Background: Trachoma, a preventable blinding eye disease, is initiated by ocular infection with Chlamydia trachomatis\n(Ct). We previously showed that microRNAs (miR) -147b and miR-1285 were up-regulated in inflammatory\ntrachomatous scarring. During the initial stage of disease, follicular trachoma with current Ct infection, the\ndifferential expression of miR has not yet been investigated.\nMethods: Conjunctival samples were collected from 163 children aged 1ââ?¬â??9 years old living in a trachoma-endemic\nregion of Guinea Bissau, West Africa. Small RNA sequencing (RNAseq) was carried out on samples from five children\nwith follicular trachoma and current Ct infection and five children with healthy conjunctivae and no Ct infection.\nSmall RNAseq was also carried out on human epithelial cell lines infected with ocular Ct strains A2497 and\nisogenic plasmid-free A2497 in vitro. Results were validated by quantitative PCR (qPCR) in 163 clinical samples.\nResults: Differential expression of RNAseq data identified 12 miR with changes in relative expression during\nfollicular trachoma, of which 9 were confirmed as differentially expressed by qPCR (miR-155, miR-150, miR-142,\nmiR-181b, miR-181a, miR-342, miR-132, miR-4728 and miR-184). MiR-155 and miR-184 expression had a direct\nrelationship with the degree of clinical inflammation. MiR-155 was up-regulated (OR = 2.533 ((95 % CI = 1.291ââ?¬â??4.971);\nP = 0.0069) and miR-184 was down-regulated (OR = 0.416 ((95 % CI = 0.300ââ?¬â??0.578); P = 1.61*10âË?â??7) as the severity\nof clinical inflammation increased. Differential miR expression was not detected in HEp-2 or HCjE epithelial\ncells 48 h post infection with Ct in vitro. HCjE cells, a conjunctival epithelial cell line, had a markedly different\nmiR background expression compared to HEp-2 cells.\nConclusions: In follicular trachoma, expression of miR-155 and miR-184 is correlated with the severity of\ninflammation. This likely reflects host regulation of the immune response and a prolonged period of wound\nhealing following the clearance of Ct. Prolonged healing may be associated with subsequent development of\nscarring trachoma.
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