Interleukin-27 as a candidate diagnostic biomarker for bacterial infection in immunocompromised pediatric patients

Role of IL-27 in COVID-19: A Thin Line between Protection and Disease Promotion

Cytokine storm is usually described as one of the main reasons behind COVID-associated mortality. Cytokines are essential protein molecules engaged in immune responses; they play a critical role in protection against infections. However, they also contribute to inflammatory reactions and tissue damage, becoming a double-edged sword in the context of COVID-19. Recent studies have suggested various cytokines and chemokines that play a crucial role in the immune response to SARS-CoV-2 infection. One such cytokine is interleukin 27 (IL-27), which has been found to be elevated in the blood plasma of patients with COVID-19. Within this study, we will explore the role of IL-27 in immune responses and analyze both the existing literature and our own prior research findings on this cytokine in the context of COVID-19. It affects a wide variety of immune cells. Regardless of the pathological process it is involved in, IL-27 is critical for upholding the necessary balance between tissue damage and cytotoxicity against infectious agents and/or tumors. In COVID-19, it is involved in multiple processes, including antiviral cytotoxicity via CD8+ cells, IgG subclass switching, and even the activation of Tregs.

Assessment of Serum Interleukin-27 and Mean Platelet Volume in Late-Onset Neonatal Sepsis

OBJECTIVE

Late-onset sepsis (LOS) is a substantial contributor to morbidity and mortality among neonates. The use of nonculture-based tools for early diagnosis is an area of active investigation. Therefore, we aimed to evaluate the diagnostic value of serum interleukin-27 (IL-27) and mean platelet volume (MPV) in full-term neonates with LOS.

STUDY DESIGN

In this single-center, cross-sectional study, 90 full-term newborns were assigned to two equal-matched groups as follows: (1) culture-proven sepsis and (2) control groups. Clinical data and laboratory findings as complete blood pictures, including MPV, highly sensitive C-reactive protein, and blood culture results, were recorded. Moreover, IL-27 levels were measured using enzyme-linked immunosorbent assay.

RESULTS

IL-27 levels (median = 4,364 pg/mL) and MPV (mean = 12.02 ± 1.54 FL) were significantly higher in the culture-proven sepsis group than in the control group (p < 0.001). For IL-27, the optimum cut-off value for the diagnosis of LOS was 283.8 pg/mL with sensitivity and specificity of 97.8 and 100%, respectively. For MPV, the optimum cut-off value was 11.6 FL, with diagnostic sensitivity and specificity of 77.8 and 97.8%, respectively.

CONCLUSION

IL-27 and MPV are promising markers for the diagnosis of LOS in full-term neonates. The diagnostic performance of IL-27 was superior to MPV.

KEY POINTS

· Late-onset neonatal sepsis diagnosis is time consuming.. · Nonculture-based rapid diagnostic tests are much needed.. · IL-27 is superior in LOS diagnosis to MPV..

Febrile illness in high-risk children: a prospective, international observational study

To assess and describe the aetiology and management of febrile illness in children with primary or acquired immunodeficiency at high risk of serious bacterial infection, as seen in emergency departments in tertiary hospitals. Prospective data on demographics, presenting features, investigations, microbiology, management, and outcome of patients within the 'Biomarker Validation in HR patients' database in PERFORM, were analysed. Immunocompromised children (< 18 years old) presented to fifteen European hospitals in nine countries, and one Gambian hospital, with fever or suspected infection and clinical indication for blood investigations. Febrile episodes were assigned clinical phenotypes using the validated PERFORM algorithm. Logistic regression was used to assess the effect size of predictive features of proven/presumed bacterial or viral infection. A total of 599 episodes in 482 children were analysed. Seventy-eight episodes (13.0%) were definite bacterial, 67 episodes probable bacterial (11.2%), and 29 bacterial syndrome (4.8%). Fifty-five were definite viral (9.2%), 49 probable viral (8.2%), and 23 viral syndrome (3.8%). One hundred ninety were unknown bacterial or viral infections (31.7%), and 108 had inflammatory or other non-infectious causes of fever (18.1%). Predictive features of proven/presumed bacterial infection were ill appearance (OR 3.1 (95% CI 2.1-4.6)) and HIV (OR 10.4 (95% CI 2.0-54.4)). Ill appearance reduced the odds of having a proven/presumed viral infection (OR 0.5 (95% CI 0.3-0.9)). A total of 82.1% had new empirical antibiotics started on admission (N = 492); 94.3% proven/presumed bacterial (N = 164), 66.1% proven/presumed viral (N = 84), and 93.2% unknown bacterial or viral infections (N = 177). Mortality was 1.9% (N = 11) and 87.1% made full recovery (N = 522).   Conclusion: The aetiology of febrile illness in immunocompromised children is diverse. In one-third of cases, no cause for the fever will be identified. Justification for standard intravenous antibiotic treatment for every febrile immunocompromised child is debatable, yet effective. Better clinical decision-making tools and new biomarkers are needed for this population. What is Known: • Immunosuppressed children are at high risk for morbidity and mortality of serious bacterial and viral infection, but often present with fever as only clinical symptom. • Current diagnostic measures in this group are not specific to rule out bacterial infection, and positivity rates of microbiological cultures are low. What is New: • Febrile illness and infectious complications remain a significant cause of mortality and morbidity in HR children, yet management is effective. • The aetiology of febrile illness in immunocompromised children is diverse, and development of pathways for early discharge or cessation of intravenous antibiotics is debatable, and requires better clinical decision-making tools and biomarkers.

Systemic IL-27 administration prevents abscess formation and osteolysis via local neutrophil recruitment and activation

Interleukin-27 is a pleiotropic cytokine whose functions during bacterial infections remain controversial, and its role in patients with S. aureus osteomyelitis is unknown. To address this knowledge gap, we completed a clinical study and observed elevated serum IL-27 levels (20-fold higher, P < 0.05) in patients compared with healthy controls. Remarkably, IL-27 serum levels were 60-fold higher in patients immediately following septic death than in uninfected patients (P < 0.05), suggesting a pathogenic role of IL-27. To test this hypothesis, we evaluated S. aureus osteomyelitis in WT and IL-27Rα-/- mice with and without exogenous IL-27 induction by intramuscular injection of rAAV-IL-27p28 or rAAV-GFP, respectively. We found that IL-27 was induced at the surgical site within 1 day of S. aureus infection of bone and was expressed by M0, M1 and M2 macrophages and osteoblasts but not by osteoclasts. Unexpectedly, exogenous IL-27p28 (~2 ng·mL-1 in serum) delivery ameliorated soft tissue abscesses and peri-implant bone loss during infection, accompanied by enhanced local IL-27 expression, significant accumulation of RORγt+ neutrophils at the infection site, a decrease in RANK+ cells, and compromised osteoclast formation. These effects were not observed in IL-27Rα-/- mice compared with WT mice, suggesting that IL-27 is dispensable for immunity but mediates redundant immune and bone cell functions during infection. In vitro studies and bulk RNA-seq of infected tibiae showed that IL-27 increased nos1, nos2, il17a, il17f, and rorc expression but did not directly stimulate chemotaxis. Collectively, these results identify a novel phenomenon of IL-27 expression by osteoblasts immediately following S. aureus infection of bone and suggest a protective role of systemic IL-27 in osteomyelitis.

Clinical Characteristics of Bloodstream Infection in Immunosuppressed Patients: A 5-Year Retrospective Cohort Study

Introduction

Immunosuppressed patients with bloodstream infection are at risk of mortality. Our objective was to assess the independent risk factors of bloodstream infection with mortality in immunosuppressive states.

Methods

The medical data of a total of 896 patients who were hospitalized in our hospital were collected from January 2015 to December 2019. Evaluation of the independent risk factors of mortality was done by univariate and multivariate logistic regression analyses.

Results

Of the 896 immunosuppressed patients with bloodstream infection, 698 had over 60-day survivals and 198 had 60-day mortality. In our study, PCT (mean ±; standard: 11.40 ±; 31.89 µg/l vs. 62.45 ±; 17.10 µg/l, p = 0.007) and presence of age >60 years (40% vs. 14.19%, p = 0.001) were significantly different between situations with and without 60-day survivals in both univariate and multivariate logistic regression analyses. Age >60 years and PCT could be used as indicators for bloodstream infection with 60-day death in immunosuppressive states; the OR (95% CI) were 1.532 (1.099–2.135) and 2.063 (1.413–3.013), respectively. In different subgroups, PCT and age were also independent risk factors of blood system diseases, Klebsiella pneumoniae infection, diabetes, and ICU-stay subgroups.

Conclusions

Age and PCT were independently associated with mortality in immunosuppressive states, which may help to identify the highly risky situation of bloodstream infection in immunosuppressive states.

Biomarkers for Diagnosing Febrile Illness in Immunocompromised Children: A Systematic Review of the Literature

OBJECTIVE

This study aims to assess the performance of biomarkers used for the prediction of bacterial, viral, and fungal infection in immunocompromised children upon presentation with fever.

METHODS

We performed a literature search using PubMed and MEDLINE and In-Process & Other Non-indexed Citations databases. Cohort and case-control studies assessing biomarkers for the prediction of bacterial, viral, or fungal infection in immunocompromised children vs. conventional microbiological investigations were eligible. Studies including adult patients were eligible if pediatric data were separately assessable. Data on definitions used for infections, fever, and neutropenia and predictive values were collected. Risk of bias was assessed with the Quality Assessment of Diagnostic Accuracy Studies-2 tool.

RESULTS

Fifty-two studies involving 13,939 febrile episodes in 7,059 children were included. In total, 92.2% were in cancer patients (n = 48), and 15.7% also included hematopoietic stem cell transplantation patients (n = 8). Forty-three biomarkers were investigated, of which 6 (CRP, PCT, IL-8, IL-6, IL-10, and TNFα) were significantly associated with bacterial infection at admission, studied in multiple studies, and provided predictive data. Literature on the prediction of viral and fungal infection was too limited. Eight studies compared C-reactive protein (CRP) and procalcitonin (PCT), with PCT demonstrating superiority in 5. IL-6, IL-8, and IL-10 were compared with CRP in six, four, and one study, respectively, with mixed results on diagnostic superiority. No clear superior biomarker comparing PCT vs. IL-6, IL-8, or IL-10 was identified.

DISCUSSION

There is great heterogeneity in the biomarkers studied and cutoff values and definitions used, thus complicating the analysis. Literature for immunocompromised children with non-malignant disease and for non-bacterial infection is sparse. Literature on novel diagnostics was not available. We illustrated the challenges of diagnosing fever adequately in this study population and the need for improved biomarkers and clinical decision-making tools.

Interleukin-27 and Its Diverse Effects on Bacterial Infections

Innate and adaptive immune responses against pathogens are known to be carefully orchestrated by specific cytokines that initiate and down regulate immune cell functions from the initial infection through tissue repair and homeostasis. However, some cytokines, including interleukin-27, are expressed at multiple phases of the infection, such that their pro and anti-inflammatory functions have been difficult to interpret. As elucidation of specific cytokine functions throughout infection is central to our understanding of protective vs. susceptible immunity and return to homeostasis vs. prolonged inflammation leading to septic shock, here we review the literature on IL-27 signaling and the various functions of this heterodimeric ligand member of the IL-12 cytokine family. Canonically, IL-27 is produced by antigen-presenting cells, and is thought of as an immunostimulatory cytokine due to its capacity to induce Th1 differentiation. However, many studies have also identified various immunosuppressive effects of IL-27 signaling, including suppression of Th17 differentiation and induction of co-inhibitory receptors on T cells. Thus, the exact role of IL-27 in the context of infectious diseases remains a topic of debate and active research. Additionally, as recent interest has focused on clinical management of acute vs. chronic infections, and life-threatening “cytokine storm” from sepsis, we propose a hypothetical model to explain the biphasic role of IL-27 during the early and late phases of immune responses to reconcile its known pro and anti-inflammatory functions, which could be therapeutically regulated to improve patient outcomes of infection.

Bronchoalveolar Lavage and Blood Markers of Infection in Critically Ill Patients-A Single Center Registry Study

Microbiological sampling is an indispensable targeted antibiotic therapy for critically ill patients. Invasive respiratory sampling by bronchoalveolar lavage (BAL) can be performed to obtain samples from the lower respiratory tract. It is debated as to whether blood markers of infection can predict the outcome of BAL in a medical intensive care unit (ICU). Retrospectively, all ICU patients undergoing BAL from 2009-2018 were included. A total of 468 BAL samples from 276 patients (average age 60 years, SAPS2 47, ICU-mortality 41.7%) were analyzed. At the time of BAL, 94.4% patients were mechanically ventilated, 92.9% had suspected pneumonia, 96.2% were on antibiotic therapy and 36.3% were immunocompromised. Relevant bacteria were cultured in 114/468 (24.4%) cases of BAL. Patients with relevant bacteria in the culture had a higher ICU mortality rate (45.6 vs. 40.4%, p = 0.33) and were significantly less likely to be on a steroid (36 vs. 52%, p < 0.01) or antimycotic (14.9 vs. 34.2%, p < 0.01), while procalcitonin (PCT), C-reactive protein (CRP), and white blood cell (WBC) counts were similar. The area under the receiver operating curve (AUC) values for positive culture and PCT, CRP and WBC counts were low (0.53, 0.54 and 0.51, respectively). In immunocompromised patients, AUC values were higher (0.65, 0.57 and 0.61, respectively). Therefore, microbiological cultures by BAL revealed relevant bacteria in 24.4% of samples. Our data, therefore, might suggest that indication for BAL should not be based on blood markers of infection.

Exploration of the Serum Interleukin-17 and Interleukin-27 Expression Levels in Children with Bronchial Asthma and Their Correlation with Indicators of Lung Function

Aims: To investigate the expression levels of serum interleukin-17 (IL-17) and interleukin-27 (IL-27) in children with bronchial asthma and to correlate these expression levels with lung function indicators. Methods: A total of 106 children with bronchial asthma (observation group: 76 in the acute attack phase, 30 in remission) and 60 healthy children (control group) aged 1-10 years were enrolled. Results: Levels of IL-17, IL-27, and fractional exhaled nitric oxide (FeNO) in the peripheral blood of children with bronchial asthma were higher compared to the control group. In addition, blood IL-17, IL-27, and FeNO levels in the children in the acute stage of bronchial asthma were higher compared with those in remission. The respiratory rate of children in the remission stage was lower compared with those in the acute stage, however, the other indicators were higher. IL-17, IL-27, and FeNO levels positively correlated with the respiratory rate and were negatively correlated with inspiratory time, expiratory time, peak time, and time to reach peak tidal expiratory flow/total expiratory time (TPTEF/TE; all p < 0.05). Conclusion: IL-17 and IL-27 levels are associated with the incidence and the development of bronchial asthma in children, and could be useful diagnostic markers. They may also effectively improve the specificity of FeNO for diagnosing the extent of lung injury in children.