Whole blood transcriptome of survivors and nonsurvivors of sepsis

There is currently no reliable tool available to measure immune dysfunction in septic patients in the clinical setting. This proof-of-concept study assesses the potential of gene expression profiling of whole blood as a tool to monitor immune dysfunction in critically ill septic patients. Whole blood samples were collected daily for up to 5 days from patients admitted to the intensive care unit with sepsis. RNA isolated from whole blood samples was assayed on Illumina HT-12 gene expression microarrays consisting of 48,804 probes. Microarray analysis identified 3677 genes as differentially expressed across 5 days between septic patients and healthy controls. Of the 3677 genes, biological pathway analysis identified 86 genes significantly down-regulated in the sepsis patients were present in pathways relating to immune response. These 86 genes correspond to known immune pathways implicated in sepsis including lymphocyte depletion, reduced T lymphocyte activation and deficient antigen presentation. Furthermore, expression levels of these genes correlated with clinical severity, with a significantly greater degree of down-regulation found in non-survivors compared to survivors. The results show that whole blood gene-expression analysis can capture systemic immune dysfunctions in septic patients. Our study provides an experimental basis to support further study on the use of a gene expression based assay, to assess immunosuppression and guide immunotherapy in future clinical trials. Daily PAXgene samples for up to 5 days for sepsis survivors (n=26), sepsis nonsurvivors (n=9), and healthy controls (n=18).