Circulating microtranscriptome profiles reveal distinct expression of microRNAs in severe leptospirosis.

Biomarkers to predict the severity of leptospirosis are still lacking. This study aimed to identify and validate microRNAs in patients with severe leptospirosis, that could potentially be used as biomarkers for predicting an unfavorable outcome. Serum samples were collected from participants with definite diagnosis of leptospirosis. The participants were divided into two groups, non-severe and severe leptospirosis, as defined by the Specific Organ Sequential Organ Failure (SOFA) Score of more than two in any organ. Microtranscriptome analysis was performed using the NanoString miRNA Expression Assay. The expression level of candidate miRNAs was then validated by quantitative RT-PCR. Based on the NanoString, the microtranscriptome profile of the severe group was significantly different from that of the non-severe group. Upregulation of miR155-5p, miR362-3p, miR502-5p, miR601, miR1323, and miR630 in the severe group were identified, and further investigated. A total of 119 participants were enrolled in the validation cohort. Serum miR155-5p and miR630 levels were significantly higher in the severe group compared to the non-severe group. The combined use of miR155-5p or miR-630 with serum bicarbonate levels had an AUC of 0.79 (95%CI; 0.69-0.89, p<0.001) in identifying the severity of the disease. This data provides the first evidence that the microtranscriptome profiles of patients with severe leptospirosis were different from the non-severe group. Serum miR155-5p and miR630 levels might be novel biomarkers for identifying severe leptospirosis.