MicroRNA expression profiling of peripheral blood mononuclear cells associated with syphilis.

Background: Treponema pallidum (T. pallidum) infection evokes significant immune responses, resulting in tissue damage. The immune mechanism underlying T. pallidum infection is still unclear, although microRNAs (miRNAs) have been shown to influence immune cell function and, consequently, the generation of antibody responses during other microbe infections. However, these mechanisms are unknown for T. pallidum.

Methods: In this study, we performed a comprehensive analysis of differentially expressed miRNAs in healthy individuals, untreated patients with syphilis, patients in the serofast state, and serologically cured patients. miRNAs were profiled from the peripheral blood of patients obtained at the time of serological diagnosis. Then, both the target sequence analysis of these different miRNAs and pathway analysis were performed to identify important immune and cell signaling pathways. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed for microRNA analysis.

Results: A total of 74 differentially regulated miRNAs were identified. Following RT-qPCR confirmation, three miRNAs (hsa-miR-195-5p, hsa-miR-223-3p, hsa-miR-589-3p) showed significant differences in the serofast and serologically cured states (P < 0.05). One miRNA (hsa-miR-195-5p) showed significant differences between untreated patients and healthy individuals.

Conclusions: This is the first study of miRNA expression differences in peripheral blood mononuclear cells (PBMCs) in different stages of T. pallium infection. Our study suggests that the combination of three miRNAs has great potential to serve as a non-invasive biomarker of T. pallium infections, which will facilitate better diagnosis and treatment of T. pallium infections.