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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)-1β, IL-10, IL-12p40, interferon (IFN)-γ and tumour necrosis factor (TNF)-α 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-1β, IFN-γ and IL-12p40. Clinically apparent infections were associated with the elevation of mRNA for the multi-functional cytokine TNF-α (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-γ transcript levels and the amount of CT 16S rRNA expressed in conjunctiva was found. [ABSTRACT FROM AUTHOR]

The role of HLA-A*6802-restricted CD8+ T cells in chlamydial disease was investigated in human ocular infections. Peptides with predicted binding motifs for HLA-A*6802 were synthesized using sequences based on chlamydial antigens, major outer membrane protein (MOMP), macrophage infectivity potentiator (MIP) and heat shock protein (hsp70). Peptides were pooled according to Chlamydia trachomatis protein type and serovar, and were tested in 51Cr-release cytotoxic T lymphocyte (CTL) and enzyme-linked immunospot (ELISPOT) assays, using peripheral blood mononuclear cells (PBMC) isolated from subjects living in trachoma-endemic communities in The Gambia. Significant CTL activity or interferon-gamma release was not detected in any of the subjects, suggesting either that HLA-A*6802 CD8+ T cells may not be important in ocular infections or that the peptides chosen did not represent epitopes. [ABSTRACT FROM AUTHOR]

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-γ) and IL-4 were detected at the single-cell level by ELISPOT assay. Transcription of the genes encoding IFN-γ, 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 lL-4-producing cells in PBMC isolated from patients with scarring disease and increased secretion of IFN-γ from PBMC of control subjects. Incubation with the chlamydial major outer membrane protein (MOMP) increased the number of IFN-γ-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-γ) mRNA and IL-10 mRNA were also more frequently detected in this group. Thirty-eight subjects were HLA-DRBI and -DQBI 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. [ABSTRACT FROM AUTHOR]