IL-17 is elevated in cerebrospinal fluids in bacterial meningitis in children

Efficacy and safety of ketamine for pediatric and adolescent super-refractory status epilepticus and the effect of cerebral inflammatory conditions

OBJECTIVE

To investigate the short-term benefits and adverse effects of ketamine in the treatment of pediatric and adolescent super-refractory status epilepticus (SRSE), with a focus on the inflammatory etiology.

METHODS

This retrospective observational cohort study included a consecutive series of 18 pediatric to adolescent patients with SRSE admitted between 2008 and 2023 and treated with ketamine. Seizure frequency per hour before and after ketamine administration and response rate were calculated. Neurological decline, catecholamine administration, and adverse effects were also assessed. The patients were divided into inflammatory and non-inflammatory etiology groups.

RESULTS

The median age at SRSE onset was 1 year 5 months (range: 11 days-24 years), and 78% of the patients were male individuals. The median duration of treatment was 7.5 days (interquartile range: 2.8-15.5 days). Fifteen (83%) patients achieved >50% seizure reduction. The median seizure frequency before and after ketamine treatment was 5.9 and 0.9, respectively, showing a significant reduction in seizure frequency (p < 0.0001). Ten patients had inflammatory etiologies including bacterial meningitis (n = 2), viral encephalitis (n = 3), and febrile infection related epilepsy syndrome (n = 5). The inflammatory etiology group required a longer treatment duration (p = 0.0453) and showed lower seizure reduction (p = 0.0264), lower response rate (p = 0.0044), and higher neurological decline (p = 0.0003) than the non-inflammatory etiology group. Three (17%) patients experienced transient adverse events requiring intervention within 24 h of initiating ketamine administration.

CONCLUSIONS

Ketamine administration was associated with fewer serious adverse events and a reduced seizure frequency. Additionally, inflammatory conditions may weaken the efficacy of ketamine in patients with SRSE.

Gene polymorphisms of IL-17A and bacterial meningitis in Angolan children

Interleukin (IL)-17 A plays a crucial role in protecting hosts from invading bacterial pathogens. In this study, we investigated if single nucleotide polymorphisms (SNPs) in IL-17A are associated with susceptibility and outcome of bacterial meningitis (BM) in Angolan children. The study sample comprised 241 confirmed BM patients and 265 controls, which were matched for age and ethnicity. Three IL-17A SNPs - rs2275913 (-197G > A), rs8193036 (-737C > T) and rs4711998 (-877 A > G) - were determined by high-resolution melting analysis (HRMA). The frequency of variant genotype rs4711998 was significantly higher in patients with BM caused by Haemophilus influenzae (odds ratio [OR] 3.5; 95% confidence interval [CI] 1.49-8.23; P = 0.0025) than in controls. Also, patients with BM caused by Gram-negative bacteria and who carried the variant genotype rs2275913 had a lower glucose level (P = 0.0051) in cerebrospinal fluid (CSF). Patients with BM caused by Streptococcus pneumoniae who carried the variant type rs8193036 had a reduced risk for severe neurological sequelae (OR: 0.14; 95% CI: 0.029-0.68; P = 0.0079), blindness (OR: 0.012; 95% CI: 0.012-0.87; P = 0.017) and ataxia (OR: 0.28; 95% CI: 0.091-0.83; P = 0.023). This study suggests an association of IL-17A genetic variations with susceptibility and outcome of bacterial meningitis in Angolan children.

Immunologic biomarkers for bacterial meningitis

Meningitis is defined as the inflammation of the meninges that is most often caused by various bacterial and viral pathogens, and is associated with high rates of mortality and morbidity. Early detection of bacterial meningitis is essential to appropriate antibiotic therapy. Alterations in immunologic biomarkers levels have been considered the diagnostic approach in medical laboratories for the identifying of infections. The early increasing immunologic mediators such as cytokines and acute phase proteins (APPs) during bacterial meningitis have made they significant indicators for laboratory diagnosis. Immunology biomarkers showed wide variable sensitivity and specificity values that influenced by different reference values, selected a certain cutoff point, methods of detection, patient characterization and inclusion criteria, as well as etiology of meningitis and time of CSF or blood specimens' collection. This study provides an overview of different immunologic biomarkers as diagnostic markers for the identification of bacterial meningitis and their efficiencies in the differentiating of bacterial from viral meningitis.

Deciphering the TLR transcriptome and downstream signaling pathway in cerebrospinal fluid in pediatric meningitis

OBJECTIVE/DESIGN

Pediatric meningitis is characterized by a colossal inflammatory response to the pathogen in the central nervous system (CNS). This unabated inflammatory response persists even after the removal of the pathogen by antibiotics/steroids causing collateral damage to CNS tissue. Toll-like receptors (TLRs) are the key players in the recognition and elicitation of innate-immune response against bacterial/viral components in cerebrospinal fluid (CSF). Till date, the precise understanding of TLR-triggered inflammatory response in pediatric meningitis is lacking. The present study was designed to delineate the role of TLR transcriptome and downstream signaling pathways in CSF of pediatric meningitis.

METHODS

Children in the age group of > 3 months to 12 years with pediatric meningitis were included. A total of 249 cases of pediatric meningitis (bacterial = 89, viral = 160) were included. In addition, 71 children who tested negative to the pathogen in CSF tap and did not have signs of infection clinically constituted the controls. RNA was extracted from the CSF samples of both cases and controls. The relative gene expression profile of 42 TLR signaling pathway genes was performed. For the analysis of secretory cytokines and chemokines in CSF, Luminex assay was performed.

RESULTS

We report global upregulation of TLR genes in patients with acute bacterial meningitis (ABM). The downstream signaling molecules were upregulated as well. The CSF of pediatric ABM patients revealed a predominant pro-inflammatory milieu marked by increased levels of pro-inflammatory cytokines. A significant correlation between poor clinical outcomes of patients and an increased expression of TLR/pro-inflammatory cytokine genes was observed.

CONCLUSION

Our findings provide support for future studies exploring TLR-based adjunct therapy to limit the neurological sequelae, owing to persistent inflammation in pediatric ABM patients.

Interleukin-17A Contributed to the Damage of Blood-CNS Barriers During Streptococcus suis Meningitis

Streptococcus suis (S. suis) is an emerging zoonotic agent that can cause meningitis in humans with high mortality and morbidity. Meningitic S. suis can induce higher level of IL-17 than non-meningitic S. suis. Besides, IL-17A plays various roles on bacterial clearance or disruption of blood-CNS barriers through the downregulation and reorganization of tight junction (TJ) molecules. However, it remains to be elucidated for the role of IL-17A on the infection with meningitic S. suis. Here, we found that meningitic S. suis infection could not only cause acute death due to the damage of multiple organs, but also cause meningitis and clinical nervous signs since 60 h of post-infection due to the penetration of blood-CNS barriers after lasting bacteremia. In contrast, the mice with deficiency of il17a gene could not significantly change the acute inflammatory response and acute death, but it could not show obvious meningitis and clinical nervous signs caused by the meningitic S. suis infection. In addition, we also found that IL-17A could inhibit the transcription and expression of TJ proteins that facilitated the leakage of blood-CNS barriers since 60 h of post-infection during meningitic S. suis infection. Thus, our findings demonstrated that IL-17A could downregulate TJ proteins, which undoubtedly facilitated the leakage of blood-CNS barriers for bacterial invasion and then caused S. suis meningitis, providing potential targets for future prevention and treatment of this disease.

Interleukin-17A Contributes to Bacterial Clearance in a Mouse Model of Streptococcal Toxic Shock-Like Syndrome

Streptococcus suis (S. suis), an emerging zoonotic pathogen, can cause streptococcal toxic shock-like syndrome (STSLS) in humans with high mortality. STSLS is characterized by high bacterial burden, an inflammatory cytokine storm, multi-organ dysfunction, and ultimately acute host death. Although it has been found that a significantly high level of IL-17A was induced in an NLRP3-dependent manner during STSLS development, the role of IL-17A on S. suis STSLS remains to be elucidated. In this study, we found that the epidemic strain SC 19 caused a significantly higher level of IL-17A than the non-epidemic strain P1/7. In addition, higher bacterial burden was observed from SC 19-infected il17a−/− mice than il17a+/+ mice, although acute death, tissue injury and inflammatory cytokines storm were observed in both types of mice. Furthermore, compared with il17a+/+ mice, the level of neutrophils recruitment was lower in il17a−/− mice, and the levels of induced antimicrobial proteins, such as CRAMP, S100A8 and lipocalin-2, were also decreased in il17a−/− mice. In conclusion, this study demonstrated that IL-17A does not contribute to the severe inflammation, although it may play a minor role for bacterial clearance by inducing antimicrobial proteins and promoting neutrophil recruitment during STSLS.

Neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios as inflammation markers in patients with papilledema due to idiopathic intracranial hypertension

Purpose:

The aim of this study was to investigate the role of inflammation in the pathogenesis of idiopathic intracranial hypertension (IIH) using the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) as inflammation markers.

Methods:

The files of 33 IIH patients and 33 controls were screened for this retrospective study. For each patient, the NLR and PLR values were calculated using a single fasting blood sample. For both eyes, papilledema (PE) grades, best-corrected visual acuity (BCVA), retinal nerve fiber layer thickness (RNFLT), and ganglion cell layer thickness (GCLT) measurements were recorded along with the demographic data, including body mass index (BMI), and complete neurological and ophthalmological findings. Comparisons between the two groups and between the IIH patients with and without PE were made. The associations of NLR and PLR with all other parameters were analyzed independently from age, gender, and BMI.

Results:

NLR and PLR were higher in patients with IIH than controls (P < 0.05). They were also higher in patients with PE (P < 0.05) in the IIH group. NLR and PLR were found to be associated with BCVA (P < 0.001 and P = 0.023, respectively), global RNFLT (P = 0.004 and 0.012, respectively), RNFLT of the temporal quadrant (P < 0.001 and P = 0.042, respectively) and PE grade (P < 0.001 and P = 0.035, respectively).

Conclusion:

The NLR and PLR values and their associations with BCVA, RNFLT, and PE support the hypothesis that inflammation is a very important component of the pathogenesis of IIH.

Toll-like receptor linked cytokine profiles in cerebrospinal fluid discriminate neurological infection from sterile inflammation

Rapid determination of an infective aetiology causing neurological inflammation in the cerebrospinal fluid can be challenging in clinical practice. Post-surgical nosocomial infection is difficult to diagnose accurately, as it occurs on a background of altered cerebrospinal fluid composition due to the underlying pathologies and surgical procedures involved. There is additional diagnostic difficulty after external ventricular drain or ventriculoperitoneal shunt surgery, as infection is often caused by pathogens growing as biofilms, which may fail to elicit a significant inflammatory response and are challenging to identify by microbiological culture. Despite much research effort, a single sensitive and specific cerebrospinal fluid biomarker has yet to be defined which reliably distinguishes infective from non-infective inflammation. As a result, many patients with suspected infection are treated empirically with broad-spectrum antibiotics in the absence of definitive diagnostic criteria. To begin to address these issues, we examined cerebrospinal fluid taken at the point of clinical equipoise to diagnose cerebrospinal fluid infection in 14 consecutive neurosurgical patients showing signs of inflammatory complications. Using the guidelines of the Infectious Diseases Society of America, six cases were subsequently characterized as infected and eight as sterile inflammation. Twenty-four contemporaneous patients with idiopathic intracranial hypertension or normal pressure hydrocephalus were included as non-inflamed controls. We measured 182 immune and neurological biomarkers in each sample and used pathway analysis to elucidate the biological underpinnings of any biomarker changes. Increased levels of the inflammatory cytokine interleukin-6 and interleukin-6-related mediators such as oncostatin M were excellent indicators of inflammation. However, interleukin-6 levels alone could not distinguish between bacterially infected and uninfected patients. Within the patient cohort with neurological inflammation, a pattern of raised interleukin-17, interleukin-12p40/p70 and interleukin-23 levels delineated nosocomial bacteriological infection from background neuroinflammation. Pathway analysis showed that the observed immune signatures could be explained through a common generic inflammatory response marked by interleukin-6 in both nosocomial and non-infectious inflammation, overlaid with a toll-like receptor-associated and bacterial peptidoglycan-triggered interleukin-17 pathway response that occurred exclusively during infection. This is the first demonstration of a pathway dependent cerebrospinal fluid biomarker differentiation distinguishing nosocomial infection from background neuroinflammation. It is especially relevant to the commonly encountered pathologies in clinical practice, such as subarachnoid haemorrhage and post-cranial neurosurgery. While requiring confirmation in a larger cohort, the current data indicate the potential utility of cerebrospinal fluid biomarker strategies to identify differential initiation of a common downstream interleukin-6 pathway to diagnose nosocomial infection in this challenging clinical cohort.

Interleukin-6-Mediated Inflammation May Cause Methotrexate-Induced Leukoencephalopathy

Children with leukemia treated with methotrexate (MTX) may develop MTX-induced leukoencephalopathy, which can present as seizures or focal neurological deficits. However, the precise pathophysiology has not been fully elucidated. Differences in cytokine/chemokine profiles in cerebrospinal fluid (CSF) between children with MTX-induced leukoencephalopathy and those with posterior reversible encephalopathy syndrome (PRES), an acute neurological condition associated with hypertension, were investigated. Interleukin (IL)-1β, 2, 4, 5, 6, 7, 8, 10, 12, 13, and 17, tumor necrosis factor-alpha, interferon-gamma, granulocyte monocyte colony-stimulating factor, granulocyte colony-stimulating factor, macrophage inflammatory protein-1β, and monocyte chemoattractant protein-1 concentrations were measured in CSF supernatants from 3 children with acute leukemia with MTX-induced leukoencephalopathy, 3 children with acute leukemia with PRES, 6 children with acute leukemia without neurological complications, and 8 children with acute encephalopathy. CSF IL-6 concentrations were higher in children with MTX-induced leukoencephalopathy than in children with acute leukemia with PRES, with acute leukemia without neurological complications, and with acute encephalopathy. We concluded that IL-6 may be involved in the pathogenesis of MTX-induced leukoencephalopathy.

Cytokine and immune cell profiling in the cerebrospinal fluid of patients with neuro-inflammatory diseases

BACKGROUND

Cytokines play multiple roles during neuro-inflammatory processes and several cytokines have been studied in the context of specific diseases. This study provides a comprehensive picture of cerebrospinal fluid (CSF) changes during neuro-inflammation by analyzing multiple cytokines in combination with immune cell subsets and standard CSF parameters.

METHODS

Using multiplex assays, we simultaneously measured 36 cytokines (CCL1-3, CCL7, CCL8, CCL11, CCL13, CCL19, CCL20, CCL22-27, CXCL1, CXCL2, CXCL5, CXCL6, CXCL8, CXCL9, CXCL11-13, CXCL16, CX3CL1, IL2, IL4, IL6, IL10, IL16, GM-CSF, IFNγ, MIF, TNFα, and MIB1β) in the CSF and serum of 75 subjects. Diagnoses included clinically isolated syndrome and relapsing-remitting multiple sclerosis (MS, n = 18), secondary progressive MS (n = 8), neuro-syphilis (n = 6), Lyme neuro-borreliosis (n = 13), bacterial and viral meningitis (n = 20), and patients with non-inflammatory neurological diseases (NIND, n = 10). Cytokine concentrations were correlated with CSF standard parameters and CSF immune cell subsets (CD4 and CD8 T cells, B cells, plasmablasts, monocytes, and NK cells) quantified by flow cytometry.

RESULTS

We observed increased levels of multiple cytokines (26/36) in patients with neuro-inflammatory diseases when compared to NIND that consistently correlated with CSF cell count and Q_Albumin. Most CSF cytokine concentrations correlated with each other, but correlations between CSF and serum values were scarce (3/36). Within the CSF compartment, CXCL13 showed a strong association with B cells when analyzing all patients, as well as patients with an intact blood-brain barrier (BBB). NK cells positively correlated with CSF concentrations of multiple cytokines (22/36) when analyzing all patients. These correlations were maintained when looking at patients with a disrupted BBB but not detectable in patients with an intact BBB.

CONCLUSIONS

Under conditions of neuro-inflammation, multiple CSF cytokines are regulated in parallel and most likely produced locally. A combined increase of CSF CXCL13 levels and B cells occurs under conditions of an intact BBB. Under conditions of a disrupted BBB, CSF NK cells show significantly increased values and seem to have a major contribution to overall inflammatory processes, reflected by a strong correlation with multiple cytokines. Future studies are necessary to address the exact kinetics of these cytokines during neuro-inflammation and their relation to specific diseases phenotypes.

High neopterin and IP-10 levels in cerebrospinal fluid are associated with neurotoxic tryptophan metabolites in acute central nervous system infections

Background

The host response to intruders in the central nervous system (CNS) may be beneficial but could also be harmful and responsible for neurologic symptoms and sequelae in CNS infections. This immune response induces the activation of the kynurenine pathway (KP) with the production of neuroactive metabolites. Herein, we explored cytokine and KP responses in cerebrospinal fluid (CSF) and serum in patients with encephalitis, aseptic, and bacterial meningitis.

Methods

Cytokines were measured in CSF and serum by multiplex assay in adult patients with encephalitis of infectious, autoimmune or unknown etiology (n = 10), aseptic meningitis (ASM, n = 25), acute bacterial meningitis (ABM, n = 6), and disease control patients with similar symptoms but without pleocytosis in CSF (n = 42). Liquid chromatography-tandem mass spectrometry (LC-MS/ MS) was used to measure KP metabolites in CSF and serum.

Results

A characteristic pattern of increasing cytokine levels and KP metabolites was found in CSF from encephalitis to ASM, with the highest levels in ABM. In ASM and ABM, most inflammatory mediators, including IL-6, IL-8, and IFN-inducible protein-10 (IP-10), showed markedly elevated levels in CSF compared with serum, indicating production within the CNS. In contrast to most mediators, the highest level of IP-10 was found in the ASM group, suggesting a potential role for IP-10 in aseptic/viral meningitis. Neopterin and IP-10 were associated with marked changes in KP metabolites in CSF with increasing kynurenine/tryptophan ratio reflecting indoleamine 2,3-dioxygenase activity. Neopterin, a marker of IFN-γ activity, was associated with an unfavorable balance between neuroprotective and neurotoxic tryptophan metabolites.

Conclusion

We show that parenchymal and meningeal inflammations in CNS share a characteristic cytokine profile with a general immune response in the CSF with limited influence from the systemic circulation. IFN-γ activity, assessed by neopterin and IP-10 levels, may play a role in the activation of the KP pathway in these patients, potentially mediating neurotoxic effects.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1366-3) contains supplementary material, which is available to authorized users.

Cytokine profiles in cerebrospinal fluid of patients with meningitis at a tertiary general hospital in China

BACKGROUND

There has been a great deal of evidence indicating that cytokines participate in meningeal inflammation. Different cytokine profiles may be presented in central nervous system (CNS) infection due to different pathogens. We have attempted to investigate cytokine profiles in cerebrospinal fluid (CSF) of patients with CNS infection.

METHODS

Forty-three patients with CNS infection including tuberculous meningitis, purulent meningitis and cryptococcal meningitis were enrolled and 11 patients with normal CSF were enrolled as control group. The concentrations of Th1-, Th2- and Th17-type cytokines in CSF were detected using multiplex cytokine assay. Furthermore, the correlation between CSF cytokines and CSF parameters in CNS infection was analyzed.

RESULTS

The CSF levels of IL-1β, IL-4, IL-6, IL-10, IL-17, IL-23, IL-33, IFN-γ, TNF-α and sCD40L among the patients with CNS infection were all higher than control group (all P < 0.05). A remarkable elevation of CSF IL-6 in the patients with CNS infection was observed with the least overlap of the CSF concentrations compared to controls. Moreover, CSF IL-6 levels were strongly negatively correlated with CSF glucose and the CSF/blood glucose ratio (r = -0.4375, P = 0.0042; r = -0.4991, P = 0.0009).

CONCLUSIONS

The excessive activation of immune response characterized by elevated levels of CSF Th1-, Th2- and Th17-type cytokines has been observed during CNS infection. Furthermore, we observed negative correlations between CSF IL-6 levels and CSF glucose and CSF/blood glucose ratio in CNS infection. And we suggested that combined CSF IL-6 levels with CSF glucose may serve as a novel biomarker pool for the differential of CNS infection.

Characteristic Comparison of Meningitis and Non-meningitis of Streptococcus suis in an Experimentally Infected Porcine Model

This study tested the differences of meningitis and non-meningitis of Streptococcus suis (SS). In this study, an infected pig model of streptococcal meningitis was established. Compared with the non-meningitis Streptococcus suis group (JZLQ001 group), the meningitis Streptococcus suis group (JZLQ022) exhibited neurological symptoms, such as ataxia and foaming at the mouth, and the brain showed a large area of congestion at 5 days post-infection (p.i.). Moreover, bacterial counts, white blood cells (WBCs), neutrophils, and blood glucose in the blood reached a peak and were significantly higher than those of the JZLQ001 group at 3 days p.i. These values then decreased at 5 days p.i. However, the content of total protein in the blood was lower in the JZLQ022 group than that in the JZLQ001 group, and the difference was most significant at 5 days p.i. When neurological symptoms appeared on 5 days p.i., the bacterial counts in the brain in the JZLQ022 group were significantly higher than those in the JZLQ001 group. The levels of cytokines in the peripheral blood and cerebrospinal fluid (CSF) were an important indicator of inflammation. By ELISA detection, the secretion levels of IL-6, IL-8, and IL-17 in the peripheral blood in the JZLQ022 group were significantly higher than those in the JZLQ001 group at 12 and 24 h and 3 days p.i.; however, TNF-α showed no difference. At 5 days p.i., the secretion levels of IL-6, IL-8, and IL-17 in the JZLQ022 group were significantly lower than those in the JZLQ001 group. The results were similar in CSF. HE staining revealed that the JZLQ022 group exhibited neuronophagia and hyperemia in the brain, but no change was found in the JZLQ001 group. A further study investigating the impact of meningitis Streptococcus suis on blood-brain barrier (BBB) integrity found that the brain tissue content of endogenous IgG in the JZLQ022 group was significantly higher than that in the JZLQ001 group. The present study demonstrated that pigs infected with meningitis and non-meningitis Streptococcus suis exhibit significant differences in immunological aspects such as bacterial counts, WBCs, neutrophils, blood glucose and total protein in the peripheral blood, the secretion levels of IL-6, IL-8, and IL-17, and BBB integrity. These data provide the necessary evidence to better understand SS meningitis.

Advances in Biomarker-Guided Therapy for Pediatric- and Adult-Onset Neuroinflammatory Disorders: Targeting Chemokines/Cytokines

The concept and recognized components of “neuroinflammation” are expanding at the intersection of neurobiology and immunobiology. Chemokines (CKs), no longer merely necessary for immune cell trafficking and positioning, have multiple physiologic, developmental, and modulatory functionalities in the central nervous system (CNS) through neuron–glia interactions and other mechanisms affecting neurotransmission. They issue the “help me” cry of neurons and astrocytes in response to CNS injury, engaging invading lymphoid cells (T cells and B cells) and myeloid cells (dendritic cells, monocytes, and neutrophils) (adaptive immunity), as well as microglia and macrophages (innate immunity), in a cascade of events, some beneficial (reparative), others destructive (excitotoxic). Human cerebrospinal fluid (CSF) studies have been instrumental in revealing soluble immunobiomarkers involved in immune dysregulation, their dichotomous effects, and the cells—often subtype specific—that produce them. CKs/cytokines continue to be attractive targets for the pharmaceutical industry with varying therapeutic success. This review summarizes the developing armamentarium, complexities of not compromising surveillance/physiologic functions, and insights on applicable strategies for neuroinflammatory disorders. The main approach has been using a designer monoclonal antibody to bind directly to the chemo/cytokine. Another approach is soluble receptors to bind the chemo/cytokine molecule (receptor ligand). Recombinant fusion proteins combine a key component of the receptor with IgG1. An additional approach is small molecule antagonists (protein therapeutics, binding proteins, and protein antagonists). CK neutralizing molecules (“neutraligands”) that are not receptor antagonists, high-affinity neuroligands (“decoy molecules”), as well as neutralizing “nanobodies” (single-domain camelid antibody fragment) are being developed. Simultaneous, more precise targeting of more than one cytokine is possible using bispecific agents (fusion antibodies). It is also possible to inhibit part of a signaling cascade to spare protective cytokine effects. “Fusokines” (fusion of two cytokines or a cytokine and CK) allow greater synergistic bioactivity than individual cytokines. Another promising approach is experimental targeting of the NLRP3 inflammasome, amply expressed in the CNS and a key contributor to neuroinflammation. Serendipitous discovery is not to be discounted. Filling in knowledge gaps between pediatric- and adult-onset neuroinflammation by systematic collection of CSF data on CKs/cytokines in temporal and clinical contexts and incorporating immunobiomarkers in clinical trials is a challenge hereby set forth for clinicians and researchers.

Neonatal Meningitis: Overcoming Challenges in Diagnosis, Prognosis, and Treatment with Omics

Neonatal meningitis is a devastating condition. Prognosis has not improved in decades, despite the advent of improved antimicrobial therapy and heightened index of suspicion among clinicians caring for affected infants. One in ten infants die from meningitis, and up to half of survivors develop significant lifelong complications, including seizures, impaired hearing and vision, and delayed or arrested development of such basic skills as talking and walking. At present, it is not possible to predict which infants will suffer poor outcomes. Early treatment is critical to promote more favorable outcomes, though diagnosis of meningitis in infants is technically challenging, time-intensive, and invasive. Profound neuronal injury has long been described in the setting of neonatal meningitis, as has elevated levels of many pro- and anti-inflammatory cytokines. Mechanisms of the host immune response that drive clearance of the offending organism and underlie brain injury due to meningitis are not well understood, however. In this review, we will discuss challenges in diagnosis, prognosis, and treatment of neonatal meningitis. We will highlight transcriptomic, proteomic, and metabolomic data that contribute to suggested mechanisms of inflammation and brain injury in this setting with a view toward fruitful areas for future investigation.

Interferon-γ-Induced Nitric Oxide Synthase-2 Contributes to Blood/Brain Barrier Dysfunction and Acute Mortality in Experimental Streptococcus pneumoniae Meningitis

The proinflammatory cytokine interferon-gamma (IFNγ) recently was shown to play a crucial role in experimental pneumococcal meningitis (PM) pathogenesis, and we aimed in this study to investigate IFNγ-driven nitric oxide synthase-2 (NOS2)-mediated pathogenesis of murine PM. We demonstrate that costimulation of toll-like receptors and IFNγ receptors was synergistic for NOS2 expression in cultured murine microglia. Using an experimental PM model, wild-type mice treated with anti-IFNγ antibody, as well as IFNγ and NOS2 gene knockout (GKO) mice, were inoculated intracerebroventricularly with 10(3) colony-forming units of Streptococcus pneumoniae (WU2 strain). Mice were monitored daily during a 200-h disease course to assess survival rate and blood-brain barrier (BBB) permeability measured at 48 h. IFNγ deficiency was protective in PM, with an approximate 3-fold increase in survival rates in both antibody-treated and IFNγ GKO mice compared to controls (P < 0.01). At 48 h postinoculation, brain NOS2 mRNA expression was significantly increased in an IFNγ-dependent manner. Mortality was significantly delayed in NOS2 GKO mice compared to controls (P < 0.01), and BBB dysfunction was reduced by 54% in IFNγ GKO mice and abolished in NOS2 GKO. These data suggest that IFNγ-dependent expression of NOS2 in the brain contributes to BBB breakdown and early mortality in murine PM.

Leukocyte attraction by CCL20 and its receptor CCR6 in humans and mice with pneumococcal meningitis

We previously identified CCL20 as an early chemokine in the cerebrospinal fluid (CSF) of patients with pneumococcal meningitis but its functional relevance was unknown. Here we studied the role of CCL20 and its receptor CCR6 in pneumococcal meningitis. In a prospective nationwide study, CCL20 levels were significantly elevated in the CSF of patients with pneumococcal meningitis and correlated with CSF leukocyte counts. CCR6-deficient mice with pneumococcal meningitis and WT mice with pneumococcal meningitis treated with anti-CCL20 antibodies both had reduced CSF white blood cell counts. The reduction in CSF pleocytosis was also accompanied by an increase in brain bacterial titers. Additional in vitro experiments showed direct chemoattractant activity of CCL20 for granulocytes. In summary, our results identify the CCL20-CCR6 axis as an essential component of the innate immune defense against pneumococcal meningitis, controlling granulocyte recruitment.

Increased levels of cytokines in cerebrospinal fluid of children with aseptic meningitis caused by mumps virus and echovirus 30

We measured levels of pro-inflammatory cytokines in the cerebrospinal fluid (CSF) of patients with mumps meningitis, enteroviral echovirus 30 meningitis and children without central nervous system infection to investigate whether these molecules were involved in the pathogenesis of viral meningitis. The CSF was obtained from 62 children suspected with meningitis. These patients were classified to the mumps meningitis (n = 19), echovirus 30 meningitis (n = 22) and non-meningitis (n = 21) groups. The concentrations of interleukin-1 (IL-1), interleukin-1 soluble receptor type 2 (IL-1R2), interleukin-8 (IL-8), human interferon gamma (IFN-γ) and human tumour necrosis factor alpha (TNF-α) were determined by immunoassay. A significant increase was noted in the levels of IL-8, TNF-α and IL-1R2 in the CSF of both meningitis groups as compared to controls. The concentrations of IFN-γ and IL-1 differed significantly only between the mumps group and control. The levels of IL-1, IFN-γ and TNF-α were significantly higher in mumps meningitis when compared to the echovirus 30 group. Of all cytokines examined, only IFN-γ correlated with pleocytosis (r = 0.58) in the mumps meningitis group. The increased CSF cytokine levels are markers of meningeal inflammation, and each virus may cause a specific profile of the cytokine pattern.

Pediatric reference ranges for proinflammatory and anti-inflammatory cytokines in cerebrospinal fluid and serum by multiplexed immunoassay

To define cytokine concentrations and detectability in children with noninflammatory neurological disorders (NIND). The multiplex bead assay technology was used for simultaneous measurement of 34 soluble cytokines/chemokines in cerebrospinal fluid (CSF) from 73 NIND. Sera from 36 healthy children and 37 NIND also were analyzed. In CSF, CXCL10 had the highest concentration; CCL2, CXCL10, and interleukin (IL)-6 were detectable in all samples, and CXCL8, CCL22, CXCL1, IL-16, and IL-1 receptor antagonist were found in ≥50% of the samples. In serum, CXCL1 had the highest concentration; sIL-2Ra, CXCL1, CXCL10, and CCL22 were detectable in all samples, and CCL2, IL-12, CCL5, and granulocyte monocyte colony-stimulating factor (GM-CSF) were found in ≥50% of the samples. The mean CSF:serum ratio for CCL2 was several-fold higher than the rest, with the CXCL10 and CXCL8 ratios also >1. Intercorrelations between CSF cytokines included CCL2 versus CXCL8 and IL-6, and CXCL1 versus CCL22, reflecting both T-helper-1 (Th1)/Th1 and Th1/Th2 relations. Serum correlations included CCL11 versus CCL2, GM-CSF, and IL-4. For serum cytokines, the agreement between healthy children and NIND was good, with the exception of higher CCL4 in NIND. Cytokines in children varied greatly in concentration and detectability, with chemokines predominating in the CSF. These data allow investigators to select their own kit cytokines, instead of manufacturer-selected cytokines, for greater cost-effectiveness and interpretability.

Circulating concentrations, cerebral output of the CINC-1 and blood–brain barrier disruption in Wistar rats after pneumococcal meningitis induction

Pneumococcal meningitis is a severe infectious illness of the central nervous system (CNS), with high rates of lethality and morbidity, being that the microorganism and the host's inflammatory response are responsible for cerebral complications. Moreover, the blood–brain barrier (BBB) itself secretes cytokines and, because of the bipolar nature of the BBB, these substances can be secreted into either the CNS compartment or in the blood, so patients with acute bacterial meningitis frequently develop sepsis. Therefore, the aim of this study was to evaluate the cytokine/chemokine levels in different vessels and the BBB integrity after pneumococcal meningitis induction. Wistar rats were infected with Streptococcus pneumoniae, and the BBB integrity was investigated using Evan's blue dye. Also, blood from the carotid artery and jugular vein was collected in order to perform tumour necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-60 and cytokine-induced neutrophil chemoattractant-1 (CINC-1) analyses by enzyme-linked immunosorbent assay (ELISA). CINC-1 levels were increased at 6 h in the arterial plasma and at 3 and 6 h in the jugular plasma. We observed BBB breakdown between 12 and 24 h in the hippocampus and at 12 and 18 h in the cortex after pneumococcal meningitis induction. The increase of CINC-1 occurred prior to the BBB breakdown. CINC-1 is a neutrophil chemoattractant and it may be related to early events in the pneumococcal meningitis pathophysiology.