Genetic variations of toll-like receptors: Impact on susceptibility, severity and prognosis of bacterial meningitis

Ureaplasma urealyticum GrpE protein elicits glycolysis-mediated inflammatory responses through TLR2 in macrophages

The pathogenesis of Ureaplasma urealyticum infection is linked to the host inflammatory response; however, the specific molecular mechanisms underlying this phenomenon have not been fully elucidated. GrpE is a chaperonin that accelerates ADP release and ATP binding to DnaK, thereby enhancing the chaperone function of the HSP70 system under stress. However, alternative activities such as pro-inflammatory responses remain poorly understood. In this study, we report that the U. urealyticum GrpE exerts as a cytokine-inducing virulence factor toward macrophages. Using gene-knockout mice and specific inhibitors, we found that GrpE-induced pro-inflammatory cytokine expression was mediated by the TLR2/STAT3 pathway. We also found that glycolysis was essential for this pro-inflammatory response. Mechanistically, GrpE treatment stimulated STAT3-dependent accumulation of citric acid and acetyl-CoA, promoting histone acetylation and potent pro-inflammatory responses. Our results indicate that glycolysis plays a role in the inflammatory response induced by GrpE through the TLR2/STAT3 pathway and contributes to the glycolysis-mediated inflammatory response, offering a fresh understanding of the development of U. urealyticum infection.

Assessing the Impact of TLR4 rs4986790 Polymorphism on Bacterial Meningitis Risk: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Toll-like receptor ( TLR2 ) gene plays an important role in the pathogenesis of bacterial meningitis (such as meningococcal meningitis and pneumococcal meningitis). The association between TLR4 rs4986790 polymorphism and the susceptibility to bacterial meningitis has been extensively studied. However, the results of these studies remain inconsistent. Therefore, we performed a meta-analysis to evaluate the association between TLR4 rs4986790 polymorphism and the susceptibility to meningococcal meningitis and pneumococcal meningitis.

METHODS

Google Scholar, Embase, and PubMed databases were searched for case-control studies on TLR4 polymorphisms and the risks of meningococcal meningitis and pneumococcal meningitis, published up to May 31, 2024. To assess the strength of the association between TLR4 polymorphism and meningococcal meningitis and pneumococcal meningitis, the odds ratios (ORs) with 95% confidence intervals (CIs) were used. The meta-analysis of the associations between the TLR4 rs4986790 polymorphism and meningococcal meningitis and pneumococcal meningitis was carried out under different genetic models. Meta-analyses were conducted using Cochrane RoB 2 tool and Metagenyo to calculate the ORs and 95% CIs. Fourteen published studies with 3599 cases and 7438 controls were included.

RESULTS

Overall, there was a strong correlation between TLR4 polymorphisms and meningococcal meningitis observed across three genetic models using a random-effects model: GG + GA vs. AA (OR: 0.34, 95% CI: 0.14-0.79, P = 0.01, I ² = 60%); GA vs. AA (OR: 0.34, 95% CI: 0.13-0.91, P = 0.03, I ² = 65%); and GG vs. AA (OR: 0.34, 95% CI: 0.14-0.78, P = 0.01, I ² = 59%). Conversely, a fixed-effects model also revealed a significant association in the G vs. A model (OR: 0.84, 95% CI: 0.73-0.96, P = 0.01, I ² = 38%). In pneumococcal meningitis, a fixed-effects model analysis demonstrated a significant association in the GG vs. AA model (OR: 0.35, 95% CI: 0.14-0.87, P = 0.02, I ² = 48%) respectively.

CONCLUSION

This meta-analysis showed a strong correlation between TLR4 rs4986790 polymorphism and susceptibility to meningococcal meningitis and pneumococcal meningitis. Further studies with diverse populations are needed to validate and strengthen these findings.

Cerebrospinal fluid cytokines and chemokines exhibit distinct profiles in bacterial meningitis and viral meningitis

Differential diagnosis of bacterial meningitis (BM) and viral meningitis (VM) is a critical clinical challenge, as the early and accurate identification of the causative agent determines the appropriate treatment regimen and markedly improves patient outcomes. Clinical and experimental studies have demonstrated that the pathogen and the host immune response contribute to mortality and neurological sequelae. As BM is associated with the activation of an inflammatory cascade, the patterns of pro- and anti-inflammatory cytokines/chemokines (CTs/CKs) present in the cerebrospinal fluid (CSF) in response to the immune assault may be useful as sensitive markers for differentiating BM from VM. In the present study, the ability of CTs/CKs in the CSF to differentiate between BM and VM was investigated. For this, biochemical markers and CT/CK profiles were analysed in 145 CSF samples, divided into three groups: BM (n=61), VM (n=58) and the control group (C; n=26) comprising patients with meningism. The CSF concentrations of monocyte chemoattractant protein-1, interleukin (IL)-8, IL-1β, IL-6, macrophage inflammatory protein-1α (MIP-1α), epithelial-neutrophil activating peptide, IL-10, tumour necrosis factor-α (TNF-α), proteins and white blood cells were significantly higher and the CSF glucose level was significantly lower in the BM group compared with the VM and C groups (P<0.01). Correlation analysis identified 28 significant correlations between various CTs/CKs in the BM group (P<0.01), with the strongest positive correlations being for TNF-α/IL-6 (r=0.75), TNF-α/MIP-1α (r=0.69), TNF-α/IL-1β (r=0.64) and IL-1β/MIP-1α (r=0.64). To identify the optimum CT/CK patterns for predicting and classifying BM and VM, a dataset of 119 BM and VM samples was divided into training (n=90) and testing (n=29) subsets for use as input for a Random Forest (RF) machine learning algorithm. For the 29 test samples (15 BM and 14 VM), the RF algorithm correctly classified 28 samples, with 92% sensitivity and 93% specificity. The results show that the patterns of CT/CK levels in the CSF can be used to aid discrimination of BM and VM.

Blood-Brain Barrier Integrity Damage in Bacterial Meningitis: The Underlying Link, Mechanisms, and Therapeutic Targets

Despite advances in supportive care and antimicrobial treatment, bacterial meningitis remains the most serious infection of the central nervous system (CNS) that poses a serious risk to life. This clinical dilemma is largely due to our insufficient knowledge of the pathology behind this disease. By controlling the entry of molecules into the CNS microenvironment, the blood-brain barrier (BBB), a highly selective cellular monolayer that is specific to the CNS's microvasculature, regulates communication between the CNS and the rest of the body. A defining feature of the pathogenesis of bacterial meningitis is the increase in BBB permeability. So far, several contributing factors for BBB disruption have been reported, including direct cellular damage brought on by bacterial virulence factors, as well as host-specific proteins or inflammatory pathways being activated. Recent studies have demonstrated that targeting pathological factors contributing to enhanced BBB permeability is an effective therapeutic complement to antimicrobial therapy for treating bacterial meningitis. Hence, understanding how these meningitis-causing pathogens affect the BBB permeability will provide novel perspectives for investigating bacterial meningitis's pathogenesis, prevention, and therapies. Here, we summarized the recent research progress on meningitis-causing pathogens disrupting the barrier function of BBB. This review provides handy information on BBB disruption by meningitis-causing pathogens, and helps design future research as well as develop potential combination therapies.

Gene polymorphisms of TLR10: effects on bacterial meningitis outcomes in Angolan children

This study examined whether gene polymorphisms for toll-like receptor 10 (TLR10) associated with the susceptibility to and outcomes of bacterial meningitis (BM) in Angolan children. The study cohort consisted of 190 BM patients and the determination of ten single-nucleotide polymorphisms (SNPs) by Sanger sequencing. Patients with BM caused by Streptococcus pneumoniae who carried the following variants of TLR10 SNPs exhibited an increased risk of coexisting pneumonia: rs10004195 (T > A) (p = 0.025), rs10856837 (G > A) (p = 0.018) or rs11096956 (G > T) (p = 0.010). Yet, TLR10 SNPs rs11466652 (A > G), rs10856837 (G > A) and rs11096956 (G > T) influenced the protein levels in the cerebrospinal fluid (CSF). Moreover, compared with the wild type, patients with pneumococcal meningitis carrying a variant genotype of TLR10 SNP rs11466648 (A > G) exhibited an increased risk of developing blindness (p = 0.025), whereas patients with TLR10 SNP rs10004195 (T > A) exhibited a lower risk of convulsions at admission (p = 0.039) and a lower risk of altered consciousness (p = 0.029). This study suggests a relationship exists between coexisting pneumonia, protein levels in CSF, blindness, convulsions and an altered consciousness with genetic variations of TLR10 in BM in Angolan children.