Elevated interleukin-1 receptor antagonist levels in pediatric sepsis syndrome

Targeting cytokines as a treatment for patients with sepsis: A lost cause or a strategy still worthy of pursuit?

Despite often knowing the aetiology of sepsis and its clinical course there has not been the anticipated advances in treatment strategies. Cytokines are influential mediators of immune/inflammatory reactions and in patients with sepsis high circulating levels are implicated in the onset and perpetuation of organ failure. Antagonising the activities of pro-inflammatory cytokines enhances survival in animal models of sepsis but, so far, such a therapeutic strategy has not improved patient outcome. This article addresses the questions of why encouraging laboratory findings have failed to be translated into successful treatments of critically ill patients and whether modifying cytokine activity still remains a promising avenue for therapeutic advance in severe sepsis. In pursuing this task we have selected reports that we believe provide an incisive, critical and balanced view of the topic.

Host response biomarkers in the diagnosis of sepsis: a general overview

Critically ill patients who display a systemic inflammatory response syndrome (SIRS) are prone to develop nosocomial infections. The challenge remains to distinguish as early as possible among SIRS patients those who are developing sepsis. Following a sterile insult, damage-associated molecular patterns (DAMPs) released by damaged tissues and necrotic cells initiate an inflammatory response close to that observed during sepsis. During sepsis, pathogen-associated molecular patterns (PAMPs) trigger the release of host mediators involved in innate immunity and inflammation through identical receptors as DAMPs. In both clinical settings, a compensatory anti-inflammatory response syndrome (CARS) is concomitantly initiated. The exacerbated production of pro- or anti-inflammatory mediators allows their detection in biological fluids and particularly within the bloodstream. Some of these mediators can be used as biomarkers to decipher among the patients those who developed sepsis, and eventually they can be used as prognosis markers. In addition to plasma biomarkers, the analysis of some surface markers on circulating leukocytes or the study of mRNA and miRNA can be helpful. While there is no magic marker, a combination of few biomarkers might offer a high accuracy for diagnosis.

Interleukin-1alpha, interleukin-6 and tumor necrosis factor-alpha levels in children with sepsis and meningitis

BACKGROUND

Cytokines are thought to be important endogenous mediators of the host immune response to infection. The purpose of the present study was to evaluate the utility of serum levels of interleukin (IL)-1alpha, IL-6 and tumor necrosis factor (TNF)-alpha in the prediction and differentiation of sepsis and meningitis in children.

METHODS

Blood was collected from 50 children admitted to hospital for suspicion of infection. On the basis of predetermined criteria and investigation, the children were classified into sepsis (n = 30) and meningitis (n = 20) groups, as well as into healthy controls (n = 24) and non-infected sick controls (n = 12). The sepsis group was subdivided according to culture results into S1 (proven sepsis, n = 11) and S2 (clinical sepsis, n = 19). Serum IL-1alpha, IL-6 and TNF-alpha were measured by enzyme-linked immunosorbent assay (ELISA) while C-reactive protein (CRP) was measured by nephelometer.

RESULTS

In non-infected sick controls, sepsis and meningitis groups, levels of CRP (P < 0.001, P < 0.05 and P < 0.01, respectively), IL-1alpha (P < 0.001 for all), and IL-6 (P < 0.01, P < 0.001, P < 0.001, respectively) were significantly elevated compared to healthy controls. In sepsis, levels of IL-1alpha increased in the S2 subgroup (P < 0.001) and IL-6 increased in the S1 and S2 subgroups (P < 0.05, P < 0.001, respectively) compared with healthy controls. In meningitis, IL-1alpha had the highest sensitivity and negative predictive value, while IL-6 had the highest specificity and positive predictive value in non-infected sick controls, sepsis and meningitis groups.

CONCLUSION

Interleukin-1alpha, IL-6 and CRP are increased in non-infected sick controls, sepsis and meningitis patients but it is not possible to differentiate between them. IL-1alpha had the highest sensitivity in meningitis while IL-6 had the highest specificity in prediction of sepsis and meningitis and their assessment together may improve accuracy in the diagnosis of childhood infection.

Bloodstream infection in children

OBJECTIVE

To establish the definitions of bloodstream infection (BSI) in children for the purposes of identifying BSI for early therapy, enrollment in sepsis trials, and epidemiology and surveillance studies.

METHODS

Generalized medical literature search using various combinations of the terms "bloodstream infection," "children," and "sepsis."

RESULTS

The medical literature is sparse on these topics; therefore, these recommendations are adapted from guidelines designed for adults. BSI overlaps with other areas of sepsis, such as catheter-related BSI, which will be covered separately. This discussion focuses on BSI of unknown origin, also known as primary BSI.

CONCLUSION

A BSI is the presence of a pathogen in the blood. Its clinical significance should be determined by the presence of the host response as defined by the modified criteria for systemic inflammatory response syndrome SIRS in children or a clinically recognizable syndrome. Definitions of BSI for the purposes of sepsis trials may differ from those for epidemiologic or surveillance studies.

Pediatric sepsis definitions: past, present, and future

OBJECTIVE

To review the past, present, and future definitions of sepsis and the systemic inflammatory response syndrome in children.

METHODS

Review of the literature.

RESULTS

The history and development of the adult-derived sepsis syndrome and its application to pediatric-specific sepsis definitions is provided. Initially, only adult definitions were applied to pediatric studies. Recently, pediatric-specific definitions have been published. The pediatric consensus conference-derived definitions for systemic inflammatory response syndrome, sepsis, severe sepsis, and septic shock are summarized, and their limitations are discussed.

CONCLUSIONS

The potential value and inconsistencies of the current pediatric-specific sepsis definitions are discussed. Future direction of the definitions and their applications are presented.

Definitions of bloodstream infection in the newborn

OBJECTIVE

To develop definitions of bloodstream infections in the newborn that would enable clinicians to identify infection early, so patients can be enrolled in clinical trials. The definitions should be useful for surveillance and epidemiologic purposes.

METHOD

Search of EMBASE, MEDLINE, and Cochrane Library using age and English language limited key words sepsis, septicemia, and shock. Extensive study of textbook of neonatology and discussions with experts in the field.

RESULTS

The search identified >2,000 references. The most appropriate were selected and reviewed. Definitions of bloodstream infection were developed after consultation with an international faculty.

CONCLUSION

Current definitions of neonatal infection (and associated categories) used by neonatal clinicians and researchers have been either adapted/modified from definitions developed for adults or generated by individuals to suit their local needs or the needs of a particular study. It is clear that definitions generated for adults are not applicable to children or to newborn infants. In addition, developing and using unique definitions to suit individual or local needs make comparisons of outcome data and result of studies very difficult. This article proposes a set of definitions that are based as much as possible on current evidence. These definitions may be applicable widely for daily management of an infant with an infection and for research and epidemiologic studies.

International pediatric sepsis consensus conference: definitions for sepsis and organ dysfunction in pediatrics

OBJECTIVE

Although general definitions of the sepsis continuum have been published for adults, no such work has been done for the pediatric population. Physiologic and laboratory variables used to define the systemic inflammatory response syndrome (SIRS) and organ dysfunction require modification for the developmental stages of children. An international panel of 20 experts in sepsis and clinical research from five countries (Canada, France, Netherlands, United Kingdom, and United States) was convened to modify the published adult consensus definitions of infection, sepsis, severe sepsis, septic shock, and organ dysfunction for children.

DESIGN

Consensus conference.

METHODS

This document describes the issues surrounding consensus on four major questions addressed at the meeting: a) How should the pediatric age groups affected by sepsis be delineated? b) What are the specific definitions of pediatric SIRS, infection, sepsis, severe sepsis, and septic shock? c) What are the specific definitions of pediatric organ failure and the validity of pediatric organ failure scores? d) What are the appropriate study populations and study end points required to successfully conduct clinical trials in pediatric sepsis? Five subgroups first met separately and then together to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiological data, and coagulation variables. All conference participants approved the final draft of the proceedings of the meeting.

RESULTS

Conference attendees modified the current criteria used to define SIRS and sepsis in adults to incorporate pediatric physiologic variables appropriate for the following subcategories of children: newborn, neonate, infant, child, and adolescent. In addition, the SIRS definition was modified so that either criteria for fever or white blood count had to be met. We also defined various organ dysfunction categories, severe sepsis, and septic shock specifically for children. Although no firm conclusion was made regarding a single appropriate study end point, a novel nonmortality end point, organ failure-free days, was considered optimal for pediatric clinical trials given the relatively low incidence of mortality in pediatric sepsis compared with adult populations.

CONCLUSION

We modified the adult SIRS criteria for children. In addition, we revised definitions of severe sepsis and septic shock for the pediatric population. Our goal is for these first-generation pediatric definitions and criteria to facilitate the performance of successful clinical studies in children with sepsis.

CD14+CD16+ monocytes in the course of sepsis in neonates and small children: monitoring and functional studies

The phenotype and function of peripheral blood monocytes change after trauma and during sepsis. The aim of the study was to evaluate monocyte expression of human leucocyte antigen (HLA)-DR and Fc receptor III (FcR III) (CD16) in neonates and small children with high risk of sepsis (hospitalized at the intensive care unit). The reduced proportion of CD14+HLA-DR+ monocytes was observed in all patients at the intensive care unit, while the increase of CD16 expression on monocytes was observed in the course of sepsis. The measurement of CD16 expression on monocytes also proved to be more useful for monitoring patient. The proportion of both CD14dimCD16+ and CD14highCD16+ monocytes increased during sepsis; however, monocytes showed reduced ability to phagocytose Escherichia coli, compromised ability to cooperate with T cells and reduced CD86 expression in parallel to HLA-DR depression. The reduced interleukin (IL)-1 but rather increased IL-10 production was associated with sepsis. The differences between CD14+CD16+ monocytes of healthy donors and patients with sepsis are discussed.

Interleukin-1 receptor antagonist in ascites indicates acute graft rejection after pediatric liver transplantation

Acute graft rejection is one of the most frequent complications after pediatric liver transplantation (LTx). In clinical practice, it is sometimes difficult to differentiate acute cellular graft rejection from other complications because clinical and chemical findings are often nonspecific. We therefore investigated the value of cytokine quantification in drained ascites, in addition to quantification of cytokine concentrations of serum, in 30 children in the first 2 weeks after orthotopic liver transplantation (OLT). Six of 30 patients showed acute graft rejection, with rising levels of alanine aminotransferase (ALT) and alpha-glutathione-S-transferase (alpha-GST) in serum up to 24 h prior to biopsy-proven rejection. There were no significant elevations of interleukin-2 receptor (IL-2r) and interleukin-6 (IL-6) in serum and ascites. In contrast to these findings, the concentration in ascites of the interleukin-1 receptor antagonist (IL-1ra) increased 48 h before rejection was proven by liver biopsy (p < 0.01, in comparison with the non-rejecting group, n = 24). The IL-1ra concentration in ascites was up to 11-fold higher than in serum during rejection (15.43 vs. 1.38 ng/mL). Two children with early infectious complication showed no significant increase in ascitic IL-1ra concentration. We conclude from these data that quantification of IL-1ra in ascites indicates the start of graft rejection after LTx. As long as abdominal drainage is performed, this non-invasive procedure may be of additional value in differential diagnoses and early diagnosis of rejection.

Interleukin-1 receptor antagonist production during infectious and noninfectious systemic inflammatory response syndrome

OBJECTIVE

To analyze the levels of circulating and cell-associated forms of interleukin-1 receptor antagonist (IL-1ra) and the spontaneous and the lipopolysaccharide- or streptococcus-induced ex vivo production of IL-1ra by isolated neutrophils.

DESIGN

Cohort study.

SETTING

A collaborative study between an intensive care unit and a research laboratory.

PATIENTS

Septic patients (those with infectious systemic inflammatory response syndrome [SIRS]) and patients undergoing cardiac surgery with cardiopulmonary bypass (noninfectious SIRS).

MEASUREMENTS AND MAIN RESULTS

Both noninfectious and infectious SIRS patients had enhanced levels of plasma IL-1ra. In septic patients, the increased level of IL-1ra associated with circulating leukocytes reflected the higher number of circulating neutrophils, because these cells, as well as peripheral blood mononuclear cells, contained similar levels of cell-associated forms of IL-1ra than those found at homeostasis in healthy controls. The analysis of the in vitro production of IL-1ra by neutrophils showed a decreased capacity of these cells to release the secreted form of IL-1ra on activation in all patients when compared with that capacity in healthy controls. In contrast, the production of the intracellular forms of IL-1ra was not altered in septic patients, but it was diminished in post-cardiopulmonary bypass patients.

CONCLUSIONS

The capacity of releasing IL-1ra by activated neutrophils from infectious or noninfectious SIRS patients was diminished. In contrast, the accumulation of intracellular IL-1ra in septic patients was not modified when compared with that in healthy controls. These ex vivo data illustrate that a different gene regulation of the secreted and intracellular forms of IL-1 ra occurs during a pathologic situation like sepsis.

Improving the outcome of septic shock in children

Sepsis is an important cause of pediatric morbidity and mortality. Improving the outcome of pediatric sepsis requires diverse efforts, including prevention, early recognition, improvements in early management and transport, and physiology-directed care. Awareness that septic shock represents a pathophysiologic host response to infection has prompted investigation of immune mediators and coagulation factors as potential targets for anti-sepsis therapies. Advancements thus far include: the potential prevention of neonatal sepsis with granulocyte colony-stimulating factor; recognition of clindamycin as a potential inhibitor of endotoxin release; improved outcome from meningococcal disease in children treated with bactericidal/permeability-increasing protein (rBPI21); and improved outcome from sepsis in premature infants treated with pentoxifylline. Further randomized controlled studies of immunomodulatory agents are indicated and a few are in progress. Current studies on genetic propensities in cytokine and coagulation protein expression may explain variability in patient outcomes and eventually lead to genomics-based therapeutics.

Circulating pro- and counterinflammatory cytokine levels and severity in necrotizing enterocolitis

OBJECTIVES

To evaluate the relationship between the severity of necrotizing enterocolitis (NEC) and circulating concentrations of proinflammatory cytokines interleukin (IL)-1beta and IL-8 and counterinflammatory cytokines IL-1 receptor antagonist (IL-1ra) and IL-10. These cytokines have been associated with bowel injury or inflammation and may be released more slowly or later than previously examined cytokines. Also, to determine if any one of these cytokines will predict the eventual severity of NEC when measured at symptom onset.

METHOD

Serial blood samples at onset, 8, 24, 48, and 72 hours were obtained from newborn infants with predefined signs and symptoms of NEC. Normal levels were defined from weight-, gestation-, and age-matched controls. Concentrations of the four cytokines were determined by enzyme-linked immunosorbent assay and compared throughout the time period by stage of NEC, using sepsis as a co-factor. Mean concentrations of each cytokine at onset were compared with the controls. Threshold values were obtained with the best combination of high sensitivity and high specificity for defining stage 1 NEC or for diagnosing stage 3 NEC at onset.

RESULTS

There were 12 cases of stage 1, 18 cases of stage 2, and 6 cases of stage 3 NEC included in the study, as well as 20 control infants. Concentrations of IL-8 and IL-10 were significantly higher in infants with stage 3 NEC from onset through 24 hours compared with infants with less severe NEC. At onset, concentrations of all four cytokines were significantly higher in stage 3 NEC. To identify, at onset, the infants with a final diagnosis of stage 3 NEC, an IL-1ra concentration of >130 000 pg/mL had a sensitivity of 100% and a specificity of 92%. At 8 hours, an IL-10 concentration of >250 pg/mL had a sensitivity of 100% and a specificity of 90% in identifying stage 3 NEC in infants with symptoms suggestive of NEC at onset.

CONCLUSIONS

The severity of NEC and its systemic signs and symptoms are not due to a deficiency of counterregulatory cytokines. In fact, mean concentrations of IL-1ra in NEC are higher than what has been reported in other populations. The cytokines IL-8, IL-1ra, and IL-10 are released later or more slowly after a stimulus and may be more useful in identifying, within hours of symptom onset, which infant will develop significant NEC.