IL-1β, IL-17A, and IL-10: A Novel Axis Linked to Immunological Dysfunction May Pre-Empt Early Diagnosis of Sepsis after Cardiac Surgery

INTRODUCTION Sepsis caused by a dysregulated host response to infection, is a serious healthcare problem that results in very high mortality every year-round the globe. When left untreated, sepsis can potentially turn fulminant, making early diagnosis and intervention an essential component of the therapeutic strategy. Proinflammatory cytokines are necessary for initiating an effective inflammatory response against infection, whereas their excess production has been associated with tissue injury in multiple organ systems leading to increased mortality. In contrast, anti-inflammatory cytokines seem to be a prerequisite for controlling and down regulating the initial inflammatory response. But a sustained release of these biomolecules leads to a turn-down of immune activation within the host organism. In the clinical conundrums associated with sepsis, it was often observed that pathogen-responsive cells were exposed to a complex cytokine milieu. The excess production of proinflammatory cytokines is essential for the survival, replication and activation of phagocytic and cytotoxic immune cells. In conjunction with this proinflammatory activity, anti-inflammatory cytokines are also released which are involved in the occurrence of cellular anergy and impaired response to aetiologic agents, causing a compensatory anti-inflammatory response syndrome (CARS). Current practice in cardiac surgery is to review laboratory test results (CRP, PCT, blood culture) and clinical criteria (SOFA and STS) 48 h after surgery to diagnose sepsis. CRP and PCT lack sensitivity and specificity, whereas blood culture requires a long turnaround time and lacks sensitivity. Sepsis being an interplay between pro and anti-inflammatory response, the relative expression of immune biomarkers may provide a useful criterion for early diagnosis of sepsis. Thus, we aimed at investigating the variations in circulating levels of prominent cytokines and their potential use as a diagnostic marker of adult sepsis post cardiac surgery. MATERIALS AND METHODS In this double-blinded cohort study, blood samples of adult patients undergoing cardiac surgery were collected before surgery (D -1), and on the post-operative day 1 (D +1) after the approval from the appropriate Institutional Ethics Committee. Patients who were deemed risky by EuroSCORE II risk stratification were included and immuno-compromised as well as patients with active infection before surgery were excluded. Plasma levels of IL-1β, IL-5, IL-6, IL-10, IL-17A and TNFα were determined using cytometric bead assay by flow cytometry and the results were analyzed using FCAP Array™ software. The data sets were analyzed (GraphPad Prism 5.02) and a p value of < 0.05 was considered statistically significant. RESULTS The study was conducted with 34 patients (n=34) and un-blinded after retrieval of data. The cohort has 8 patients diagnosed with sepsis and 26 without sepsis based on STS criteria. Demographic details for both groups are summarized in Table 1. Cytokine and other biomarker expression levels before (D-1) and after (D+1) Surgery is summarized in Table 2. At D +1, IL-1β, TNF-α, IL-17A and IL-10 showed significantly higher concentration in sepsis group compared to non-sepsis group (Fig 1B). CRP, PCT, WBC and differential blood count were not showing any discriminatory potential between sepsis and non-sepsis patients at D +1. The ROC curves of the above four cytokine expression levels at D+1 was analyzed between sepsis and non-sepsis groups. A plasma IL-1β level of 0.25 pg/ml had a sensitivity of 87.5 % and a specificity of 53.8 % and a plasma IL-17A level of 1.78 pg/ml had a sensitivity of 75 % and specificity of 46.2 %. In addition, IL-10 level of 8.99 pg/ml in plasma showed a diagnostic sensitivity of 87.5 % and a specificity of 53.8% (Fig 1C). Based on the current observation we proposed a model of inflammatory cytokine dynamics involving IL-1β, IL-17A and IL-10 suggesting their role, which may lead to the development of sepsis (Fig 1D). CONCLUSION We identified a significant up regulation of circulating inflammatory cytokines at 24 h in patients who developed sepsis after cardiac surgery, earlier than any noticeable changes in conventional sepsis biomarkers. These results suggest the possibility of inflammatory cytokines as a diagnostic marker and may be a potential therapeutic target as well. The study needs to be validated further on a larger cohort of patients. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.