MicroRNAs modulate Chlamydia trachomatis infection- and vaccine-induced immunity in macrophages

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Abstract Recent studies indicate that microRNAs (miRNAs), including immune cell type-specific miRNAs modulate inflammation and immune response to Chlamydia trachomatis (CT) genital infection. However, the role of these miRNAs in modulation of immune cell function following CT infection or vaccine stimulation has not been investigated. We hypothesized that pretreatment of CT-infected and vaccine-stimulated macrophages with miRNA mimics or inhibitors will modulate secretion of inflammatory cytokines and expression of IFN-γ pathway-related genes. Thus, THP-1-differentiated macrophages (TDM) transfected with miRNA mimics or inhibitors were infected with CT or stimulated with a Vibrio cholerae ghost (rVCG)-based vaccine (rVCG-MECA) and the level of inflammatory cytokines secreted in culture supernatants was assessed by cytokine ELISA. Also, TDM expression of IFN-γ pathway-related genes was assessed by RT-qPCR. The results show that CT infection of TDM resulted in the downregulation of miR-15a, miR-29a, miR-146a and miR-222 while stimulation with rVCG-MECA resulted in their upregulation, as we previously reported. The level of TNF-α, IL-8, IL-1β and IFN-γ secreted by miRNA mimic- or inhibitor-treated TDM following infection or vaccine stimulation was dependent on the miRNA type. Furthermore, CT infection of untreated macrophages increased mRNA expression of INFGR1, JAK2, STAT1 and SOCS1. However, pretreatment of CT-infected cells with miR-146a mimic or inhibitor showed significantly decreased expression of these genes. The study demonstrated that miRNAs differentially modulate macrophage secretion of inflammatory cytokines and expression of IFN-γ pathway-related genes following CT infection or vaccine stimulation. Supported by None.