Differentiating children with sepsis with and without acute respiratory distress syndrome using proteomics

Abstract

Both sepsis and acute respiratory distress syndrome (ARDS) rely on imprecise clinical definitions leading to heterogeneity, which has contributed to negative trials. Because circulating protein/DNA complexes have been implicated in sepsis and ARDS, we aimed to develop a proteomic signature of DNA-bound proteins to discriminate between children with sepsis with and without ARDS. We performed a prospective case-control study in 12 children with sepsis with ARDS matched to 12 children with sepsis without ARDS on age, severity of illness score, and source of infection. We performed co-immunoprecipitation and downstream proteomics in plasma collected ≤ 24 h of intensive care unit admission. Expression profiles were generated, and a random forest classifier was used on differentially expressed proteins to develop a signature which discriminated ARDS. The classifier was tested in six independent blinded samples. Neutrophil and nucleosome proteins were over-represented in ARDS, including two S100A proteins, superoxide dismutase (SOD), and three histones. Random forest produced a 10-protein signature that accurately discriminated between children with sepsis with and without ARDS. This classifier perfectly assigned six independent blinded samples as having ARDS or not. We validated higher expression of the most informative discriminating protein, galectin-3-binding protein, in children with ARDS. Our methodology has applicability to isolation of DNA-bound proteins from plasma. Our results support the premise of a molecular definition of ARDS, and give preliminary insight into why some children with sepsis, but not others, develop ARDS.

Keywords: ARDS; DAMPs; PARDS; damage-associated molecular patterns; histones.

Figure 1.

Unsupervised hierarchical clustering of the top 50 differentially expressed DNA-bound proteins between children with sepsis with (blue along top axis) and without (pink along top axis) acute respiratory distress syndrome (ARDS). Red (upregulated) and green (downregulated) shadings represent increasing and decreasing fold change.

Figure 2.

Proximity plot of first two dimensions of random forest classifier-derived top 10 protein predictor, and distribution of acute respiratory distress syndrome (ARDS; pink) and non-ARDS (blue) subjects from derivation set. A single ARDS subject is misclassified. The independent samples (n = 6, labeled X) are also shown.

Figure 3.

Differences in galectin-3-binding protein (Gal-3BP) between children with sepsis with and without acute respiratory distress syndrome (ARDS). Gal-3BP modestly discriminates the presence of ARDS, with an area under the receiver operating characteristic (AUROC) curve of 0.76 (95% CI, 0.59–0.94). CI, confidence interval.