. Haplotype and linkage disequilibrium analysis demonstrated two haplotypes, differing at position TNF-308, conferring an increased risk of trichiasis. The TNF-308A allele, and its bearing haplotype, correlated with increased TNF production in lymphocyte cultures stimulated with chlamydial elementary body antigen. Thus TNF-308A may determine directly, or be a marker of a high TNF producer phenotype associated with increased risk of sequelae of chlamydial infection. Multivariate analysis provided evidence for the presence of additional risk-associated variants near the TNF locus.

Background: Trachoma is the leading infectious cause of blindness. Routes of transmission remain unclear. In this study, the relationship between Chlamydia trachomatis Amplicor-positive nasal discharge and Amplicor-positive ocular swabs was investigated (Amplicor; Roche, Indianapolis, IN)., Methods: A longitudinal study was conducted in Tanzania and The Gambia. Eyes were graded for active trachoma; ocular swabs were taken to test for C. trachomatis. Children with visible nasal discharge had swabs taken of this material. Participants were offered systemic antibiotics. Two months after treatment, participants were re-examined., Results: Of the 1128 children participating, 188 (17%) had nasal discharge. Among 188 children with nasal discharge, 64 (34%) nasal swabs were PCR positive. There was a strong correlation between active disease/ocular chlamydial positivity and positive nasal discharge. Children with Amplicor-positive ocular swabs were 9.9 times more likely to have Amplicor-positive nasal discharge than were children without ocular positivity (95% CI: 4.34-22.53). Two months after treatment, 16% had an Amplicor-positive ocular swab. Children with positive nasal discharge at baseline were 5.2 times more likely to have an Amplicor-positive ocular swab at 2 months than were children without Amplicor-positive nasal discharge at baseline (95% CI: 1.54-17.23), after adjusting for baseline ocular positivity, gender, and study site., Conclusions: Nasal discharge may provide a source of reinfection with C. trachomatis, after antibiotic treatment for trachoma, either through transfer of secretions from nose to eye or from nasal secretions transferred to bed sheets or dirty clothes and back to the eye; alternatively, nasal discharge may be an indicator of severe persistent ocular chlamydial infection that is not cleared with a single dose of antibiotics.

Ocular chlamydial disease is clinically diagnosed by the appearance of characteristic inflammatory changes and development of lymphoid follicles in the conjunctiva. Nucleic acid amplification tests and relatively non-invasive methods of sampling the conjunctival surface can be used to quantify the expression of chlamydial and host genes. Using quantitative real-time polymerase chain reaction to detect the presence of Chlamydia trachomatis (CT) 16S rRNA and human interleukin (IL)-1beta, IL-10, IL-12p40, interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha transcripts we examined the immune response at the conjunctival surface in a cohort of children living in a trachoma-endemic village in The Gambia. Elevated cytokine transcript levels were associated with the presence of CT 16S rRNA. Subclinical infection (CT infection without clinical signs of disease) elicited an immune response that is proinflammatory in nature, with elevations in the transcription of IL-1beta, IFN-gamma and IL-12p40. Clinically apparent infections were associated with the elevation of mRNA for the multi-functional cytokine TNF-alpha (fibrotic, type 1 inflammatory and regulatory) and the counter regulatory cytokine, IL-10, in addition to the other proinflammatory cytokines. A positive correlation between IFN-gamma transcript levels and the amount of CT 16S rRNA expressed in conjunctiva was found.

Experimental evidence implicates interferon gamma (IFNgamma) in protection from and resolution of chlamydial infection. Conversely, interleukin 10 (IL10) is associated with susceptibility and persistence of infection and pathology. We studied genetic variation within the IL10 and IFNgamma loci in relation to the risk of developing severe complications of human ocular Chlamydia trachomatis infection. A total of 651 Gambian subjects with scarring trachoma, of whom 307 also had potentially blinding trichiasis and pair-matched controls with normal eyelids, were screened for associations between single-nucleotide polymorphisms (SNPs), SNP haplotypes and the risk of disease. MassEXTEND (Sequenom) and MALDI-TOF mass spectrometry were used for detection and analysis of SNPs and the programs PHASE and SNPHAP used to infer haplotypes from population genetic data. Multivariate conditional logistic regression analysis identified IL10 and IFNgamma SNP haplotypes associated with increased risk of both trachomatous scarring and trichiasis. SNPs in putative IFNgamma and IL10 regulatory regions lay within the disease-associated haplotypes. The IFNgamma +874A allele, previously linked to lower IFNgamma production, lies in the IFNgamma risk haplotype and was more common among cases than controls, but not significantly so. The promoter IL10-1082G allele, previously associated with high IL10 expression, is in both susceptibility and resistance haplotypes.

Quantitative PCR (Q-PCR) technology has recently been applied to the measurement of ocular loads of Chlamydia trachomatis. We present an index called the community ocular C. trachomatis load (COCTL) which is similar to the community microfilarial load (CMFL) of onchocerciasis. Our index has the advantage of being scale-independent so that, for example, percentage changes are the same whether calculated per eye swab or per Q-PCR capillary. The COCTL for a population or subgroup is formed by adding the arbitrary concentration of 1 organism per ml to each individual Q-PCR quantification, calculating the geometric mean, and finally subtracting 1 per ml again. The use of the COCTL is illustrated in a study of trachoma in northern Tanzania. The COCTL is higher in people with clinical trachoma than those without (5.8 organisms per swab vs. 0.1), and in children aged six months to ten years than in the overall population (1.1 vs. 0.4). The COCTL index is potentially useful for sentinel sites, operational research and calibration of clinical measures of trachoma.

To determine if serum antibody response to the 60-kDa chlamydial heat-shock protein (Chsp60) was associated with scarring trachoma, responses to Chlamydia trachomatis and to Chsp60 from 148 Gambian subjects with trachomatous scarring and from 148 controls without clinical evidence of disease from trachoma-endemic communities were characterized. Chsp60 response was found in 32% of cases and 16% of controls (P < .001). Although C. trachomatis titer was also higher in cases than controls, the prevalence of Chsp60 response between the 2 groups remained significantly different after stratifying for C. trachomatis titer (weighted odds ratio [OR] = 2.1, P = .02). Chsp60 response and C. trachomatis serovar A titer of > or =128 were independently associated with scarring trachoma. The presence of HLA class II allele DRB1*0701 was positively correlated with Chsp60 response (OR = 2.6, P = .02), and DQB1*0301 and DQB1*0501 were negatively associated (OR = 0.42, P < .001; OR = 0.55, P = .46, respectively).

Tumor necrosis factor alpha (TNF-alpha) may play a central role in the disease pathogenesis which occurs as a consequence of chlamydial infection. To investigate the importance of TNF-alpha gene promoter polymorphisms and TNF-alpha levels in tear fluid in scarring trachoma, a large matched-pair case-control study was performed in The Gambia. The -308A allele was present in a higher proportion of patients (28.4%) than controls (18.4%), with an increasing association for homozygotes (chi2 for trend, P = 0.032; allele frequency, 0.163 in patients and 0.099 in controls; chi2, P = 0.025). For the -238A allele, the association was similar but not significant. The disease association was highly significant when the number of either -308A or -238A sites in an individual was considered (P = 0.003). TNF-alpha promoter alleles are tightly linked to some HLA class I and II alleles, but multivariate analysis confirmed that the disease associations were independent of HLA, although a class I allele, A*6802, is also associated with disease. TNF-alpha was more frequently detected in tear samples from patients (27.6%) than from controls (15.9%), increasingly so for higher levels of detectable TNF-alpha (P = 0.015). Among patients, detectable TNF-alpha in tears was highly associated with the presence of ocular chlamydial infection (P < 0.001). The results indicate that TNF-alpha plays a major role in the tissue damage and scarring which occurs as a consequence of Chlamydia trachomatis infection.

CD8+ cytotoxic T lymphocytes (CTL) recognize peptide antigens in the context of class I MHC antigen molecules. To identify peptides capable of eliciting anti-Chlamydia trachomatis CTL responses, 13 synthetic peptides conforming to human leucocyte antigen (HLA)-B8- or -B35-predicted binding motifs were synthesized using sequences based on C. trachomatis major outer membrane protein (MOMP) and heat shock protein 60 (hsp60). Two of 11 HLA-B35-predicted binding peptides were able to stabilize HLA-B35 in an in vitro binding assay. All peptides were tested in CTL assays using peripheral blood mononuclear cells (PBMC) isolated from 26 HLA-B8 or -B35 individuals resident in a trachoma-endemic community. Responses to MOMP and hsp60 peptides were identified in a minority of both HLA-B8 and -B35 individuals. Two of 12 HLA-B8 subjects responded to MOMP and 1/13 to hsp60 peptides. Responses in HLA-B35 subjects were similar, 1/13 subjects responding to MOMP and 2/13 to hsp60 peptides. CTL responses were observed only in children resolving current infection and in adults without scarring of the conjunctiva. These results suggest that anti-chlamydial CTL occur at low levels in peripheral blood, but may be important in the resolution of naturally acquired human ocular chlamydial infection.

Immune responses to Chlamydia trachomatis contribute to protection from infection and to immunopathologic disease. To test whether subjects' HLA class I (A, B, and Cw) or class II (DRbeta1 and DQbeta1) types influence risk of trachomatous scarring from chronic infection with C trachomatis, 153 cases and pair-matched controls in Gambia were studied. No HLA type was associated with protection from scarring, indicating that protective immune responses are not limited to only one or a few HLA-restricted epitopes in C. trachomatis antigens. One class I antigen, HLA-A28, was significantly more common among cases than controls (25.8% vs. 15.9%, respectively; McNemar's odds ratio [OR], 1.88; 95% confidence interval [CI] = 1.01-3.49; P = .046). In DNA subtyping of the A28 specificity, the A*6801 allele was equally common among cases and controls, but the A*6802 allele was significantly overrepresented among cases (McNemar's OR, 3.14; 95% CI = 1.32-7.44; P = .009). This association may be due to an immunopathologic HLA-A*6802-restricted cytotoxic T lymphocyte response.

Increased stimulation of Th2 cytokines may contribute to the development of persistent ocular chlamydial infection, resulting in the blinding pathological changes of trachoma. Proliferation and cytokine production profiles of PBMC in response to stimulation with antigens of Chlamydia trachomatis were compared in 30 patients with severe conjunctival scarring due to trachoma and in 30 age-, sex- and location-matched controls. Interferon-gamma (IFN-gamma) and IL-4 were detected at the single-cell level by ELISPOT assay. Transcription of the genes encoding IFN-gamma, IL-4 and IL-10 was detected in mRNA isolated from parallel cultures of PBMC using reverse transcriptase-polymerase chain reaction (RT-PCR). Incubation with the chlamydial heat shock protein (hsp)60 resulted in increased numbers of IL-4-producing cells in PBMC isolated from patients with scarring disease and increased secretion of IFN-gamma from PBMC of control subjects. Incubation with the chlamydial major outer membrane protein (MOMP) increased the number of IFN-gamma-producing cells in the control group only. Messenger RNA encoding IL-4 was only detected in PBMC of patients with scarring disease after in vitro stimulation with chlamydial antigens, but IFN-gamma mRNA and IL-10 mRNA were also more frequently detected in this group. Thirty-eight subjects were HLA-DRB1 and -DQB1 typed. Associations were observed between certain HLA class II alleles and cellular immune responses to chlamydial antigens. No HLA associations were found with clinical status, and overall we found no evidence of strong associations and the type of immune response. These data are consistent with a role for Th2 cells and cytokines in the pathogenesis of trachomatous scarring.

Cell-mediated immune responses to chlamydial and common recall antigens were measured in 26 subjects whose clinical signs of trachoma persisted over 6 months of follow-up and in 21 subjects whose clinical signs resolved spontaneously over the same period. Seven-day lymphocyte proliferative responses to chlamydial but not common recall antigens were significantly greater in subjects whose disease resolved spontaneously. There was, however, no detectable difference between the two groups in gamma interferon levels in supernatants from lymphocyte cultures stimulated with these antigens. These results are consistent with the hypothesis that cell-mediated immune responses play an important role in the clearance of ocular chlamydial infection in humans.

In vitro responses of peripheral blood mononuclear cells (PBMC) were measured to antigens of Chlamydia trachomatis in 29 subjects with severe conjunctival scarring and compared with responses from 29 age-, sex-, and location-matched controls from a trachoma-endemic area in The Gambia. Proliferative and interferon-gamma responses were measured against chlamydial elementary bodies, recombinant major outer membrane protein, and affinity-purified recombinant chlamydial heat shock protein 60. Serum antibody levels in response to these antigens were also compared between the two groups, and the presence of ocular chlamydial antigen and DNA was assessed. PBMC from donors with conjunctival scarring had reduced proliferative responses to chlamydial antigens but not control antigens or mitogens compared with matched controls. By contrast, subjects with scarring had significantly higher levels of anti-chlamydial IgG antibody compared with matched controls and were more likely to be harboring ocular chlamydial antigen or DNA (or both).

In order to study the relationship between cell-mediated immune responses to Chlamydia trachomatis and the pathogenesis of human chlamydial eye disease, we have measured the peripheral blood lymphocyte proliferative responses to whole chlamydial elementary bodies in 40 subjects with oculogenital chlamydial infection of varying severity, 13 subjects with genital chlamydial infections and 12 healthy seronegative controls. The mean stimulation index was significantly higher in those with oculogenital infections than in controls. There was a strong correlation between the response to C. trachomatis serotypes B and L1. We studied the relationship between proliferative responses and four clinical parameters: follicular conjunctivitis, papillary hypertrophy, corneal pannus and epithelial punctate keratitis, but were unable to show a significant association with any of these. Nor was there any association between proliferative response and serum antibody titre to C. trachomatis (pooled serotypes D-K), duration of disease or quantitative isolation of chlamydia from the conjunctiva. The depletion of CD8+ cells had no consistent effect on proliferative responses to serotype L1 in 13 subjects.

Background: Chlamydia trachomatis (Ct) is the most common infectious cause of blindness and bacterial sexually transmitted infection worldwide. Ct strain-specific differences in clinical trachoma suggest that genetic polymorphisms in Ct may contribute to the observed variability in severity of clinical disease. Methods: Using Ct whole genome sequences obtained directly from conjunctival swabs, we studied Ct genomic diversity and associations between Ct genetic polymorphisms with ocular localization and disease severity in a treatment-naïve trachoma-endemic population in Guinea-Bissau, West Africa. Results: All Ct sequences fall within the T2 ocular clade phylogenetically. This is consistent with the presence of the characteristic deletion in trpA resulting in a truncated non-functional protein and the ocular tyrosine repeat regions present in tarP associated with ocular tissue localization. We have identified 21 Ct non-synonymous single nucleotide polymorphisms (SNPs) associated with ocular localization, including SNPs within pmpD (odds ratio, OR = 4.07, p* = 0.001) and tarP (OR = 0.34, p* = 0.009). Eight synonymous SNPs associated with disease severity were found in yjfH (rlmB) (OR = 0.13, p* = 0.037), CTA0273 (OR = 0.12, p* = 0.027), trmD (OR = 0.12, p* = 0.032), CTA0744 (OR = 0.12, p* = 0.041), glgA (OR = 0.10, p* = 0.026), alaS (OR = 0.10, p* = 0.032), pmpE (OR = 0.08, p* = 0.001) and the intergenic region CTA0744–CTA0745 (OR = 0.13, p* = 0.043). Conclusions: This study demonstrates the extent of genomic diversity within a naturally circulating population of ocular Ct and is the first to describe novel genomic associations with disease severity. These findings direct investigation of host-pathogen interactions that may be important in ocular Ct pathogenesis and disease transmission. [ABSTRACT FROM AUTHOR]