Biomarkers of Cerebral Injury and Inflammation in Pediatric Tuberculous Meningitis

Recent Developments in Tuberculous Meningitis Pathogenesis and Diagnostics

The pathogenesis of Tuberculous meningitis (TBM) is poorly understood, but contemporary molecular biology technologies have allowed for recent improvements in our understanding of TBM. For instance, neutrophils appear to play a significant role in the immunopathogenesis of TBM, and either a paucity or an excess of inflammation can be detrimental in TBM. Further, severity of HIV-associated immunosuppression is an important determinant of inflammatory response; patients with the advanced immunosuppression (CD4+ T-cell count of <150 cells/μL) having higher CSF neutrophils, greater CSF cytokine concentrations and higher mortality than those with CD4+ T-cell counts > 150 cells/μL. Host genetics may also influence outcomes with LT4AH genotype predicting inflammatory phenotype, steroid responsiveness and survival in Vietnamese adults with TBM. Whist in Indonesia, CSF tryptophan level was a predictor of survival, suggesting tryptophan metabolism may be important in TBM pathogenesis. These varying responses mean that we must consider whether a "one-size-fits-all" approach to anti-bacillary or immunomodulatory treatment in TBM is truly the best way forward. Of course, to allow for proper treatment, early and rapid diagnosis of TBM must occur. Diagnosis has always been a challenge but the field of TB diagnosis is evolving, with sensitivities of at least 70% now possible in less than two hours with GeneXpert MTB/Rif Ultra. In addition, advanced molecular techniques such as CRISPR-MTB and metagenomic next generation sequencing may hold promise for TBM diagnosis. Host-based biomarkers and signatures are being further evaluated in childhood and adult TBM as adjunctive biomarkers as even with improved molecular assays, cases are still missed. A better grasp of host and pathogen behaviour may lead to improved diagnostics, targeted immunotherapy, and possibly biomarker-based, patient-specific treatment regimens.

Noninvasive 11C-rifampin positron emission tomography reveals drug biodistribution in tuberculous meningitis

Tuberculous meningitis (TBM) is a devastating form of tuberculosis (TB), and key TB antimicrobials, including rifampin, have restricted brain penetration. A lack of reliable data on intralesional drug biodistribution in infected tissues has limited pharmacokinetic (PK) modeling efforts to optimize TBM treatments. Current methods to measure intralesional drug distribution rely on tissue resection, which is difficult in humans and generally limited to a single time point even in animals. In this study, we developed a multidrug treatment model in rabbits with experimentally induced TBM and performed serial noninvasive dynamic ¹¹C-rifampin positron emission tomography (PET) over 6 weeks. Area under the curve brain/plasma ratios were calculated using PET and correlated with postmortem mass spectrometry. We demonstrate that rifampin penetration into infected brain lesions is limited, spatially heterogeneous, and decreases rapidly as early as 2 weeks into treatment. Moreover, rifampin concentrations in the cerebrospinal fluid did not correlate well with those in the brain lesions. First-in-human ¹¹C-rifampin PET performed in a patient with TBM confirmed these findings. PK modeling predicted that rifampin doses (≥30 mg/kg) were required to achieve adequate intralesional concentrations in young children with TBM. These data demonstrate the proof of concept of PET as a clinically translatable tool to noninvasively measure intralesional antimicrobial distribution in infected tissues.

Collection and Analyses of Cerebrospinal Fluid for Pediatric Translational Research

Cerebrospinal fluid sample collection and analysis is imperative to better elucidate central nervous system injury and disease in children. Sample collection methods are varied and carry with them certain ethical and biologic considerations, complications, and contraindications. Establishing best practices for sample collection, processing, storage, and transport will ensure optimal sample quality. Cerebrospinal fluid samples can be affected by a number of factors including subject age, sampling method, sampling location, volume extracted, fraction, blood contamination, storage methods, and freeze-thaw cycles. Indicators of sample quality can be assessed by matrix-associated laser desorption/ionization time-of-flight mass spectrometry and include cystatin C fragments, oxidized proteins, prostaglandin D synthase, and evidence of blood contamination. Precise documentation of sample collection processes and the establishment of meticulous handling procedures are essential for the creation of clinically relevant biospecimen repositories. In this review we discuss the ethical considerations and best practices for cerebrospinal fluid collection, as well as the influence of preanalytical factors on cerebrospinal fluid analyses. Cerebrospinal fluid biomarkers in highly researched pediatric diseases or disorders are discussed.

Tuberculous meningitis in children is characterized by compartmentalized immune responses and neural excitotoxicity

Tuberculous meningitis (TBM) is the most severe form of TB with high rates of mortality and morbidity. Here we conduct RNA-sequencing on whole blood as well as on ventricular and lumbar cerebrospinal fluid (CSF) of pediatric patients treated for TBM. Differential transcript expression of TBM cases are compared with healthy controls in whole blood and with non-TB cerebral infection controls in CSF. Whole blood RNA-Seq analysis demonstrates a distinct immune response pattern in TBM, with significant increase in both canonical and non-canonical inflammasome activation and decrease in T-cell activation. In ventricular CSF, a significant enrichment associated with neuronal excitotoxicity and cerebral damage is detected in TBM. Finally, compartmental comparison in TBM indicates that the ventricular profile represents brain injury whereas the lumbar profile represents protein translation and cytokine signaling. Together, transcriptomic analysis shows that disease processes differ between the periphery and the central nervous system, and within brain compartments.

Tuberculosis meningitis (TBM) is a severe form of TB with limited treatment options. Here, the authors perform RNA sequencing on whole blood and on ventricular and lumbar cerebrospinal fluid (CSF) samples from pediatric patients treated for TBM to characterize the immune response and tissue damage.

Reconstruction of the lncRNA-miRNA-mRNA network based on competitive endogenous RNA reveal functional lncRNAs in Cerebral Infarction

Functioning as miRNA sponges, long non-coding RNA (lncRNA) exert its pharmacological action via regulating expression of protein-coding genes. However, the lncRNA-mediated ceRNA in cerebral Infarction (CI) remains unclear. In this study, the expression recordsets of mRNA, lncRNA and miRNA of CI samples were obtained from the NCBI GEO datasets separately. The differentially expressed lncRNAs (DELs), miRNAs (DEMis) and mRNAs (DEMs) were identified by limma package in R platform. A total of 267 DELs, 26 DEMis, and 760 DEMs were identified as differentially expressed profiles, with which we constructed the ceRNA network composed of DELs-DEMis-DEMs. Further, clusterProfiler package in R platform is employed for performing Gene Ontology (GO) and KEGG pathway analysis. An aberrant ceRNA network was constructed according to node degrees in CI, including 28 DELs, 19 DEMs and 12 DEMis, from which we extracted the core network, in which 9 nodes were recognized as kernel genes including Tspan3, Eif4a2, rno-miR-208a-3p, rno-miR-194-5p, Pdpn, H3f3b, Stat3, Cd63 and Sdc4. Finally, with the DELs-DEMis-DEMs ceRNA network provided above, we can improve our understanding of the pathogenesis of CI mediated by lncRNA.

The neurocritical care of tuberculous meningitis

Tuberculous meningitis is the most severe form of tuberculosis and often causes critical illness with high mortality. Two primary management objectives are reducing intracranial pressure, and optimising cerebral perfusion, while killing the bacteria and controlling intracerebral inflammation. However, the evidence base guiding the care of critically ill patients with tuberculous meningitis is poor and many patients do not have access to neurocritical care units. Invasive intracranial pressure monitoring is often unavailable and although new non-invasive monitoring techniques show promise, further evidence for their use is required. Optimal management regimens of neurological complications (eg, hydrocephalus and paradoxical reactions) and of hyponatraemia, which frequently accompanies tuberculous meningitis, remain to be elucidated. Advances in the field of tuberculous meningitis predominantly focus on diagnosis, inflammatory processes, and antituberculosis chemotherapy. However, clinical trials are required to provide robust evidence guiding the most effective supportive, therapeutic, and neurosurgical interventions for tuberculous meningitis that will improve morbidity and mortality.

Enteroviral meningitis reduces CSF concentration of Aβ42, but does not affect markers of parenchymal damage

Biomarkers classically studied in Alzheimer’s disease have been analyzed in numerous central nervous system infections in adults, but there are scarce data on these biomarkers in children. Enteroviruses appear to be the most common cause of aseptic meningitis throughout the world. The aim of the study was to investigate neuroinflammatory properties of non-polio enteroviruses by measuring CSF concentrations of biomarkers that are involved in neuropathological pathways of neurodegenerative disorders. We measured Aβ42, t-tau, and S100B concentrations in 42 children with enteroviral meningitis (EM) compared to control group without central nervous system infection. We found enteroviral meningitis (EM) to reduce CSF concentration of Aβ42 (median, 1051.1 pg/mL; interquartile range (IQR), 737.6–1559.5 vs. median, 459.4 pg/mL; IQR, 312.0–662.0, p < 0.001). In contrast, CSF concentrations of t-tau and S100B were not affected by EM. There was a correlation between total neutrophil count in CSF and Aβ42 (R = − 0.59, p < 0.001). Absolute number of mononuclear cells in the CSF correlated with CSF t-tau (R = 0.41, p < 0.05). Both correlations remained significant after adjustment for age, blood leukocytes, serum CRP, CSF leukocytes, and CSF protein concentration.

The pathogenesis of tuberculous meningitis

Tuberculosis (TB) remains a leading cause of death globally. Dissemination of TB to the brain results in the most severe form of extrapulmonary TB, tuberculous meningitis (TBM), which represents a medical emergency associated with high rates of mortality and disability. Via various mechanisms the Mycobacterium tuberculosis (M.tb) bacillus disseminates from the primary site of infection and overcomes protective barriers to enter the CNS. There it induces an inflammatory response involving both the peripheral and resident immune cells, which initiates a cascade of pathologic mechanisms that may either contain the disease or result in significant brain injury. Here we review the steps from primary infection to cerebral disease, factors that contribute to the virulence of the organism and the vulnerability of the host and discuss the immune response and the clinical manifestations arising. Priorities for future research directions are suggested.

Potential of Host Serum Protein Biomarkers in the Diagnosis of Tuberculous Meningitis in Children

Background: Tuberculous meningitis (TBM) is the most severe form of tuberculosis and results in high morbidity and mortality in children. Diagnostic delay contributes to the poor outcome. There is an urgent need for new tools for the rapid diagnosis of TBM, especially in children. Methods: We collected serum samples from children in whom TBM was suspected at a tertiary hospital in Cape Town, South Africa. Children were subsequently classified as having TBM or no TBM using a published uniform research case-definition. Using a multiplex cytokine array platform, we investigated the concentrations of serum biomarkers comprising biomarkers that were previously found to be of value in the diagnosis of adult pulmonary TB (CRP, SAA, CFH, IFN-γ, IP-10, Apo-AI, and transthyretin) plus other potentially useful host biomarkers as diagnostic candidates for TBM. Findings: Out of 47 children included in the study, 23 (48.9%) had a final diagnosis of TBM and six were HIV infected. A modified version of the adult 7-marker biosignature in which transthyretin was replaced by NCAM1, diagnosed TBM in children with AUC of 0.80 (95% CI, 0.67-0.92), sensitivity of 73.9% (95% CI, 51.6-89.8%) and specificity of 66.7% (95% CI, 44.7-84.4%), with the other six proteins in the signature (CRP, IFN-γ, IP-10, CFH, Apo-A1, and SAA) only achieving and AUC of 0.75 (95% CI, 0.61-0.90) when used in combination. A new childhood TBM specific 3-marker biosignature (adipsin, Aβ42, and IL-10) showed potential in the diagnosis of TBM, with AUC of 0.84 (95% CI, 0.73-0.96), sensitivity of 82.6% (95 CI, 61.2-95.0%) and specificity of 75.0% (95% CI, 53.3-90.2%) after leave-one-out cross validation. Conclusion: A previously described adult 7-marker serum protein biosignature showed potential in the diagnosis of TBM in children. However, a smaller childhood TBM-specific 3-marker signature demonstrated improved performance characteristics. Our data indicates that blood-based biomarkers may be useful in the diagnosis of childhood TBM and requires further validation in larger cohort studies.

Treatment of Tuberculous Meningitis and Its Complications in Adults

PURPOSE OF REVIEW

Tuberculous meningitis (TBM) is a global health problem. In this review, we systematically evaluate the evidence for current and emerging antimicrobials, host-directed therapies and supportive managements.

RECENT FINDINGS

Current antimicrobial regimes do not factor the differing ability of drugs to cross the blood-brain barrier. Rifampicin may be more effective at higher doses yet the most recent clinical trial failed to demonstrate survival benefit at 15 mg/kg/day. Dose finding studies suggest that higher doses still may be safe and more effective. Fluoroquinolones are currently listed as important second-line agents in drug-resistant TBM; however, a survival benefit as a first-line agent has yet to be shown. Linezolid may be a promising antimicrobial with good central nervous system penetrance. Dexamethasone reduces mortality in HIV-uninfected individuals yet evidence for its use in HIV co-infection is lacking. Aspirin has anti-inflammatory and anti-thrombotic properties. Small studies have demonstrated efficacy in reducing stroke but further research is required to better understand its effect on controlling the host inflammatory response. Discovery of genetic polymorphisms may direct individualized immune therapies and mediators of the innate immune response may provide targets for the development of novel therapies. There is at present no significant evidence base to guide management of hydrocephalus in HIV co-infection. Further clinical trial data is required to improve treatment outcomes in TBM in particularly in regard to the value of high-dose rifampicin, newer antimicrobials with improved central nervous system penetration and host-directed therapies. Supportive measures in particular the management of hydrocephalus in HIV co-infection should be an area for future research.