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ABSTRACTTrachoma is the most common infectious cause of blindness and a major public health problem in many developing countries. It is caused by recurrent ocular infection with Chlamydia trachomatisin childhood, with conjunctival scarring seen later in life. The pathogenesis of trachomatous scarring, however, is poorly understood, and this study was carried out to investigate the immunofibrogenic correlates of trachomatous conjunctival scarring. A case-control study of 363 cases with conjunctival scarring and 363 control participants was conducted. Investigations included in vivoconfocal microscopy (IVCM) assessment, quantitative real-time PCR gene expression, C. trachomatisdetection, and nonchlamydial bacterial culture. Trachomatous scarring was found to be strongly associated with a proinflammatory, innate immune response with increased expression of psoriasin, interleukin-1β, tumor necrosis factor alpha, defensin-β4A, chemokine ligand 5, and serum amyloid A1. There was also differential expression of various modifiers of the extracellular matrix, including metalloproteinases 7, 9, 10, and 12, tissue inhibitor of matrix metalloproteinase 1, and secreted protein acidic cystein-rich-like 1. The expression of many of these genes was also significantly associated with the presence of nonchlamydial bacterial infection. These infections had a marked effect on conjunctival immune processes, including an increased inflammatory infiltrate and edema seen with IVCM. This study supports the possibility that the immunofibrogenic response in scarring trachoma is partly stimulated by nonchlamydial bacterial infection, which is characterized by the expression of innate factors.

ABSTRACTThe immunological basis of scarring trachoma is not well understood. It is unclear whether it is driven primarily through cell-mediated adaptive or epithelial-cell-derived innate responses. The purpose of this study was to investigate the expression of the inflammatory and fibrogenic mediators which may be involved. We conducted a cross-sectional survey of children living in an untreated trachoma-endemic community in Tanzania. The children were examined for signs of trachoma, and swabs were collected for bacteriological culture and RNA and DNA isolation. Chlamydia trachomatiswas detected by the Amplicor PCR test. The expression of the following genes was measured by quantitative reverse transcription-PCR (RT-PCR): S100A7, IL1B, IL17A, IL23A, CXCL5, CCL18, TLR2, NLRP3, KLRD1, CTGF, and MMP9. Four hundred seventy children under the age of 10 years were included. Follicular trachoma (TF) was detected in 65 children (14%), C. trachomatiswas detected in 25 (5%), and bacterial pathogens were cultured in 161 (34%). TF was associated with significantly increased expression of S100A7, IL17A, CCL18, CXCL5, and CTGF.Expression was increased further in the presence of papillary inflammation. Nonchlamydial bacterial infection was associated with increased expression of IL17A, CXCL5, CCL18, and KLRD1. IL17Aexpression was associated with increased expression of S100A7, CXCL5, CCL18, KLRD1, and CTGF.These data are consistent with a role for IL-17A in orchestrating the proinflammatory response in trachoma. Its activity may be promoted either as part of the cell-mediated response or through innate pathways. It may drive a range of proinflammatory factors leading to excessive tissue damage and repair involving fibrosis.

Trachoma is a poorly understood immunofibrogenic disease process, initiated by Chlamydia trachomatis. Differences in conjunctival gene expression profiles between Ethiopians with trachomatous trichiasis (with [TTI] or without [TT] inflammation) and controls (C) were investigated to identify relevant host responses. Tarsal conjunctival swab samples were collected for RNA isolation and C. trachomatis PCR. Transcriptome-wide microarray experiments were conducted on 42 samples (TTI, n = 13; TT, n = 15; C, n =14). Specific results were confirmed by using multiplex quantitative reverse transcription-PCR for 16 mRNA targets in an independent collection of case-control samples: 386 case-control pairs (TTI, n = 244; TT, n = 142; C, n = 386). The gene expression profiles of cases were consistent with squamous metaplasia (keratins, SPRR), proinflammatory cytokine production (IL1β, CXCL5, and S100A7), and tissue remodeling (MMP7, MMP9, MMP12, and HAS3). There was no difference in the level of IFN between cases and controls. However, cases had increased INDO, NOS2A, and IL13RA2 and reduced IL13. C. trachomatis was detected in 1/772. Cases show evidence of ongoing inflammation and tissue remodeling, which were more marked where clinical inflammation was also present. Significantly, these processes appear to be active in the absence of current C. trachomatis infection. There was limited evidence of a TH1 response (INDO and NOS2A) and no association between a TH2 response and cases. The epithelium appears to be actively involved in late cicatricial stages of trachoma through the production of proinflammatory factors (IL1β, CXCL5, and S100A7). Longitudinal studies are needed to investigate which etiological factors and pathways are associated with progressive scarring and whether simply controlling chlamydial infection will halt progression in people with established cicatricial disease.

ABSTRACTChlamydia trachomatisis the leading cause of infectious blindness worldwide and is the most commonly reported pathogen causing sexually transmitted infections. Tarp (translocated actin recruiting phosphoprotein), a type III secreted effector that mediates actin nucleation, is central to C. trachomatisinfection. The phylogenetic analysis of tarPfrom reference strains as well as ocular, genital, and lymphogranuloma venereum (LGV) clinical isolates demonstrated an evolutionary relationship with disease phenotype, with LGV and ocular isolates branched into clades that were separate from the urogenital isolates. The sequence analysis of Tarp indicated a high degree of variability and identified trends within clinical groupings. Tarps from LGV strains contained the highest number of tyrosine-rich repeat regions (up to nine) and the fewest (two) predicted actin binding domains. The converse was noted for Tarp proteins from ocular isolates that contained up to four actin binding domains and as few as one tyrosine-rich repeat region. The results suggest that Tarp is among the few known genes to play a role in C. trachomatisadaptations to specific niches within the host.

Chlamydia-specific cytotoxic T lymphocytes are able to control model infections but may be implicated in disease pathogenesis. HLA-A2 peptide tetramers to Chlamydia trachomatis major outer membrane protein 258-266 (MOMP258-266) and MOMP260-268 were used to characterize HLA class I-restricted CD8+ T cells in Gambian children aged 4 to 15 years with clinical signs of active trachoma and/or infection with C. trachomatis. The frequencies of circulating HLA-A2 tetramer binding cells (TBC) were determined in whole blood samples by flow cytometric analysis. Initial screening of subjects with an anti-HLA-A2 antibody confirmed the presence of either HLA-A2 or HLA-A28. These were subsequently further divided by molecular subtyping. The C. trachomatis-specific HLA-A2 peptide tetramers were able to bind T cells with receptors from subjects which were restricted by either the HLA-A2 or the HLA-A28 restriction element. In this population, the median value of C. trachomatis-specific CD8+ T cells was 0.02%, with frequencies of up to 3.71% of CD8+ T cells reactive with a single tetramer in a minority of subjects. TBC were detected more often in subjects who were infected at the ocular surface, and their presence was associated with infection episodes of longer duration. Detection of C. trachomatis-specific TBC was not associated with the presence of disease or with the estimated load of ocular C. trachomatis infection at the time of sample collection. High frequencies of C. trachomatis-specific cells did not predict subsequent appearance or resolution of the clinical disease signs of active trachoma.

ABSTRACTChlamydia-specific cytotoxic T lymphocytes are able to control model infections but may be implicated in disease pathogenesis. HLA-A2 peptide tetramers to Chlamydia trachomatismajor outer membrane protein 258-266 (MOMP258-266) and MOMP260-268 were used to characterize HLA class I-restricted CD8+T cells in Gambian children aged 4 to 15 years with clinical signs of active trachoma and/or infection with C. trachomatis. The frequencies of circulating HLA-A2 tetramer binding cells (TBC) were determined in whole blood samples by flow cytometric analysis. Initial screening of subjects with an anti-HLA-A2 antibody confirmed the presence of either HLA-A2 or HLA-A28. These were subsequently further divided by molecular subtyping. The C. trachomatis-specific HLA-A2 peptide tetramers were able to bind T cells with receptors from subjects which were restricted by either the HLA-A2 or the HLA-A28 restriction element. In this population, the median value of C. trachomatis-specific CD8+T cells was 0.02%, with frequencies of up to 3.71% of CD8+T cells reactive with a single tetramer in a minority of subjects. TBC were detected more often in subjects who were infected at the ocular surface, and their presence was associated with infection episodes of longer duration. Detection of C. trachomatis-specific TBC was not associated with the presence of disease or with the estimated load of ocular C. trachomatisinfection at the time of sample collection. High frequencies of C. trachomatis-specific cells did not predict subsequent appearance or resolution of the clinical disease signs of active trachoma.