Exosomal miR‐1246 in Syphilis Serofast State: Diagnostic Value and NLRP3 Inflammasome Suppression

BACKGROUND: Serofast state (SF), defined as persistent low-titer antibodies after treatment, poses a diagnostic challenge because of the overlap with serologic features of active infection. Exosomal miRNAs are stable in body fluids and have potential as diagnostic markers. OBJECTIVES: This study aimed to identify plasma exosomal miR-1246 as a diagnostic biomarker for SF and elucidate its role in NLRP3 inflammasome suppression, providing mechanistic insights into SF pathogenesis. METHODS: Using microarray analysis and reverse transcription quantitative polymerase chain reaction (RT-qPCR), differential miRNA expression was measured in the plasma samples of SF patients. Microarray analysis, target gene prediction, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to identify differentially expressed microRNAs (DEmiRNAs). The plasma levels of NLRP3 and related cytokines were quantified using enzyme-linked immunosorbent assay (ELISA), and the regulatory effect of miR-1246 on NLRP3 was measured in vitro. Diagnostic performance was assessed based on receiver operating characteristic (ROC) curve analysis for miR-1246 alone and in combination with the rapid plasma reagin (RPR) test. RESULTS: Plasma exosomal miR-1246 was significantly upregulated in SF patients (p < 0.001), whereas NLRP3 and its associated factors were downregulated (p < 0.05). In vitro experiments confirmed that miR-1246 negatively regulated NLRP3 inflammasome activity. GO and KEGG analyses revealed that the target genes of DEmiRNAs were involved in multiple biological processes and signalling pathways. ROC analysis showed that miR-1246 alone yielded an area under the curve (AUC) of 0.760 (sensitivity 77.4%, specificity 62.9%). When combined with RPR, the AUC increased to 0.824 (sensitivity 83.3%, specificity 65.7%). CONCLUSIONS: Exosomal miR-1246 is elevated in SF and may contribute to its pathogenesis by inhibiting NLRP3 inflammasome. It demonstrates potential as a diagnostic biomarker, particularly when combined with RPR.