Use of IFNγ/IL10 Ratio for Stratification of Hydrocortisone Therapy in Patients With Septic Shock

Abstract

Large clinical trials testing hydrocortisone therapy in septic shock have produced conflicting results. Subgroups may benefit of hydrocortisone treatment depending on their individual immune response. We performed an exploratory analysis of the database from the international randomized controlled clinical trial Corticosteroid Therapy of Septic Shock (CORTICUS) employing machine learning to a panel of 137 variables collected from the Berlin subcohort comprising 83 patients including demographic and clinical measures, organ failure scores, leukocyte counts and levels of circulating cytokines. The identified theranostic marker was validated against data from a cohort of the Hellenic Sepsis Study Group (HSSG) (n = 246), patients enrolled in the clinical trial of Sodium Selenite and Procalcitonin Guided Antimicrobial Therapy in Severe Sepsis (SISPCT, n = 118), and another, smaller clinical trial (Crossover study, n = 20). In addition, in vitro blood culture experiments and in vivo experiments in mouse models were performed to assess biological plausibility. A low serum IFNγ/IL10 ratio predicted increased survival in the hydrocortisone group whereas a high ratio predicted better survival in the placebo group. Using this marker for a decision rule, we applied it to three validation sets and observed the same trend. Experimental studies in vitro revealed that IFNγ/IL10 was negatively associated with the load of (heat inactivated) pathogens in spiked human blood and in septic mouse models. Accordingly, an in silico analysis of published IFNγ and IL10 values in bacteremic and non-bacteremic patients with the Systemic Inflammatory Response Syndrome supported this association between the ratio and pathogen burden. We propose IFNγ/IL10 as a molecular marker supporting the decision to administer hydrocortisone to patients in septic shock. Prospective clinical studies are necessary and standard operating procedures need to be implemented, particularly to define a generic threshold. If confirmed, IFNγ/IL10 may become a suitable theranostic marker for an urging clinical need.

Keywords: IFNgamma/IL10; hydrocortisone; immune therapy; machine learning; sepsis; steroids; theranostics.

Figure 1

Forest plot showing the outcome in the investigated cohorts depending on hydrocortisone administration according to the theranostic marker. Odds ratios including confidence intervals and thresholds between low and high ratios are shown regarding the IFNγ/IL10 prediction rule for the sub-cohorts of CORTICUS (discovery set), HSSG (validation set), SISPCT (validation set) and the crossover study (validation set).

Figure 2

Time courses of serum lactate and norepinephrine requirement are depending on the proposed theranostic rule. Shown are patient values and linear models including color-shaded confidence intervals (95%) for the sub-populations of CORTICUS treated in compliance (red) and not in compliance (blue) to our rule. The time course is given in days after start of the study, (A) shows the course of serum lactate, and (B) shows the course of the norepinephrine requirement.

Figure 3

IFNγ/IL10 reflects the immunological load of immune cells in vitro. Whole blood from five healthy donors was challenged with varying dilutions of E. coli fragments mimicking the bacterial burden on the immune system in sepsis. IFNγ (A) and IL10 (B) were elevated with increasing bacterial challenge while their ratio (C) showed the opposite behavior, i.e., a high stimulus was associated with a lower ratio (given in log-two-fold-changes).