Thrombin-activatable fibrinolysis inhibitor influences disease severity in humans and mice with pneumococcal meningitis

Systemic Inflammatory Response Syndrome, Thromboinflammation, and Septic Shock in Fetuses and Neonates

This article explores systemic inflammatory response syndrome (SIRS), thromboinflammation, and septic shock in fetuses and neonates, offering a comprehensive examination of their pathophysiology, diagnostic criteria, and clinical implications. It identifies SIRS as an exaggerated response to external stress, disrupting the balance between inflammation and adaptive mechanisms, driven by cytokines such as TNF-α and IL-1. The fetal inflammatory response syndrome (FIRS), a subset of SIRS, is noted for its role in adverse neonatal outcomes, including organ damage, inflammation, and long-term developmental disorders. The article discusses the extensive effects of FIRS on critical systems, including the blood, lungs, central nervous system, and kidneys. It highlights the challenges in diagnosing and managing septic shock in neonates, focusing on the relationship between inflammation and the hemostatic system. Additionally, the paper points out recent advancements, such as the convergent model of coagulation and emerging biomarkers like microRNAs for early detection. Despite this progress, gaps remain in understanding the molecular mechanisms underlying these conditions and in developing effective therapeutic strategies. This highlights the necessity for targeted research to mitigate the morbidity and mortality associated with septic shock in neonates.

Single-cell transcriptome reveals highly complement activated microglia cells in association with pediatric tuberculous meningitis

Background

Tuberculous meningitis (TBM) is a devastating form of tuberculosis (TB) causing high mortality and disability. TBM arises due to immune dysregulation, but the underlying immune mechanisms are unclear.

Methods

We performed single-cell RNA sequencing on peripheral blood mononuclear cells (PBMCs) and cerebrospinal fluid (CSF) cells isolated from children (n=6) with TBM using 10 xGenomics platform. We used unsupervised clustering of cells and cluster visualization based on the gene expression profiles, and validated the protein and cytokines by ELISA analysis.

Results

We revealed for the first time 33 monocyte populations across the CSF cells and PBMCs of children with TBM. Within these populations, we saw that CD4_C04 cells with Th17 and Th1 phenotypes and Macro_C01 cells with a microglia phenotype, were enriched in the CSF. Lineage tracking analysis of monocyte populations revealed myeloid cell populations, as well as subsets of CD4 and CD8 T-cell populations with distinct effector functions. Importantly, we discovered that complement-activated microglial Macro_C01 cells are associated with a neuroinflammatory response that leads to persistent meningitis. Consistently, we saw an increase in complement protein (C1Q), inflammatory markers (CRP) and inflammatory factor (TNF-α and IL-6) in CSF cells but not blood. Finally, we inferred that Macro_C01 cells recruit CD4_C04 cells through CXCL16/CXCR6.

Discussion

We proposed that the microglial Macro_C01 subset activates complement and interacts with the CD4_C04 cell subset to amplify inflammatory signals, which could potentially contribute to augment inflammatory signals, resulting in hyperinflammation and an immune response elicited by Mtb-infected tissues.

Brain Expression of CPB2 and Effects of Cpb2 Deficiency in Mouse Models of Behavior

BACKGROUND

 Procarboxypeptidase B2 (proCPB2 or TAFI) is a zymogen that after activation cleaves C-terminal basic residues from peptides or proteins with many identified targets. A splice variant of CPB2 has been found in the brain lacking essential residues for its carboxypeptidase function. The aim was to determine CPB2 expression in the brain and effects of CPB2 deficiency (Cpb2 -/-) on behavior.

MATERIALS AND METHODS

 Behavioral effects were tested by comparing Cpb2 -/- mice in short-term (open field and elevated zero maze tests) and long-term (Phenotyper) observations with wild-type (WT) controls.

RESULTS

 Long-term observation compared day 1 (acclimatizing to novel environment) to day 4 (fully acclimatized) with the inactive (day) and active (night) periods analyzed separately. Brain expression of CPB2 mRNA and protein was interrogated in publicly available databases. Long-term observation demonstrated differences between WT and Cpb2 -/- mice in several parameters. For example, Cpb2 -/- mice moved more frequently on both days 1 and 4, especially in the normally inactive periods. Cpb2 -/- mice spent more time on the shelter and less time in it. Differences were more pronounced on day 4 after the mice had fully acclimatized. In short-term observations, no differences were observed between Cpb2 -/- mice and WT mice. Brain expression of CBP2 was not detectable in the human protein atlas. Databases of single-cell RNAseq did not show expression of CPB2 mRNA in either human or mouse brain.

CONCLUSION

 Continuous observation of home-cage behavior suggests that Cpb2 -/- mice are more active than WT mice, show different day-night activity levels, and might have a different way of processing information.

Role of Thrombin in Central Nervous System Injury and Disease

Thrombin is a Na+-activated allosteric serine protease of the chymotrypsin family involved in coagulation, inflammation, cell protection, and apoptosis. Increasingly, the role of thrombin in the brain has been explored. Low concentrations of thrombin are neuroprotective, while high concentrations exert pathological effects. However, greater attention regarding the involvement of thrombin in normal and pathological processes in the central nervous system is warranted. In this review, we explore the mechanisms of thrombin action, localization, and functions in the central nervous system and describe the involvement of thrombin in stroke and intracerebral hemorrhage, neurodegenerative diseases, epilepsy, traumatic brain injury, and primary central nervous system tumors. We aim to comprehensively characterize the role of thrombin in neurological disease and injury.

Post-Traumatic Sepsis Is Associated with Increased C5a and Decreased TAFI Levels

Background: Sepsis frequently occurs after major trauma and is closely associated with dysregulations in the inflammatory/complement and coagulation system. Thrombin-activatable fibrinolysis inhibitor (TAFI) plays a dual role as an anti-fibrinolytic and anti-inflammatory factor by downregulating complement anaphylatoxin C5a. The purpose of this study was to investigate the association between TAFI and C5a levels and the development of post-traumatic sepsis. Furthermore, the predictive potential of both TAFI and C5a to indicate sepsis occurrence in polytraumatized patients was assessed. Methods: Upon admission to the emergency department (ED) and daily for the subsequent ten days, circulating levels of TAFI and C5a were determined in 48 severely injured trauma patients (injury severity score (ISS) ≥ 16). Frequency matching according to the ISS in septic vs. non-septic patients was performed. Trauma and physiologic characteristics, as well as outcomes, were assessed. Statistical correlation analyses and cut-off values for predicting sepsis were calculated. Results: Fourteen patients developed sepsis, while 34 patients did not show any signs of sepsis (no sepsis). Overall injury severity, as well as demographic parameters, were comparable between both groups (ISS: 25.78 ± 2.36 no sepsis vs. 23.46 ± 2.79 sepsis). Septic patients had significantly increased C5a levels (21.62 ± 3.14 vs. 13.40 ± 1.29 ng/mL; p < 0.05) and reduced TAFI levels upon admission to the ED (40,951 ± 5637 vs. 61,865 ± 4370 ng/mL; p < 0.05) compared to the no sepsis group. Negative correlations between TAFI and C5a (p = 0.0104) and TAFI and lactate (p = 0.0423) and positive correlations between C5a and lactate (p = 0.0173), as well as C5a and the respiratory rate (p = 0.0266), were found. In addition, correlation analyses of both TAFI and C5a with the sequential (sepsis-related) organ failure assessment (SOFA) score have confirmed their potential as early sepsis biomarkers. Cut-off values for predicting sepsis were 54,857 ng/mL for TAFI with an area under the curve (AUC) of 0.7550 (p = 0.032) and 17 ng/mL for C5a with an AUC of 0.7286 (p = 0.034). Conclusion: The development of sepsis is associated with early decreased TAFI and increased C5a levels after major trauma. Both elevated C5a and decreased TAFI may serve as promising predictive factors for the development of sepsis after polytrauma.

Host genetic variability and pneumococcal disease: a systematic review and meta-analysis

Background

Pneumonia, sepsis, meningitis, and empyema due to Streptococcus pneumoniae is a major cause of morbidity and mortality. We provide a systemic overview of genetic variants associated with susceptibility, phenotype and outcome of community acquired pneumococcal pneumonia (CAP) and invasive pneumococcal disease (IPD).

Methods

We searched PubMed for studies on the influence of host genetics on susceptibility, phenotype, and outcome of CAP and IPD between Jan 1, 1983 and Jul 4, 2018. We listed methodological characteristics and when genetic data was available we calculated effect sizes. We used fixed or random effect models to calculate pooled effect sizes in the meta-analysis.

Results

We identified 1219 studies of which 60 studies involving 15,358 patients were included. Twenty-five studies (42%) focused on susceptibility, 8 (13%) on outcome, 1 (2%) on disease phenotype, and 26 (43%) on multiple categories. We identified five studies with a hypothesis free approach of which one resulted in one genome wide significant association in a gene coding for lincRNA with pneumococcal disease susceptibility. We performed 17 meta-analyses of which two susceptibility polymorphisms had a significant overall effect size: variant alleles of MBL2 (odds ratio [OR] 1·67, 95% confidence interval [CI] 1·04–2·69) and a variant in CD14 (OR 1·77, 95% CI 1·18–2·66) and none of the outcome polymorphisms.

Conclusions

Studies have identified several host genetics factors influencing risk of pneumococcal disease, but many result in non-reproducible findings due to methodological limitations. Uniform case definitions and pooling of data is necessary to obtain more robust findings.

Electronic supplementary material

The online version of this article (10.1186/s12920-019-0572-x) contains supplementary material, which is available to authorized users.

Characterization of a Listeria monocytogenes meningitis mouse model

BACKGROUND

Listeria monocytogenes is a common cause of bacterial meningitis. We developed an animal model of listerial meningitis.

METHODS

In survival studies, C57BL/6 mice received intracisternal injections with different L. monocytogenes sequence type 1 (ST1) colony forming units per milliliter (CFU; n = 48, 105, 106, 107, 108, and 109 CFU/ml). Second, mice were inoculated with 108 CFU/ml ST1 and sacrificed at 6 h and 24 h (n = 12/group). Outcome parameters were clinical score, CFUs, cyto- and chemokine levels, and brain histopathology. Third, 84 mice were inoculated (109 CFU/ml ST1) to determine optimal antibiotic treatment with different doses of amoxicillin and gentamicin. Fourth, mice were inoculated with 109 CFU/ml ST1, treated with amoxicillin, and sacrificed at 16 h and 24 h (n = 12/group) for outcome assessment. Finally, time point experiments were repeated with ST6 (n = 24/group).

RESULTS

Median survival time for inoculation with 108 and 109 CFU/ml ST1 was 46 h and 40 h; lower doses of bacteria led to minimal clinical signs of disease. Brain levels of IL-6, IL-17A, and IFN-γ were elevated at 24 h, and IL-1β, IL-6, IL-10, IFN-γ, and TNF-α were elevated in blood at 6 h and 24 h. Histopathology showed increased meningeal infiltration, vascular inflammation of meningeal vessels, hemorrhages, and ventriculitis. In the treatment model, brain levels of IL-6 and IL-17A and blood levels of IL-6 and IFN-γ were elevated. Compared to ST6, infection with ST1 led initially to higher levels of IL-1β and TNF-α in blood and more profound neuropathological damage. At 16 h post inoculation, IL-1β, IL-10, and TNF-α in blood and IL-6, IL17A, TNF-α, and IFN-γ levels in brain were higher in ST1 compared to ST6 without differences in CFUs between STs. At 24 h, neuropathology score was higher in ST1 compared to ST6 (p = 0.002) infected mice.

CONCLUSIONS

We developed and validated a murine model of listerial meningitis. ST1-infected mice had a more severe inflammatory response and brain damage as compared to ST6-infected mice.

Carboxypeptidase B2 and carboxypeptidase N in the crosstalk between coagulation, thrombosis, inflammation, and innate immunity

Two basic carboxypeptidases, carboxypeptidase B2 (CPB2) and carboxypeptidase N (CPN) are present in plasma. CPN is constitutively active, whereas CPB2 circulates as a precursor, procarboxypeptidase B2 (proCPB2), that needs to be activated by the thrombin-thrombomodulin complex or plasmin bound to glycosaminoglycans. The substrate specificities of CPB2 and CPN are similar; they both remove C-terminal basic amino acids from bioactive peptides and proteins, thereby inactivating them. The complement cascade is a cascade of proteases and cofactors activated by pathogens or dead cells, divided into two phases, with the second phase only being triggered if sufficient C3b is present. Complement activation generates anaphylatoxins: C3a, which stimulates macrophages; and C5a, which is an activator and attractant for neutrophils. Pharmacological intervention with inhibitors has shown that CPB2 delays fibrinolysis, whereas CPN is responsible for systemic inactivation of C3a and C5a. Among mice genetically deficient in either CPB2 or CPN, in a model of hemolytic-uremic syndrome, Cpb2-/- mice had the worst disease, followed by Cpn-/- mice, with wild-type (WT) mice being the most protected. This model is driven by C5a, and shows that CPB2 is important in inactivating C5a. In contrast, when mice were challenged acutely with cobra venom factor, the reverse phenotype was observed; Cpn-/- mice had markedly worse disease than Cpb2-/- mice, and WT mice were resistant. These observations need to be confirmed in humans. Therefore, CPB2 and CPN have different roles. CPN inactivates C3a and C5a generated spontaneously, whereas proCPB2 is activated at specific sites, where it inactivates bioactive peptides that would overwhelm CPN.

Variation in coagulation and fibrinolysis genes evaluated for their contribution to cerebrovascular complications in adults with bacterial meningitis in the Netherlands

OBJECTIVE

To study whether genetic variation in coagulation and fibrinolysis genes contributes to cerebrovascular complications in bacterial meningitis.

METHODS

We performed a nationwide prospective genetic association study in adult community-acquired bacterial meningitis patients. The exons and flanking regions of 16 candidate genes involved in coagulation and fibrinolysis pathways were sequenced. We analyzed whether genetic variation in these genes resulted in a higher risk of cerebrovascular complications, unfavorable outcome and differences in thrombocyte count on admission.

RESULTS

From 2006 to 2011, a total of 1101 bacterial meningitis patients were identified of whom 622 supplied DNA for genotyping and passed genetic quality control steps. In 139 patients (22%) the episode of bacterial meningitis was complicated by cerebral infarction, and 188 (30%) had an unfavorable outcome. We identified the functional variant rs494860 in the protein Z (PROZ) gene as our strongest association with occurrence of cerebral infarction (odds ratio (OR) 0.49 (95% confidence interval 0.33-0.73), p = 5.2 × 10^-4). After Bonferroni correction for multiple testing no genetic variant was significantly associated (p-value threshold 2.7 × 10^-4).

CONCLUSION

Our study suggests a functional genetic variation in the PROZ gene, rs494860, may be of importance in bacterial meningitis pathogenesis and cerebral infarction risk. Replication of this finding in other cohort studies populations is needed.

Procarboxypeptidase U (proCPU, TAFI, proCPB2) in cerebrospinal fluid during ischemic stroke is associated with stroke progression, outcome and blood-brain barrier dysfunction

Essentials Little is known of procarboxypeptidase U (proCPU) in cerebrospinal fluid (CSF) of stroke patients. ProCPU levels were studied in CSF of controls and non-thrombolyzed acute ischemic stroke patients. ProCPU is elevated in CSF of stroke patients compared with controls. ProCPU in CSF correlates with stroke progression, outcome, and blood-brain barrier dysfunction.

SUMMARY

Background Procarboxypeptidase U (proCPU, TAFI, proCPB2), the zymogen of CPU, which is a potent antifibrinolytic enzyme and a modulator of inflammation, has previously been investigated in plasma of stroke patients, but so far, no information on the proCPU levels in cerebrospinal fluid (CSF) during acute ischemic stroke (AIS) is available. Objectives This case-control observational study investigates proCPU in CSF of AIS patients compared with controls with an intact blood-brain barrier (BBB) and evaluates the relationship of CSF/plasma proCPU ratios with stroke parameters. Methods A sensitive HPLC-based enzymatic assay was used to determine proCPU levels in CSF of non-thrombolyzed patients in the hyperacute phase (< 24 h after onset) of AIS (n = 72). Individuals (n = 32) without stroke, an intact BBB and no apparent abnormalities in biochemical and microbiological tests, served as controls. Relations between the CSF/plasma proCPU ratio and (i) stroke severity, (ii) stroke progression/recurrence, (iii) stroke outcome and (iv) BBB dysfunction (CSF/serum albumin ratio) were assessed. Results Mean (SEM) proCPU levels were elevated in the CSF of stroke patients compared with controls (4.36 (0.23) U L-1 vs. 3.50 (0.23) U L-1 ). Higher median [IQR] CSF/plasma proCPU ratios were found in patients with stroke progression ((6.0 [4.2-6.9]) × 10-3 ) and poor outcome ((6.4 [3.9-7.0]) × 10-3 ) after 3 months (modified Rankin Scale; mRS > 3) compared with patients without progression ((3.9 [2.7-5.4]) × 10-3 ) or better outcome ((4.0 [2.8-5.0]) × 10-3 ). In stroke patients with a disrupted BBB, proCPU ratios were higher compared with stroke patients with an intact BBB ((6.4 [5.8-9.0]) × 10-3 vs. (3.7 [2.8-5.0]) × 10-3 ). Conclusions ProCPU is increased in CSF during hyperacute ischemic stroke and is associated with stroke progression and outcome after 3 months, most likely due to BBB dysfunction in the hyperacute phase of ischemic stroke.

Immunohaemostasis: a new view on haemostasis during sepsis

Host infection by a micro-organism triggers systemic inflammation, innate immunity and complement pathways, but also haemostasis activation. The role of thrombin and fibrin generation in host defence is now recognised, and thrombin has become a partner for survival, while it was seen only as one of the "principal suspects" of multiple organ failure and death during septic shock. This review is first focused on pathophysiology. The role of contact activation system, polyphosphates and neutrophil extracellular traps has emerged, offering new potential therapeutic targets. Interestingly, newly recognised host defence peptides (HDPs), derived from thrombin and other "coagulation" factors, are potent inhibitors of bacterial growth. Inhibition of thrombin generation could promote bacterial growth, while HDPs could become novel therapeutic agents against pathogens when resistance to conventional therapies grows. In a second part, we focused on sepsis-induced coagulopathy diagnostic challenge and stratification from "adaptive" haemostasis to "noxious" disseminated intravascular coagulation (DIC) either thrombotic or haemorrhagic. Besides usual coagulation tests, we discussed cellular haemostasis assessment including neutrophil, platelet and endothelial cell activation. Then, we examined therapeutic opportunities to prevent or to reduce "excess" thrombin generation, while preserving "adaptive" haemostasis. The fail of international randomised trials involving anticoagulants during septic shock may modify the hypothesis considering the end of haemostasis as a target to improve survival. On the one hand, patients at low risk of mortality may not be treated to preserve "immunothrombosis" as a defence when, on the other hand, patients at high risk with patent excess thrombin and fibrin generation could benefit from available (antithrombin, soluble thrombomodulin) or ongoing (FXI and FXII inhibitors) therapies. We propose to better assess coagulation response during infection by an improved knowledge of pathophysiology and systematic testing including determination of DIC scores. This is one of the clues to allocate the right treatment for the right patient at the right moment.

Endothelial protein C receptor polymorphisms and risk of sepsis in a Chinese population

Objective

To examine the potential relationship of EPCR polymorphisms and the risk of sepsis in a Chinese population.

Methods

Snapshot SNP genotyping assays and DNA sequencing methods were used to detect polymorphisms of the EPCR gene, rs2069948C/T (2532C/T) and rs867186A/G (6936A/G), in 64 patients with sepsis and in 113 controls. Soluble EPCR (sEPCR) was measured by ELISA.

Results

There were significant differences in the allele and genotype frequencies of EPCR gene rs2069948C/T and allele frequencies of rs867186A/G between male and female patients and controls. Females carrying rs2069948 C/T genotype or T allele and males carrying rs867186 A allele were associated with a significantly increased risk of sepsis. Plasma sEPCR levels of sepsis patients were higher than controls and showed no correlation with EPCR gene polymorphisms.

Conclusions

EPCR polymorphisms may be associated with increased risk of sepsis, but this has no effect on the release of sEPCR in patients with sepsis.

Pneumococcal meningitis: clinical-pathological correlations (MeninGene-Path)

Pneumococcal meningitis is associated with substantial mortality and morbidity. We systematically assessed brain histopathology of 31 patients who died of pneumococcal meningitis from a nationwide study (median age 67 years; 21 (67 %) were male) using a pathology score including inflammation and vascular damage. Of the 27 patients with known time from the admission to death, 14 patients died within 7 days of admission and 13 after 7 days of admission. Eleven of 25 (44 %) patients had been treated with adjunctive dexamethasone therapy. Observed pathological processes were inflammation of medium-large arteries in 30 brains (97 %), cerebral haemorrhage in 24 (77 %), cerebritis in 24 (77 %), thrombosis in 21 (68 %), infarction in 19 (61 %) and ventriculitis in 19 (of 28 cases, 68 %). Inflammation of medium-large arteries led to obstruction of the vascular lumen in 14 (of 31 cases, 45 %). Vascular inflammation was associated with infarction and thrombosis of brain parenchymal vessels. Hippocampal dentate gyrus apoptosis between patients treated with and without dexamethasone was similar (p = 0.66); however, dexamethasone treated patients had higher total pathology score than non-dexamethasone treated patients (p = 0.003). Our study shows that vascular damage is key in the process of brain damage in pneumococcal meningitis. Data and material of this study will be made open-access for translational research in pneumococcal meningitis (MeninGene-Path).

Community-acquired bacterial meningitis in adults in the Netherlands, 2006-14: a prospective cohort study

BACKGROUND

We studied causative pathogens, clinical characteristics, and outcome of adult community-acquired bacterial meningitis after the introduction of adjunctive dexamethasone treatment and nationwide implementation of paediatric conjugate vaccines.

METHODS

In this cohort study, we prospectively assessed adults (age >16 years) with community-acquired bacterial meningitis in the Netherlands, identified through the National Reference Laboratory for Bacterial Meningitis or individual physicians between Jan 1, 2006, and July 1, 2014. We identified independent predictors of an unfavourable outcome (Glasgow Outcome Scale score 1-4) by logistic regression.

FINDINGS

We assessed 1412 episodes of community-acquired bacterial meningitis. Incidence declined from 1·72 cases per 100,000 adults per year in 2007-08, to 0·94 per 100,000 per year in 2013-14. Streptococcus pneumoniae caused 1017 (72%) of 1412 episodes. Rates of adult bacterial meningitis decreased most sharply among pneumococcal serotypes included in paediatric conjugate vaccine, and in meningococcal meningitis. We found no evidence of serotype or serogroup replacement. The overall case fatality rate was 244 (17%) of 1412 episodes and unfavourable outcome occurred in 531 (38%) of 1412 episodes. Predictors of unfavourable outcome were advanced age, absence of otitis or sinusitis, alcoholism, tachycardia, lower score on the Glasgow Coma Scale, cranial nerve palsy, a cerebrospinal fluid white-cell count lower than 1000 cells per μL, a positive blood culture, and a high serum C-reactive protein concentration. Adjunctive dexamethasone was administered for 1234 (89%) of 1384 assessed episodes. The multivariable adjusted odds ratio of dexamethasone treatment for unfavourable outcome was 0·54 (95% CI 0·39-0·73).

INTERPRETATION

The incidence of adult bacterial meningitis has decreased substantially, which is partly explained by herd protection by paediatric conjugate vaccines. Adjunctive dexamethasone treatment was associated with substantially improved outcome.

FUNDING

European Research Council, National Institute of Public Health and the Environment, European Union, Academic Medical Center, and Netherlands Organization for Health Research and Development.