Blood transcriptomics to characterize key biological pathways and identify biomarkers for predicting mortality in melioidosis

Melioidosis is an often lethal tropical disease caused by the Gram-negative bacillus, <i>Burkholderia pseudomallei</i>. The study objective was to characterize transcriptomes in melioidosis patients and identify genes associated with outcome. Whole blood RNA-seq was performed in a discovery set of 29 melioidosis patients and 3 healthy controls. Transcriptomic profiles of patients who did not survive to 28 days were compared with patients who survived and healthy controls, showing 65 genes were significantly up-regulated and 218 were down-regulated in non-survivors compared to survivors. Up-regulated genes were involved in myeloid leukocyte activation, Toll-like receptor cascades and reactive oxygen species metabolic processes. Down-regulated genes were hematopoietic cell lineage, adaptive immune system and lymphocyte activation pathways. RT-qPCR was performed for 28 genes in a validation set of 60 melioidosis patients and 20 healthy controls, confirming differential expression. <i>IL1R2, GAS7, S100A9, IRAK3,</i> and <i>NFKBIA</i> were significantly higher in non-survivors compared with survivors (<i>P</i> &lt; 0.005) and healthy controls (<i>P</i> &lt; 0.0001). The AUROCC of these genes for mortality discrimination ranged from 0.80-0.88. In survivors, expression of <i>IL1R2</i>, <i>S100A9</i> and <i>IRAK3</i> genes decreased significantly over 28 days (<i>P</i> &lt; 0.05). These findings augment our understanding of this severe infection, showing expression levels of specific genes are potential biomarkers to predict melioidosis outcomes.